/*
 *  File:       misc.cc
 *  Summary:    Misc functions.
 *  Written by: Linley Henzell
 */

#include "AppHdr.h"

#include "misc.h"
#include "notes.h"

#include <string.h>
#include <algorithm>

#if !defined(__IBMCPP__) && !defined(TARGET_COMPILER_VC)
#include <unistd.h>
#endif

#ifdef TARGET_COMPILER_MINGW
#include <io.h>
#endif

#include <cstdlib>
#include <cstdio>
#include <cmath>

#include "externs.h"
#include "options.h"
#include "misc.h"

#include "abyss.h"
#include "branch.h"
#include "chardump.h"
#include "clua.h"
#include "cloud.h"
#include "coordit.h"
#include "database.h"
#include "delay.h"
#include "dgn-shoals.h"
#include "directn.h"
#include "dgnevent.h"
#include "directn.h"
#include "fprop.h"
#include "fight.h"
#include "files.h"
#include "food.h"
#include "hiscores.h"
#include "itemname.h"
#include "itemprop.h"
#include "items.h"
#include "item_use.h"
#include "lev-pand.h"
#include "macro.h"
#include "makeitem.h"
#include "mapmark.h"
#include "message.h"
#include "mon-place.h"
#include "coord.h"
#include "mon-pathfind.h"
#include "mon-iter.h"
#include "mon-util.h"
#include "mon-stuff.h"
#include "ouch.h"
#include "output.h"
#include "overmap.h"
#include "place.h"
#include "player.h"
#include "random.h"
#include "religion.h"
#include "shopping.h"
#include "skills.h"
#include "skills2.h"
#include "spells1.h"
#include "spells3.h"
#include "stash.h"
#include "state.h"
#include "stuff.h"
#include "env.h"
#include "areas.h"
#include "tiles.h"
#include "terrain.h"
#include "transform.h"
#include "traps.h"
#include "travel.h"
#include "tutorial.h"
#include "view.h"
#include "shout.h"
#include "viewchar.h"
#include "xom.h"

static void _create_monster_hide(const item_def corpse)
{
    // receive_corpses() in spells3.cc creates corpses that
    // are easily scummed for hides.  We prevent this by setting
    // "DoNotDropHide" as an item property of corpses it creates.
    if (corpse.props.exists("DoNotDropHide"))
        return;

    int mons_class = corpse.plus;

    int o = get_item_slot();
    if (o == NON_ITEM)
        return;

    item_def& item = mitm[o];

    // These values are common to all: {dlb}
    item.base_type = OBJ_ARMOUR;
    item.quantity  = 1;
    item.plus      = 0;
    item.plus2     = 0;
    item.special   = 0;
    item.flags     = 0;
    item.colour    = mons_class_colour(mons_class);

    // These values cannot be set by a reasonable formula: {dlb}
    switch (mons_class)
    {
    case MONS_DRAGON:         item.sub_type = ARM_DRAGON_HIDE;         break;
    case MONS_TROLL:          item.sub_type = ARM_TROLL_HIDE;          break;
    case MONS_ICE_DRAGON:     item.sub_type = ARM_ICE_DRAGON_HIDE;     break;
    case MONS_STEAM_DRAGON:   item.sub_type = ARM_STEAM_DRAGON_HIDE;   break;
    case MONS_MOTTLED_DRAGON: item.sub_type = ARM_MOTTLED_DRAGON_HIDE; break;
    case MONS_STORM_DRAGON:   item.sub_type = ARM_STORM_DRAGON_HIDE;   break;
    case MONS_GOLDEN_DRAGON:  item.sub_type = ARM_GOLD_DRAGON_HIDE;    break;
    case MONS_SWAMP_DRAGON:   item.sub_type = ARM_SWAMP_DRAGON_HIDE;   break;

    case MONS_SHEEP:
    case MONS_YAK:
    default:
        item.sub_type = ARM_ANIMAL_SKIN;
        break;
    }

    monster_type mtype = static_cast<monster_type>(corpse.orig_monnum - 1);
    if (!invalid_monster_type(mtype) && mons_is_unique(mtype))
        item.inscription = mons_type_name(mtype, DESC_PLAIN);

    move_item_to_grid(&o, you.pos());
}

void turn_corpse_into_skeleton(item_def &item)
{
    ASSERT(item.base_type == OBJ_CORPSES && item.sub_type == CORPSE_BODY);

    // Some monsters' corpses lack the structure to leave skeletons
    // behind.
    if (!mons_skeleton(item.plus))
        return;

    // While it is possible to distinguish draconian corpses by colour,
    // their skeletons are indistinguishable.
    if (mons_genus(item.plus) == MONS_DRACONIAN && item.plus != MONS_DRACONIAN)
        item.plus = MONS_DRACONIAN;
    // The same goes for rat corpses.
    else if (mons_genus(item.plus) == MONS_RAT && item.plus != MONS_RAT)
        item.plus = MONS_RAT;

    item.sub_type = CORPSE_SKELETON;
    item.special  = 200; // reset rotting counter
    item.colour   = LIGHTGREY;
}

void turn_corpse_into_chunks(item_def &item)
{
    ASSERT(item.base_type == OBJ_CORPSES && item.sub_type == CORPSE_BODY);
    const monster_type montype = static_cast<monster_type>(item.plus);
    const int max_chunks = mons_weight(montype) / 150;

    // Only fresh corpses bleed enough to colour the ground.
    if (!food_is_rotten(item))
        bleed_onto_floor(you.pos(), montype, max_chunks, true);

    item.base_type = OBJ_FOOD;
    item.sub_type  = FOOD_CHUNK;
    item.quantity  = 1 + random2(max_chunks);
    item.quantity  = stepdown_value(item.quantity, 4, 4, 12, 12);

    if (you.species != SP_VAMPIRE)
        item.flags &= ~(ISFLAG_THROWN | ISFLAG_DROPPED);

    // Happens after the corpse has been butchered.
    if (monster_descriptor(item.plus, MDSC_LEAVES_HIDE) && !one_chance_in(3))
        _create_monster_hide(item);
}

void turn_corpse_into_skeleton_and_chunks(item_def &item)
{
    item_def chunks = item;

    if (mons_skeleton(item.plus))
        turn_corpse_into_skeleton(item);

    int o = get_item_slot();
    if (o != NON_ITEM)
    {
        turn_corpse_into_chunks(chunks);
        copy_item_to_grid(chunks, you.pos());
    }
}

// Initialise blood potions with a vector of timers.
void init_stack_blood_potions(item_def &stack, int age)
{
    ASSERT(is_blood_potion(stack));

    CrawlHashTable &props = stack.props;
    props.clear(); // sanity measure
    props["timer"].new_vector(SV_LONG, SFLAG_CONST_TYPE);
    CrawlVector &timer = props["timer"].get_vector();

    if (age == -1)
    {
        if (stack.sub_type == POT_BLOOD)
            age = 2500;
        else // coagulated blood
            age = 500;
    }
    // For a newly created stack, all potions use the same timer.
    const long max_age = you.num_turns + age;
#ifdef DEBUG_BLOOD_POTIONS
    mprf(MSGCH_DIAGNOSTICS, "newly created stack will time out at turn %d",
                            max_age);
#endif
    for (int i = 0; i < stack.quantity; i++)
        timer.push_back(max_age);

    stack.special = 0;
    ASSERT(timer.size() == stack.quantity);
    props.assert_validity();
}

// Sort a CrawlVector<long>, should probably be done properly with templates.
static void _long_sort(CrawlVector &vec)
{
    std::vector<long> help;
    while (!vec.empty())
    {
        help.push_back(vec[vec.size()-1].get_long());
        vec.pop_back();
    }

    std::sort(help.begin(), help.end());

    while (!help.empty())
    {
        vec.push_back(help[help.size()-1]);
        help.pop_back();
    }
}

static void _compare_blood_quantity(item_def &stack, int timer_size)
{
    if (timer_size != stack.quantity)
    {
        mprf(MSGCH_WARN,
             "ERROR: blood potion quantity (%d) doesn't match timer (%d)",
             stack.quantity, timer_size);

        // sanity measure
        stack.quantity = timer_size;
    }
}

void maybe_coagulate_blood_potions_floor(int obj)
{
    item_def &blood = mitm[obj];
    ASSERT(blood.is_valid());
    ASSERT(is_blood_potion(blood));

    CrawlHashTable &props = blood.props;
    if (!props.exists("timer"))
        init_stack_blood_potions(blood, blood.special);

    ASSERT(props.exists("timer"));
    CrawlVector &timer = props["timer"].get_vector();
    ASSERT(!timer.empty());
    _compare_blood_quantity(blood, timer.size());

    // blood.sub_type could be POT_BLOOD or POT_BLOOD_COAGULATED
    // -> need different handling
    int rot_limit  = you.num_turns;
    int coag_limit = you.num_turns + 500; // check 500 turns later

    // First count whether coagulating is even necessary.
    int rot_count  = 0;
    int coag_count = 0;
    std::vector<long> age_timer;
    long current;
    while (!timer.empty())
    {
        current = timer[timer.size()-1].get_long();
        if (current > coag_limit
            || blood.sub_type == POT_BLOOD_COAGULATED && current > rot_limit)
        {
            // Still some time until rotting/coagulating.
            break;
        }

        timer.pop_back();
        if (current <= rot_limit)
            rot_count++;
        else if (blood.sub_type == POT_BLOOD && current <= coag_limit)
        {
            coag_count++;
            age_timer.push_back(current);
        }
    }

    if (!rot_count && !coag_count)
        // Nothing to be done.
        return;

#ifdef DEBUG_BLOOD_POTIONS
    mprf(MSGCH_DIAGNOSTICS, "in maybe_coagulate_blood_potions_FLOOR "
                            "(turns: %d)", you.num_turns);

    mprf(MSGCH_DIAGNOSTICS, "Something happened at pos (%d, %d)!",
                            blood.x, blood.y);
    mprf(MSGCH_DIAGNOSTICS, "coagulated: %d, rotted: %d, total: %d",
                            coag_count, rot_count, blood.quantity);
    more();
#endif

    if (!coag_count) // Some potions rotted away.
    {
        dec_mitm_item_quantity(obj, rot_count);
        // Timer is already up to date.
        return;
    }

    // Coagulated blood cannot coagulate any further...
    ASSERT(blood.sub_type == POT_BLOOD);

    if (!blood.held_by_monster())
    {
        // Now that coagulating is necessary, check square for
        // !coagulated blood.
        ASSERT(blood.pos.x >= 0 && blood.pos.y >= 0);
        for (stack_iterator si(blood.pos); si; ++si)
        {
            if (si->base_type == OBJ_POTIONS
                && si->sub_type == POT_BLOOD_COAGULATED)
            {
                // Merge with existing stack.
                CrawlHashTable &props2 = si->props;
                if (!props2.exists("timer"))
                    init_stack_blood_potions(*si, si->special);

                ASSERT(props2.exists("timer"));
                CrawlVector &timer2 = props2["timer"].get_vector();
                ASSERT(timer2.size() == si->quantity);

                // Update timer -> push(pop).
                while (!age_timer.empty())
                {
                    const long val = age_timer.back();
                    age_timer.pop_back();
                    timer2.push_back(val);
                }
                _long_sort(timer2);
                inc_mitm_item_quantity(si.link(), coag_count);
                ASSERT(timer2.size() == si->quantity);
                dec_mitm_item_quantity(obj, rot_count + coag_count);
                return;
            }
        }
    }
    // If we got here, nothing was found! (Or it's in a monster's
    // inventory.)

