path: root/crawl-ref/source/travel.cc

/**
 * @file
 * @brief Travel stuff
**/
/* Known issues:
 *   Hardcoded dungeon features all over the place - this thing is a devil to
 *   refactor.
 */
#include "AppHdr.h"

#include "artefact.h"
#include "branch.h"
#include "cio.h"
#include "cloud.h"
#include "clua.h"
#include "command.h"
#include "coord.h"
#include "coordit.h"
#include "dactions.h"
#include "delay.h"
#include "dgn-overview.h"
#include "directn.h"
#include "env.h"
#include "exclude.h"
#include "fight.h"
#include "files.h"
#include "fixedarray.h"
#include "food.h"
#include "godabil.h"
#include "godprayer.h"
#include "hints.h"
#include "itemname.h"
#include "itemprop.h"
#include "items.h"
#include "libutil.h"
#include "macro.h"
#include "map_knowledge.h"
#include "message.h"
#include "misc.h"
#include "mon-death.h"
#include "mon-util.h"
#include "options.h"
#include "output.h"
#include "place.h"
#include "player.h"
#include "prompt.h"
#include "religion.h"
#include "stairs.h"
#include "stash.h"
#include "state.h"
#include "strings.h"
#include "tags.h"
#include "terrain.h"
#include "traps.h"
#include "travel.h"
#include "unicode.h"
#include "unwind.h"
#include "view.h"

#include <algorithm>
#include <cctype>
#include <cstdarg>
#include <cstdio>
#include <memory>
#include <set>
#include <sstream>

enum IntertravelDestination
{
    // Go down a level
    ID_DOWN     = -100,

    // Go up a level
    ID_UP       = -99,

    // Repeat last travel
    ID_REPEAT   = -101,

    // Cancel interlevel travel
    ID_CANCEL   = -1000,
};

TravelCache travel_cache;

// Tracks the distance between the target location on the target level and the
// stairs on the level.
static vector<stair_info> curr_stairs;

// Squares that are not safe to travel to on the current level.
exclude_set curr_excludes;

// This is where we last tried to take a stair during interlevel travel.
// Note that last_stair.depth should be set to -1 before initiating interlevel
// travel.
static level_id last_stair;

// Where travel wants to get to.
static travel_target level_target;

// How many stairs there are between the source and destination of
// interlevel travel, as estimated by level_distance.
static int _Src_Dest_Level_Delta = -1;

// Source level where interlevel travel was last activated.
static level_id _Src_Level;

// Remember the last place explore stopped because autopickup failed.
static coord_def explore_stopped_pos;

// The place in the Vestibule of Hell where all portals to Hell land.
static level_pos travel_hell_entry;

static string trans_travel_dest;

// Array of points on the map, each value being the distance the character
// would have to travel to get there. Negative distances imply that the point
// is a) a trap or hostile terrain or b) only reachable by crossing a trap or
// hostile terrain.
travel_distance_grid_t travel_point_distance;

// Apply slime wall checks when checking if squares are travelsafe.
bool g_Slime_Wall_Check = true;

static uint8_t curr_waypoints[GXM][GYM];

// If true, feat_is_traversable_now() returns the same as feat_is_traversable().
// FIXME: eliminate this.  It's needed for RMODE_CONNECTIVITY.
static bool ignore_player_traversability = false;

// Map of terrain types that are forbidden.
static FixedVector<int8_t,NUM_FEATURES> forbidden_terrain;

/*
 * Warn if interlevel travel is going to take you outside levels in
 * the range [src,dest].
 */
class deviant_route_warning
{
private:
    travel_target target;
    bool warned;

public:
    deviant_route_warning(): target(), warned(false)
    {
    }

    void new_dest(const travel_target &dest);
    bool warn_continue_travel(const travel_target &des,
                              const level_id &deviant);
};

void deviant_route_warning::new_dest(const travel_target &dest)
{
    if (target != dest)
    {
        warned = false;
        target = dest;
    }
}

// Returns true if the player wants to continue travelling after the warning.
bool deviant_route_warning::warn_continue_travel(
    const travel_target &dest, const level_id &deviant)
{
    // We've already prompted, don't ask again, on the player's head be it.
    if (target == dest && warned)
        return true;

    target = dest;
    const string prompt = make_stringf("Have to go through %s. Continue?",
                                       deviant.describe().c_str());
    // If the user says "Yes, shut up and take me there", we won't ask
    // again for that destination. If the user says "No", we will
    // prompt again.
    return warned = yesno(prompt.c_str(), true, 'n', true, false);
}

static deviant_route_warning _Route_Warning;

static command_type _trans_negotiate_stairs();
static bool _find_transtravel_square(const level_pos &pos,
                                     bool verbose = true);

static bool _loadlev_populate_stair_distances(const level_pos &target);
static void _populate_stair_distances(const level_pos &target);
static bool _is_greed_inducing_square(const LevelStashes *ls,
                                      const coord_def &c, bool autopickup,
                                      bool sacrifice);
static bool _is_travelsafe_square(const coord_def& c,
                                  bool ignore_hostile = false,
                                  bool ignore_danger = false,
                                  bool try_fallback = false);

// Returns true if there is a known trap at (x,y). Returns false for non-trap
// squares as also for undiscovered traps.
//
static inline bool is_trap(const coord_def& c)
{
    return feat_is_trap(env.map_knowledge(c).feat());
}

static inline bool _is_safe_cloud(const coord_def& c)
{
    const cloud_type ctype = env.map_knowledge(c).cloud();
    if (ctype == CLOUD_NONE)
        return true;

    // We can also safely run through smoke, or any of our own clouds if
    // following Qazlal.
    return !is_damaging_cloud(ctype, true)
           || you_worship(GOD_QAZLAL)
              && !player_under_penance()
              && YOU_KILL(env.map_knowledge(c).cloudinfo()->killer);
}

// Returns an estimate for the time needed to cross this feature.
// This is done, so traps etc. will usually be circumvented where possible.
static inline int _feature_traverse_cost(dungeon_feature_type feature)
{
    if (feature == DNGN_SHALLOW_WATER || feat_is_closed_door(feature))
        return 2;
    else if (feat_is_trap(feature))
        return 3;

    return 1;
}

bool is_unknown_stair(const coord_def &p)
{
    dungeon_feature_type feat = env.map_knowledge(p).feat();

    return feat_is_travelable_stair(feat) && !travel_cache.know_stair(p)
           && feat != DNGN_EXIT_DUNGEON;
}

// Returns true if the character can cross this dungeon feature, and
// the player hasn't requested that travel avoid the feature.
bool feat_is_traversable_now(dungeon_feature_type grid, bool try_fallback)
{
    if (!ignore_player_traversability)
    {
        // If the feature is in travel_avoid_terrain, respect that.
        if (forbidden_terrain[grid])
            return false;

        // Swimmers get deep water.
        if (grid == DNGN_DEEP_WATER && player_likes_water(true))
            return true;

        // Likewise for lava
        if (grid == DNGN_LAVA && player_likes_lava(true))
            return true;

        // Permanently flying players can cross most hostile terrain.
        if (grid == DNGN_DEEP_WATER || grid == DNGN_LAVA
            || grid == DNGN_TRAP_MECHANICAL || grid == DNGN_TRAP_SHAFT)
        {
            return you.permanent_flight();
        }

        // You can't open doors in bat form.
        if (grid == DNGN_CLOSED_DOOR || grid == DNGN_RUNED_DOOR)
            return player_can_open_doors();
    }

    return feat_is_traversable(grid, try_fallback);
}

// Returns true if a generic character can cross this dungeon feature.
// Ignores swimming, flying, and travel_avoid_terrain.
bool feat_is_traversable(dungeon_feature_type feat, bool try_fallback)
{
    if (feat_is_trap(feat) && feat != DNGN_PASSAGE_OF_GOLUBRIA)
    {
        if (ignore_player_traversability)
            return !(feat == DNGN_TRAP_SHAFT || feat == DNGN_TRAP_TELEPORT);
        return false;
    }
    else if (feat == DNGN_TELEPORTER) // never ever enter it automatically
        return false;
    else if (feat >= DNGN_MINWALK || feat == DNGN_RUNED_DOOR
             || feat == DNGN_CLOSED_DOOR
             || (feat == DNGN_SEALED_DOOR && try_fallback))
    {
        return true;
    }
    else
        return false;
}

static const char *_run_mode_name(int runmode)
{
    return runmode == RMODE_TRAVEL         ? "travel" :
           runmode == RMODE_INTERLEVEL     ? "intertravel" :
           runmode == RMODE_EXPLORE        ? "explore" :
           runmode == RMODE_EXPLORE_GREEDY ? "explore_greedy" :
           runmode > 0                     ? "run"
                                           : "";
}

uint8_t is_waypoint(const coord_def &p)
{
    if (!can_travel_interlevel())
        return 0;
    return curr_waypoints[p.x][p.y];
}

static inline bool is_stash(const LevelStashes *ls, const coord_def& p)
{
    if (!ls)
        return false;

    const Stash *s = ls->find_stash(p);
    return s && s->enabled;
}

static bool _monster_blocks_travel(const monster_info *mons)
{
    // [ds] No need to check if the monster is a known mimic, since it
    // won't even be a monster_info if it's an unknown mimic.
    return mons
           && mons_class_is_stationary(mons->type)
           && !fedhas_passthrough(mons)
           && !travel_kill_monster(mons->type);
}

/*
 * Returns true if the square at (x,y) is a dungeon feature the character
 * can't (under normal circumstances) safely cross.
 *
 * Note: is_reseedable can return true for dungeon features that is_traversable
 *       also returns true for. This is okay, because is_traversable always
 *       takes precedence over is_reseedable. is_reseedable is used only to
 *       decide which squares to reseed from when flood-filling outwards to
 *       colour the level map. It does not affect pathing of actual
 *       travel/explore.
 */
static bool _is_reseedable(const coord_def& c, bool ignore_danger = false)
{
    if (!ignore_danger && is_excluded(c))
        return true;

    map_cell &cell(env.map_knowledge(c));
    const dungeon_feature_type grid = cell.feat();

    if (feat_is_wall(grid) || grid == DNGN_TREE)
        return false;

    return feat_is_water(grid)
           || grid == DNGN_LAVA
           || grid == DNGN_RUNED_DOOR
           || is_trap(c)
           || !ignore_danger && _monster_blocks_travel(cell.monsterinfo())
           || g_Slime_Wall_Check && slime_wall_neighbour(c)
           || !_is_safe_cloud(c);
}

struct cell_travel_safety
{
    bool safe;
    bool safe_if_ignoring_hostile_terrain;

    cell_travel_safety() : safe(false), safe_if_ignoring_hostile_terrain(false)
    {
    }
};

typedef FixedArray<cell_travel_safety, GXM, GYM> travel_safe_grid;
static unique_ptr<travel_safe_grid> _travel_safe_grid;

class precompute_travel_safety_grid
{
private:
    bool did_compute;

public:
    precompute_travel_safety_grid() : did_compute(false)
    {
        if (!_travel_safe_grid.get())
        {
            did_compute = true;
            unique_ptr<travel_safe_grid> tsgrid(new travel_safe_grid);
            travel_safe_grid &safegrid(*tsgrid);
            for (rectangle_iterator ri(1); ri; ++ri)
            {
                const coord_def p(*ri);
                cell_travel_safety &ts(safegrid(p));
                ts.safe = _is_travelsafe_square(p, false);
                ts.safe_if_ignoring_hostile_terrain =
                    _is_travelsafe_square(p, true);
            }
            _travel_safe_grid = move(tsgrid);
        }
    }
    ~precompute_travel_safety_grid()
    {
        if (did_compute)
            _travel_safe_grid.reset(NULL);
    }
};

bool is_stair_exclusion(const coord_def &p)
{
    if (feat_stair_direction(env.map_knowledge(p).feat()) == CMD_NO_CMD)
        return false;

    return get_exclusion_radius(p) == 1;
}

// Returns true if the square at (x,y) is okay to travel over. If ignore_hostile
// is true, returns true even for dungeon features the character can normally
// not cross safely (deep water, lava, traps).
static bool _is_travelsafe_square(const coord_def& c, bool ignore_hostile,
                                  bool ignore_danger, bool try_fallback)
{
    if (!in_bounds(c))
        return false;

    if (_travel_safe_grid.get())
    {
        const cell_travel_safety &cell((*_travel_safe_grid)(c));
        return ignore_hostile? cell.safe_if_ignoring_hostile_terrain
               : cell.safe;
    }

    if (!env.map_knowledge(c).known())
        return false;

    const dungeon_feature_type grid = env.map_knowledge(c).feat();

    // Only try pathing through temporary obstructions we remember, not
    // those we can actually see (since the latter are clearly still blockers)
    try_fallback = (try_fallback
                    && (!you.see_cell(c) || grid == DNGN_RUNED_DOOR));

    // Also make note of what's displayed on the level map for
    // plant/fungus checks.
    const map_cell& levelmap_cell = env.map_knowledge(c);

    // Travel will not voluntarily cross squares blocked by immobile
    // monsters.
    if (!ignore_danger && !ignore_hostile)
    {
        const monster_info *minfo = levelmap_cell.monsterinfo();
        if (minfo && _monster_blocks_travel(minfo))
            return false;
    }

    // If 'ignore_hostile' is true, we're ignoring hazards that can be
    // navigated over if the player is willing to take damage or fly.
    if (ignore_hostile && _is_reseedable(c, true))
        return true;

    // Excluded squares are only safe if marking stairs, i.e. another level.
    if (!ignore_danger && is_excluded(c) && !is_stair_exclusion(c))
        return false;

    if (g_Slime_Wall_Check && slime_wall_neighbour(c)
        && !actor_slime_wall_immune(&you))
    {
        return false;
    }

    if (!_is_safe_cloud(c) && !try_fallback)
        return false;

    if (is_trap(c))
    {
        trap_def trap;
        trap.pos = c;
        trap.type = env.map_knowledge(c).trap();
        trap.ammo_qty = 1;
        if (trap.is_safe())
            return true;
    }

    if (levelmap_cell.feat() == DNGN_RUNED_DOOR && !try_fallback)
        return false;

    return feat_is_traversable_now(grid, try_fallback);
}

// Returns true if the location at (x,y) is monster-free and contains
// no clouds. Travel uses this to check if the square the player is
// about to move to is safe.
static bool _is_safe_move(const coord_def& c)
{
    if (const monster* mon = monster_at(c))
    {
        // Stop before wasting energy on plants and fungi,
        // unless worshipping Fedhas.
        if (you.can_see(mon)
            && mons_class_flag(mon->type, M_NO_EXP_GAIN)
            && mon->is_stationary()
            && !fedhas_passthrough(mon)
            && !travel_kill_monster(mon->type))
        {
            return false;
        }

        // If this is any *other* monster, it'll be visible and
        // a) Friendly, in which case we'll displace it, no problem.
        // b) Unfriendly, in which case we're in deep trouble, since travel
        //    should have been aborted already by the checks in view.cc.
    }

    if (is_trap(c) && !find_trap(c)->is_safe())
        return false;

    return _is_safe_cloud(c);
}

void travel_init_load_level()
{
    curr_excludes.clear();
    travel_cache.set_level_excludes();
    travel_cache.update_waypoints();
}

// This is called after the player changes level.
void travel_init_new_level()
{
    // Clear run details, but preserve the runmode, because we might be in
    // the middle of interlevel travel.
    int runmode = you.running;
    you.running.clear();
    you.running = runmode;

    travel_init_load_level();

    explore_stopped_pos.reset();
}

// Given a dungeon feature description, returns the feature number. This is a
// crude hack and currently recognises only (deep/shallow) water. (XXX)
//
// Returns -1 if the feature named is not recognised, else returns the feature
// number (guaranteed to be 0-255).
static int _get_feature_type(const string &feature)
{
    if (feature.find("deep water") != string::npos)
        return DNGN_DEEP_WATER;
    if (feature.find("shallow water") != string::npos)
        return DNGN_SHALLOW_WATER;
    return -1;
}

// Given a feature description, prevents travel to locations of that feature
// type.
void prevent_travel_to(const string &feature)
{
    int feature_type = _get_feature_type(feature);
    if (feature_type != -1)
        forbidden_terrain[feature_type] = 1;
}

static bool _is_branch_stair(const coord_def& pos)
{
    const level_id curr = level_id::current();
    const level_id next = level_id::get_next_level_id(pos);

    return next.branch != curr.branch;
}

// Prompts the user to stop explore if necessary for the given
// explore-stop condition, returns true if explore should be stopped.
static bool _prompt_stop_explore(int es_why)
{
    return !(Options.explore_stop_prompt & es_why)
           || yesno("Stop exploring?", true, 'y', true, false);
}