    // Entire stack is gone, rotted or coagulated.
    // -> Change potions to coagulated type.
    if (rot_count + coag_count == blood.quantity)
    {
        ASSERT(timer.empty());

        // Update subtype.
        blood.sub_type = POT_BLOOD_COAGULATED;
        item_colour(blood);

        // Re-fill vector.
        long val;
        while (!age_timer.empty())
        {
            val = age_timer[age_timer.size() - 1];
            age_timer.pop_back();
            timer.push_back(val);
        }
        dec_mitm_item_quantity(obj, rot_count);
        _compare_blood_quantity(blood, timer.size());
        return;
    }

    // Else, create a new stack of potions.
    int o = get_item_slot(20);
    if (o == NON_ITEM)
        return;

    item_def &item = mitm[o];
    item.base_type = OBJ_POTIONS;
    item.sub_type  = POT_BLOOD_COAGULATED;
    item.quantity  = coag_count;
    item.plus      = 0;
    item.plus2     = 0;
    item.special   = 0;
    item.flags     = 0;
    item_colour(item);

    CrawlHashTable &props_new = item.props;
    props_new["timer"].new_vector(SV_LONG, SFLAG_CONST_TYPE);
    CrawlVector &timer_new = props_new["timer"].get_vector();

    long val;
    while (!age_timer.empty())
    {
        val = age_timer[age_timer.size() - 1];
        age_timer.pop_back();
        timer_new.push_back(val);
    }
    ASSERT(timer_new.size() == coag_count);
    props_new.assert_validity();

    if (blood.held_by_monster())
        move_item_to_grid(&o, blood.holding_monster()->pos());
    else
        move_item_to_grid(&o, blood.pos);

    dec_mitm_item_quantity(obj, rot_count + coag_count);
    _compare_blood_quantity(blood, timer.size());
}

static std::string _get_desc_quantity(const int quant, const int total)
{
    if (total == quant)
        return "Your";
    else if (quant == 1)
        return "One of your";
    else if (quant == 2)
        return "Two of your";
    else if (quant >= (total * 3) / 4)
        return "Most of your";
    else
        return "Some of your";
}

// Prints messages for blood potions coagulating in inventory (coagulate = true)
// or whenever potions are cursed into potions of decay (coagulate = false).
static void _potion_stack_changed_message(item_def &potion, int num_changed,
                                          std::string verb)
{
    ASSERT(num_changed > 0);

    verb = replace_all(verb, "%s", num_changed == 1 ? "s" : "");
    mprf(MSGCH_ROTTEN_MEAT, "%s %s %s.",
         _get_desc_quantity(num_changed, potion.quantity).c_str(),
         potion.name(DESC_PLAIN, false).c_str(),
         verb.c_str());
}

// Returns true if "equipment weighs less" message needed.
// Also handles coagulation messages.
bool maybe_coagulate_blood_potions_inv(item_def &blood)
{
    ASSERT(blood.is_valid());
    ASSERT(is_blood_potion(blood));

    CrawlHashTable &props = blood.props;
    if (!props.exists("timer"))
        init_stack_blood_potions(blood, blood.special);

    ASSERT(props.exists("timer"));
    CrawlVector &timer = props["timer"].get_vector();
    _compare_blood_quantity(blood, timer.size());
    ASSERT(!timer.empty());

    // blood.sub_type could be POT_BLOOD or POT_BLOOD_COAGULATED
    // -> need different handling
    int rot_limit  = you.num_turns;
    int coag_limit = you.num_turns + 500; // check 500 turns later

    // First count whether coagulating is even necessary.
    int rot_count  = 0;
    int coag_count = 0;
    std::vector<long> age_timer;
    long current;
    const int size = timer.size();
    for (int i = 0; i < size; i++)
    {
        current = timer[timer.size()-1].get_long();
        if (current > coag_limit
            || blood.sub_type == POT_BLOOD_COAGULATED && current > rot_limit)
        {
            // Still some time until rotting/coagulating.
            break;
        }

        timer.pop_back();
        if (current <= rot_limit)
            rot_count++;
        else if (blood.sub_type == POT_BLOOD && current <= coag_limit)
        {
            coag_count++;
            age_timer.push_back(current);
        }
    }

    if (!rot_count && !coag_count)
        return (false); // Nothing to be done.

#ifdef DEBUG_BLOOD_POTIONS
    mprf(MSGCH_DIAGNOSTICS, "in maybe_coagulate_blood_potions_INV "
                            "(turns: %d)", you.num_turns);

    mprf(MSGCH_DIAGNOSTICS, "coagulated: %d, rotted: %d, total: %d",
                            coag_count, rot_count, blood.quantity);
    more();
#endif

    // just in case
    you.wield_change  = true;
    you.redraw_quiver = true;

    const bool knew_coag  = (get_ident_type(OBJ_POTIONS, POT_BLOOD_COAGULATED)
                                == ID_KNOWN_TYPE);

    if (!coag_count) // Some potions rotted away, but none coagulated.
    {
        // Only coagulated blood can rot.
        ASSERT(blood.sub_type == POT_BLOOD_COAGULATED);
        _potion_stack_changed_message(blood, rot_count, "rot%s away");
        blood.quantity -= rot_count;

        if (!knew_coag)
        {
            set_ident_type( OBJ_POTIONS, POT_BLOOD_COAGULATED, ID_KNOWN_TYPE );
            if (blood.quantity >= 1)
                mpr(blood.name(DESC_INVENTORY).c_str());
        }

        if (blood.quantity < 1)
        {
            if (you.equip[EQ_WEAPON] == blood.link)
                you.equip[EQ_WEAPON] = -1;

            destroy_item(blood);
        }
        else
            _compare_blood_quantity(blood, timer.size());

        return (true);
    }

    // Coagulated blood cannot coagulate any further...
    ASSERT(blood.sub_type == POT_BLOOD);

    const bool knew_blood = get_ident_type(OBJ_POTIONS, POT_BLOOD)
                                == ID_KNOWN_TYPE;

    _potion_stack_changed_message(blood, coag_count, "coagulate%s");

    // Identify both blood and coagulated blood, if necessary.
    if (!knew_blood)
        set_ident_type( OBJ_POTIONS, POT_BLOOD, ID_KNOWN_TYPE );

    if (!knew_coag)
        set_ident_type( OBJ_POTIONS, POT_BLOOD_COAGULATED, ID_KNOWN_TYPE );

    // Now that coagulating is necessary, check inventory for !coagulated blood.
    for (int m = 0; m < ENDOFPACK; m++)
    {
        if (!you.inv[m].is_valid())
            continue;

        if (you.inv[m].base_type == OBJ_POTIONS
            && you.inv[m].sub_type == POT_BLOOD_COAGULATED)
        {
            CrawlHashTable &props2 = you.inv[m].props;
            if (!props2.exists("timer"))
                init_stack_blood_potions(you.inv[m], you.inv[m].special);

            ASSERT(props2.exists("timer"));
            CrawlVector &timer2 = props2["timer"].get_vector();

            blood.quantity -= coag_count + rot_count;
            if (blood.quantity < 1)
            {
                if (you.equip[EQ_WEAPON] == blood.link)
                    you.equip[EQ_WEAPON] = -1;

                destroy_item(blood);
            }
            else
            {
                _compare_blood_quantity(blood, timer.size());
                if (!knew_blood)
                    mpr(blood.name(DESC_INVENTORY).c_str());
            }

            // Update timer -> push(pop).
            long val;
            while (!age_timer.empty())
            {
                val = age_timer[age_timer.size() - 1];
                age_timer.pop_back();
                timer2.push_back(val);
            }

            you.inv[m].quantity += coag_count;
            ASSERT(timer2.size() == you.inv[m].quantity);
            if (!knew_coag)
                mpr(you.inv[m].name(DESC_INVENTORY).c_str());

            // re-sort timer
            _long_sort(timer2);

            return (rot_count > 0);
        }
    }

    // If entire stack has coagulated, simply change subtype.
    if (rot_count + coag_count == blood.quantity)
    {
        ASSERT(timer.empty());
        // Update subtype.
        blood.sub_type = POT_BLOOD_COAGULATED;
        item_colour(blood);

        // Re-fill vector.
        long val;
        while (!age_timer.empty())
        {
            val = age_timer[age_timer.size() - 1];
            age_timer.pop_back();
            timer.push_back(val);
        }
        blood.quantity -= rot_count;
        // Stack still exists because of coag_count.
        _compare_blood_quantity(blood, timer.size());

        if (!knew_coag)
            mpr(blood.name(DESC_INVENTORY).c_str());

        return (rot_count > 0);
    }

    // Else, create new stack in inventory.
    int freeslot = find_free_slot(blood);
    if (freeslot >= 0 && freeslot < ENDOFPACK)
    {
        item_def &item   = you.inv[freeslot];
        item.clear();

        item.link        = freeslot;
        item.slot        = index_to_letter(item.link);
        item.base_type   = OBJ_POTIONS;
        item.sub_type    = POT_BLOOD_COAGULATED;
        item.quantity    = coag_count;
        item.plus        = 0;
        item.plus2       = 0;
        item.special     = 0;
        item.flags       = (ISFLAG_KNOW_TYPE & ISFLAG_BEEN_IN_INV);
        item.pos.set(-1, -1);
        item_colour(item);

        CrawlHashTable &props_new = item.props;
        props_new["timer"].new_vector(SV_LONG, SFLAG_CONST_TYPE);
        CrawlVector &timer_new = props_new["timer"].get_vector();

        long val;
        while (!age_timer.empty())
        {
            val = age_timer[age_timer.size() - 1];
            age_timer.pop_back();
            timer_new.push_back(val);
        }

        ASSERT(timer_new.size() == coag_count);
        props_new.assert_validity();

        blood.quantity -= coag_count + rot_count;
        _compare_blood_quantity(blood, timer.size());

        if (!knew_blood)
            mpr(blood.name(DESC_INVENTORY).c_str());
        if (!knew_coag)
            mpr(item.name(DESC_INVENTORY).c_str());

        return (rot_count > 0);
    }

    // No space in inventory, check floor.
    int o = igrd(you.pos());
    while (o != NON_ITEM)
    {
        if (mitm[o].base_type == OBJ_POTIONS
            && mitm[o].sub_type == POT_BLOOD_COAGULATED)
        {
            // Merge with existing stack.
            CrawlHashTable &props2 = mitm[o].props;
            if (!props2.exists("timer"))
                init_stack_blood_potions(mitm[o], mitm[o].special);

            ASSERT(props2.exists("timer"));
            CrawlVector &timer2 = props2["timer"].get_vector();
            ASSERT(timer2.size() == mitm[o].quantity);

            // Update timer -> push(pop).
            long val;
            while (!age_timer.empty())
            {
                val = age_timer[age_timer.size() - 1];
                age_timer.pop_back();
                timer2.push_back(val);
            }
            _long_sort(timer2);

            inc_mitm_item_quantity(o, coag_count);
            ASSERT(timer2.size() == mitm[o].quantity);
            dec_inv_item_quantity(blood.link, rot_count + coag_count);
            _compare_blood_quantity(blood, timer.size());
            if (!knew_blood)
                mpr(blood.name(DESC_INVENTORY).c_str());

            return (true);
        }
        o = mitm[o].link;
    }
    // If we got here nothing was found!

    // Create a new stack of potions.
    o = get_item_slot();
    if (o == NON_ITEM)
        return (false);

    // These values are common to all: {dlb}
    mitm[o].base_type = OBJ_POTIONS;
    mitm[o].sub_type  = POT_BLOOD_COAGULATED;
    mitm[o].quantity  = coag_count;
    mitm[o].plus      = 0;
    mitm[o].plus2     = 0;
    mitm[o].special   = 0;
    mitm[o].flags     = (ISFLAG_KNOW_TYPE & ISFLAG_BEEN_IN_INV);
    item_colour(mitm[o]);

    CrawlHashTable &props_new = mitm[o].props;
    props_new["timer"].new_vector(SV_LONG, SFLAG_CONST_TYPE);
    CrawlVector &timer_new = props_new["timer"].get_vector();

    long val;
    while (!age_timer.empty())
    {
        val = age_timer[age_timer.size() - 1];
        age_timer.pop_back();
        timer_new.push_back(val);
    }

    ASSERT(timer_new.size() == coag_count);
    props_new.assert_validity();
    move_item_to_grid(&o, you.pos());

    blood.quantity -= rot_count + coag_count;
    if (blood.quantity < 1)
    {
        if (you.equip[EQ_WEAPON] == blood.link)
            you.equip[EQ_WEAPON] = -1;

        destroy_item(blood);
    }
    else
    {
        _compare_blood_quantity(blood, timer.size());
        if (!knew_blood)
            mpr(blood.name(DESC_INVENTORY).c_str());
    }
    return (true);
}

// Removes the oldest timer of a stack of blood potions.
// Mostly used for (q)uaff, (f)ire, and Evaporate.
long remove_oldest_blood_potion(item_def &stack)
{
    ASSERT(stack.is_valid());
    ASSERT(is_blood_potion(stack));

    CrawlHashTable &props = stack.props;
    if (!props.exists("timer"))
        init_stack_blood_potions(stack, stack.special);
    ASSERT(props.exists("timer"));
    CrawlVector &timer = props["timer"].get_vector();
    ASSERT(!timer.empty());

    // Assuming already sorted, and first (oldest) potion valid.
    const long val = timer[timer.size() - 1].get_long();
    timer.pop_back();

    // The quantity will be decreased elsewhere.
    return (val);
}

// Used whenever copies of blood potions have to be cleaned up.
void remove_newest_blood_potion(item_def &stack, int quant)
{
    ASSERT(stack.is_valid());
    ASSERT(is_blood_potion(stack));

    CrawlHashTable &props = stack.props;
    if (!props.exists("timer"))
        init_stack_blood_potions(stack, stack.special);
    ASSERT(props.exists("timer"));
    CrawlVector &timer = props["timer"].get_vector();
    ASSERT(!timer.empty());

    if (quant == -1)
        quant = timer.size() - stack.quantity;

    // Overwrite newest potions with oldest ones.
    int repeats = stack.quantity;
    if (repeats > quant)
        repeats = quant;

    for (int i = 0; i < repeats; i++)
    {
        timer[i] = timer[timer.size() - 1];
        timer.pop_back();
    }

    // Now remove remaining oldest potions...
    repeats = quant - repeats;
    for (int i = 0; i < repeats; i++)
        timer.pop_back();

    // ... and re-sort.
    _long_sort(timer);
}

void merge_blood_potion_stacks(item_def &source, item_def &dest, int quant)
{
    if (!source.is_valid() || !dest.is_valid())
        return;

    ASSERT(quant > 0 && quant <= source.quantity);
    ASSERT(is_blood_potion(source) && is_blood_potion(dest));

    CrawlHashTable &props = source.props;
    if (!props.exists("timer"))
        init_stack_blood_potions(source, source.special);
    ASSERT(props.exists("timer"));
    CrawlVector &timer = props["timer"].get_vector();
    ASSERT(!timer.empty());

    CrawlHashTable &props2 = dest.props;
    if (!props2.exists("timer"))
        init_stack_blood_potions(dest, dest.special);
    ASSERT(props2.exists("timer"));
    CrawlVector &timer2 = props2["timer"].get_vector();

    // Update timer -> push(pop).
    for (int i = 0; i < quant; i++)
    {
        timer2.push_back(timer[timer.size() - 1].get_long());
        timer.pop_back();
    }

    // Re-sort timer.
    _long_sort(timer2);
}

// Deliberately don't check for rottenness here, so this check
// can also be used to verify whether you *could* have bottled
// a now rotten corpse.
bool can_bottle_blood_from_corpse(int mons_type)
{
    if (you.species != SP_VAMPIRE || you.experience_level < 6
        || !mons_has_blood(mons_type))
    {
        return (false);
    }

    int chunk_type = mons_corpse_effect( mons_type );
    if (chunk_type == CE_CLEAN || chunk_type == CE_CONTAMINATED)
        return (true);

    return (false);
}

int num_blood_potions_from_corpse(int mons_class, int chunk_type)
{
    if (chunk_type == -1)
        chunk_type = mons_corpse_effect(mons_class);

    // Max. amount is about one third of the max. amount for chunks.
    const int max_chunks = mons_weight( mons_class ) / 150;

    // Max. amount is about one third of the max. amount for chunks.
    int pot_quantity = max_chunks/3;
        pot_quantity = stepdown_value( pot_quantity, 2, 2, 6, 6 );

    // Halve number of potions obtained from contaminated chunk type corpses.
    if (chunk_type == CE_CONTAMINATED)
        pot_quantity /= 2;

    if (pot_quantity < 1)
        pot_quantity = 1;

    return (pot_quantity);
}

// If autopickup is active, the potions are auto-picked up after creation.
void turn_corpse_into_blood_potions(item_def &item)
{
    ASSERT(item.base_type == OBJ_CORPSES);
    ASSERT(!food_is_rotten(item));

    item_def corpse = item;
    const int mons_class = corpse.plus;

    ASSERT(can_bottle_blood_from_corpse(mons_class));

    item.base_type = OBJ_POTIONS;
    item.sub_type  = POT_BLOOD;
    item_colour(item);
    item.flags    &= ~(ISFLAG_THROWN | ISFLAG_DROPPED);

    item.quantity = num_blood_potions_from_corpse(mons_class);

    // Initialise timer depending on corpse age:
    // almost rotting: age = 100 --> potion timer =  500 --> will coagulate soon
    // freshly killed: age = 200 --> potion timer = 2500 --> fresh !blood
    init_stack_blood_potions(item, (item.special - 100) * 20 + 500);

    // Happens after the blood has been bottled.
    if (monster_descriptor(mons_class, MDSC_LEAVES_HIDE) && !one_chance_in(3))
        _create_monster_hide(corpse);
}

void turn_corpse_into_skeleton_and_blood_potions(item_def &item)
{
    item_def blood_potions = item;

    if (mons_skeleton(item.plus))
        turn_corpse_into_skeleton(item);

    int o = get_item_slot();
    if (o != NON_ITEM)
    {
        turn_corpse_into_blood_potions(blood_potions);
        copy_item_to_grid(blood_potions, you.pos());
    }
}

// A variation of the mummy curse:
// Instead of trashing the entire stack, split the stack and only turn part
// of it into POT_DECAY.
void split_potions_into_decay( int obj, int amount, bool need_msg )
{
    ASSERT(obj != -1);
    item_def &potion = you.inv[obj];

    ASSERT(potion.is_valid());
    ASSERT(potion.base_type == OBJ_POTIONS);
    ASSERT(amount > 0);
    ASSERT(amount <= potion.quantity);

    // Output decay message.
    if (need_msg && get_ident_type(OBJ_POTIONS, POT_DECAY) == ID_KNOWN_TYPE)
        _potion_stack_changed_message(potion, amount, "decay%s");

    if (you.equip[EQ_WEAPON] == obj)
        you.wield_change = true;
    you.redraw_quiver = true;

    if (is_blood_potion(potion))
    {
        // We're being nice here, and only decay the *oldest* potions.
        for (int i = 0; i < amount; i++)
            remove_oldest_blood_potion(potion);
    }

    // Try to merge into existing stacks of decayed potions.
    for (int m = 0; m < ENDOFPACK; m++)
    {
        if (you.inv[m].base_type == OBJ_POTIONS
            && you.inv[m].sub_type == POT_DECAY)
        {
            if (potion.quantity == amount)
            {
                if (you.equip[EQ_WEAPON] == obj)
                    you.equip[EQ_WEAPON] = -1;

                destroy_item(potion);
            }
            else
                you.inv[obj].quantity -= amount;

            you.inv[m].quantity += amount;
            return;
        }
    }

    // Else, if entire stack affected just change subtype.
    if (amount == potion.quantity)
    {
        you.inv[obj].sub_type = POT_DECAY;
        unset_ident_flags( you.inv[obj], ISFLAG_IDENT_MASK ); // all different
        return;
    }

    // Else, create new stack in inventory.
    int freeslot = find_free_slot(you.inv[obj]);
    if (freeslot >= 0 && freeslot < ENDOFPACK
        && !you.inv[freeslot].is_valid())
    {
        item_def &item   = you.inv[freeslot];
        item.link        = freeslot;
        item.slot        = index_to_letter(item.link);
        item.base_type   = OBJ_POTIONS;
        item.sub_type    = POT_DECAY;
        item.quantity    = amount;
        // Keep description as it was.
        item.plus        = potion.plus;
        item.plus2       = 0;
        item.special     = 0;
        item.flags       = 0;
        item.colour      = potion.colour;
        item.inscription.clear();
        item.pos.set(-1, -1);

        you.inv[obj].quantity -= amount;
        return;
    }
    // Okay, inventory is full.

    // Check whether we can merge with an existing stack on the floor.
    for (stack_iterator si(you.pos()); si; ++si)
    {
        if (si->base_type == OBJ_POTIONS && si->sub_type == POT_DECAY)
        {
            dec_inv_item_quantity(obj, amount);
            inc_mitm_item_quantity(si->index(), amount);
            return;
        }
    }

    item_def potion2;
    potion2.base_type = OBJ_POTIONS;
    potion2.sub_type  = POT_DECAY;
    // Keep description as it was.
    potion2.plus      = potion.plus;
    potion2.quantity  = amount;
    potion2.colour    = potion.colour;
    potion2.plus2     = 0;
    potion2.flags     = 0;
    potion2.special   = 0;

    copy_item_to_grid(potion2, you.pos());

    // Is decreased even if the decay stack goes splat.
    dec_inv_item_quantity(obj, amount);
}

static bool allow_bleeding_on_square(const coord_def& where)
{
    // No bleeding onto sanctuary ground, please.
    // Also not necessary if already covered in blood.
    if (is_bloodcovered(where) || is_sanctuary(where))
        return (false);

    // No spattering into lava or water.
    if (grd(where) >= DNGN_LAVA && grd(where) < DNGN_FLOOR)
        return (false);

    // No spattering into fountains (other than blood).
    if (grd(where) == DNGN_FOUNTAIN_BLUE
        || grd(where) == DNGN_FOUNTAIN_SPARKLING)
    {
        return (false);
    }

    // The good gods like to keep their altars pristine.
    if (is_good_god(feat_altar_god(grd(where))))
        return (false);

    return (true);
}

bool maybe_bloodify_square(const coord_def& where)
{
    if (!allow_bleeding_on_square(where))
        return (false);

    env.pgrid(where) |= FPROP_BLOODY;
    return(true);
}

static void _maybe_bloodify_square(const coord_def& where, int amount,
                                   bool spatter = false,
                                   bool smell_alert = true)
{
    if (amount < 1)
        return;

    bool may_bleed = allow_bleeding_on_square(where);
    if (!spatter && !may_bleed)
        return;

    if (x_chance_in_y(amount, 20))
    {
        dprf("might bleed now; square: (%d, %d); amount = %d",
             where.x, where.y, amount);
        if (may_bleed)
        {
            env.pgrid(where) |= FPROP_BLOODY;

            if (smell_alert)
                blood_smell(12, where);
        }

        if (spatter)
        {
            // Smaller chance of spattering surrounding squares.
            for (adjacent_iterator ai(where); ai; ++ai)
            {
                // Spattering onto walls etc. less likely.
                if (grd(*ai) < DNGN_MINMOVE && !one_chance_in(3))
                    continue;

                _maybe_bloodify_square(*ai, amount/15);
            }
        }
    }
}

// Currently flavour only: colour ground (and possibly adjacent squares) red.
// "damage" depends on damage taken (or hitpoints, if damage higher),
// or, for sacrifices, on the number of chunks possible to get out of a corpse.
void bleed_onto_floor(const coord_def& where, monster_type montype,
                      int damage, bool spatter, bool smell_alert)
{
    ASSERT(in_bounds(where));

    if (montype == MONS_PLAYER && !you.can_bleed())
        return;

    if (montype != NUM_MONSTERS && montype != MONS_PLAYER)
    {
        monsters m;
        m.type = montype;
        if (!m.can_bleed())
            return;
    }