#define ES_item   (Options.explore_stop & ES_ITEM)
#define ES_greedy (Options.explore_stop & ES_GREEDY_ITEM)
#define ES_glow   (Options.explore_stop & ES_GLOWING_ITEM)
#define ES_art    (Options.explore_stop & ES_ARTEFACT)
#define ES_rune   (Options.explore_stop & ES_RUNE)
#define ES_shop   (Options.explore_stop & ES_SHOP)
#define ES_stair  (Options.explore_stop & ES_STAIR)
#define ES_altar  (Options.explore_stop & ES_ALTAR)
#define ES_portal (Options.explore_stop & ES_PORTAL)
#define ES_branch (Options.explore_stop & ES_BRANCH)
#define ES_rdoor  (Options.explore_stop & ES_RUNED_DOOR)
#define ES_stack  (Options.explore_stop & ES_GREEDY_VISITED_ITEM_STACK)
#define ES_sacrificeable (Options.explore_stop & ES_GREEDY_SACRIFICEABLE)

// Adds interesting stuff on the point p to explore_discoveries.
static inline void _check_interesting_square(const coord_def pos,
                                             explore_discoveries &ed)
{
    if ((ES_item || ES_greedy || ES_glow || ES_art || ES_rune)
        && you.visible_igrd(pos) != NON_ITEM)
    {
        ed.found_item(pos, mitm[ you.visible_igrd(pos) ]);
    }

    ed.found_feature(pos, grd(pos));
}

static void _userdef_run_stoprunning_hook()
{
#ifdef CLUA_BINDINGS
    if (you.running)
        clua.callfn("ch_stop_running", "s", _run_mode_name(you.running));
#else
    UNUSED(_run_mode_name);
#endif
}

static void _userdef_run_startrunning_hook()
{
#ifdef CLUA_BINDINGS
    if (you.running)
        clua.callfn("ch_start_running", "s", _run_mode_name(you.running));
#endif
}

bool is_resting()
{
    return you.running.is_rest();
}

static int _slowest_ally_speed()
{
    vector<monster* > followers = get_on_level_followers();
    int min_speed = INT_MAX;
    for (vector<monster* >::iterator fol = followers.begin();
         fol != followers.end(); ++fol)
    {
        int speed = (*fol)->speed * BASELINE_DELAY
                    / (*fol)->action_energy(EUT_MOVE);
        if (speed < min_speed)
            min_speed = speed;
    }
    return min_speed;
}

static void _start_running()
{
    _userdef_run_startrunning_hook();
    you.running.init_travel_speed();

    if (you.running < 0)
        start_delay(DELAY_TRAVEL, 1);
}

// Stops shift+running and all forms of travel.
void stop_running()
{
    you.running.stop();
}

static bool _is_valid_explore_target(const coord_def& where)
{
    // If a square in LOS is unmapped, it's valid.
    for (radius_iterator ri(where, LOS_DEFAULT, true); ri; ++ri)
        if (!env.map_knowledge(*ri).seen())
            return true;

    if (you.running == RMODE_EXPLORE_GREEDY)
    {
        LevelStashes *lev = StashTrack.find_current_level();
        return lev && lev->needs_visit(where, can_autopickup(),
                                       god_likes_items(you.religion, true));
    }

    return false;
}

enum explore_status_type
{
    EST_FULLY_EXPLORED    = 0,

    // Could not explore because of hostile terrain
    EST_PARTLY_EXPLORED   = 1,

    // Could not pick up interesting items because of hostile terrain. Note
    // that this and EST_PARTLY_EXPLORED are not mutually exclusive.
    EST_GREED_UNFULFILLED = 2,
};

// Determines if the level is fully explored.
static int _find_explore_status(const travel_pathfind &tp)
{
    int explore_status = 0;

    const coord_def greed = tp.greedy_square();
    if (greed.x || greed.y)
        explore_status |= EST_GREED_UNFULFILLED;

    const coord_def unexplored = tp.unexplored_square();
    if (unexplored.x || unexplored.y || !tp.get_unreachables().empty())
        explore_status |= EST_PARTLY_EXPLORED;

    return explore_status;
}

static int prev_travel_moves[2] = {-1, -1};
static int prev_travel_index    = 0;

static int anti_zigzag_dir = -1;

static void _reset_zigzag_info()
{
    prev_travel_moves[0] = -1;
    prev_travel_moves[1] = -1;
    prev_travel_index    =  0;
    anti_zigzag_dir      = -1;
}

static void _set_target_square(const coord_def &target)
{
    you.running.pos = target;
}

static void _explore_find_target_square()
{
    bool fallback = false;
    bool runed_door_pause = false;

    travel_pathfind tp;
    tp.set_floodseed(you.pos(), true);

    coord_def whereto =
        tp.pathfind(static_cast<run_mode_type>(you.running.runmode));

    // If we didn't find an explore target the first time, try fallback mode
    if (!whereto.x && !whereto.y)
    {
        fallback = true;
        travel_pathfind fallback_tp;
        fallback_tp.set_floodseed(you.pos(), true);
        whereto = fallback_tp.pathfind(static_cast<run_mode_type>(you.running.runmode), true);

        if (whereto.distance_from(you.pos()) == 1
            && grd(whereto) == DNGN_RUNED_DOOR)
        {
            runed_door_pause = true;
            whereto.reset();
        }
    }

    if (whereto.x || whereto.y)
    {
        // Make sure this is a square that is reachable, since we asked
        // travel_pathfind to give us even unreachable squares.  The
        // player's starting position may in some cases not have its
        // travel_point_distance set, but we know it's reachable, since
        // we're there.
        if (travel_point_distance[whereto.x][whereto.y] <= 0
            && whereto != you.pos())
        {
            whereto.reset();
        }
    }

    if (whereto.x || whereto.y)
    {
        // Anti-zigzag turned off, or found a greedy target so we
        // don't need anti-zigzaging.
        if (!Options.explore_improved || whereto != tp.unexplored_square())
        {
            _set_target_square(whereto);
            _reset_zigzag_info();
            return;
        }

        // If the two previous travel moves are perpendicular to each
        // other...
        if (prev_travel_moves[0] != -1
            && prev_travel_moves[1] != -1
            && (abs(prev_travel_moves[1] - prev_travel_moves[0]) % 4) == 2)
        {
            ASSERT(anti_zigzag_dir == -1);

            // Try moving along the line that bisects the right angle.
            if ((abs(prev_travel_moves[0] - prev_travel_moves[1]) == 6)
                && prev_travel_moves[0] + prev_travel_moves[1] == 8)
            {
                anti_zigzag_dir = 0;
            }
            else
            {
                anti_zigzag_dir = min(prev_travel_moves[0],
                                      prev_travel_moves[1]) + 1;
            }
        }

        // anti_zigzag_dir might have just been set, or might have
        // persisted from the previous call to
        // _explore_find_target_square().
        if (anti_zigzag_dir != -1)
        {
            coord_def target = you.pos();
            coord_def delta  = Compass[anti_zigzag_dir];

            dungeon_feature_type feature;
            do
            {
                target += delta;
                feature = grd(target);
            }
            while (_is_travelsafe_square(target, fallback)
                   && feat_is_traversable_now(feature, fallback)
                   && _feature_traverse_cost(feature) == 1);

            target -= delta;

            // Has moving along the straight line found an unexplored
            // square?
            if (!env.map_knowledge(target + delta).seen() && target != you.pos()
                && target != whereto)
            {
                // Auto-explore is only zigzagging if the preferred
                // target (whereto) and the anti-zigzag target are
                // close together.
                if (grid_distance(target, whereto) <= 5
                    && distance2(target, whereto) <= 34)
                {
                    _set_target_square(target);
                    return;
                }
            }
            anti_zigzag_dir = -1;
        }

        _set_target_square(whereto);
    }
    else
    {
        if (runed_door_pause)
            mpr("Partly explored, obstructed by runed door.");
        else
        {
            // No place to go? Report to the player.
            const int estatus = _find_explore_status(tp);

            if (!estatus)
            {
                mpr("Done exploring.");
                learned_something_new(HINT_DONE_EXPLORE);
            }
            else
            {
                vector<string> inacc;
                if (estatus & EST_GREED_UNFULFILLED)
                    inacc.push_back("items");
                if (estatus & EST_PARTLY_EXPLORED)
                    inacc.push_back("places");

                mprf("Partly explored, can't reach some %s.",
                    comma_separated_line(inacc.begin(),
                                        inacc.end()).c_str());
            }
        }
        stop_running();
    }
}

void explore_pickup_event(int did_pickup, int tried_pickup)
{
    if (!did_pickup && !tried_pickup)
        return;

    if (!you.running.is_explore())
        return;

    if (did_pickup)
    {
        const int estop =
            (you.running == RMODE_EXPLORE_GREEDY) ? ES_GREEDY_PICKUP_MASK
                                                  : ES_NONE;

        if ((Options.explore_stop & estop) && _prompt_stop_explore(estop))
        {
            stop_delay();
            _reset_zigzag_info();
        }
    }

    // Greedy explore has no good way to deal with an item that we can't
    // pick up, so the only thing to do is to stop.
    if (tried_pickup && you.running == RMODE_EXPLORE_GREEDY)
    {
        if (explore_stopped_pos == you.pos())
        {
            const string prompt =
                make_stringf("Could not pick up %s here; shall I ignore %s?",
                             tried_pickup == 1? "an item" : "some items",
                             tried_pickup == 1? "it" : "them");

            // Make Escape => 'n' and stop run.
            explicit_keymap map;
            map[ESCAPE] = 'n';
            map[CONTROL('G')] = 'n';
            if (yesno(prompt.c_str(), true, 'y', true, false, false, &map))
            {
                mark_items_non_pickup_at(you.pos());
                // Don't stop explore.
                return;
            }
            canned_msg(MSG_OK);
        }
        explore_stopped_pos = you.pos();
        stop_delay();
        _reset_zigzag_info();
    }
}

static bool _sacrificeable_at(const coord_def& p)
{
    for (stack_iterator si(p, true); si; ++si)
        if (si->is_greedy_sacrificeable())
            return true;

    return false;
}

// Top-level travel control (called from input() in main.cc).
//
// travel() is responsible for making the individual moves that constitute
// (interlevel) travel and explore and deciding when travel and explore
// end.
//
// Don't call travel() if you.running >= 0.
command_type travel()
{
    int holdx, holdy;
    int *move_x = &holdx;
    int *move_y = &holdy;
    holdx = holdy = 0;

    command_type result = CMD_NO_CMD;

    if (Options.travel_key_stop && kbhit())
    {
        mprf("Key pressed, stopping %s.", you.running.runmode_name().c_str());
        stop_running();
        return CMD_NO_CMD;
    }

    if (you.confused())
    {
        mprf("You're confused, stopping %s.",
             you.running.runmode_name().c_str());
        stop_running();
        return CMD_NO_CMD;
    }

    // Excluded squares are only safe if marking stairs, i.e. another level.
    if (is_excluded(you.pos()) && !is_stair_exclusion(you.pos()))
    {
        mprf("You're in a travel-excluded area, stopping %s.",
             you.running.runmode_name().c_str());
        stop_running();
        return CMD_NO_CMD;
    }

    if (you.running.is_explore())
    {
        // Exploring.
        if (grd(you.pos()) == DNGN_ENTER_SHOP
            && you.running == RMODE_EXPLORE_GREEDY)
        {
            LevelStashes *lev = StashTrack.find_current_level();
            if (lev && lev->shop_needs_visit(you.pos()))
            {
                you.running = 0;
                return CMD_GO_UPSTAIRS;
            }
        }

        // Speed up explore by not doing a double-floodfill if we have
        // a valid target.
        if (!you.running.pos.x
            || you.running.pos == you.pos()
            || !_is_valid_explore_target(you.running.pos))
        {
            _explore_find_target_square();
        }
    }

    if (you.running == RMODE_INTERLEVEL && !you.running.pos.x)
    {
        // Interlevel travel. Since you.running.x is zero, we've either just
        // initiated travel, or we've just climbed or descended a staircase,
        // and we need to figure out where to travel to next.
        if (!_find_transtravel_square(level_target.p) || !you.running.pos.x)
            stop_running();
        else
            you.running.init_travel_speed();
    }

    if (you.running < 0)
    {
        // Remember what run-mode we were in so that we can resume
        // explore/interlevel travel correctly.
        int runmode = you.running;

        // Get the next step to make. If the travel command can't find a route,
        // we turn off travel (find_travel_pos does that automatically).
        find_travel_pos(you.pos(), move_x, move_y);

        if (you.running < 0 && (*move_x || *move_y))
        {
            const int delta_to_dir[9] =
            {
                7,  0, 1,
                6, -1, 2,
                5,  4, 3,
            };
            prev_travel_moves[prev_travel_index] =
                delta_to_dir[(*move_x + 1) + 3 * (*move_y + 1)];
            prev_travel_index = !prev_travel_index;
        }

        // Stop greedy explore when visiting an unverified stash.
        if ((*move_x || *move_y)
            && you.running == RMODE_EXPLORE_GREEDY
            && (ES_stack || ES_sacrificeable))
        {
            const coord_def newpos = you.pos() + coord_def(*move_x, *move_y);
            if (newpos == you.running.pos)
            {
                const LevelStashes *lev = StashTrack.find_current_level();
                const bool stack = lev && lev->needs_stop(newpos)
                                   && ES_stack;
                const bool sacrificeable = _sacrificeable_at(newpos)
                                           && ES_sacrificeable;
                if (stack || sacrificeable)
                {
                    if ((stack && _prompt_stop_explore(ES_GREEDY_VISITED_ITEM_STACK)
                         || sacrificeable && _prompt_stop_explore(ES_GREEDY_SACRIFICEABLE))
                        && (Options.auto_sacrifice != AS_YES || !sacrificeable
                            || stack))
                    {
                        explore_stopped_pos = newpos;
                        stop_running();
                    }
                    return direction_to_command(*move_x, *move_y);
                }
            }
        }

        if (!*move_x && !*move_y)
        {
            // If we've reached the square we were traveling towards, travel
            // should stop if this is simple travel. If we're exploring, we
            // should continue doing so (explore has its own end condition
            // upstairs); if we're traveling between levels and we've reached
            // our travel target, we're on a staircase and should take it.
            if (you.pos() == you.running.pos)
            {
                if (runmode == RMODE_EXPLORE || runmode == RMODE_EXPLORE_GREEDY)
                    you.running = runmode;       // Turn explore back on

                // For interlevel travel, we'll want to take the stairs unless
                // the interlevel travel specified a destination square and
                // we've reached that destination square.
                else if (runmode == RMODE_INTERLEVEL
                         && (level_target.p.pos != you.pos()
                             || level_target.p.id != level_id::current()))
                {
                    if (last_stair.depth != -1
                        && last_stair == level_id::current())
                    {
                        // We're trying to take the same stairs again. Baaad.