    _maybe_bloodify_square(where, damage, spatter, smell_alert);
}

void blood_spray(const coord_def& origin, monster_type montype, int level)
{
    los_def ld(origin, opc_solid);

    ld.update();

    int tries = 0;
    for (int i = 0; i < level; ++i)
    {
        // Blood drops are small and light and suffer a lot of wind
        // resistance.
        int range = random2(8) + 1;

        while (tries < 5000)
        {
            ++tries;

            coord_def bloody = origin;
            bloody.x += random_range(-range, range);
            bloody.y += random_range(-range, range);

            if (in_bounds(bloody) && ld.see_cell(bloody))
            {
                if (feat_is_solid(grd(bloody)) && coinflip())
                    continue;

                bleed_onto_floor(bloody, montype, 99);
                break;
            }
        }
    }
}

static void _spatter_neighbours(const coord_def& where, int chance)
{
    for (adjacent_iterator ai(where, false); ai; ++ai)
    {
        if (!allow_bleeding_on_square(*ai))
            continue;

        if (grd(*ai) < DNGN_MINMOVE && !one_chance_in(3))
            continue;

        if (one_chance_in(chance))
        {
            env.pgrid(*ai) |= FPROP_BLOODY;
            _spatter_neighbours(*ai, chance+1);
        }
    }
}

void generate_random_blood_spatter_on_level()
{
    int startprob;

    // startprob is used to initialise the chance for neighbours being
    // spattered, which will be decreased by 1 per recursion round.
    // We then use one_chance_in(chance) to determine whether to spatter a
    // given grid or not. Thus, startprob = 1 means that initially all
    // surrounding grids will be spattered (3x3), and the _higher_ startprob
    // the _lower_ the overall chance for spattering and the _smaller_ the
    // bloodshed area.

    const int max_cluster = 7 + random2(9);

    // Lower chances for large bloodshed areas if we have many clusters,
    // but increase chances if we have few.
    // Chances for startprob are [1..3] for 7-9 clusters,
    //                       ... [1..4] for 10-12 clusters, and
    //                       ... [2..5] for 13-15 clusters.

    int min_prob = 1;
    int max_prob = 4;

    if (max_cluster < 10)
        max_prob--;
    else if (max_cluster > 12)
        min_prob++;

    for (int i = 0; i < max_cluster; ++i)
    {
        coord_def c = random_in_bounds();
        startprob = min_prob + random2(max_prob);

        maybe_bloodify_square(c);

        _spatter_neighbours(c, startprob);
    }
}

void search_around(bool only_adjacent)
{
    ASSERT(!crawl_state.arena);

    // Traps and doors stepdown skill:
    // skill/(2x-1) for squares at distance x
    int max_dist = (you.skills[SK_TRAPS_DOORS] + 1) / 2;
    if (max_dist > 5)
        max_dist = 5;
    if (only_adjacent && max_dist > 1 || max_dist < 1)
        max_dist = 1;

    for (radius_iterator ri(you.pos(), max_dist); ri; ++ri )
    {
        // Must have LOS, with no translucent walls in the way.
        if (you.see_cell_no_trans(*ri))
        {
            // Maybe we want distance() instead of feat_distance()?
            int dist = grid_distance(*ri, you.pos());

            // Don't exclude own square; may be levitating.
            // XXX: Currently, levitating over a trap will always detect it.
            if (dist == 0)
                ++dist;

            // Making this harsher by removing the old +1...
            int effective = you.skills[SK_TRAPS_DOORS] / (2*dist - 1);

            if (grd(*ri) == DNGN_SECRET_DOOR && x_chance_in_y(effective+1, 17))
            {
                mpr("You found a secret door!");
                reveal_secret_door(*ri);
                exercise(SK_TRAPS_DOORS, (coinflip() ? 2 : 1));
            }
            else if (grd(*ri) == DNGN_UNDISCOVERED_TRAP
                     && x_chance_in_y(effective + 1, 17))
            {
                trap_def* ptrap = find_trap(*ri);
                if (ptrap)
                {
                    ptrap->reveal();
                    mpr("You found a trap!");
                    learned_something_new(TUT_SEEN_TRAP, *ri);
                    exercise(SK_TRAPS_DOORS, (coinflip() ? 2 : 1));
                }
                else
                {
                    // Maybe we shouldn't kill the trap for debugging
                    // purposes - oh well.
                    grd(*ri) = DNGN_FLOOR;
                    dprf("You found a buggy trap! It vanishes!");
                }
            }
        }
    }
}

bool merfolk_change_is_safe(bool quiet)
{
    // If already transformed, no subsequent transformation necessary.
    if (!you.airborne() && feat_is_water(grd(you.pos())))
        return (true);

    std::set<equipment_type> r;
    r.insert(EQ_BOOTS);

    if (check_transformation_stat_loss(r, quiet))
        return (false);

    return (true);
}

void merfolk_start_swimming()
{
    if (you.attribute[ATTR_TRANSFORMATION] != TRAN_NONE)
        untransform();

    remove_one_equip(EQ_BOOTS);
    you.redraw_evasion = true;
}

static void exit_stair_message(dungeon_feature_type stair, bool /* going_up */)
{
    if (feat_is_escape_hatch(stair))
        mpr("The hatch slams shut behind you.");
}

static void climb_message(dungeon_feature_type stair, bool going_up,
                          level_area_type old_level_type)
{
    if (old_level_type != LEVEL_DUNGEON)
        return;

    if (feat_is_portal(stair))
        mpr("The world spins around you as you enter the gateway.");
    else if (feat_is_escape_hatch(stair))
    {
        if (going_up)
            mpr("A mysterious force pulls you upwards.");
        else
        {
            mprf("You %s downwards.",
                 you.flight_mode() == FL_FLY ? "fly" :
                     (you.airborne() ? "float" : "slide"));
        }
    }
    else if (feat_is_gate(stair))
    {
        mprf("You %s %s through the gate.",
             you.flight_mode() == FL_FLY ? "fly" :
                   (you.airborne() ? "float" : "go"),
             going_up ? "up" : "down");
    }
    else
    {
        mprf("You %s %swards.",
             you.flight_mode() == FL_FLY ? "fly" :
                   (you.airborne() ? "float" : "climb"),
             going_up ? "up" : "down");
    }
}

static void leaving_level_now()
{
    // Note the name ahead of time because the events may cause markers
    // to be discarded.
    const std::string newtype =
        env.markers.property_at(you.pos(), MAT_ANY, "dst");

    // Extension to use for bones files.
    const std::string newext =
        env.markers.property_at(you.pos(), MAT_ANY, "dstext");

    const std::string oldname = you.level_type_name;
    std::string newname =
        env.markers.property_at(you.pos(), MAT_ANY, "dstname");

    std::string neworigin =
        env.markers.property_at(you.pos(), MAT_ANY, "dstorigin");

    const std::string oldname_abbrev = you.level_type_name_abbrev;
    std::string newname_abbrev =
        env.markers.property_at(you.pos(), MAT_ANY, "dstname_abbrev");

    dungeon_events.fire_position_event(DET_PLAYER_CLIMBS, you.pos());
    dungeon_events.fire_event(DET_LEAVING_LEVEL);

    // Lua scripts explicitly set level_type_name, so use that.
    if (you.level_type_name != oldname)
        newname = you.level_type_name;

    // Lua scripts explicitly set level_type_name_abbrev, so use that.
    if (you.level_type_name_abbrev != oldname_abbrev)
        newname_abbrev = you.level_type_name_abbrev;

    if (newname_abbrev.length() > MAX_NOTE_PLACE_LEN)
    {
        mprf(MSGCH_ERROR, "'%s' is too long for a portal vault name "
                          "abbreviation, truncating");
        newname_abbrev = newname_abbrev.substr(0, MAX_NOTE_PLACE_LEN);
    }

    you.level_type_origin = "";
    // Lua scripts explicitly set level_type_origin, so use that.
    if (!you.level_type_origin.empty())
        neworigin = you.level_type_origin;

    // Don't clobber level_type_name for stairs in portal vaults.
    if (you.level_type_name.empty() || !newname.empty()
        || you.level_type != LEVEL_PORTAL_VAULT)
    {
        you.level_type_name = newname;
    }

    // Don't clobber level_type_name_abbrev for stairs in portal vaults.
    if (you.level_type_name_abbrev.empty() || !newname_abbrev.empty()
        || you.level_type != LEVEL_PORTAL_VAULT)
    {
        you.level_type_name_abbrev = newname_abbrev;
    }

    if (you.level_type_tag.empty() || !newtype.empty()
        || you.level_type != LEVEL_PORTAL_VAULT)
    {
        you.level_type_tag = newtype;
    }

    const std::string spaced_tag = replace_all(you.level_type_tag, "_", " ");

    if (!you.level_type_tag.empty() && you.level_type_name.empty())
        you.level_type_name = spaced_tag;

    if (!you.level_type_name.empty() && you.level_type_name_abbrev.empty())
    {
        if (you.level_type_name.length() <= MAX_NOTE_PLACE_LEN)
            you.level_type_name_abbrev = you.level_type_name;
        else if (you.level_type_tag.length() <= MAX_NOTE_PLACE_LEN)
            you.level_type_name_abbrev = spaced_tag;
        else
        {
            const std::string shorter =
                you.level_type_name.length() < you.level_type_tag.length() ?
                    you.level_type_name : spaced_tag;

            you.level_type_name_abbrev = shorter.substr(0, MAX_NOTE_PLACE_LEN);
        }
    }

    if (!newext.empty())
        you.level_type_ext = newext;
    else if (!you.level_type_tag.empty())
        you.level_type_ext = lowercase_string(you.level_type_tag);

    if (you.level_type_ext.length() > 3)
        you.level_type_ext = you.level_type_ext.substr(0, 3);

    if (!neworigin.empty())
        you.level_type_origin = neworigin;
    else if (!you.level_type_name.empty())
    {
        std::string lname = lowercase_string(you.level_type_name);
        std::string article, prep;

        if (starts_with(lname, "level ")
            || lname.find(":") != std::string::npos)
        {
            prep = "on ";
        }
        else
            prep = "in ";

        if (starts_with(lname, "a ") || starts_with(lname, "an ")
            || starts_with(lname, "the ") || starts_with(lname, "level ")
            || lname.find(":") != std::string::npos)
        {
            ; // Doesn't need an article
        }
        else
        {
            char letter = you.level_type_name[0];
            if (isupper(letter))
                article = "the ";
            else if (is_vowel(letter))
                article = "an ";
            else
                article = "a ";
        }

        you.level_type_origin  = prep + article + you.level_type_name;
    }
}

static void set_entry_cause(entry_cause_type default_cause,
                            level_area_type old_level_type)
{
    ASSERT(default_cause != NUM_ENTRY_CAUSE_TYPES);

    if (old_level_type == you.level_type && you.entry_cause != EC_UNKNOWN)
        return;

    if (crawl_state.is_god_acting())
    {
        if (crawl_state.is_god_retribution())
            you.entry_cause = EC_GOD_RETRIBUTION;
        else
            you.entry_cause = EC_GOD_ACT;

        you.entry_cause_god = crawl_state.which_god_acting();
    }
    else if (default_cause != EC_UNKNOWN)
    {
        you.entry_cause     = default_cause;
        you.entry_cause_god = GOD_NO_GOD;
    }
    else
    {
        you.entry_cause     = EC_SELF_EXPLICIT;
        you.entry_cause_god = GOD_NO_GOD;
    }
}

static int runes_in_pack(std::vector<int> &runes)
{
    int num_runes = 0;

    for (int i = 0; i < ENDOFPACK; i++)
    {
        if (you.inv[i].is_valid()
            && you.inv[i].base_type == OBJ_MISCELLANY
            && you.inv[i].sub_type == MISC_RUNE_OF_ZOT)
        {
            num_runes += you.inv[i].quantity;
            for (int q = 1;
                 runes.size() < 3 && q <= you.inv[i].quantity; ++q)
            {
                runes.push_back(i);
            }
        }
    }

    return num_runes;
}

bool check_annotation_exclusion_warning()
{
    // Players might not realise the implications of teleport mutations
    // in the labyrinth.
    if (grd(you.pos()) == DNGN_ENTER_LABYRINTH
        && player_mutation_level(MUT_TELEPORT))
    {
        mpr("Within the labyrinth you'll only be able to teleport away from "
            "the exit!");
        if (!yesno("Continue anyway?", false, 'N', true, false))
        {
            canned_msg(MSG_OK);
            interrupt_activity( AI_FORCE_INTERRUPT );
            return (false);
        }
        return (true);
    }

    level_id  next_level_id = level_id::get_next_level_id(you.pos());

    crawl_state.level_annotation_shown = false;
    bool might_be_dangerous = false;

    if (level_annotation_has("!", next_level_id)
        && next_level_id != level_id::current()
        && next_level_id.level_type == LEVEL_DUNGEON)
    {
        mpr("Warning: level annotation for next level is:", MSGCH_PROMPT);
        mpr(get_level_annotation(next_level_id).c_str(), MSGCH_PLAIN, YELLOW);
        might_be_dangerous = true;
        crawl_state.level_annotation_shown = true;
    }
    else if (is_exclude_root(you.pos()))
    {
        mpr("This staircase is marked as excluded!", MSGCH_WARN);
        might_be_dangerous = true;
    }

    if (might_be_dangerous
        && !yesno("Enter next level anyway?", true, 'n', true, false))
    {
        canned_msg(MSG_OK);
        interrupt_activity( AI_FORCE_INTERRUPT );
        crawl_state.level_annotation_shown = false;
        return (false);
    }
    return (true);
}

static void _player_change_level_reset()
{
    you.prev_targ  = MHITNOT;
    if (you.pet_target != MHITYOU)
        you.pet_target = MHITNOT;

    you.prev_grd_targ.reset();
}

static level_id _stair_destination_override()
{
    const std::string force_place =
        env.markers.property_at(you.pos(), MAT_ANY, "dstplace");
    if (!force_place.empty())
    {
        try
        {
            const level_id place = level_id::parse_level_id(force_place);
            return (place);
        }
        catch (const std::string &err)
        {
            end(1, false, "Marker set with invalid level name: %s",
                force_place.c_str());
        }
    }

    const level_id invalid;
    return (invalid);
}

static bool _stair_force_destination(const level_id &override)
{
    if (override.is_valid())
    {
        if (override.level_type == LEVEL_DUNGEON)
        {
            you.where_are_you = override.branch;
            you.your_level    = override.absdepth();
            you.level_type    = override.level_type;
        }
        else
        {
            you.level_type = override.level_type;
        }
        return (true);
    }
    return (false);
}

static void _player_change_level_upstairs(dungeon_feature_type stair_find,
                                          const level_id &place_override)
{
    if (_stair_force_destination(place_override))
        return;

    if (you.level_type == LEVEL_DUNGEON)
        you.your_level--;

    // Make sure we return to our main dungeon level... labyrinth entrances
    // in the abyss or pandemonium are a bit trouble (well the labyrinth does
    // provide a way out of those places, its really not that bad I suppose).
    if (level_type_exits_up(you.level_type))
        you.level_type = LEVEL_DUNGEON;

    if (player_in_branch( BRANCH_VESTIBULE_OF_HELL ))
    {
        you.where_are_you = BRANCH_MAIN_DUNGEON;
        you.your_level = you.hell_exit;
    }

    if (player_in_hell())
    {
        you.where_are_you = BRANCH_VESTIBULE_OF_HELL;
        you.your_level = 27;
    }

    // Did we take a branch stair?
    for (int i = 0; i < NUM_BRANCHES; ++i)
    {
        if (branches[i].exit_stairs == stair_find
            && you.where_are_you == i)
        {
            you.where_are_you = branches[i].parent_branch;

            // If leaving a branch which wasn't generated in this
            // particular game (like the Swamp or Shoals), then
            // its startdepth is set to -1; compensate for that,
            // so we don't end up on "level -1".
            if (branches[i].startdepth == -1)
                you.your_level += 2;
            break;
        }
    }
}

static bool _marker_vetoes_level_change()
{
    return (marker_vetoes_operation("veto_level_change"));
}

static bool _stair_moves_pre(dungeon_feature_type stair)
{
    if (crawl_state.prev_cmd == CMD_WIZARD)
        return (false);

    if (stair != grd(you.pos()))
        return (false);

    if (feat_stair_direction(stair) == CMD_NO_CMD)
        return (false);

    if (!you.duration[DUR_REPEL_STAIRS_CLIMB])
        return (false);

    int pct;
    if (you.duration[DUR_REPEL_STAIRS_MOVE])
        pct = 29;
    else
        pct = 50;

    // When the effect is still strong, the chance to actually catch a stair
    // is smaller. (Assuming the duration starts out at 500.)
    const int dur = std::max(0, you.duration[DUR_REPEL_STAIRS_CLIMB] - 200);
    pct += dur/20;

    if (!x_chance_in_y(pct, 100))
        return (false);

    // Get feature name before sliding stair over.
    std::string stair_str =
        feature_description(you.pos(), false, DESC_CAP_THE, false);

    if (!slide_feature_over(you.pos(), coord_def(-1, -1), false))
        return (false);

    std::string verb = stair_climb_verb(stair);

    mprf("%s moves away as you attempt to %s it!", stair_str.c_str(),
         verb.c_str());

    you.turn_is_over = true;

    return (true);
}

static bool _check_carrying_orb()
{
    // We never picked up the Orb, no problem.
    if (you.char_direction != GDT_ASCENDING)
        return (true);

    // So we did pick up the Orb. Now check whether we're carrying it.
    for (int i = 0; i < ENDOFPACK; i++)
    {
        if (you.inv[i].is_valid()
            && you.inv[i].base_type == OBJ_ORBS
            && you.inv[i].sub_type == ORB_ZOT)
        {
            return (true);
        }
    }
    return (yes_or_no("You're not carrying the Orb! Leave anyway"));
}

void up_stairs(dungeon_feature_type force_stair,
               entry_cause_type entry_cause)
{
    dungeon_feature_type stair_find = (force_stair ? force_stair
                                       : grd(you.pos()));
    const branch_type     old_where      = you.where_are_you;
    const level_area_type old_level_type = you.level_type;

    // Up and down both work for shops.
    if (stair_find == DNGN_ENTER_SHOP)
    {
        shop();
        return;
    }

    // Up and down both work for portals.
    if (get_feature_dchar(stair_find) == DCHAR_ARCH
        && feat_stair_direction(stair_find) != CMD_NO_CMD
        && stair_find != DNGN_ENTER_ZOT
        && stair_find != DNGN_RETURN_FROM_ZOT
        && stair_find != DNGN_EXIT_HELL)
    {
        down_stairs(you.your_level, force_stair, entry_cause);
        return;
    }
    // Probably still need this check here (teleportation) -- bwr
    else if (feat_stair_direction(stair_find) != CMD_GO_UPSTAIRS)
    {
        if (stair_find == DNGN_STONE_ARCH)
            mpr("There is nothing on the other side of the stone arch.");
        else if (stair_find == DNGN_ABANDONED_SHOP)
            mpr("This shop appears to be closed.");
        else
            mpr("You can't go up here.");
        return;
    }

    if (_stair_moves_pre(stair_find))
        return;

    // Since the overloaded message set turn_is_over, I'm assuming that
    // the overloaded character makes an attempt... so we're doing this
    // check before that one. -- bwr
    if (!you.airborne()
        && you.confused()
        && old_level_type == LEVEL_DUNGEON
        && !feat_is_escape_hatch(stair_find)
        && coinflip())
    {
        const char* fall_where = "down the stairs";
        if (!feat_is_staircase(stair_find))
            fall_where = "through the gate";

        mprf("In your confused state, you trip and fall back %s.", fall_where);
        if (!feat_is_staircase(stair_find))
            ouch(1, NON_MONSTER, KILLED_BY_FALLING_THROUGH_GATE);
        else
            ouch(1, NON_MONSTER, KILLED_BY_FALLING_DOWN_STAIRS);
        you.turn_is_over = true;
        return;
    }

    if (you.burden_state == BS_OVERLOADED && !feat_is_escape_hatch(stair_find)
        && !feat_is_gate(stair_find))
    {
        mpr("You are carrying too much to climb upwards.");
        you.turn_is_over = true;
        return;
    }

    const level_id destination_override(_stair_destination_override());
    const bool leaving_dungeon =
        level_id::current() == level_id(BRANCH_MAIN_DUNGEON, 1)
        && !destination_override.is_valid();

    if (leaving_dungeon
        && (!yesno("Are you sure you want to leave the Dungeon?", false, 'n')
            || !_check_carrying_orb()))
    {
        if (Tutorial.tutorial_left)
        {
            if (!yesno("Are you *sure*?  Doing so will end the game!", false,
                       'n'))
            {
                mpr("Alright.");
                return;
            }
        }
        mpr("Alright, then stay!");
        return;
    }

    // Bail if any markers veto the move.
    if (_marker_vetoes_level_change())
        return;

    // Magical level changes (don't exist yet in this direction)
    // need this.
    clear_trapping_net();

    // Checks are done, the character is committed to moving between levels.
    leaving_level_now();

    const int old_level  = you.your_level;

    // Interlevel travel data.
    const bool collect_travel_data = can_travel_interlevel();

    level_id  old_level_id    = level_id::current();
    LevelInfo &old_level_info = travel_cache.get_level_info(old_level_id);

    if (collect_travel_data)
        old_level_info.update();

    _player_change_level_reset();
    _player_change_level_upstairs(stair_find, destination_override);

    if (you.your_level < 0)
    {
        mpr("You have escaped!");

        for (int i = 0; i < ENDOFPACK; i++)
        {
            if (you.inv[i].is_valid()
                && you.inv[i].base_type == OBJ_ORBS)
            {
                ouch(INSTANT_DEATH, NON_MONSTER, KILLED_BY_WINNING);
            }
        }

        ouch(INSTANT_DEATH, NON_MONSTER, KILLED_BY_LEAVING);
    }

    if (old_level_id.branch == BRANCH_VESTIBULE_OF_HELL
        && !player_in_branch( BRANCH_VESTIBULE_OF_HELL ))
    {
        mpr("Thank you for visiting Hell. Please come again soon.");
    }

    // Fixup exits from the Hell branches.
    if (player_in_branch(BRANCH_VESTIBULE_OF_HELL))
    {
        switch (old_level_id.branch)
        {
        case BRANCH_COCYTUS:  stair_find = DNGN_ENTER_COCYTUS;  break;
        case BRANCH_DIS:      stair_find = DNGN_ENTER_DIS;      break;
        case BRANCH_GEHENNA:  stair_find = DNGN_ENTER_GEHENNA;  break;
        case BRANCH_TARTARUS: stair_find = DNGN_ENTER_TARTARUS; break;
        default: break;
        }
    }

    const dungeon_feature_type stair_taken = stair_find;

    if (you.flight_mode() == FL_LEVITATE && !feat_is_gate(stair_find))
        mpr("You float upwards... And bob straight up to the ceiling!");
    else if (you.flight_mode() == FL_FLY && !feat_is_gate(stair_find))
        mpr("You fly upwards.");
    else
        climb_message(stair_find, true, old_level_type);

    exit_stair_message(stair_find, true);

    if (old_where != you.where_are_you && you.level_type == LEVEL_DUNGEON)
    {
        mprf("Welcome back to %s!",
             branches[you.where_are_you].longname);
    }

    const coord_def stair_pos = you.pos();

    load(stair_taken, LOAD_ENTER_LEVEL, old_level_type,
         old_level, old_where);

    set_entry_cause(entry_cause, old_level_type);
    entry_cause = you.entry_cause;

    you.turn_is_over = true;

    save_game_state();

    new_level();

    viewwindow(true);