                        // We don't directly call stop_running() because
                        // you.running is probably 0, and stop_running() won't
                        // notify Lua hooks if you.running == 0.
                        you.running = runmode;
                        stop_running();
                        return CMD_NO_CMD;
                    }

                    // Check for entrance-only thang. If we've reached the
                    // entrance, kill travel.
                    if (level_target.entrance_only)
                    {
                        LevelInfo &li =
                            travel_cache.get_level_info(level_id::current());

                        const stair_info *si = li.get_stair(you.pos());
                        if (si && si->destination.id == level_target.p.id)
                        {
                            you.running = runmode;
                            stop_running();
                            return CMD_NO_CMD;
                        }
                    }

                    you.running = RMODE_INTERLEVEL;
                    result = _trans_negotiate_stairs();

                    // If, for some reason, we fail to use the stairs, we
                    // need to make sure we don't go into an infinite loop
                    // trying to take it again and again. We'll check
                    // last_stair before attempting to take stairs again.
                    last_stair = level_id::current();

                    // This is important, else we'll probably stop traveling
                    // the moment we clear the stairs. That's because the
                    // (running.x, running.y) destination will no longer be
                    // valid on the new level. Setting running.x to zero forces
                    // us to recalculate our travel target next turn (see
                    // previous if block).
                    you.running.pos.reset();
                }
                else
                {
                    you.running = runmode;
                    stop_running();
                }
            }
            else
            {
                you.running = runmode;
                stop_running();
            }
        }
        else if (you.running.is_explore() && Options.explore_delay > -1)
            delay(Options.explore_delay);
        else if (Options.travel_delay > 0)
            delay(Options.travel_delay);
    }

    if (!you.running)
        return CMD_NO_CMD;

    if (result != CMD_NO_CMD)
        return result;

    return direction_to_command(*move_x, *move_y);
}

command_type direction_to_command(int x, int y)
{
    if (x == -1 && y == -1) return CMD_MOVE_UP_LEFT;
    if (x == -1 && y ==  0) return CMD_MOVE_LEFT;
    if (x == -1 && y ==  1) return CMD_MOVE_DOWN_LEFT;
    if (x ==  0 && y == -1) return CMD_MOVE_UP;
    if (x ==  0 && y ==  0)
    {
        return you.running == RMODE_EXPLORE_GREEDY ? CMD_INSPECT_FLOOR
                                                   : CMD_NO_CMD;
    }
    if (x ==  0 && y ==  1) return CMD_MOVE_DOWN;
    if (x ==  1 && y == -1) return CMD_MOVE_UP_RIGHT;
    if (x ==  1 && y ==  0) return CMD_MOVE_RIGHT;
    if (x ==  1 && y ==  1) return CMD_MOVE_DOWN_RIGHT;

    ASSERT(0);
    return CMD_NO_CMD;
}

static void _fill_exclude_radius(const travel_exclude &exc)
{
    const int radius = exc.radius;
    const coord_def &c = exc.pos;
    for (int y = c.y - radius; y <= c.y + radius; ++y)
        for (int x = c.x - radius; x <= c.x + radius; ++x)
        {
            const coord_def p(x, y);
            if (!map_bounds(x, y) || !env.map_knowledge(p).known()
                || travel_point_distance[x][y])
            {
                continue;
            }

            if (is_exclude_root(p))
                travel_point_distance[x][y] = PD_EXCLUDED;
            else if (is_excluded(p))
                travel_point_distance[x][y] = PD_EXCLUDED_RADIUS;
        }
}

/////////////////////////////////////////////////////////////////////////////
// travel_pathfind

FixedVector<coord_def, GXM * GYM> travel_pathfind::circumference[2];

// already defined in header
// const int travel_pathfind::UNFOUND_DIST;
// const int travel_pathfind::INFINITE_DIST;

travel_pathfind::travel_pathfind()
    : runmode(RMODE_NOT_RUNNING), start(), dest(), next_travel_move(),
      floodout(false), double_flood(false), ignore_hostile(false),
      ignore_danger(false), annotate_map(false), ls(NULL),
      need_for_greed(false), autopickup(false), sacrifice(false),
      unexplored_place(), greedy_place(), unexplored_dist(0), greedy_dist(0),
      refdist(NULL), reseed_points(), features(NULL), unreachables(),
      point_distance(travel_point_distance), points(0), next_iter_points(0),
      traveled_distance(0), circ_index(0)
{
}

travel_pathfind::~travel_pathfind()
{
}

static bool _is_greed_inducing_square(const LevelStashes *ls,
                                      const coord_def &c, bool autopickup,
                                      bool sacrifice)
{
    return ls && ls->needs_visit(c, autopickup, sacrifice);
}

bool travel_pathfind::is_greed_inducing_square(const coord_def &c) const
{
    return _is_greed_inducing_square(ls, c, autopickup, sacrifice);
}

void travel_pathfind::set_src_dst(const coord_def &src, const coord_def &dst)
{
    // Yes, this is backwards - for travel, we always start from the destination
    // and search outwards for the starting position.
    start = dst;
    dest  = src;

    floodout = double_flood = false;
}

void travel_pathfind::set_floodseed(const coord_def &seed, bool dblflood)
{
    start = seed;
    dest.reset();

    floodout = true;
    double_flood = dblflood;
}

void travel_pathfind::set_annotate_map(bool annotate)
{
    annotate_map = annotate;
}

void travel_pathfind::set_distance_grid(travel_distance_grid_t grid)
{
    point_distance = grid;
}

void travel_pathfind::set_feature_vector(vector<coord_def> *feats)
{
    features = feats;

    if (features)
    {
        double_flood = true;
        annotate_map = true;
    }
}

const coord_def travel_pathfind::travel_move() const
{
    return next_travel_move;
}

const coord_def travel_pathfind::explore_target() const
{
    if (unexplored_dist != UNFOUND_DIST && greedy_dist != UNFOUND_DIST)
    {
        return unexplored_dist < greedy_dist ? unexplored_place
                                             : greedy_place;
    }
    else if (unexplored_dist != UNFOUND_DIST)
        return unexplored_place;
    else if (greedy_dist != UNFOUND_DIST)
        return greedy_place;

    return coord_def(0, 0);
}

const coord_def travel_pathfind::greedy_square() const
{
    return greedy_place;
}

const coord_def travel_pathfind::unexplored_square() const
{
    return unexplored_place;
}

// The travel algorithm is based on the NetHack travel code written by Warwick
// Allison - used with his permission.
coord_def travel_pathfind::pathfind(run_mode_type rmode, bool fallback_explore)
{
    unwind_bool saved_ipt(ignore_player_traversability);

    if (rmode == RMODE_INTERLEVEL)
        rmode = RMODE_TRAVEL;

    runmode = rmode;

    try_fallback = fallback_explore;

    if (runmode == RMODE_CONNECTIVITY)
        ignore_player_traversability = true;
    else
    {
        ASSERTM(crawl_state.need_save,
                "Pathfind with mode %d without a game?", runmode);

        if (runmode == RMODE_EXPLORE_GREEDY)
        {
            autopickup = can_autopickup();
            sacrifice = god_likes_items(you.religion, true);
            need_for_greed = (autopickup || sacrifice);
        }
    }

    if (!ls && (annotate_map || need_for_greed))
        ls = StashTrack.find_current_level();

    next_travel_move.reset();

    // For greedy explore, keep track of the closest unexplored territory and
    // the closest greedy square. Exploring to the nearest (unexplored / greedy)
    // square is easier, but it produces unintuitive explore behaviour where
    // grabbing items is not favoured over simple exploring.
    //
    // Greedy explore instead uses the explore_item_greed option to weight
    // greedy explore towards grabbing items over exploring. An
    // explore_item_greed set to 10, for instance, forces explore to prefer
    // items that are less than 10 squares farther away from the player than the
    // nearest unmapped square. Negative explore_item_greed values force greedy
    // explore to favour unexplored territory over picking up items. For the
    // most natural greedy explore behaviour, explore_item_greed should be set
    // to 10 or more.
    //
    unexplored_place = greedy_place = coord_def(0, 0);
    unexplored_dist  = greedy_dist  = UNFOUND_DIST;

    refdist = (Options.explore_item_greed > 0) ? &unexplored_dist
                                               : &greedy_dist;

    // Zap out previous distances array: this must happen before the
    // early exit checks below, since callers may want to inspect
    // point_distance after this call returns.
    //
    // point_distance will hold the distance of all points from the starting
    // point, i.e. the distance travelled to get there.
    memset(point_distance, 0, sizeof(travel_distance_grid_t));

    if (!in_bounds(start))
        return coord_def();

    // Abort run if we're trying to go someplace evil. Travel to traps is
    // specifically allowed here if the player insists on it.
    if (!floodout
        && !_is_travelsafe_square(start, false, ignore_danger, true)
        && !is_trap(start))          // player likes pain
    {
        return coord_def();
    }

    // Nothing to do?
    if (!floodout && start == dest)
        return start;

    unwind_bool slime_wall_check(g_Slime_Wall_Check,
                                 !actor_slime_wall_immune(&you));
    unwind_slime_wall_precomputer slime_neighbours(g_Slime_Wall_Check);

    // How many points are we currently considering? We start off with just one
    // point, and spread outwards like a flood-filler.
    points = 1;

    // How many points we'll consider next iteration.
    next_iter_points = 0;

    // How far we've traveled from (start_x, start_y), in moves (a diagonal move
    // is no longer than an orthogonal move).
    traveled_distance = 1;

    // Which index of the circumference array are we currently looking at?
    circ_index = 0;

    ignore_hostile = false;

    // For each round, circumference will store all points that were discovered
    // in the previous round of a given distance. Because we check all grids of
    // a certain distance from the starting point in one round, and move
    // outwards in concentric circles, this is an implementation of Dijkstra.
    // We use an array of size 2, so we can comfortably switch between the list
    // of points to be investigated this round and the slowly growing list of
    // points to be inspected next round. Once we've finished with the current
    // round, i.e. there are no more points to be looked at in the current
    // array, we switch circ_index over to !circ_index (between 0 and 1), so
    // the "next round" becomes the current one, and the old points can be
    // overwritten with newer ones. Since we count the number of points for
    // next round in next_iter_points, we don't even need to reset the array.
    circumference[circ_index][0] = start;

    bool found_target = false;

    for (; points > 0; ++traveled_distance, circ_index = !circ_index,
                        points = next_iter_points, next_iter_points = 0)
    {
        for (int i = 0; i < points; ++i)
        {
            // Look at all neighbours of the current grid.
            // path_examine_point() returns true if the target is reached
            // and marked as such.
            if (path_examine_point(circumference[circ_index][i]))
            {
                if (runmode == RMODE_TRAVEL)
                    return travel_move();
                else if (!Options.explore_wall_bias)
                    return explore_target();
                else
                    found_target = true;
            }
        }

        // Handle exploration with wall bias
        if (next_iter_points == 0 && found_target)
            return explore_target();

        // If there are no more points to look at, we're done, but we did
        // not find a path to our target.
        if (next_iter_points == 0)
        {
            // Don't reseed unless we've found no target for explore, OR
            // we're doing map annotation or feature tracking.
            if ((runmode == RMODE_EXPLORE || runmode == RMODE_EXPLORE_GREEDY
                 || runmode == RMODE_CONNECTIVITY)
                && double_flood
                && !ignore_hostile
                && !features
                && !annotate_map
                && (unexplored_dist != UNFOUND_DIST
                    || greedy_dist != UNFOUND_DIST))
            {
                break;
            }

            if (double_flood
                && !ignore_hostile
                && !reseed_points.empty())
            {
                // Reseed here
                for (unsigned i = 0, size = reseed_points.size(); i < size; ++i)
                    circumference[!circ_index][i] = reseed_points[i];

                next_iter_points  = reseed_points.size();
                ignore_hostile    = true;
            }
        }
    } // for (; points > 0 ...

    if (features && floodout)
    {
        exclude_set::const_iterator it;
        for (it = curr_excludes.begin(); it != curr_excludes.end(); ++it)
        {
            const travel_exclude &exc = it->second;
            // An exclude - wherever it is - is always a feature.
            if (find(features->begin(), features->end(), exc.pos)
                    == features->end())
            {
                features->push_back(exc.pos);
            }

            _fill_exclude_radius(exc);
        }
    }

    return runmode == RMODE_TRAVEL ? travel_move()
                                   : explore_target();
}

void travel_pathfind::get_features()
{
    ASSERT(features);

    if (!ls && (annotate_map || need_for_greed))
        ls = StashTrack.find_current_level();

    memset(point_distance, 0, sizeof(travel_distance_grid_t));

    coord_def dc;
    for (dc.x = X_BOUND_1; dc.x <= X_BOUND_2; ++dc.x)
        for (dc.y = Y_BOUND_1; dc.y <= Y_BOUND_2; ++dc.y)
        {
            const dungeon_feature_type feature = env.map_knowledge(dc).feat();

            if ((feature != DNGN_FLOOR
                    && !feat_is_water(feature)
                    && feature != DNGN_LAVA)
                || is_waypoint(dc)
                || is_stash(ls, dc)
                || is_trap(dc))
            {
                features->push_back(dc);
            }
        }

    exclude_set::const_iterator it;
    for (it = curr_excludes.begin(); it != curr_excludes.end(); ++it)
    {
        const travel_exclude &exc = it->second;

        // An exclude - wherever it is - is always a feature.
        if (find(features->begin(), features->end(), exc.pos) == features->end())
            features->push_back(exc.pos);

        _fill_exclude_radius(exc);
    }
}

const set<coord_def> travel_pathfind::get_unreachables() const
{
    return unreachables;
}

bool travel_pathfind::square_slows_movement(const coord_def &c)
{
    // c is a known (explored) location - we never put unknown points in the
    // circumference vector, so we don't need to examine the map array, just the
    // grid array.
    const dungeon_feature_type feature = env.map_knowledge(c).feat();

    // If this is a feature that'll take time to travel past, we simulate that
    // extra turn by taking this feature next turn, thereby artificially
    // increasing traveled_distance.
    //
    // Walking through shallow water and opening closed doors is considered to
    // have the cost of two normal moves for travel purposes.
    const int feat_cost = _feature_traverse_cost(feature);
    if (feat_cost > 1
        && point_distance[c.x][c.y] > traveled_distance - feat_cost)
    {
        circumference[!circ_index][next_iter_points++] = c;
        return true;
    }

    return false;
}

void travel_pathfind::check_square_greed(const coord_def &c)
{
    if (greedy_dist == UNFOUND_DIST
        && is_greed_inducing_square(c)
        && _is_travelsafe_square(c, ignore_hostile, ignore_danger))
    {
        int dist = traveled_distance;

        // Penalize distance for negative explore_item_greed
        if (Options.explore_item_greed < 0)
            dist -= Options.explore_item_greed;

        // The addition of explore_wall_bias makes items as interesting
        // as a room's perimeter (with one of four known adjacent walls).
        if (Options.explore_wall_bias)
            dist += Options.explore_wall_bias * 3;

        greedy_dist = dist;
        greedy_place = c;
    }
}

bool travel_pathfind::path_flood(const coord_def &c, const coord_def &dc)
{
    if (!in_bounds(dc) || unreachables.count(dc))
        return false;

    if (floodout
        && (runmode == RMODE_EXPLORE || runmode == RMODE_EXPLORE_GREEDY))
    {
        if (!env.map_knowledge(dc).seen())
        {
            if (ignore_hostile && !player_in_branch(BRANCH_SHOALS))
            {
                // This point is unexplored but unreachable. Let's find a
                // place from where we can see it.
                for (radius_iterator ri(dc, LOS_DEFAULT, true); ri; ++ri)
                {
                    const int dist = point_distance[ri->x][ri->y];
                    if (dist > 0
                        && (dist < unexplored_dist || unexplored_dist < 0))
                    {
                        unexplored_dist = dist;
                        unexplored_place = *ri;
                    }

                    // We can't do better than that.
                    if (unexplored_dist == 1)
                    {
                        _set_target_square(unexplored_place);
                        return true;
                    }
                }

                // We can't even see the place.
                // Let's store it and look for another.
                if (unexplored_dist < 0)
                    unreachables.insert(dc);
                else
                    _set_target_square(unexplored_place);
            }
            else
            {
                // Found explore target!
                int dist = traveled_distance;

                if (need_for_greed && Options.explore_item_greed > 0)
                {
                    // Penalize distance to favor item pickup
                    dist += Options.explore_item_greed;
                }

                if (Options.explore_wall_bias)
                {
                    dist += Options.explore_wall_bias * 4;

                    // Favor squares directly adjacent to walls
                    for (int dir = 0; dir < 8; dir += 2)
                    {
                        const coord_def ddc = dc + Compass[dir];

                        if (feat_is_wall(env.map_knowledge(ddc).feat()))
                            dist -= Options.explore_wall_bias;
                    }
                }

                // Replace old target if nearer (or less penalized)
                if (dist < unexplored_dist || unexplored_dist < 0)
                {
                    unexplored_dist = dist;
                    unexplored_place = c;
                }
            }
        }

        // Short-circuit if we can. If traveled_distance (the current
        // distance from the center of the floodfill) is greater
        // than the adjusted distance to the nearest greedy explore
        // target, we have a target. Note the adjusted distance is
        // the distance with explore_item_greed applied (if
        // explore_item_greed > 0, it is added to the distance to
        // unexplored terrain, if explore_item_greed < 0, it is
        // added to the distance to interesting items.
        //
        // We never short-circuit if ignore_hostile is true. This is
        // important so we don't need to do multiple floods to work out
        // whether explore is complete.
        if (need_for_greed
            && !ignore_hostile
            && *refdist != UNFOUND_DIST
            && traveled_distance > *refdist)
        {
            if (Options.explore_item_greed > 0)
                greedy_dist = INFINITE_DIST;
            else
                unexplored_dist = INFINITE_DIST;
        }

        // greedy_dist is only ever set in greedy-explore so this check
        // implies greedy-explore.
        if (unexplored_dist != UNFOUND_DIST && greedy_dist != UNFOUND_DIST)
            return true;
    }

    if (dc == dest)
    {
        // Hallelujah, we're home!
        if (_is_safe_move(c))
            next_travel_move = c;

        return true;
    }
    else if (!_is_travelsafe_square(dc, ignore_hostile, ignore_danger, try_fallback))
    {
        // This point is not okay to travel on, but if this is a
        // trap, we'll want to put it on the feature vector anyway.
        if (_is_reseedable(dc, ignore_danger)
            && !point_distance[dc.x][dc.y]
            && dc != start)
        {
            if (features && (is_trap(dc) || is_exclude_root(dc))
                && find(features->begin(), features->end(), dc)
                   == features->end())
            {
                features->push_back(dc);
            }

            if (double_flood)
                reseed_points.push_back(dc);

            // Appropriate mystic number. Nobody else should check
            // this number, since this square is unsafe for travel.
            point_distance[dc.x][dc.y] =
                is_exclude_root(dc)   ? PD_EXCLUDED :
                is_excluded(dc)       ? PD_EXCLUDED_RADIUS :
                !_is_safe_cloud(dc)   ? PD_CLOUD
                                      : PD_TRAP;
        }
        return false;
    }

    if (!point_distance[dc.x][dc.y])
    {
        // This point is going to be on the agenda for the next
        // iteration
        circumference[!circ_index][next_iter_points++] = dc;
        point_distance[dc.x][dc.y] = traveled_distance;

        // Negative distances here so that show_map can colour
        // the map differently for these squares.
        if (ignore_hostile)
        {
            point_distance[dc.x][dc.y] = -point_distance[dc.x][dc.y];
            if (is_exclude_root(dc))
                point_distance[dc.x][dc.y] = PD_EXCLUDED;
            else if (is_excluded(dc))
                point_distance[dc.x][dc.y] = PD_EXCLUDED_RADIUS;
        }

        if (features && !ignore_hostile)
        {
            dungeon_feature_type feature = env.map_knowledge(dc).feat();

            if (dc != start
                && (feature != DNGN_FLOOR
                       && !feat_is_water(feature)
                       && feature != DNGN_LAVA
                    || is_waypoint(dc)
                    || is_stash(ls, dc))
                && find(features->begin(), features->end(), dc)
                   == features->end())
            {
                features->push_back(dc);
            }
        }

        if (features && dc != start && is_exclude_root(dc)
            && find(features->begin(), features->end(), dc)
               == features->end())
        {
            features->push_back(dc);
        }
    }

    return false;
}

void travel_pathfind::good_square(const coord_def &c)
{
    if (!point_distance[c.x][c.y])
    {
        // This point is going to be on the agenda for the next iteration.
        circumference[!circ_index][next_iter_points++] = c;
        point_distance[c.x][c.y] = traveled_distance;
    }
}

bool travel_pathfind::point_traverse_delay(const coord_def &c)
{
    if (square_slows_movement(c))
        return true;

    // Greedy explore check should happen on (x,y), not (dx,dy) as for
    // regular explore.
    if (need_for_greed)
        check_square_greed(c);

    return false;
}

// Checks all neighbours of c, adds them to next round's list of points
// - happens in path_flood() - and returns true if one of them turns out
// to be the target; otherwise, false.
bool travel_pathfind::path_examine_point(const coord_def &c)
{
    // If we've run off the map, or are pathfinding from nowhere in particular
    if (!in_bounds(c))
        return false;

    if (point_traverse_delay(c))
        return false;

    bool found_target = false;

    // For each point, we look at all surrounding points. Take them orthogonals
    // first so that the travel path doesn't zigzag all over the map. Note the
    // (dir = 1) is intentional assignment.
    for (int dir = 0; dir < 8; (dir += 2) == 8 && (dir = 1))
        if (path_flood(c, c + Compass[dir]))
            found_target = true;

    return found_target;
}

/////////////////////////////////////////////////////////////////////////////

// Try to avoid to let travel (including autoexplore) move the player right
// next to a lurking (previously unseen) monster.
void find_travel_pos(const coord_def& youpos,
                     int *move_x, int *move_y,
                     vector<coord_def>* features)
{
    travel_pathfind tp;

    if (move_x && move_y)
        tp.set_src_dst(youpos, you.running.pos);
    else
        tp.set_floodseed(youpos);

    tp.set_feature_vector(features);

    run_mode_type rmode = (move_x && move_y) ? RMODE_TRAVEL
                                             : RMODE_NOT_RUNNING;

    const coord_def dest = tp.pathfind(rmode, true);
    coord_def new_dest = dest;

    if (grd(dest) == DNGN_RUNED_DOOR)
    {
        move_x = 0;
        move_y = 0;
        return;
    }

    // Check whether this step puts us adjacent to any grid we haven't ever
    // seen or any non-wall grid we cannot currently see.
    //
    // .tx      Moving onto t puts us adjacent to an unseen grid.
    // ?#@      --> Pick x instead.

    // Only applies to diagonal moves.
    if (rmode == RMODE_TRAVEL && *move_x != 0 && *move_y != 0)
    {
        coord_def unseen = coord_def();
        for (adjacent_iterator ai(dest); ai; ++ai)
            if (!you.see_cell(*ai)
                && (!env.map_knowledge(*ai).seen()
                    || !feat_is_wall(env.map_knowledge(*ai).feat())))
            {
                unseen = *ai;
                break;
            }

        if (unseen != coord_def())
        {
            // If so, try to use an orthogonally adjacent grid that is
            // safe to enter.
            if (youpos.x == unseen.x)
                new_dest.y = youpos.y;
            else if (youpos.y == unseen.y)
                new_dest.x = youpos.x;

            // If the new grid cannot be entered, reset to dest.
            // This means that autoexplore will still sometimes move you
            // next to a previously unseen monster but the same would
            // happen by manual movement, so I don't think we need to worry
            // about this. (jpeg)
            if (!_is_travelsafe_square(new_dest)
                || !feat_is_traversable_now(env.map_knowledge(new_dest).feat()))
            {
                new_dest = dest;
            }
#ifdef DEBUG_SAFE_EXPLORE
            mprf(MSGCH_DIAGNOSTICS, "youpos: (%d, %d), dest: (%d, %d), unseen: (%d, %d), "
                 "new_dest: (%d, %d)",
                 youpos.x, youpos.y, dest.x, dest.y, unseen.x, unseen.y,
                 new_dest.x, new_dest.y);
            more();
#endif
        }
    }

    if (new_dest.origin())
    {
        if (move_x && move_y)
            you.running = RMODE_NOT_RUNNING;
    }
    else if (move_x && move_y)
    {
        *move_x = new_dest.x - youpos.x;
        *move_y = new_dest.y - youpos.y;
    }
}

extern map<branch_type, set<level_id> > stair_level;

static void _find_parent_branch(branch_type br, int depth,
                                branch_type *pb, int *pd)
{
    *pb = parent_branch(br);   // Check depth before using *pb.
    map<branch_type, set<level_id> >::iterator i = stair_level.find(br);
    if (i == stair_level.end() || i->second.size() == 0)
        *pd = 0;
    else
        *pd = i->second.begin()->depth;
}

// Appends the passed in branch/depth to the given vector, then attempts to
// repeat the operation with the parent branch of the given branch.
//
// As an example of what it does, assume this dungeon structure
//   Stairs to lair on D:11
//   Stairs to snake pit on lair:5
//
// If level 3 of the snake pit is the level we want to track back from,
// we'd call _trackback(vec, BRANCH_SNAKE, 3), and the resulting vector will
// look like:
// { BRANCH_SNAKE, 3 }, { BRANCH_LAIR, 5 }, { BRANCH_DUNGEON, 11 }
// (Assuming, of course, that the vector started out empty.)
//
static void _trackback(vector<level_id> &vec, branch_type branch, int subdepth)
{
    if (subdepth < 1)
        return;
    ASSERT(subdepth <= 27);

    level_id lid(branch, subdepth);
    vec.push_back(lid);

    if (branch != root_branch)
    {
        branch_type pb;
        int pd;
        _find_parent_branch(branch, subdepth, &pb, &pd);
        if (pd)
            _trackback(vec, pb, pd);
    }
}

static void _track_intersect(vector<level_id> &cur, vector<level_id> &targ,
                             level_id *cx)
{
    cx->branch = BRANCH_DUNGEON;
    cx->depth  = -1;

    int us = int(cur.size()) - 1, them = int(targ.size()) - 1;

    for (; us >= 0 && them >= 0; us--, them--)
        if (cur[us].branch != targ[them].branch)
            break;

    us++, them++;

    if (us < (int) cur.size() && them < (int) targ.size() && us >= 0
        && them >= 0)
    {
        *cx = targ[them];
    }
}

// Returns the number of stairs the player would need to take to go from
// the 'first' level to the 'second' level. If there's no obvious route between
// 'first' and 'second', returns -1. If first == second, returns 0.
int level_distance(level_id first, level_id second)
{
    if (first == second)
        return 0;

    vector<level_id> fv, sv;

    // If in the same branch, easy.
    if (first.branch == second.branch)
        return abs(first.depth - second.depth);

    // Figure out the dungeon structure between the two levels.
    _trackback(fv, first.branch, first.depth);
    _trackback(sv, second.branch, second.depth);

    level_id intersect;
    _track_intersect(fv, sv, &intersect);

    if (intersect.depth == -1)          // No common ground?
        return -1;

    int distance = 0;
    // If the common branch is not the same as the current branch, we'll
    // have to walk up the branch tree until we get to the common branch.
    while (first.branch != intersect.branch)
    {
        distance += first.depth;

        _find_parent_branch(first.branch, first.depth,
                            &first.branch, &first.depth);
        if (!first.depth)
            return -1;
    }

    // Now first.branch == intersect.branch
    distance += abs(first.depth - intersect.depth);

    bool ignore_end = true;
    for (int i = sv.size() - 1; i >= 0; --i)
    {
        if (ignore_end)
        {
            if (sv[i].branch == intersect.branch)
                ignore_end = false;
            continue;
        }
        distance += sv[i].depth;
    }

    return distance;
}

static string _get_trans_travel_dest(const travel_target &target,
                                     bool skip_branch = false,
                                     bool skip_coord = false)
{
    const int branch_id = target.p.id.branch;
    const char *branch = branches[branch_id].abbrevname;

    if (!branch)
        return "";

    ostringstream dest;

    if (!skip_branch)
        dest << branch;
    if (brdepth[branch_id] != 1)
    {
        if (!skip_branch)
            dest << ":";
        dest << target.p.id.depth;
    }
    if (target.p.pos.x != -1 && !skip_coord)
        dest << " @ (x,y)";
    else if (target.entrance_only)
        dest << " (entrance)";

    return dest.str();
}

// Returns the level on the given branch that's closest to the player's
// current location.
static int _get_nearest_level_depth(uint8_t branch)
{
    int depth = 1;

    // Hell needs special treatment, because we can't walk up
    // Hell and its branches to the main dungeon.
    if (branch == BRANCH_DEPTHS
        && (player_in_branch(BRANCH_VESTIBULE)
            || player_in_branch(BRANCH_COCYTUS)
            || player_in_branch(BRANCH_TARTARUS)
            || player_in_branch(BRANCH_DIS)
            || player_in_branch(BRANCH_GEHENNA)))
    {
        // BUG: hell gates in the Lair
        return brentry[BRANCH_VESTIBULE].depth;
    }

    level_id id = level_id::current();
    do
    {
        _find_parent_branch(id.branch, id.depth,
                            &id.branch, &id.depth);
        if (id.depth && id.branch == branch)
        {
            depth = id.depth;
            break;
        }
    }
    while (id.depth);

    return depth;
}

// Returns true if the player character knows of the existence of the given
// branch (which would make the branch a valid target for interlevel travel).
bool is_known_branch_id(branch_type branch)
{
    // The main dungeon is always known
    if (branch == root_branch)
        return true;

    // If we're in the branch, it darn well is known.
    if (you.where_are_you == branch)
        return true;

    // The Vestibule is special: there are no stairs to it, just a
    // portal.
    if (branch == BRANCH_VESTIBULE)
        return overview_knows_portal(branch);

    // Guaranteed portal vault, don't show in interlevel travel.
    if (branch == BRANCH_ZIGGURAT)
        return false;

    // If the overview knows the stairs to this branch, we know the branch.
    return stair_level.find(static_cast<branch_type>(branch))
           != stair_level.end();
}

static bool _is_known_branch(const Branch &br)
{
    return is_known_branch_id(br.id);
}

// Returns a list of the branches that the player knows the location of the
// stairs to, in the same order as dgn-overview.cc lists them.
static vector<branch_type> _get_branches(bool (*selector)(const Branch &))
{
    vector<branch_type> result;

    for (branch_iterator it; it; ++it)
        if (selector(**it))
            result.push_back(it->id);

    return result;
}

static bool _is_valid_branch(const Branch &br)
{
    return br.shortname != NULL && brdepth[br.id] != -1;
}

static bool _is_disconnected_branch(const Branch &br)
{
    return !is_connected_branch(br.id);
}

static int _prompt_travel_branch(int prompt_flags, bool* to_entrance)
{
    int branch = BRANCH_DUNGEON;     // Default
    vector<branch_type> br =
        _get_branches(
            (prompt_flags & TPF_SHOW_ALL_BRANCHES) ? _is_valid_branch :
            (prompt_flags & TPF_SHOW_PORTALS_ONLY) ? _is_disconnected_branch
                                                   : _is_known_branch);

    // Don't kill the prompt even if the only branch we know is the main dungeon
    // This keeps things consistent for the player.
    if (br.size() < 1)
        return branch;

    const bool allow_waypoints = (prompt_flags & TPF_ALLOW_WAYPOINTS);
    const bool allow_updown    = (prompt_flags & TPF_ALLOW_UPDOWN);
    const bool remember_targ   = (prompt_flags & TPF_REMEMBER_TARGET);

    bool waypoint_list = false;
    const int waycount = allow_waypoints? travel_cache.get_waypoint_count() : 0;

    level_id curr = level_id::current();
    while (true)
    {
        clear_messages();

        if (waypoint_list)
            travel_cache.list_waypoints();
        else
        {
            int linec = 0;
            string line;
            for (int i = 0, count = br.size(); i < count; ++i, ++linec)
            {
                if (linec == 4)
                {
                    linec = 0;
                    mpr(line.c_str());
                    line = "";
                }
                line += make_stringf("(%c) %-14s ",
                                     branches[br[i]].travel_shortcut,
                                     branches[br[i]].shortname);
            }
            if (!line.empty())
                mpr(line.c_str());
        }

        string shortcuts = "(";
        {
            vector<string> segs;
            if (allow_waypoints)
            {
                if (waypoint_list)
                    segs.push_back("* - list branches");
                else if (waycount)
                    segs.push_back("* - list waypoints");
            }

            if (!trans_travel_dest.empty() && remember_targ)
            {
                segs.push_back(
                    make_stringf("Enter - %s", trans_travel_dest.c_str()));
            }

            segs.push_back("? - help");

            shortcuts += comma_separated_line(segs.begin(), segs.end(),
                                              ", ", ", ");
            shortcuts += ") ";
        }
        mprf(MSGCH_PROMPT, "%s? %s",
             *to_entrance ? "Entrance to where" : "Where to",
             shortcuts.c_str());

        int keyin = get_ch();
        switch (keyin)
        {
        CASE_ESCAPE
            return ID_CANCEL;
        case '?':
            show_interlevel_travel_branch_help();
            redraw_screen();
            break;
        case '\n': case '\r':
            return ID_REPEAT;
        case '<':
            return allow_updown ? ID_UP : ID_CANCEL;
        case '>':
            return allow_updown ? ID_DOWN : ID_CANCEL;
        case CONTROL('P'):
            {
                const branch_type parent = parent_branch(curr.branch);
                if (parent < NUM_BRANCHES)
                    return parent;
            }
            break;
        case '.':
            return curr.branch;
        case '*':
            if (waypoint_list || waycount)
                waypoint_list = !waypoint_list;
            break;
        case '^':
            if (*to_entrance)
                return ID_CANCEL;
            else
            {
                *to_entrance = true;
                return _prompt_travel_branch(prompt_flags, to_entrance);
            }
        default:
            // Is this a branch hotkey?
            for (int i = 0, count = br.size(); i < count; ++i)
            {
                if (toupper(keyin) == branches[br[i]].travel_shortcut)
                {
#ifdef WIZARD
                    const Branch &target = branches[br[i]];
                    string msg;

                    if (!brentry[br[i]].is_valid()
                        && is_random_subbranch((branch_type)i)
                        && you.wizard) // don't leak mimics
                    {
                        msg += "Branch not generated this game. ";
                    }

                    if (target.entry_stairs == NUM_FEATURES
                        && br[i] != BRANCH_DUNGEON)
                    {
                        msg += "Branch has no entry stairs. ";
                    }

                    if (!msg.empty())
                    {
                        msg += "Go there anyway?";
                        if (!yesno(msg.c_str(), true, 'n'))
                            return ID_CANCEL;
                    }
#endif
                    return br[i];
                }
            }