    // Left Zot without enough runes to get back in (because they were
    // destroyed), but need to get back in Zot to get the Orb?
    // Xom finds that funny.
    if (stair_find == DNGN_RETURN_FROM_ZOT
        && branches[BRANCH_HALL_OF_ZOT].branch_flags & BFLAG_HAS_ORB)
    {
        int runes_avail = you.attribute[ATTR_UNIQUE_RUNES]
                          + you.attribute[ATTR_DEMONIC_RUNES]
                          + you.attribute[ATTR_ABYSSAL_RUNES];

        if (runes_avail < NUMBER_OF_RUNES_NEEDED)
            xom_is_stimulated(255, "Xom snickers loudly.", true);
    }

    if (you.skills[SK_TRANSLOCATIONS] > 0 && !allow_control_teleport( true ))
        mpr( "You sense a powerful magical force warping space.", MSGCH_WARN );

    if (collect_travel_data)
    {
        // Update stair information for the stairs we just ascended, and the
        // down stairs we're currently on.
        level_id  new_level_id    = level_id::current();

        if (can_travel_interlevel())
        {
            LevelInfo &new_level_info =
                        travel_cache.get_level_info(new_level_id);
            new_level_info.update();

            // First we update the old level's stair.
            level_pos lp;
            lp.id  = new_level_id;
            lp.pos = you.pos();

            bool guess = false;
            // Ugly hack warning:
            // The stairs in the Vestibule of Hell exhibit special behaviour:
            // they always lead back to the dungeon level that the player
            // entered the Vestibule from. This means that we need to pretend
            // we don't know where the upstairs from the Vestibule go each time
            // we take it. If we don't, interlevel travel may try to use portals
            // to Hell as shortcuts between dungeon levels, which won't work,
            // and will confuse the dickens out of the player (well, it confused
            // the dickens out of me when it happened).
            if (new_level_id == BRANCH_MAIN_DUNGEON
                && old_level_id == BRANCH_VESTIBULE_OF_HELL)
            {
                old_level_info.clear_stairs(DNGN_EXIT_HELL);
            }
            else
            {
                old_level_info.update_stair(stair_pos, lp, guess);
            }

            // We *guess* that going up a staircase lands us on a downstair,
            // and that we can descend that downstair and get back to where we
            // came from. This assumption is guaranteed false when climbing out
            // of one of the branches of Hell.
            if (new_level_id != BRANCH_VESTIBULE_OF_HELL)
            {
                // Set the new level's stair, assuming arbitrarily that going
                // downstairs will land you on the same upstairs you took to
                // begin with (not necessarily true).
                lp.id = old_level_id;
                lp.pos = stair_pos;
                new_level_info.update_stair(you.pos(), lp, true);
            }
        }
    }
    request_autopickup();
}

// Adds a dungeon marker at the point of the level where returning from
// a labyrinth or portal vault should drop the player.
static void _mark_portal_return_point(const coord_def &pos)
{
    // First toss all markers of this type. Stale markers are possible
    // if the player goes to the Abyss from a portal vault /
    // labyrinth, thus returning to this level without activating a
    // previous portal vault exit marker.
    const std::vector<map_marker*> markers = env.markers.get_all(MAT_FEATURE);
    for (int i = 0, size = markers.size(); i < size; ++i)
    {
        if (dynamic_cast<map_feature_marker*>(markers[i])->feat ==
            DNGN_EXIT_PORTAL_VAULT)
        {
            env.markers.remove(markers[i]);
        }
    }

    if (!env.markers.find(pos, MAT_FEATURE))
    {
        map_feature_marker *mfeat =
            new map_feature_marker(pos, DNGN_EXIT_PORTAL_VAULT);
        env.markers.add(mfeat);
    }
}

// All changes to you.level_type, you.where_are_you and you.your_level
// for descending stairs should happen here.
static void _player_change_level_downstairs(dungeon_feature_type stair_find,
                                            const level_id &place_override,
                                            bool shaft,
                                            int shaft_level,
                                            const level_id &shaft_dest)
{
    if (_stair_force_destination(place_override))
        return;

    const level_area_type original_level_type(you.level_type);

    if (you.level_type != LEVEL_DUNGEON
        && (you.level_type != LEVEL_PANDEMONIUM
            || stair_find != DNGN_TRANSIT_PANDEMONIUM)
        && (you.level_type != LEVEL_PORTAL_VAULT
            || !feat_is_stone_stair(stair_find)))
    {
        you.level_type = LEVEL_DUNGEON;
    }

    if (stair_find == DNGN_ENTER_HELL)
    {
        you.where_are_you = BRANCH_VESTIBULE_OF_HELL;
        you.hell_exit = you.your_level;

        you.your_level = 26;
    }

    // Welcome message.
    // Try to find a branch stair.
    for (int i = 0; i < NUM_BRANCHES; ++i)
    {
        if (branches[i].entry_stairs == stair_find)
        {
            you.where_are_you = branches[i].id;
            break;
        }
    }

    if (stair_find == DNGN_ENTER_LABYRINTH)
        you.level_type = LEVEL_LABYRINTH;
    else if (stair_find == DNGN_ENTER_ABYSS)
        you.level_type = LEVEL_ABYSS;
    else if (stair_find == DNGN_ENTER_PANDEMONIUM)
        you.level_type = LEVEL_PANDEMONIUM;
    else if (stair_find == DNGN_ENTER_PORTAL_VAULT)
        you.level_type = LEVEL_PORTAL_VAULT;

    if (shaft)
    {
        you.your_level    = shaft_level;
        you.where_are_you = shaft_dest.branch;
    }
    else if (original_level_type == LEVEL_DUNGEON
             && you.level_type == LEVEL_DUNGEON)
    {
        you.your_level++;
    }
}

void _maybe_destroy_trap(const coord_def &p)
{
    trap_def* trap = find_trap(p);
    if (trap)
        trap->destroy();
}

void down_stairs( int old_level, dungeon_feature_type force_stair,
                  entry_cause_type entry_cause )
{
    const level_area_type  old_level_type = you.level_type;
    const dungeon_feature_type stair_find =
        force_stair? force_stair : grd(you.pos());

    branch_type old_where = you.where_are_you;

    const bool shaft = (!force_stair
                            && get_trap_type(you.pos()) == TRAP_SHAFT
                        || force_stair == DNGN_TRAP_NATURAL);
    level_id shaft_dest;
    int      shaft_level = -1;

    // Up and down both work for shops.
    if (stair_find == DNGN_ENTER_SHOP)
    {
        shop();
        return;
    }

    // Up and down both work for portals.
    if (get_feature_dchar(stair_find) == DCHAR_ARCH
        && feat_stair_direction(stair_find) != CMD_NO_CMD
        && stair_find != DNGN_ENTER_ZOT
        && stair_find != DNGN_RETURN_FROM_ZOT
        && stair_find != DNGN_EXIT_HELL)
    {
        ;
    }
    // Probably still need this check here (teleportation) -- bwr
    else if (feat_stair_direction(stair_find) != CMD_GO_DOWNSTAIRS && !shaft)
    {
        if (stair_find == DNGN_STONE_ARCH)
            mpr("There is nothing on the other side of the stone arch.");
        else if (stair_find == DNGN_ABANDONED_SHOP)
            mpr("This shop appears to be closed.");
        else
            mpr("You can't go down here!");
        return;
    }

    if (stair_find == DNGN_ENTER_HELL && you.level_type != LEVEL_DUNGEON)
    {
        mpr("You can't enter Hell from outside the dungeon!",
            MSGCH_ERROR);
        return;
    }

    if (stair_find >= DNGN_ENTER_LABYRINTH
        && stair_find <= DNGN_ESCAPE_HATCH_DOWN
        && player_in_branch( BRANCH_VESTIBULE_OF_HELL ))
    {
        // Down stairs in vestibule are one-way!
        mpr("A mysterious force prevents you from descending the staircase.");
        return;
    }

    if (stair_find == DNGN_STONE_ARCH)
    {
        mpr("There is nothing on the other side of the stone arch.");
        return;
    }

    if (!force_stair && you.flight_mode() == FL_LEVITATE
        && !feat_is_gate(stair_find))
    {
        mpr("You're floating high up above the floor!");
        return;
    }

    if (_stair_moves_pre(stair_find))
        return;

    if (shaft)
    {
        const bool known_trap = (grd(you.pos()) != DNGN_UNDISCOVERED_TRAP
                                 && !force_stair);

        if (you.flight_mode() == FL_LEVITATE && !force_stair)
        {
            if (known_trap)
                mpr("You can't fall through a shaft while levitating.");
            return;
        }

        if (!is_valid_shaft_level())
        {
            if (known_trap)
                mpr("The shaft disappears is a puff of logic!");
            _maybe_destroy_trap(you.pos());
            return;
        }

        shaft_dest = you.shaft_dest(known_trap);
        if (shaft_dest == level_id::current())
        {
            if (known_trap)
            {
                mpr("Strange, the shaft seems to lead back to this level.");
                mpr("The strain on the space-time continuum destroys the "
                    "shaft!");
            }
            _maybe_destroy_trap(you.pos());
            return;
        }
        shaft_level = absdungeon_depth(shaft_dest.branch, shaft_dest.depth);

#ifdef DGL_MILESTONES
        if (!known_trap && shaft_level - you.your_level > 1)
            mark_milestone("shaft", "fell down a shaft to " +
                                    short_place_name(shaft_dest) + ".");
#endif

        if (you.flight_mode() != FL_FLY || force_stair)
            mpr("You fall through a shaft!");

        // Shafts are one-time-use.
        mpr("The shaft crumbles and collapses.");
        _maybe_destroy_trap(you.pos());
    }

    if (stair_find == DNGN_ENTER_ZOT && !you.opened_zot)
    {
        std::vector<int> runes;
        const int num_runes = runes_in_pack(runes);

        if (num_runes < NUMBER_OF_RUNES_NEEDED)
        {
            switch (NUMBER_OF_RUNES_NEEDED)
            {
            case 1:
                mpr("You need a rune to enter this place.");
                break;

            default:
                mprf("You need at least %d runes to enter this place.",
                     NUMBER_OF_RUNES_NEEDED);
            }
            return;
        }

        ASSERT(runes.size() >= 3);

        mprf("You insert %s into the lock.",
             you.inv[runes[0]].name(DESC_NOCAP_THE).c_str());
#ifdef USE_TILE
        tiles.add_overlay(you.pos(), tileidx_zap(GREEN));
        update_screen();
#else
        flash_view(LIGHTGREEN);
#endif
        mpr("The lock glows an eerie green colour!");
        more();

        mprf("You insert %s into the lock.",
             you.inv[runes[1]].name(DESC_NOCAP_THE).c_str());
        big_cloud(CLOUD_BLUE_SMOKE, KC_YOU, you.pos(), 20, 7 + random2(7));
        viewwindow(false, true);
        mpr("Heavy smoke blows from the lock!");
        more();

        mprf("You insert %s into the lock.",
             you.inv[runes[2]].name(DESC_NOCAP_THE).c_str());

        if (silenced(you.pos()))
            mpr("The gate opens wide!");
        else
            mpr("With a loud hiss the gate opens wide!");
        more();

        you.opened_zot = true;
    }

    // Bail if any markers veto the move.
    if (_marker_vetoes_level_change())
        return;

    const level_id destination_override(_stair_destination_override());

    // All checks are done, the player is on the move now.