            // Possibly a waypoint number?
            if (allow_waypoints && keyin >= '0' && keyin <= '9')
                return -1 - (keyin - '0');

            return ID_CANCEL;
        }
    }
}

level_id find_up_level(level_id curr, bool up_branch)
{
    --curr.depth;

    if (up_branch)
        curr.depth = 0;

    if (curr.depth < 1)
    {
        if (curr.branch != BRANCH_DUNGEON && curr.branch != root_branch)
        {
            level_id parent;
            _find_parent_branch(curr.branch, curr.depth,
                                &parent.branch, &parent.depth);
            if (parent.depth > 0)
                return parent;
            else if (curr.branch == BRANCH_VESTIBULE)
                return brentry[BRANCH_VESTIBULE];
        }
        return level_id();
    }

    return curr;
}

static level_id _find_up_level()
{
    return find_up_level(level_id::current());
}

level_id find_down_level(level_id curr)
{
    if (curr.depth < brdepth[curr.branch])
        ++curr.depth;
    return curr;
}

level_id find_deepest_explored(level_id curr)
{
    ASSERT(curr.branch != NUM_BRANCHES);

    for (int i = brdepth[curr.branch]; i > 0; --i)
    {
        const level_id lid(curr.branch, i);
        LevelInfo *linf = travel_cache.find_level_info(lid);
        if (linf && !linf->empty())
            return lid;
    }

    // If the player's currently in the same place, report their current
    // level_id if the travel cache hasn't been updated.
    const level_id player_level = level_id::current();
    if (player_level == curr.branch)
        return player_level;

    return curr;
}

bool branch_entered(branch_type branch)
{
    const level_id lid(branch, 1);
    LevelInfo *linf = travel_cache.find_level_info(lid);
    return linf && !linf->empty();
}

static level_id _find_down_level()
{
    return find_down_level(level_id::current());
}

static int _travel_depth_keyfilter(int &c)
{
    switch (c)
    {
    case '<': case '>': case '?': case '$': case '^':
        return -1;
    case '-':
    case CONTROL('P'): case 'p':
        c = '-';  // Make uniform.
        return -1;
    default:
        return 1;
    }
}

static travel_target _parse_travel_target(string s, travel_target &targ)
{
    trim_string(s);

    const string ekey("(entrance)");
    string::size_type epos = s.find(ekey);

    if (!s.empty())
        targ.entrance_only = (epos != string::npos);

    if (targ.entrance_only && !s.empty())
        s = trimmed_string(s.substr(0, epos) + s.substr(epos + ekey.length()));

    if (!s.empty())
        targ.p.id.depth = atoi(s.c_str());

    if (!targ.p.id.depth && !s.empty() && s[0] == '0')
    {
        targ.p.id.depth = 1;
        targ.entrance_only = true;
    }

    return targ;
}

static void _travel_depth_munge(int munge_method, const string &s,
                                travel_target &targ)
{
    _parse_travel_target(s, targ);
    level_id lid(targ.p.id);
    switch (munge_method)
    {
    case '?':
        show_interlevel_travel_depth_help();
        redraw_screen();
        return;
    case '<':
        lid = find_up_level(lid);
        break;
    case '>':
        lid = find_down_level(lid);
        break;
    case '-':
        lid = find_up_level(lid, true);
        break;
    case '$':
        lid = find_deepest_explored(lid);
        break;
    case '^':
        targ.entrance_only = !targ.entrance_only;
        break;
    }
    targ.p.id = lid;
    if (targ.p.id.depth < 1)
        targ.p.id.depth = 1;
}

static travel_target _prompt_travel_depth(const level_id &id,
                                          bool already_entrance)
{
    travel_target target = travel_target(level_pos(id), already_entrance);

    // Handle one-level branches by not prompting.
    if (single_level_branch(target.p.id.branch))
        return travel_target(level_id(target.p.id.branch, 1), already_entrance);

    target.p.id.depth = _get_nearest_level_depth(target.p.id.branch);
    while (true)
    {
        clear_messages();
        mprf(MSGCH_PROMPT, "What level of %s? "
             "(default %s, ? - help) ",
             branches[target.p.id.branch].longname,
             _get_trans_travel_dest(target, true).c_str());

        char buf[100];
        const int response =
            cancellable_get_line(buf, sizeof buf, NULL, _travel_depth_keyfilter, "", "travel_depth");

        if (!response)
            return _parse_travel_target(buf, target);

        if (key_is_escape(response))
            return travel_target(level_id(BRANCH_DUNGEON, 0));

        _travel_depth_munge(response, buf, target);
    }
}

bool travel_kill_monster(monster_type mons)
{
    if (mons != MONS_TOADSTOOL)
        return false;

    if (!wielded_weapon_check(you.weapon(), true))
        return false;

    // Don't auto-kill things with berserkitis or *rage.
    if (player_mutation_level(MUT_BERSERK) || you.angry())
    {
        return you.stasis(false)
               || you.clarity(false)
               || you.is_undead == US_UNDEAD
               || you.is_undead == US_HUNGRY_DEAD;
    }

    return true;
}

travel_target prompt_translevel_target(int prompt_flags, string& dest_name)
{
    travel_target target;
    bool to_entrance = false;
    int branch = _prompt_travel_branch(prompt_flags, &to_entrance);
    const bool remember_targ = (prompt_flags & TPF_REMEMBER_TARGET);

    if (branch == ID_CANCEL)
        return target;

    // If user chose to repeat last travel, return that.
    if (branch == ID_REPEAT)
        return level_target;

    if (branch == ID_UP)
    {
        target.p = _find_up_level();
        if (target.p.id.depth > 0 && remember_targ)
            dest_name = _get_trans_travel_dest(target);
        return target;
    }

    if (branch == ID_DOWN)
    {
        target.p = _find_down_level();
        if (target.p.id.depth > 0 && remember_targ)
            dest_name = _get_trans_travel_dest(target);
        return target;
    }

    if (branch < 0)
    {
        target = travel_cache.get_waypoint(-branch - 1);
        if (target.p.id.depth > 0 && remember_targ)
            dest_name = _get_trans_travel_dest(target);
        return target;
    }

    target.p.id.branch = static_cast<branch_type>(branch);

    // User's chosen a branch, so now we ask for a level.
    target = _prompt_travel_depth(target.p.id, to_entrance);

    if (target.p.id.depth < 1
        || target.p.id.depth > brdepth[target.p.id.branch])
    {
        target.p.id.depth = -1;
    }

    if (target.p.id.depth > -1 && remember_targ)
        dest_name = _get_trans_travel_dest(target);

    return target;
}

static void _start_translevel_travel()
{
    // Update information for this level.
    travel_cache.get_level_info(level_id::current()).update();

    if (level_id::current() == level_target.p.id
        && (level_target.p.pos.x == -1 || level_target.p.pos == you.pos()))
    {
        mpr("You're already here!");
        return ;
    }

    if (level_target.p.id.depth > 0)
    {
        you.running = RMODE_INTERLEVEL;
        you.running.pos.reset();
        last_stair.depth = -1;

        _Route_Warning.new_dest(level_target);

        _Src_Level = level_id::current();
        _Src_Dest_Level_Delta = level_distance(_Src_Level,
                                               level_target.p.id);

        _start_running();
    }
}

void start_translevel_travel(const travel_target &pos)
{
    if (!can_travel_to(pos.p.id))
    {
        if (!can_travel_interlevel())
            mpr("Sorry, you can't auto-travel out of here.");
        else
            mpr("Sorry, I don't know how to get there.");
        return;
    }

    if (pos.p.is_valid() && !in_bounds(pos.p.pos))
    {
        mpr("Sorry, I don't know how to get there.");
        return;
    }

    // Remember where we're going so we can easily go back if interrupted.
    you.travel_x = pos.p.pos.x;
    you.travel_y = pos.p.pos.y;
    you.travel_z = pos.p.id;

    if (!can_travel_interlevel())
    {
        start_travel(pos.p.pos);
        return;
    }

    level_target = pos;

    // Check that it's level + position, not just level.
    if (pos.p.is_valid())
    {
        if (pos.p.id != level_id::current())
        {
            if (!_loadlev_populate_stair_distances(pos.p))
            {
                mpr("Level memory is imperfect, aborting.");
                return ;
            }
        }
        else
            _populate_stair_distances(pos.p);
    }

    trans_travel_dest = _get_trans_travel_dest(level_target);

    if (!i_feel_safe(true, true))
        return;
    if (you.confused())
    {
        canned_msg(MSG_TOO_CONFUSED);
        return;
    }

    _start_translevel_travel();
}

static void _start_translevel_travel_prompt()
{
    // Update information for this level. We need it even for the prompts, so
    // we can't wait to confirm that the user chose to initiate travel.
    travel_cache.get_level_info(level_id::current()).update();

    travel_target target = prompt_translevel_target(TPF_DEFAULT_OPTIONS,
            trans_travel_dest);
    if (target.p.id.depth <= 0)
    {
        canned_msg(MSG_OK);
        return;
    }

    start_translevel_travel(target);
}

static command_type _trans_negotiate_stairs()
{
    return feat_stair_direction(grd(you.pos()));
}

static int _target_distance_from(const coord_def &pos)
{
    for (int i = 0, count = curr_stairs.size(); i < count; ++i)
        if (curr_stairs[i].position == pos)
            return curr_stairs[i].distance;

    return -1;
}

/*
 * Sets best_stair to the coordinates of the best stair on the player's current
 * level to take to get to the 'target' level. Should be called with 'distance'
 * set to 0, 'stair' set to (you.x_pos, you.y_pos) and 'best_distance' set to
 * -1. 'cur' should be the player's current level.
 *
 * If best_stair remains unchanged when this function returns, there is no
 * travel-safe path between the player's current level and the target level OR
 * the player's current level *is* the target level.
 *
 * This function relies on the travel_point_distance array being correctly
 * populated with a floodout call to find_travel_pos starting from the player's
 * location.
 */
static int _find_transtravel_stair(const level_id &cur,
                                    const level_pos &target,
                                    int distance,
                                    // This is actually the current position
                                    // on cur, not necessarily a stair.
                                    const coord_def &stair,
                                    level_id &closest_level,
                                    int &best_level_distance,
                                    coord_def &best_stair,
                                    const bool target_has_excludes)
{
    int local_distance = -1;
    level_id player_level = level_id::current();

    LevelInfo &li = travel_cache.get_level_info(cur);

    // Have we reached the target level?
    if (cur == target.id)
    {
        // Are we in an exclude? If so, bail out. Unless it is just a stair exclusion.
        if (is_excluded(stair, li.get_excludes()) && !is_stair_exclusion(stair))
            return -1;

        // If there's no target position on the target level, or we're on the
        // target, we're home.
        if (target.pos.x == -1 || target.pos == stair)
            return distance;

        // If there *is* a target position, we need to work out our distance
        // from it.
        int deltadist = _target_distance_from(stair);

        if (deltadist == -1 && cur == player_level)
        {
            // Okay, we don't seem to have a distance available to us, which
            // means we're either (a) not standing on stairs or (b) whoever
            // initiated interlevel travel didn't call
            // _populate_stair_distances.  Assuming we're not on stairs, that
            // situation can arise only if interlevel travel has been triggered
            // for a location on the same level. If that's the case, we can get
            // the distance off the travel_point_distance matrix.
            deltadist = travel_point_distance[target.pos.x][target.pos.y];
            if (!deltadist && stair != target.pos)
                deltadist = -1;
        }

        if (deltadist != -1)
        {
            local_distance = distance + deltadist;

            // See if this is a degenerate case of interlevel travel:
            // A degenerate case of interlevel travel decays to normal travel;
            // we identify this by checking if:
            // a. The current level is the target level.
            // b. The target square is reachable from the 'current' square.
            // c. The current square is where the player is.
            //
            // Note that even if this *is* degenerate, interlevel travel may
            // still be able to find a shorter route, since it can consider
            // routes that leave and reenter the current level.
            if (player_level == target.id && stair == you.pos())
                best_stair = target.pos;

            // The local_distance is already set, but there may actually be
            // stairs we can take that'll get us to the target faster than the
            // direct route, so we also try the stairs.
        }
    }

    vector<stair_info> &stairs = li.get_stairs();

    // this_stair being NULL is perfectly acceptable, since we start with
    // coords as the player coords, and the player need not be standing on
    // stairs.
    stair_info *this_stair = li.get_stair(stair);

    if (!this_stair && cur != player_level)
    {
        // Whoops, there's no stair in the travel cache for the current
        // position, and we're not on the player's current level (i.e., there
        // certainly *should* be a stair here). Since we can't proceed in any
        // reasonable way, bail out.
        return local_distance;
    }

    for (int i = 0, count = stairs.size(); i < count; ++i)
    {
        stair_info &si = stairs[i];

        // Skip placeholders and excluded stairs.
        if (!si.can_travel() || is_excluded(si.position, li.get_excludes()))
            continue;

        int deltadist = li.distance_between(this_stair, &si);

        if (!this_stair)
        {
            deltadist = travel_point_distance[si.position.x][si.position.y];
            if (!deltadist && you.pos() != si.position)
                deltadist = -1;
        }

        // deltadist == 0 is legal (if this_stair is NULL), since the player
        // may be standing on the stairs. If two stairs are disconnected,
        // deltadist has to be negative.
        if (deltadist < 0)
            continue;

        int dist2stair = distance + deltadist;
        if (si.distance == -1 || si.distance > dist2stair)
        {
            si.distance = dist2stair;

            // Account for the cost of taking the stairs
            dist2stair += Options.travel_stair_cost;

            // Already too expensive? Short-circuit.
            if (local_distance != -1 && dist2stair >= local_distance)
                continue;

            const level_pos &dest = si.destination;

            // Never use escape hatches as the last leg of the trip, since
            // that will leave the player unable to retrace their path.
            // This does not apply if we have a destination with a specific
            // position on the target level travel wants to get to.
            if (feat_is_escape_hatch(si.grid)
                && target.pos.x == -1
                && dest.id == target.id)
            {
                continue;
            }

            // We can only short-circuit the stair-following process if we
            // have no exact target location. If there *is* an exact target
            // location, we can't follow stairs for which we have incomplete
            // information.
            //
            // We can also not use incomplete stair information if there are
            // excludes on the target level.
            if (target.pos.x == -1
                && dest.id == target.id
                && !target_has_excludes)
            {
                if (local_distance == -1 || local_distance > dist2stair)
                {
                    local_distance = dist2stair;
                    if (cur == player_level && you.pos() == stair)
                        best_stair = si.position;
                }
                continue;
            }

            if (dest.id.depth > -1) // We have a valid level descriptor.
            {
                int dist = level_distance(dest.id, target.id);
                if (dist != -1 && (dist < best_level_distance
                                   || best_level_distance == -1))
                {
                    best_level_distance = dist;
                    closest_level       = dest.id;
                }
            }

            // If we don't know where these stairs go, we can't take them.
            if (!dest.is_valid())
                continue;

            // We need to get the stairs at the new location and set the
            // distance on them as well.
            LevelInfo &lo = travel_cache.get_level_info(dest.id);
            if (stair_info *so = lo.get_stair(dest.pos))
            {
                if (so->distance == -1 || so->distance > dist2stair)
                    so->distance = dist2stair;
                else
                    continue;   // We've already been here.
            }

            // Okay, take these stairs and keep going.
            const int newdist =
                _find_transtravel_stair(dest.id, target,
                                        dist2stair, dest.pos, closest_level,
                                        best_level_distance, best_stair,
                                        target_has_excludes);
            if (newdist != -1
                && (local_distance == -1 || local_distance > newdist))
            {
                local_distance = newdist;
                if (cur == player_level && you.pos() == stair)
                    best_stair = si.position;
            }
        }
    }
    return local_distance;
}

static bool _loadlev_populate_stair_distances(const level_pos &target)
{
    level_excursion excursion;
    excursion.go_to(target.id);
    _populate_stair_distances(target);
    return true;
}

static void _populate_stair_distances(const level_pos &target)
{
    // Populate travel_point_distance.
    find_travel_pos(target.pos, NULL, NULL, NULL);

    LevelInfo &li = travel_cache.get_level_info(target.id);
    const vector<stair_info> &stairs = li.get_stairs();

    curr_stairs.clear();
    for (int i = 0, count = stairs.size(); i < count; ++i)
    {
        stair_info si = stairs[i];
        si.distance = travel_point_distance[si.position.x][si.position.y];
        if (!si.distance && target.pos != si.position
            || si.distance < -1)
        {
            si.distance = -1;
        }

        curr_stairs.push_back(si);
    }
}

static bool _find_transtravel_square(const level_pos &target, bool verbose)
{
    level_id current = level_id::current();

    coord_def best_stair(-1, -1);
    coord_def cur_stair(you.pos());

    level_id closest_level;
    int best_level_distance = -1;
    travel_cache.clear_distances();

    find_travel_pos(you.pos(), NULL, NULL, NULL);

    const LevelInfo &target_level =
        travel_cache.get_level_info(target.id);

    _find_transtravel_stair(current, target,
                            0, cur_stair, closest_level,
                            best_level_distance, best_stair,
                            !target_level.get_excludes().empty());

    if (best_stair.x != -1 && best_stair.y != -1)
    {
        // Is this stair going offlevel?
        if ((level_target.p.id != current
             || level_target.p.pos != best_stair)
            && _Src_Dest_Level_Delta != -1)
        {
            // If so, is the original level closer to the target level than
            // the destination of the stair?
            LevelInfo &li = travel_cache.get_level_info(current);
            const stair_info *dest_stair = li.get_stair(best_stair);

            if (dest_stair && dest_stair->destination.id.is_valid())
            {
                if ((_Src_Dest_Level_Delta <
                     level_distance(dest_stair->destination.id,
                                    level_target.p.id)
                        || _Src_Dest_Level_Delta <
                           level_distance(dest_stair->destination.id,
                                          _Src_Level))
                    && !_Route_Warning.warn_continue_travel(
                        level_target,
                        dest_stair->destination.id))
                {
                    canned_msg(MSG_OK);
                    return false;
                }
            }
        }

        you.running.pos = best_stair;
        return true;
    }
    else if (best_level_distance != -1 && closest_level != current
             && target.pos.x == -1)
    {
        int current_dist = level_distance(current, target.id);
        level_pos newlev;
        newlev.id = closest_level;
        if (newlev.id != target.id
            && (current_dist == -1 || best_level_distance < current_dist))
        {
            return _find_transtravel_square(newlev, verbose);
        }
    }

    if (verbose)
    {
        if (target.id != current
            || target.pos.x != -1 && target.pos != you.pos())
        {
            mpr("Sorry, I don't know how to get there.");
        }
    }

    return false;
}

void start_travel(const coord_def& p)
{
    // Redundant target?
    if (p == you.pos())
        return;

    // Can we even travel to this square?
    if (!in_bounds(p))
        return;

    if (!_is_travelsafe_square(p, true))
        return;

    you.travel_x = p.x;
    you.travel_y = p.y;
    you.travel_z = level_id::current();

    you.running.pos = p;
    level_target  = level_pos(level_id::current(), p);

    if (!can_travel_interlevel())
    {
        if (!i_feel_safe(true, true))
            return;
        if (you.confused())
        {
            canned_msg(MSG_TOO_CONFUSED);
            return;
        }

        // Start running
        you.running = RMODE_TRAVEL;
        _start_running();
    }
    else
        start_translevel_travel(level_target);
}

void start_explore(bool grab_items)
{
    if (Hints.hints_explored)
        Hints.hints_explored = false;

    if (!i_feel_safe(true, true))
        return;

    if (you_worship(GOD_FEDHAS))
    {
        bool corpse_on_pos = false;
        for (radius_iterator i(you.pos(), LOS_NO_TRANS); i && !corpse_on_pos; ++i)
        {
            for (stack_iterator j(*i); j; ++j)
            {
                if (j->base_type == OBJ_CORPSES && j->sub_type == CORPSE_BODY)
                {
                    corpse_on_pos = true;
                    break;
                }
            }
        }

         if ((corpse_on_pos
              && (Options.auto_sacrifice == AS_YES
                  || Options.auto_sacrifice == AS_BEFORE_EXPLORE)))
         {
             pray(false);
         }

    }

    you.running = (grab_items ? RMODE_EXPLORE_GREEDY : RMODE_EXPLORE);

    if (you.running == RMODE_EXPLORE_GREEDY && god_likes_items(you.religion, true))
    {
        const LevelStashes *lev = StashTrack.find_current_level();
        if (lev && lev->sacrificeable(you.pos()))
        {
            if (Options.auto_sacrifice == AS_PROMPT)
            {
                mpr_nojoin(MSGCH_FLOOR_ITEMS, "Things which can be sacrificed:");
                for (stack_iterator si(you.visible_igrd(you.pos())); si; ++si)
                    if (si->is_greedy_sacrificeable())
                        mprf_nocap("%s", get_menu_colour_prefix_tags(*si, DESC_A).c_str());

            }

            if ((Options.auto_sacrifice == AS_YES
                 || Options.auto_sacrifice == AS_BEFORE_EXPLORE
                 || Options.auto_sacrifice == AS_PROMPT
                    && yesno("Do you want to sacrifice the items here? ", true, 'n')))
            {
                pray(false);
            }
            else if (Options.auto_sacrifice == AS_PROMPT_IGNORE)
            {
                // Make Escape => 'n' and stop run.
                bool repeat_prompt = false;
                do
                {
                    mprf(MSGCH_PROMPT,
                         "There are sacrificable items here, ignore them? "
                         "[(Y)es/(p)ray/(n)o]");
                    repeat_prompt = false;

                    switch (getchm(KMC_CONFIRM))
                    {
                    case 'Y':
                        mark_items_non_visit_at(you.pos());
                        break;

                    case 'p':
                        pray();
                        //fallthrough
                    case 'n':
                    case 'N':
                    case ESCAPE:
                    case CONTROL('G'):
                        you.running = 0; // Abort explore.
                        return;

                    default:
                        repeat_prompt = true;
                        break;
                    }
                }
                while (repeat_prompt);
            }
            else
                mark_items_non_visit_at(you.pos());
        }
    }

    for (rectangle_iterator ri(0); ri; ++ri)
        if (env.map_knowledge(*ri).seen())
            env.map_seen.set(*ri);

    you.running.pos.reset();
    _start_running();
}

void do_explore_cmd()
{
    if (you.hunger_state == HS_STARVING && !you_min_hunger())
        mpr("You need to eat something NOW!");
    else if (you.berserk())
        mpr("Calm down first, please.");
    else if (player_in_branch(BRANCH_LABYRINTH))
        mpr("No exploration algorithm can help you here.");
    else                        // Start exploring
        start_explore(Options.explore_greedy);
}

//////////////////////////////////////////////////////////////////////////
// Interlevel travel classes

level_id level_id::current()
{
    const level_id id(you.where_are_you, you.depth);
    return id;
}

int level_id::absdepth() const
{
    return absdungeon_depth(branch, depth);
}

level_id level_id::get_next_level_id(const coord_def &pos)
{
    int gridc = grd(pos);
    level_id id = current();

    if (gridc == branches[id.branch].exit_stairs)
        return stair_destination(pos);
#if TAG_MAJOR_VERSION == 34
    if (gridc == DNGN_ENTER_PORTAL_VAULT)
        return stair_destination(pos);
#endif

    for (branch_iterator it; it; ++it)
    {
        if (gridc == it->entry_stairs)
        {
            id.branch = it->id;
            id.depth = 1;
            break;
        }
    }

    switch (gridc)
    {
    case DNGN_STONE_STAIRS_DOWN_I:   case DNGN_STONE_STAIRS_DOWN_II:
    case DNGN_STONE_STAIRS_DOWN_III: case DNGN_ESCAPE_HATCH_DOWN:
        id.depth++;
        break;
    case DNGN_STONE_STAIRS_UP_I:     case DNGN_STONE_STAIRS_UP_II:
    case DNGN_STONE_STAIRS_UP_III:   case DNGN_ESCAPE_HATCH_UP:
        id.depth--;
        break;
    default:
        break;
    }
    return id;
}

unsigned short level_id::packed_place() const
{
    return get_packed_place(branch, depth);
}

string level_id::describe(bool long_name, bool with_number) const
{
    return place_name(this->packed_place(), long_name, with_number);
}

level_id level_id::parse_level_id(const string &s) throw (string)
{
    string::size_type cpos = s.find(':');
    string brname  = (cpos != string::npos? s.substr(0, cpos)  : s);
    string brlev   = (cpos != string::npos? s.substr(cpos + 1) : "");

    branch_type br = str_to_branch(brname);

    if (br == NUM_BRANCHES)
    {
        throw make_stringf("Invalid branch \"%s\" in spec \"%s\"",
                           brname.c_str(), s.c_str());
    }

    // Branch:$ uses static data -- it never comes from the current game.
    const int dep = (brlev.empty() ? 1 :
                     brlev == "$"  ? branches[br].numlevels
                                   : atoi(brlev.c_str()));

    // The branch might have been longer when the save has been created.
    if (dep < 0 || dep > brdepth[br] && dep > branches[br].numlevels)
    {
        throw make_stringf("Invalid depth for %s in spec \"%s\"",
                           brname.c_str(), s.c_str());
    }

    return level_id(br, dep);
}

level_id level_id::from_packed_place(unsigned short place)
{
    level_id id;

    id.branch     = (branch_type) place_branch(place);
    id.depth      = place_depth(place);

    return id;
}

void level_id::save(writer& outf) const
{
    marshall_level_id(outf, *this);
}

void level_id::load(reader& inf)
{
    (*this) = unmarshall_level_id(inf);
}

level_pos level_pos::current()
{
    return level_pos(level_id::current(), you.pos());
}

// NOTE: see also marshall_level_pos
void level_pos::save(writer& outf) const
{
    id.save(outf);
    marshallCoord(outf, pos);
}

void level_pos::load(reader& inf)
{
    id.load(inf);
    pos = unmarshallCoord(inf);
}

void stair_info::save(writer& outf) const
{
    marshallCoord(outf, position);
    marshallShort(outf, grid);
    destination.save(outf);
    marshallByte(outf, guessed_pos? 1 : 0);
    marshallByte(outf, type);
}

void stair_info::load(reader& inf)
{
    position = unmarshallCoord(inf);
    grid = static_cast<dungeon_feature_type>(unmarshallShort(inf));
    destination.load(inf);
    guessed_pos = unmarshallByte(inf) != 0;
    type = static_cast<stair_type>(unmarshallByte(inf));
}

string stair_info::describe() const
{
    if (destination.is_valid())
    {
        const level_pos &lp(destination);
        return make_stringf(" (-> %s@(%d,%d)%s%s)", lp.id.describe().c_str(),
                             lp.pos.x, lp.pos.y,
                             guessed_pos? " guess" : "",
                             type == PLACEHOLDER ? " placeholder" : "");
    }
    else if (destination.id.is_valid())
        return make_stringf(" (->%s (?))", destination.id.describe().c_str());

    return " (?)";
}

void LevelInfo::set_level_excludes()
{
    curr_excludes = excludes;
    init_exclusion_los();
}

bool LevelInfo::empty() const
{
    return stairs.empty() && excludes.empty();
}

void LevelInfo::update_excludes()
{
    excludes = curr_excludes;
}

void LevelInfo::update()
{
    // First, set excludes, so that stair distances will be correctly populated.
    excludes = curr_excludes;

    // First, we get all known stairs.
    vector<coord_def> stair_positions;
    get_stairs(stair_positions);

    // Make sure our stair list is correct.
    correct_stair_list(stair_positions);

    sync_all_branch_stairs();

    // If the player isn't immune to slimy walls, precalculate
    // neighbours of slimy walls now.
    unwind_slime_wall_precomputer slime_wall_neighbours(
        !actor_slime_wall_immune(&you));
    precompute_travel_safety_grid travel_safety_calc;
    update_stair_distances();

    update_da_counters(this);
}

void LevelInfo::set_distance_between_stairs(int a, int b, int dist)
{
    // Note dist == 0 is illegal because we can't have two stairs on
    // the same square.
    if (dist <= 0 && a != b)
        dist = -1;
    stair_distances[a * stairs.size() + b] = dist;
    stair_distances[b * stairs.size() + a] = dist;
}

void LevelInfo::update_stair_distances()
{
    const int nstairs = stairs.size();
    // Now we update distances for all the stairs, relative to all other
    // stairs.
    for (int s = 0; s < nstairs - 1; ++s)
    {
        set_distance_between_stairs(s, s, 0);

        // For each stair, we need to ask travel to populate the distance
        // array.
        find_travel_pos(stairs[s].position, NULL, NULL, NULL);

        // Assume movement distance between stairs is commutative,
        // i.e. going from a->b is the same distance as b->a.
        for (int other = s + 1; other < nstairs; ++other)
        {
            const coord_def op = stairs[other].position;
            const int dist = travel_point_distance[op.x][op.y];
            set_distance_between_stairs(s, other, dist);
        }
    }
    if (nstairs)
        set_distance_between_stairs(nstairs - 1, nstairs - 1, 0);
}

void LevelInfo::update_stair(const coord_def& stairpos, const level_pos &p,
                             bool guess)
{
    stair_info *si = get_stair(stairpos);

    // What 'guess' signifies: whenever you take a stair from A to B, the
    // travel code knows that the stair takes you from A->B. In that case,
    // update_stair() is called with guess == false.
    //
    // Unfortunately, Crawl doesn't guarantee that A->B implies B->A, but the
    // travel code has to assume that anyway (because that's what the player
    // will expect), and call update_stair() again with guess == true.
    //
    // The idea of using 'guess' is that we'll update the stair's destination
    // with a guess only if we know that the currently set destination is
    // itself a guess.
    //
    if (si && (si->guessed_pos || !guess))
    {
        si->destination = p;
        si->guessed_pos = guess;

        if (!guess && p.id.branch == BRANCH_VESTIBULE
            && id.branch == BRANCH_DEPTHS)
        {
            travel_hell_entry = p;
        }

        // All branch stairs land on the same place on the destination level,
        // update the cache accordingly (but leave guessed_pos = true). This
        // applies for both branch exits (the usual case) and branch entrances.
        if (si->destination.id.branch != id.branch)
            sync_branch_stairs(si);
    }
    else if (!si && guess)
        create_placeholder_stair(stairpos, p);
}

void LevelInfo::create_placeholder_stair(const coord_def &stair,
                                         const level_pos &dest)
{
    // If there are any existing placeholders with the same 'dest', zap them.
    for (int i = 0, size = stairs.size(); i < size; ++i)
    {
        if (stairs[i].type == stair_info::PLACEHOLDER
            && stairs[i].destination == dest)
        {
            stairs.erase(stairs.begin() + i);
            break;
        }
    }

    stair_info placeholder;
    placeholder.position    = stair;
    placeholder.grid        = DNGN_FLOOR;
    placeholder.destination = dest;
    placeholder.type        = stair_info::PLACEHOLDER;
    stairs.push_back(placeholder);

    resize_stair_distances();
}

// If a stair leading out of or into a branch has a known destination, all
// stairs of the same type on this level should have the same destination set
// as guessed_pos == true.
void LevelInfo::sync_all_branch_stairs()
{
    set<int> synced;

    for (int i = 0, size = stairs.size(); i < size; ++i)
    {
        const stair_info &si = stairs[i];
        if (si.destination.id.branch != id.branch && si.destination.is_valid()
            && !synced.count(si.grid))
        {
            synced.insert(si.grid);
            sync_branch_stairs(&si);
        }
    }
}

void LevelInfo::sync_branch_stairs(const stair_info *si)
{
    for (int i = 0, size = stairs.size(); i < size; ++i)
    {
        stair_info &sother = stairs[i];
        if (si == &sother || !sother.guessed_pos || si->grid != sother.grid
            || sother.destination.is_valid())
        {
            continue;
        }
        sother.destination = si->destination;
    }
}

void LevelInfo::clear_stairs(dungeon_feature_type grid)
{
    for (int i = 0, size = stairs.size(); i < size; ++i)
    {
        stair_info &si = stairs[i];
        if (si.grid != grid)
            continue;

        si.destination.id.depth = -1;
        si.destination.pos.x = -1;
        si.destination.pos.y = -1;
        si.guessed_pos = true;
    }
}

stair_info *LevelInfo::get_stair(int x, int y)
{
    const coord_def c(x, y);
    return get_stair(c);
}

bool LevelInfo::know_stair(const coord_def &c) const
{
    const int index = get_stair_index(c);
    if (index == -1)
        return false;

    const level_pos &lp = stairs[index].destination;
    return lp.is_valid();
}

stair_info *LevelInfo::get_stair(const coord_def &pos)
{
    int index = get_stair_index(pos);
    return index != -1? &stairs[index] : NULL;
}

int LevelInfo::get_stair_index(const coord_def &pos) const
{
    for (int i = static_cast<int>(stairs.size()) - 1; i >= 0; --i)
        if (stairs[i].position == pos)
            return i;

    return -1;
}

void LevelInfo::correct_stair_list(const vector<coord_def> &s)
{
    stair_distances.clear();