    // Magical level changes (Portal, Banishment) need this.
    clear_trapping_net();

    // Fire level-leaving trigger.
    leaving_level_now();

#ifdef DGL_MILESTONES
    if (!force_stair && !crawl_state.arena)
    {
        // Not entirely accurate - the player could die before
        // reaching the Abyss.
        if (grd(you.pos()) == DNGN_ENTER_ABYSS)
            mark_milestone("abyss.enter", "entered the Abyss!");
        else if (grd(you.pos()) == DNGN_EXIT_ABYSS
                 && you.char_direction != GDT_GAME_START)
        {
            mark_milestone("abyss.exit", "escaped from the Abyss!");
        }
    }
#endif

    // Interlevel travel data.
    const bool collect_travel_data = can_travel_interlevel();

    const level_id  old_level_id = level_id::current();
    LevelInfo &old_level_info    = travel_cache.get_level_info(old_level_id);
    const coord_def stair_pos    = you.pos();
    if (collect_travel_data)
        old_level_info.update();

    // Preserve abyss uniques now, since this Abyss level will be deleted.
    if (you.level_type == LEVEL_ABYSS)
        save_abyss_uniques();

    if (stair_find == DNGN_ENTER_LABYRINTH)
        dungeon_terrain_changed(you.pos(), DNGN_STONE_ARCH);

    if (stair_find == DNGN_ENTER_LABYRINTH
        || stair_find == DNGN_ENTER_PORTAL_VAULT)
    {
        _mark_portal_return_point(you.pos());
    }

    const int shaft_depth = (shaft ? shaft_level - you.your_level : 1);
    _player_change_level_reset();
    _player_change_level_downstairs(stair_find, destination_override, shaft,
                                    shaft_level, shaft_dest);

    // When going downstairs into a special level, delete any previous
    // instances of it.
    if (you.level_type != LEVEL_DUNGEON)
    {
        std::string lname = make_filename(you.your_name, you.your_level,
                                          you.where_are_you,
                                          you.level_type, false);
#if DEBUG_DIAGNOSTICS
        mprf( MSGCH_DIAGNOSTICS, "Deleting: %s", lname.c_str() );
#endif
        unlink(lname.c_str());
    }

    // Did we enter a new branch.
    const bool entered_branch(
        you.where_are_you != old_level_id.branch
        && branches[you.where_are_you].parent_branch == old_level_id.branch);

    if (stair_find == DNGN_EXIT_ABYSS || stair_find == DNGN_EXIT_PANDEMONIUM)
    {
        mpr("You pass through the gate.");
        if (!you.wizard || !crawl_state.is_replaying_keys())
            more();
    }

    if (old_level_type != you.level_type && you.level_type == LEVEL_DUNGEON)
        mprf("Welcome back to %s!", branches[you.where_are_you].longname);

    if (!you.airborne()
        && you.confused()
        && !feat_is_escape_hatch(stair_find)
        && force_stair != DNGN_ENTER_ABYSS
        && coinflip())
    {
        const char* fall_where = "down the stairs";
        if (!feat_is_staircase(stair_find))
            fall_where = "through the gate";

        mprf("In your confused state, you trip and fall %s.", fall_where);
        // Note that this only does damage; it doesn't cancel the level
        // transition.
        if (!feat_is_staircase(stair_find))
            ouch(1, NON_MONSTER, KILLED_BY_FALLING_THROUGH_GATE);
        else
            ouch(1, NON_MONSTER, KILLED_BY_FALLING_DOWN_STAIRS);
    }

    dungeon_feature_type stair_taken = stair_find;

    if (you.level_type == LEVEL_ABYSS)
        stair_taken = DNGN_FLOOR;

    if (you.level_type == LEVEL_PANDEMONIUM)
        stair_taken = DNGN_TRANSIT_PANDEMONIUM;

    if (shaft)
        stair_taken = DNGN_ESCAPE_HATCH_DOWN;

    switch (you.level_type)
    {
    case LEVEL_LABYRINTH:
        if (you.species == SP_MINOTAUR)
            mpr("You feel right at home here.");
        else
            mpr("You enter a dark and forbidding labyrinth.");
        break;

    case LEVEL_ABYSS:
        if (!force_stair)
            mpr("You enter the Abyss!");

        mpr("To return, you must find a gate leading back.");
        if (you.religion == GOD_CHEIBRIADOS)
            mpr("You feel Cheibriados slowing down the madness of this place.",
                MSGCH_GOD, GOD_CHEIBRIADOS);
        learned_something_new(TUT_ABYSS);
        break;

    case LEVEL_PANDEMONIUM:
        if (old_level_type == LEVEL_PANDEMONIUM)
            mpr("You pass into a different region of Pandemonium.");
        else
        {
            mpr("You enter the halls of Pandemonium!");
            mpr("To return, you must find a gate leading back.");
        }
        break;

    default:
        if (shaft)
        {
            if (you.flight_mode() == FL_FLY && !force_stair)
                mpr("You dive down through the shaft.");
            handle_items_on_shaft(you.pos(), false);
        }
        else
            climb_message(stair_find, false, old_level_type);
        break;
    }

    if (!shaft)
        exit_stair_message(stair_find, false);

    if (entered_branch)
    {
        if (branches[you.where_are_you].entry_message)
            mpr(branches[you.where_are_you].entry_message);
        else
            mprf("Welcome to %s!", branches[you.where_are_you].longname);
    }

    if (stair_find == DNGN_ENTER_HELL)
    {
        mpr("Welcome to Hell!");
        mpr("Please enjoy your stay.");

        // Kill -more- prompt if we're traveling.
        if (!you.running && !force_stair)
            more();
    }

    const bool newlevel = load(stair_taken, LOAD_ENTER_LEVEL, old_level_type,
                               old_level, old_where);

    set_entry_cause(entry_cause, old_level_type);
    entry_cause = you.entry_cause;

    if (newlevel)
    {
        // When entering a new level, reset friendly_pickup to default.
        you.friendly_pickup = Options.default_friendly_pickup;

        switch (you.level_type)
        {
        case LEVEL_DUNGEON:
            // Xom thinks it's funny if you enter a new level via shaft
            // or escape hatch, for shafts it's funnier the deeper you fell.
            if (shaft || feat_is_escape_hatch(stair_find))
                xom_is_stimulated(shaft_depth * 50);
            else
                xom_is_stimulated(14);
            break;

        case LEVEL_PORTAL_VAULT:
            // Portal vaults aren't as interesting.
            xom_is_stimulated(25);
            break;

        case LEVEL_LABYRINTH:
            // Finding the way out of a labyrinth interests Xom,
            // but less so for Minotaurs. (though not now, as they cannot
            // map the labyrinth any more {due})
            xom_is_stimulated(98);
            break;

        case LEVEL_ABYSS:
        case LEVEL_PANDEMONIUM:
        {
            // Paranoia
            if (old_level_type == you.level_type)
                break;

            PlaceInfo &place_info = you.get_place_info();
            generate_random_blood_spatter_on_level();

            // Entering voluntarily only stimulates Xom if you've never
            // been there before
            if ((place_info.num_visits == 1 && place_info.levels_seen == 1)
                || entry_cause != EC_SELF_EXPLICIT)
            {
                if (crawl_state.is_god_acting())
                    xom_is_stimulated(255);
                else if (entry_cause == EC_SELF_EXPLICIT)
                {
                    // Entering Pandemonium or the Abyss for the first
                    // time *voluntarily* stimulates Xom much more than
                    // entering a normal dungeon level for the first time.
                    xom_is_stimulated(128, XM_INTRIGUED);
                }
                else if (entry_cause == EC_SELF_RISKY)
                    xom_is_stimulated(128);
                else
                    xom_is_stimulated(255);
            }

            break;
        }

        default:
            ASSERT(false);
        }
    }

    unsigned char pc = 0;
    unsigned char pt = random2avg(28, 3);


    switch (you.level_type)
    {
    case LEVEL_ABYSS:
        grd(you.pos()) = DNGN_FLOOR;

        init_pandemonium();     // colours only

        if (player_in_hell())
        {
            you.where_are_you = BRANCH_MAIN_DUNGEON;
            you.your_level    = you.hell_exit - 1;
        }
        break;

    case LEVEL_PANDEMONIUM:
        if (old_level_type == LEVEL_PANDEMONIUM)
        {
            init_pandemonium();

            for (pc = 0; pc < pt; pc++)
                pandemonium_mons();
        }
        else
        {
            init_pandemonium();

            for (pc = 0; pc < pt; pc++)
                pandemonium_mons();

            if (player_in_hell())
            {
                you.where_are_you = BRANCH_MAIN_DUNGEON;
                you.hell_exit  = 26;
                you.your_level = 26;
            }
        }
        break;

    default:
        break;
    }

    you.turn_is_over = true;

    save_game_state();

    new_level();

    // Clear list of beholding monsters.
    you.clear_beholders();

    if (you.skills[SK_TRANSLOCATIONS] > 0 && !allow_control_teleport( true ))
        mpr( "You sense a powerful magical force warping space.", MSGCH_WARN );

    trackers_init_new_level(true);

    viewwindow(true);
    maybe_update_stashes();

    if (collect_travel_data)
    {
        // Update stair information for the stairs we just descended, and the
        // upstairs we're currently on.
        level_id  new_level_id    = level_id::current();

        if (can_travel_interlevel())
        {
            LevelInfo &new_level_info =
                            travel_cache.get_level_info(new_level_id);
            new_level_info.update();

            // First we update the old level's stair.
            level_pos lp;
            lp.id  = new_level_id;
            lp.pos = you.pos();

            old_level_info.update_stair(stair_pos, lp);

            // Then the new level's stair, assuming arbitrarily that going
            // upstairs will land you on the same downstairs you took to begin
            // with (not necessarily true).
            lp.id = old_level_id;
            lp.pos = stair_pos;
            new_level_info.update_stair(you.pos(), lp, true);
        }
    }
    request_autopickup();
}

void trackers_init_new_level(bool transit)
{
    travel_init_new_level();
    if (transit)
        stash_init_new_level();
}

void new_level(void)
{
    if (you.level_type == LEVEL_PORTAL_VAULT)
    {
        // This here because place_name can't find the name of a level that you
        // *are no longer on* when it spits out the new notes list.
        std::string desc = "Entered " + place_name(get_packed_place(), true, true);
        take_note(Note(NOTE_DUNGEON_LEVEL_CHANGE, 0, 0, NULL,
                      desc.c_str()));
    }
    else
        take_note(Note(NOTE_DUNGEON_LEVEL_CHANGE));

    print_stats_level();
#ifdef DGL_WHEREIS
    whereis_record();
#endif
}

std::string weird_glowing_colour()
{
    return getMiscString("glowing_colour_name");
}

std::string weird_writing()
{
    return getMiscString("writing_name");
}

std::string weird_smell()
{
    return getMiscString("smell_name");
}

std::string weird_sound()
{
    return getMiscString("sound_name");
}

bool scramble(void)
{
    ASSERT(!crawl_state.arena);

    // Statues are too stiff and heavy to scramble out of the water.
    if (you.attribute[ATTR_TRANSFORMATION] == TRAN_STATUE)
        return (false);

    int max_carry = carrying_capacity();

    // When highly encumbered, scrambling out is hard to do.
    if ((max_carry / 2) + random2(max_carry / 2) <= you.burden)
        return (false);
    else
        return (true);
}

bool go_berserk(bool intentional, bool potion)
{
    ASSERT(!crawl_state.arena);

    if (!you.can_go_berserk(intentional, potion))
        return (false);

    if (stasis_blocks_effect(true,
                             "%s thrums violently and saps your rage.",
                             3,
                             "%s vibrates violently and saps your rage."))
    {
        return (false);
    }

    if (Tutorial.tutorial_left)
        Tutorial.tut_berserk_counter++;

    mpr("A red film seems to cover your vision as you go berserk!");
    mpr("You feel yourself moving faster!");
    mpr("You feel mighty!");