    // Fix up the grid for the placeholder stair.
    for (int i = 0, sz = stairs.size(); i < sz; ++i)
        stairs[i].grid = grd(stairs[i].position);

    // First we kill any stairs in 'stairs' that aren't there in 's'.
    for (int i = ((int) stairs.size()) - 1; i >= 0; --i)
    {
        if (stairs[i].type != stair_info::PHYSICAL)
            continue;

        bool found = false;
        for (int j = s.size() - 1; j >= 0; --j)
        {
            if (s[j] == stairs[i].position)
            {
                found = true;
                break;
            }
        }

        if (!found)
            stairs.erase(stairs.begin() + i);
    }

    // For each stair in 's', make sure we have a corresponding stair
    // in 'stairs'.
    for (int i = 0, sz = s.size(); i < sz; ++i)
    {
        int found = -1;
        for (int j = stairs.size() - 1; j >= 0; --j)
        {
            if (s[i] == stairs[j].position)
            {
                found = j;
                break;
            }
        }

        if (found == -1)
        {
            stair_info si;
            si.position = s[i];
            si.grid     = grd(si.position);
            si.destination.id = level_id::get_next_level_id(s[i]);
            if (si.destination.id.branch == BRANCH_VESTIBULE
                && id.branch == BRANCH_DEPTHS
                && travel_hell_entry.is_valid())
            {
                si.destination = travel_hell_entry;
            }

            // We don't know where on the next level these stairs go to, but
            // that can't be helped. That information will have to be filled
            // in whenever the player takes these stairs.
            stairs.push_back(si);
        }
        else
            stairs[found].type = stair_info::PHYSICAL;
    }

    resize_stair_distances();
}

void LevelInfo::resize_stair_distances()
{
    const int nstairs = stairs.size();
    stair_distances.reserve(nstairs * nstairs);
    stair_distances.resize(nstairs * nstairs, 0);
}

int LevelInfo::distance_between(const stair_info *s1, const stair_info *s2)
                    const
{
    if (!s1 || !s2)
        return 0;
    if (s1 == s2)
        return 0;

    int i1 = get_stair_index(s1->position),
        i2 = get_stair_index(s2->position);
    if (i1 == -1 || i2 == -1)
        return 0;

    return stair_distances[ i1 * stairs.size() + i2 ];
}

void LevelInfo::get_stairs(vector<coord_def> &st)
{
    for (rectangle_iterator ri(1); ri; ++ri)
    {
        const dungeon_feature_type feat = grd(*ri);

        if ((*ri == you.pos() || env.map_knowledge(*ri).known())
            && feat_is_travelable_stair(feat)
            && (env.map_knowledge(*ri).seen() || !_is_branch_stair(*ri)))
        {
            st.push_back(*ri);
        }
    }
}

void LevelInfo::clear_distances()
{
    for (int i = 0, count = stairs.size(); i < count; ++i)
        stairs[i].clear_distance();
}

bool LevelInfo::is_known_branch(uint8_t branch) const
{
    for (int i = 0, count = stairs.size(); i < count; ++i)
        if (stairs[i].destination.id.branch == branch)
            return true;

    return false;
}

void LevelInfo::save(writer& outf) const
{
    int stair_count = stairs.size();
    // How many stairs do we know of?
    marshallShort(outf, stair_count);
    for (int i = 0; i < stair_count; ++i)
        stairs[i].save(outf);

    if (stair_count)
    {
        // Save stair distances as short ints.
        const int sz = stair_distances.size();
        for (int i = 0, n = stair_count * stair_count; i < n; ++i)
        {
            if (i >= sz)
                marshallShort(outf, -1);
            else
                marshallShort(outf, stair_distances[i]);
        }
    }

    marshallExcludes(outf, excludes);

    marshallByte(outf, NUM_DA_COUNTERS);
    for (int i = 0; i < NUM_DA_COUNTERS; i++)
        marshallShort(outf, da_counters[i]);
}

void LevelInfo::load(reader& inf, int minorVersion)
{
    stairs.clear();
    int stair_count = unmarshallShort(inf);
    for (int i = 0; i < stair_count; ++i)
    {
        stair_info si;
        si.load(inf);
        stairs.push_back(si);

        if (id.branch == BRANCH_DUNGEON
            && si.destination.id.branch == BRANCH_VESTIBULE
            && !travel_hell_entry.is_valid()
            && si.destination.is_valid())
        {
            travel_hell_entry = si.destination;
        }
    }

    stair_distances.clear();
    if (stair_count)
    {
        stair_distances.reserve(stair_count * stair_count);
        for (int i = stair_count * stair_count - 1; i >= 0; --i)
            stair_distances.push_back(unmarshallShort(inf));
    }

    unmarshallExcludes(inf, minorVersion, excludes);

    int n_count = unmarshallByte(inf);
    ASSERT_RANGE(n_count, 0, NUM_DA_COUNTERS + 1);
    for (int i = 0; i < n_count; i++)
        da_counters[i] = unmarshallShort(inf);
}

void LevelInfo::fixup()
{
    // The only fixup we do now is for the hell entry.
    if (id.branch != BRANCH_DEPTHS || !travel_hell_entry.is_valid())
        return;

    for (int i = 0, count = stairs.size(); i < count; ++i)
    {
        stair_info &si = stairs[i];
        if (si.destination.id.branch == BRANCH_VESTIBULE
            && !si.destination.is_valid())
        {
            si.destination = travel_hell_entry;
        }
    }
}

bool TravelCache::know_stair(const coord_def &c) const
{
    travel_levels_map::const_iterator i = levels.find(level_id::current());
    return i == levels.end() ? false : i->second.know_stair(c);
}

void TravelCache::list_waypoints() const
{
    string line;
    string dest;
    char choice[50];
    int count = 0;

    for (int i = 0; i < TRAVEL_WAYPOINT_COUNT; ++i)
    {
        if (waypoints[i].id.depth == -1)
            continue;

        dest = _get_trans_travel_dest(waypoints[i], false, true);

        snprintf(choice, sizeof choice, "(%d) %-9s", i, dest.c_str());
        line += choice;
        if (!(++count % 5))
        {
            mpr(line.c_str());
            line = "";
        }
    }
    if (!line.empty())
        mpr(line.c_str());
}

uint8_t TravelCache::is_waypoint(const level_pos &lp) const
{
    for (int i = 0; i < TRAVEL_WAYPOINT_COUNT; ++i)
        if (lp == waypoints[i])
            return '0' + i;

    return 0;
}

void TravelCache::update_waypoints() const
{
    level_pos lp;
    lp.id = level_id::current();

    memset(curr_waypoints, 0, sizeof curr_waypoints);
    for (lp.pos.x = 1; lp.pos.x < GXM; ++lp.pos.x)
        for (lp.pos.y = 1; lp.pos.y < GYM; ++lp.pos.y)
        {
            uint8_t wpc = is_waypoint(lp);
            if (wpc)
                curr_waypoints[lp.pos.x][lp.pos.y] = wpc;
        }
}

void TravelCache::delete_waypoint()
{
    if (!get_waypoint_count())
        return;

    while (get_waypoint_count())
    {
        clear_messages();
        mpr("Existing waypoints:");
        list_waypoints();
        mprf(MSGCH_PROMPT, "Delete which waypoint? (* - delete all, Esc - exit) ");

        int key = getchm();
        if (key >= '0' && key <= '9')
        {
            key -= '0';
            if (waypoints[key].is_valid())
            {
                waypoints[key].clear();
                update_waypoints();
                continue;
            }
        }
        else if (key == '*')
        {
            for (int i = 0; i < TRAVEL_WAYPOINT_COUNT; ++i)
                waypoints[i].clear();

            update_waypoints();
            break;
        }

        canned_msg(MSG_OK);
        return;
    }

    clear_messages();
    mpr("All waypoints deleted. Have a nice day!");
}

void TravelCache::add_waypoint(int x, int y)
{
    if (!can_travel_interlevel())
    {
        mpr("Sorry, you can't set a waypoint here.");
        return;
    }

    clear_messages();

    const bool waypoints_exist = get_waypoint_count();
    if (waypoints_exist)
    {
        mpr("Existing waypoints:");
        list_waypoints();
    }

    mprf(MSGCH_PROMPT, "Assign waypoint to what number? (0-9%s) ",
         waypoints_exist? ", D - delete waypoint" : "");

    int keyin = toalower(get_ch());

    if (waypoints_exist && keyin == 'd')
    {
        delete_waypoint();
        return;
    }

    if (keyin < '0' || keyin > '9')
    {
        canned_msg(MSG_OK);
        return;
    }

    int waynum = keyin - '0';

    coord_def pos(x,y);
    if (x == -1 || y == -1)
        pos = you.pos();

    const level_id &lid = level_id::current();

    const bool overwrite = waypoints[waynum].is_valid();

    string old_dest =
        overwrite ? _get_trans_travel_dest(waypoints[waynum], false, true) : "";
    level_id old_lid = (overwrite ? waypoints[waynum].id : lid);

    waypoints[waynum].id  = lid;
    waypoints[waynum].pos = pos;

    string new_dest = _get_trans_travel_dest(waypoints[waynum], false, true);
    clear_messages();
    if (overwrite)
    {
        if (lid == old_lid) // same level
            mprf("Waypoint %d re-assigned to your current position.", waynum);
        else
        {
            mprf("Waypoint %d re-assigned from %s to %s.",
                 waynum, old_dest.c_str(), new_dest.c_str());
        }
    }
    else
        mprf("Waypoint %d assigned to %s.", waynum, new_dest.c_str());

    update_waypoints();
}

int TravelCache::get_waypoint_count() const
{
    int count = 0;
    for (int i = 0; i < TRAVEL_WAYPOINT_COUNT; ++i)
        if (waypoints[i].is_valid())
            count++;

    return count;
}

void TravelCache::clear_distances()
{
    map<level_id, LevelInfo>::iterator i = levels.begin();
    for (; i != levels.end(); ++i)
        i->second.clear_distances();
}

bool TravelCache::is_known_branch(uint8_t branch) const
{
    map<level_id, LevelInfo>::const_iterator i = levels.begin();
    for (; i != levels.end(); ++i)
        if (i->second.is_known_branch(branch))
            return true;

    return false;
}

void TravelCache::save(writer& outf) const
{
    // Travel cache version information
    marshallByte(outf, TAG_MAJOR_VERSION);
    marshallByte(outf, TAG_MINOR_VERSION);

    // Write level count.
    marshallShort(outf, levels.size());

    map<level_id, LevelInfo>::const_iterator i = levels.begin();
    for (; i != levels.end(); ++i)
    {
        i->first.save(outf);
        i->second.save(outf);
    }

    for (int wp = 0; wp < TRAVEL_WAYPOINT_COUNT; ++wp)
        waypoints[wp].save(outf);
}

void TravelCache::load(reader& inf, int minorVersion)
{
    levels.clear();

    // Check version. If not compatible, we just ignore the file altogether.
    int major = unmarshallByte(inf),
        minor = unmarshallByte(inf);
    if (major != TAG_MAJOR_VERSION || minor > TAG_MINOR_VERSION)
        return;

    int level_count = unmarshallShort(inf);
    for (int i = 0; i < level_count; ++i)
    {
        level_id id;
        id.load(inf);

        LevelInfo linfo;
        // Must set id before load, or travel_hell_entry will not be
        // correctly set.
        linfo.id = id;
        linfo.load(inf, minorVersion);

        levels[id] = linfo;
    }

    for (int wp = 0; wp < TRAVEL_WAYPOINT_COUNT; ++wp)
        waypoints[wp].load(inf);

    fixup_levels();
}

void TravelCache::set_level_excludes()
{
    get_level_info(level_id::current()).set_level_excludes();
}

void TravelCache::update_excludes()
{
    get_level_info(level_id::current()).update_excludes();
}

void TravelCache::update()
{
    get_level_info(level_id::current()).update();
}

void TravelCache::update_da_counters()
{
    ::update_da_counters(&get_level_info(level_id::current()));
}

unsigned int TravelCache::query_da_counter(daction_type c)
{
    // other levels are up to date, the current one not necessarily so
    update_da_counters();

    unsigned int sum = 0;

    map<level_id, LevelInfo>::const_iterator i = levels.begin();
    for (; i != levels.end(); ++i)
        sum += i->second.da_counters[c];

    return sum;
}

void TravelCache::clear_da_counter(daction_type c)
{
    map<level_id, LevelInfo>::iterator i = levels.begin();
    for (; i != levels.end(); ++i)
        i->second.da_counters[c] = 0;
}

void TravelCache::fixup_levels()
{
    map<level_id, LevelInfo>::iterator i = levels.begin();
    for (; i != levels.end(); ++i)
        i->second.fixup();
}

vector<level_id> TravelCache::known_levels() const
{
    vector<level_id> levs;

    map<level_id, LevelInfo>::const_iterator i = levels.begin();
    for (; i != levels.end(); ++i)
        levs.push_back(i->first);

    return levs;
}

bool can_travel_to(const level_id &id)
{
    return is_connected_branch(id) && can_travel_interlevel()
           || id == level_id::current();
}

bool can_travel_interlevel()
{
    return player_in_connected_branch();
}

/////////////////////////////////////////////////////////////////////////////
// Shift-running and resting.

runrest::runrest()
    : runmode(0), mp(0), hp(0), pos(0,0)
{
}

// Initialise is only called for resting/shift-running. We should eventually
// include travel and wrap it all in.
void runrest::initialise(int dir, int mode)
{
    // Note HP and MP for reference.
    hp = you.hp;
    mp = you.magic_points;
    init_travel_speed();

    if (dir == RDIR_REST)
    {
        pos.reset();
        runmode = mode;
    }
    else
    {
        ASSERT_RANGE(dir, 0, 8);

        pos = Compass[dir];
        runmode = mode;

        // Get the compass point to the left/right of intended travel:
        const int left  = (dir - 1 < 0) ? 7 : (dir - 1);
        const int right = (dir + 1 > 7) ? 0 : (dir + 1);

        // Record the direction and starting tile type for later reference:
        set_run_check(0, left);
        set_run_check(1, dir);
        set_run_check(2, right);
    }

    if (runmode == RMODE_REST_DURATION)
        start_delay(DELAY_REST, 1);
    else
        start_delay(DELAY_RUN, 1);
}

void runrest::init_travel_speed()
{
    if (you.travel_ally_pace)
        travel_speed = _slowest_ally_speed();
    else
        travel_speed = 0;
}

runrest::operator int () const
{
    return runmode;
}

const runrest &runrest::operator = (int newrunmode)
{
    runmode = newrunmode;
    return *this;
}

static dungeon_feature_type _base_feat_type(dungeon_feature_type grid)
{
    // Merge walls.
    if (feat_is_wall(grid))
        return DNGN_ROCK_WALL;

    return grid;
}

void runrest::set_run_check(int index, int dir)
{
    run_check[index].delta = Compass[dir];

    const coord_def p = you.pos() + Compass[dir];
    run_check[index].grid = _base_feat_type(env.map_knowledge(p).feat());
}

bool runrest::check_stop_running()
{
    if (runmode > 0 && runmode != RMODE_START && run_should_stop())
    {
        stop();
        return true;
    }
    return false;
}

// This function creates "equivalence classes" so that changes
// in wall and floor type aren't running stopping points.
bool runrest::run_should_stop() const
{
    const coord_def targ = you.pos() + pos;
    const map_cell& tcell = env.map_knowledge(targ);

    if (tcell.cloud() != CLOUD_NONE
        && (!you_worship(GOD_QAZLAL)
            || player_under_penance()
            || !YOU_KILL(tcell.cloudinfo()->killer)))
    {
        return true;
    }

    if (is_excluded(targ) && !is_stair_exclusion(targ))
    {
#ifndef USE_TILE_LOCAL
        // XXX: Remove this once exclusions are visible.
        mprf(MSGCH_WARN, "Stopped running for exclusion.");
#endif
        return true;
    }

    const monster_info* mon = tcell.monsterinfo();
    if (mon && !fedhas_passthrough(tcell.monsterinfo()))
        return true;

    for (adjacent_iterator ai(targ); ai; ++ai)
        if (env.grid(*ai) == DNGN_SLIMY_WALL)
            return true;

    for (int i = 0; i < 3; i++)
    {
        const coord_def p = you.pos() + run_check[i].delta;
        const dungeon_feature_type feat =
            _base_feat_type(env.map_knowledge(p).feat());

        if (run_check[i].grid != feat)
            return true;
    }

    return false;
}

void runrest::stop()
{
    bool need_redraw =
        (runmode > 0 || runmode < 0 && Options.travel_delay == -1);
    _userdef_run_stoprunning_hook();
    runmode = RMODE_NOT_RUNNING;

    // Kill the delay; this is fine because it's not possible to stack
    // run/rest/travel on top of other delays.
    stop_delay();

#ifdef USE_TILE_LOCAL
    if (Options.tile_runrest_rate > 0)
        tiles.set_need_redraw();
#endif

    if (need_redraw)
        viewwindow();

    _reset_zigzag_info();
}

bool runrest::is_rest() const
{
    return runmode > 0 && pos.origin();
}

bool runrest::is_explore() const
{
    return runmode == RMODE_EXPLORE || runmode == RMODE_EXPLORE_GREEDY;
}

bool runrest::is_any_travel() const
{
    switch (runmode)
    {
    case RMODE_INTERLEVEL:
    case RMODE_EXPLORE_GREEDY:
    case RMODE_EXPLORE:
    case RMODE_TRAVEL:
        return true;
    default:
        return false;
    }
}

string runrest::runmode_name() const
{
    switch (runmode)
    {
    case RMODE_EXPLORE:
    case RMODE_EXPLORE_GREEDY:
        return "explore";
    case RMODE_INTERLEVEL:
    case RMODE_TRAVEL:
        return "travel";
    default:
        if (runmode > 0)
            return pos.origin()? "rest" : "run";
        return "";
    }
}

void runrest::rest()
{
    // stop_running() Lua hooks will never see rest stops.
    if (runmode > 0)
        --runmode;
}

void runrest::clear()
{
    runmode = RMODE_NOT_RUNNING;
    pos.reset();
    mp = hp = travel_speed = 0;

    _reset_zigzag_info();
}

/////////////////////////////////////////////////////////////////////////////
// explore_discoveries

explore_discoveries::explore_discoveries()
    : can_autopickup(::can_autopickup()),
      sacrifice(god_likes_items(you.religion, true)), es_flags(0),
      current_level(NULL), items(), stairs(), portals(), shops(), altars(),
      runed_doors()
{
}

string explore_discoveries::cleaned_feature_description(
    const coord_def &pos) const
{
    string s = lowercase_first(feature_description_at(pos));
    if (s.length() && s[s.length() - 1] == '.')
        s.erase(s.length() - 1);
    if (s.find("a ") != string::npos)
        s = s.substr(2);
    else if (s.find("an ") != string::npos)
        s = s.substr(3);
    return s;
}

bool explore_discoveries::merge_feature(
    vector< explore_discoveries::named_thing<int> > &v,
    const explore_discoveries::named_thing<int> &feat) const
{
    for (int i = 0, size = v.size(); i < size; ++i)
        if (feat == v[i])
        {
            ++v[i].thing;
            return true;
        }

    return false;
}

void explore_discoveries::found_feature(const coord_def &pos,
                                        dungeon_feature_type feat)
{
    if (feat == DNGN_ENTER_SHOP && ES_shop)
    {
        shops.push_back(named_thing<int>(shop_name(pos), feat));
        es_flags |= ES_SHOP;
    }
    else if (feat_is_stair(feat) && ES_stair)
    {
        const named_thing<int> stair(cleaned_feature_description(pos), 1);
        add_stair(stair);
        es_flags |= ES_STAIR;
    }
    else if (feat_is_branchlike(feat) && ES_branch)
    {
        const named_thing<int> stair(cleaned_feature_description(pos), 1);
        add_stair(stair);
        es_flags |= ES_BRANCH;
    }
    else if ((feat_is_portal(feat) || feat == DNGN_ENTER_LABYRINTH)
             && ES_portal)
    {
        const named_thing<int> portal(cleaned_feature_description(pos), 1);
        add_stair(portal);
        es_flags |= ES_PORTAL;
    }
    else if (feat == DNGN_RUNED_DOOR && ES_rdoor)
    {
        for (orth_adjacent_iterator ai(pos); ai; ++ai)
        {
            // If any neighbours have been seen (and thus announced) before,
            // skip.  For parts seen for the first time this turn, announce
            // only the upper leftmost cell.
            if (env.map_knowledge(*ai).feat() == DNGN_RUNED_DOOR
                && (env.map_seen(*ai) || *ai < pos))
            {
                return;
            }
        }

        string desc = env.markers.property_at(pos, MAT_ANY, "stop_explore");
        if (desc.empty())
            desc = cleaned_feature_description(pos);
        const named_thing<int> rdoor(desc, 1);
        runed_doors.push_back(rdoor);
        es_flags |= ES_RUNED_DOOR;
    }
    else if (feat_is_altar(feat) && ES_altar)
    {
        const named_thing<int> altar(cleaned_feature_description(pos), 1);
        if (!merge_feature(altars, altar))
            altars.push_back(altar);
        es_flags |= ES_ALTAR;
    }
    // Would checking for a marker for all discovered cells slow things
    // down too much?
    else if (feat_is_statue_or_idol(feat))
    {
        const string feat_stop_msg =
            env.markers.property_at(pos, MAT_ANY, "stop_explore_msg");
        if (!feat_stop_msg.empty())
        {
            marker_msgs.push_back(feat_stop_msg);
            return;
        }

        const string feat_stop = env.markers.property_at(pos, MAT_ANY,
                                                         "stop_explore");
        if (!feat_stop.empty())
        {
            string desc = lowercase_first(feature_description_at(pos));
            marked_feats.push_back(desc);
            return;
        }
    }
}

void explore_discoveries::add_stair(
    const explore_discoveries::named_thing<int> &stair)
{
    if (merge_feature(stairs, stair) || merge_feature(portals, stair))
        return;

    // Hackadelic
    if (stair.name.find("stair") != string::npos)
        stairs.push_back(stair);
    else
        portals.push_back(stair);
}

void explore_discoveries::add_item(const item_def &i)
{
    item_def copy = i;
    copy.quantity = 1;
    const string cname = copy.name(DESC_PLAIN);

    // Try to find something to stack it with, stacking by name.
    for (int j = 0, size = items.size(); j < size; ++j)
    {
        const int orig_quantity = items[j].thing.quantity;
        items[j].thing.quantity = 1;
        if (cname == items[j].thing.name(DESC_PLAIN))
        {
            items[j].thing.quantity = orig_quantity + i.quantity;
            items[j].name =
                items[j].thing.name(DESC_A, false, false, true,
                                    !is_stackable_item(i));
            return;
        }
        items[j].thing.quantity = orig_quantity;
    }

    string itemname = get_menu_colour_prefix_tags(i, DESC_A);
    monster* mon = monster_at(i.pos);
    if (mon && mons_species(mon->type) == MONS_BUSH)
        itemname += " (under bush)";
    else if (mon && mon->type == MONS_PLANT)
        itemname += " (under plant)";

    items.push_back(named_thing<item_def>(itemname, i));

    // First item of this type?
    // XXX: Only works when travelling.
    hints_first_item(i);
}

void explore_discoveries::found_item(const coord_def &pos, const item_def &i)
{
    if (you.running == RMODE_EXPLORE_GREEDY)
    {
        // The things we need to do...
        if (!current_level)
            current_level = StashTrack.find_current_level();

        if (current_level)
        {
            const bool greed_inducing = _is_greed_inducing_square(current_level,
                                                                  pos,
                                                                  can_autopickup,
                                                                  sacrifice);

            if (greed_inducing && (Options.explore_stop & ES_GREEDY_ITEM))
                ; // Stop for this condition
            else if (!greed_inducing
                     && ((Options.explore_stop & ES_ITEM)
                         || ((Options.explore_stop & ES_GLOWING_ITEM)
                             && (i.flags & ISFLAG_COSMETIC_MASK))
                         || ((Options.explore_stop & ES_ARTEFACT)
                             && (i.flags & ISFLAG_ARTEFACT_MASK))
                         || ((Options.explore_stop & ES_RUNE)
                             && item_is_rune(i))))
            {
                ; // More conditions to stop for
            }
            else
                return; // No conditions met, don't stop for this item
        }
    } // if (you.running == RMODE_EXPLORE_GREEDY)

    add_item(i);
    es_flags |=
        (you.running == RMODE_EXPLORE_GREEDY) ? ES_GREEDY_PICKUP_MASK :
        (Options.explore_stop & ES_ITEM) ? ES_ITEM : ES_NONE;
}

// Expensive O(n^2) duplicate search, but we can live with that.
template <class citer> bool explore_discoveries::has_duplicates(
    citer begin, citer end) const
{
    for (citer s = begin; s != end; ++s)
        for (citer z = s + 1; z != end; ++z)
        {
            if (*s == *z)
                return true;
        }

    return false;
}

template <class C> void explore_discoveries::say_any(
    const C &coll, const char *category) const
{
    if (coll.empty())
        return;

    const int size = coll.size();

    string plural = pluralise(category);
    if (size != 1)
        category = plural.c_str();

    if (has_duplicates(coll.begin(), coll.end()))
    {
        mprf("Found %s %s.", number_in_words(size).c_str(), category);
        return;
    }

    const string message = "Found " +
                           comma_separated_line(coll.begin(), coll.end()) + ".";

    if (strwidth(message) >= get_number_of_cols())
        mprf("Found %s %s.", number_in_words(size).c_str(), category);
    else
        mprf("%s", message.c_str());
}

vector<string> explore_discoveries::apply_quantities(
    const vector< named_thing<int> > &v) const
{
    static const char *feature_plural_qualifiers[] =
    {
        " leading ", " back to ", " to ", " of ", " in ", " out of",
        " from ", " back into ", NULL
    };

    vector<string> things;
    for (int i = 0, size = v.size(); i < size; ++i)
    {
        const named_thing<int> &nt = v[i];
        if (nt.thing == 1)
            things.push_back(article_a(nt.name));
        else
        {
            things.push_back(number_in_words(nt.thing)
                             + " "
                             + pluralise(nt.name, feature_plural_qualifiers));
        }
    }
    return things;
}

bool explore_discoveries::prompt_stop() const
{
    const bool marker_stop = !marker_msgs.empty() || !marked_feats.empty();

    for (unsigned int i = 0; i < marker_msgs.size(); i++)
        mprf("%s", marker_msgs[i].c_str());

    for (unsigned int i = 0; i < marked_feats.size(); i++)
        mprf("Found %s", marked_feats[i].c_str());

    if (!es_flags)
        return marker_stop;

    say_any(items, "item");
    say_any(shops, "shop");
    say_any(apply_quantities(altars), "altar");
    say_any(apply_quantities(portals), "portal");
    say_any(apply_quantities(stairs), "stair");
    say_any(apply_quantities(runed_doors), "runed door");

    return (Options.explore_stop_prompt & es_flags) != es_flags
           || marker_stop
           || _prompt_stop_explore(es_flags);
}

void do_interlevel_travel()
{
    if (Hints.hints_travel)
        Hints.hints_travel = 0;

    if (!can_travel_interlevel())
    {
        if (you.running.pos == you.pos())
        {
            mpr("You're already here!");
            return;
        }
        else if (!you.running.pos.x || !you.running.pos.y)
        {
            mpr("Sorry, you can't auto-travel out of here.");
            return;
        }

        // Don't ask for a destination if you can only travel
        // within level anyway.
        start_travel(you.running.pos);
    }
    else
        _start_translevel_travel_prompt();

    if (you.running)
        clear_messages();
}

#ifdef USE_TILE
// (0,0) = same position is handled elsewhere.
const int dir_dx[8] = {-1, 0, 1, -1, 1, -1,  0,  1};
const int dir_dy[8] = { 1, 1, 1,  0, 0, -1, -1, -1};

const int cmd_array[8] =
{
    CMD_MOVE_DOWN_LEFT,  CMD_MOVE_DOWN,  CMD_MOVE_DOWN_RIGHT,
    CMD_MOVE_LEFT,                       CMD_MOVE_RIGHT,
    CMD_MOVE_UP_LEFT,    CMD_MOVE_UP,    CMD_MOVE_UP_RIGHT,
};

static int _adjacent_cmd(const coord_def &gc, bool force)
{
    const coord_def dir = gc - you.pos();
    for (int i = 0; i < 8; i++)
    {
        if (dir_dx[i] != dir.x || dir_dy[i] != dir.y)
            continue;

        int cmd = cmd_array[i];
        if (force)
            cmd += CMD_OPEN_DOOR_LEFT - CMD_MOVE_LEFT;

        return cmd;
    }

    return CK_MOUSE_CMD;
}

int click_travel(const coord_def &gc, bool force)
{
    if (!in_bounds(gc))
        return CK_MOUSE_CMD;

    const int cmd = _adjacent_cmd(gc, force);
    if (cmd != CK_MOUSE_CMD)
        return cmd;

    if ((!is_excluded(gc) || is_stair_exclusion(gc))
        && (!is_excluded(you.pos()) || is_stair_exclusion(you.pos()))
        && i_feel_safe(false, false, false, false))
    {
        map_cell &cell(env.map_knowledge(gc));
        // If there's a monster that would block travel,
        // don't start traveling.
        if (!_monster_blocks_travel(cell.monsterinfo()))
        {
            start_travel(gc);
            return CK_MOUSE_CMD;
        }
    }

    // If not safe, then take one step towards the click.
    travel_pathfind tp;
    tp.set_src_dst(you.pos(), gc);
    tp.set_ignore_danger();
    const coord_def dest = tp.pathfind(RMODE_TRAVEL);

    if (!dest.x && !dest.y)
        return CK_MOUSE_CMD;

    return _adjacent_cmd(dest, force);
}
#endif

bool check_for_interesting_features()
{
    // Scan through the shadow map, compare it with the actual map, and if
    // there are any squares of the shadow map that have just been
    // discovered and contain an item, or have an interesting dungeon
    // feature, stop exploring.
    explore_discoveries discoveries;
    for (radius_iterator ri(you.pos(), LOS_DEFAULT); ri; ++ri)
    {
        const coord_def p(*ri);

        // Find just noticed squares.
        if (env.map_knowledge(p).flags & MAP_SEEN_FLAG
            && !env.map_seen(p))
        {
            env.map_seen.set(p);
            _check_interesting_square(p, discoveries);
        }
    }

    return discoveries.prompt_stop();
}

void clear_level_target()
{
    level_target.clear();
    trans_travel_dest.clear();
}

void clear_travel_trail()
{
#ifdef USE_TILE_WEB
    for (unsigned int i = 0; i < env.travel_trail.size(); ++i)
        tiles.update_minimap(env.travel_trail[i]);
#endif
    env.travel_trail.clear();
}

int travel_trail_index(const coord_def& gc)
{
    unsigned int idx = find(env.travel_trail.begin(), env.travel_trail.end(), gc)
        - env.travel_trail.begin();
    if (idx < env.travel_trail.size())
        return idx;
    else
        return -1;
}