    // Cutting the duration in half since berserk causes haste and hasted
    // actions have half the usual delay. This keeps player turns
    // approximately consistent withe previous versions. -cao
    int berserk_duration = (20 + random2avg(19,2)) / 2;

    you.increase_duration(DUR_BERSERKER, berserk_duration);

    calc_hp();
    you.hp = you.hp * 3 / 2;

    deflate_hp(you.hp_max, false);

    if (!you.duration[DUR_MIGHT])
        modify_stat(STAT_STRENGTH, 5, true, "going berserk");

    you.increase_duration(DUR_MIGHT, berserk_duration);
    /// doubling the duration here since haste_player already cuts input
    // durations in half
    haste_player(berserk_duration * 2);

    did_god_conduct(DID_HASTY, 8, intentional);

    if (you.berserk_penalty != NO_BERSERK_PENALTY)
        you.berserk_penalty = 0;

    return (true);
}

// Returns true if the monster has a path to the player, or it has to be
// assumed that this is the case.
static bool _mons_has_path_to_player(const monsters *mon)
{
    // Don't consider sleeping monsters safe, in case the player would
    // rather retreat and try another path for maximum stabbing chances.
    // TODO: This doesn't cover monsters encaged in glass.
    if (mon->asleep())
        return (true);

    // If the monster is awake and knows a path towards the player
    // (even though the player cannot know this) treat it as unsafe.
    if (mon->travel_target == MTRAV_PLAYER)
        return (true);

    if (mon->travel_target == MTRAV_KNOWN_UNREACHABLE)
        return (false);

    // Try to find a path from monster to player, using the map as it's
    // known to the player and assuming unknown terrain to be traversable.
    monster_pathfind mp;
    const int range = mons_tracking_range(mon);
    if (range > 0)
        mp.set_range(range);

    if (mp.init_pathfind(mon, you.pos(), true, false, true))
        return (true);

    // Now we know the monster cannot possibly reach the player.
    mon->travel_target = MTRAV_KNOWN_UNREACHABLE;

    return (false);
}

bool mons_can_hurt_player(const monsters *mon)
{
    // FIXME: This takes into account whether the player knows the map!
    // It also always returns true for sleeping monsters, but that's okay
    // for its current purposes. (Travel interruptions and tension.)
    if (_mons_has_path_to_player(mon))
        return (true);

    // The monster need only see you to hurt you.
    if (mons_has_los_attack(mon))
        return (true);

    // Even if the monster can not actually reach the player it might
    // still use some ranged form of attack.
    if (you.see_cell_no_trans(mon->pos()) && mons_has_ranged_ability(mon))
        return (true);

    return (false);
}

bool mons_is_safe(const monsters *mon, bool want_move,
                  bool consider_user_options)
{
    int  dist    = grid_distance(you.pos(), mon->pos());

    bool is_safe = (mon->wont_attack()
                    || mons_class_flag(mon->type, M_NO_EXP_GAIN)
                       && mon->type != MONS_KRAKEN_TENTACLE
                    || mon->pacified() && dist > 1
                    || mon->type == MONS_BALLISTOMYCETE && mon->number == 0
#ifdef WIZARD
                    // Wizmode skill setting enforces hiddenness.
                    || you.skills[SK_STEALTH] > 27 && dist > 2
#endif
                       // Only seen through glass walls or within water?
                       // Assuming that there are no water-only/lava-only
                       // monsters capable of throwing or zapping wands.
                    || (!you.see_cell_no_trans(mon->pos())
                            || mons_class_habitat(mon->type) == HT_WATER
                            || mons_class_habitat(mon->type) == HT_LAVA)
                        && !mons_can_hurt_player(mon));

#ifdef CLUA_BINDINGS
    if (consider_user_options)
    {
        bool moving = (!you.delay_queue.empty()
                          && is_run_delay(you.delay_queue.front().type)
                          && you.delay_queue.front().type != DELAY_REST
                       || you.running < RMODE_NOT_RUNNING
                       || want_move);

        bool result = is_safe;

        if (clua.callfn("ch_mon_is_safe", "Mbbd>b",
                        mon, is_safe, moving, dist,
                        &result))
        {
            is_safe = result;
        }
    }
#endif

    return (is_safe);
}

// Return all nearby monsters in range (default: LOS) that the player
// is able to recognise as being monsters (i.e. no unknown mimics or
// submerged creatures.)
//
// want_move       (??) Somehow affects what monsters are considered dangerous
// just_check      Return zero or one monsters only
// dangerous_only  Return only "dangerous" monsters
// require_visible Require that monsters be visible to the player
// range           search radius (defaults: LOS)
//
std::vector<monsters*> get_nearby_monsters(bool want_move,
                                           bool just_check,
                                           bool dangerous_only,
                                           bool consider_user_options,
                                           bool require_visible,
                                           int range)
{
    ASSERT(!crawl_state.arena);

    if (range == -1)
        range = LOS_RADIUS;

    std::vector<monsters*> mons;

    // Sweep every visible square within range.
    for (radius_iterator ri(you.pos(), range); ri; ++ri)
    {
        if (monsters* mon = monster_at(*ri))
        {
            if (mon->alive()
                && (!require_visible || mon->visible_to(&you))
                && !mon->submerged()
                && !mons_is_unknown_mimic(mon)
                && (!dangerous_only || !mons_is_safe(mon, want_move,
                                                     consider_user_options)))
            {
                mons.push_back(mon);
                if (just_check) // stop once you find one
                    break;
            }
        }
    }
    return mons;
}

bool i_feel_safe(bool announce, bool want_move, bool just_monsters, int range)
{
    if (!just_monsters)
    {
        // check clouds
        if (in_bounds(you.pos()) && env.cgrid(you.pos()) != EMPTY_CLOUD)
        {
            const int cloudidx = env.cgrid(you.pos());
            const cloud_type type = env.cloud[cloudidx].type;

            if (is_damaging_cloud(type, want_move))
            {
                if (announce)
                {
                    mprf(MSGCH_WARN, "You're standing in a cloud of %s!",
                         cloud_name(cloudidx).c_str());
                }
                return (false);
            }
        }

        // No monster will attack you inside a sanctuary,
        // so presence of monsters won't matter -- until it starts shrinking...
        if (is_sanctuary(you.pos()) && env.sanctuary_time >= 5)
            return (true);
    }

    // Monster check.
    std::vector<monsters*> visible =
        get_nearby_monsters(want_move, !announce, true, true, true, range);

    // No monsters found.
    if (visible.empty())
        return (true);

    // Announce the presence of monsters (Eidolos).
    if (visible.size() == 1)
    {
        const monsters &m = *visible[0];
        if (announce)
        {
            std::string monname =
                (mons_is_mimic(m.type)) ? "a mimic" : m.name(DESC_NOCAP_A);

            mprf(MSGCH_WARN, "Not with %s in view!", monname.c_str());
        }
    }
    else if (announce && visible.size() > 1)
        mprf(MSGCH_WARN, "Not with these monsters around!");

    return (false);
}

bool there_are_monsters_nearby(bool dangerous_only, bool require_visible,
                               bool consider_user_options)
{
    return (!get_nearby_monsters(false, true, dangerous_only,
                                 consider_user_options,
                                 require_visible).empty());
}

static const char *shop_types[] = {
    "weapon",
    "armour",
    "antique weapon",
    "antique armour",
    "antiques",
    "jewellery",
    "wand",
    "book",
    "food",
    "distillery",
    "scroll",
    "general"
};

int str_to_shoptype(const std::string &s)
{
    if (s == "random" || s == "any")
        return (SHOP_RANDOM);

    for (unsigned i = 0; i < sizeof(shop_types) / sizeof (*shop_types); ++i)
    {
        if (s == shop_types[i])
            return (i);
    }
    return (-1);
}

// General threat = sum_of_logexpervalues_of_nearby_unfriendly_monsters.
// Highest threat = highest_logexpervalue_of_nearby_unfriendly_monsters.
static void monster_threat_values(double *general, double *highest,
                                  bool *invis)
{
    *invis = false;

    double sum = 0;
    int highest_xp = -1;

    for (monster_iterator mi(&you.get_los()); mi; ++mi)
    {
        if (!mi->friendly())
        {
            const int xp = exper_value(*mi);
            const double log_xp = log((double)xp);
            sum += log_xp;
            if (xp > highest_xp)
            {
                highest_xp = xp;
                *highest   = log_xp;
            }
            if (!you.can_see(*mi))
                *invis = true;
        }
    }

    *general = sum;
}

bool player_in_a_dangerous_place(bool *invis)
{
    bool junk;
    if (invis == NULL)
        invis = &junk;

    const double logexp = log((double)you.experience);
    double gen_threat = 0.0, hi_threat = 0.0;
    monster_threat_values(&gen_threat, &hi_threat, invis);

    return (gen_threat > logexp * 1.3 || hi_threat > logexp / 2);
}

////////////////////////////////////////////////////////////////////////////
// Living breathing dungeon stuff.
//

static std::vector<coord_def> sfx_seeds;

void setup_environment_effects()
{
    sfx_seeds.clear();

    for (int x = X_BOUND_1; x <= X_BOUND_2; ++x)
    {
        for (int y = Y_BOUND_1; y <= Y_BOUND_2; ++y)
        {
            if (!in_bounds(x, y))
                continue;

            const int grid = grd[x][y];
            if (grid == DNGN_LAVA
                    || (grid == DNGN_SHALLOW_WATER
                        && you.where_are_you == BRANCH_SWAMP))
            {
                const coord_def c(x, y);
                sfx_seeds.push_back(c);
            }
        }
    }
#ifdef DEBUG_DIAGNOSTICS
    mprf(MSGCH_DIAGNOSTICS, "%u environment effect seeds", sfx_seeds.size());
#endif
}

static void apply_environment_effect(const coord_def &c)
{
    const dungeon_feature_type grid = grd(c);
    // Don't apply if if the feature doesn't want it.
    if (testbits(env.pgrid(c), FPROP_NO_CLOUD_GEN))
        return;
    if (grid == DNGN_LAVA)
        check_place_cloud(CLOUD_BLACK_SMOKE, c, random_range(4, 8), KC_OTHER);
    else if (grid == DNGN_SHALLOW_WATER)
        check_place_cloud(CLOUD_MIST,        c, random_range(2, 5), KC_OTHER);
}

static const int Base_Sfx_Chance = 5;
void run_environment_effects()
{
    if (!you.time_taken)
        return;

    dungeon_events.fire_event(DET_TURN_ELAPSED);

    // Each square in sfx_seeds has this chance of doing something special
    // per turn.
    const int sfx_chance = Base_Sfx_Chance * you.time_taken / 10;
    const int nseeds = sfx_seeds.size();

    // If there are a large number of seeds, speed things up by fudging the
    // numbers.
    if (nseeds > 50)
    {
        int nsels = div_rand_round( sfx_seeds.size() * sfx_chance, 100 );
        if (one_chance_in(5))
            nsels += random2(nsels * 3);

        for (int i = 0; i < nsels; ++i)
            apply_environment_effect( sfx_seeds[ random2(nseeds) ] );
    }
    else
    {
        for (int i = 0; i < nseeds; ++i)
        {
            if (random2(100) >= sfx_chance)
                continue;

            apply_environment_effect( sfx_seeds[i] );
        }
    }

    run_corruption_effects(you.time_taken);
    shoals_apply_tides(div_rand_round(you.time_taken, 10));
}

coord_def pick_adjacent_free_square(const coord_def& p)
{
    int num_ok = 0;
    coord_def result(-1, -1);

    for (adjacent_iterator ai(p); ai; ++ai)
        if (grd(*ai) == DNGN_FLOOR && monster_at(*ai) == NULL)
            if (one_chance_in(++num_ok))
                result = *ai;

    return result;
}

// Converts a movement speed to a duration. i.e., answers the
// question: if the monster is so fast, how much time has it spent in
// its last movement?
//
// If speed is 10 (normal),    one movement is a duration of 10.
// If speed is 1  (very slow), each movement is a duration of 100.
// If speed is 15 (50% faster than normal), each movement is a duration of
// 6.6667.
int speed_to_duration(int speed)
{
    if (speed < 1)
        speed = 10;
    else if (speed > 100)
        speed = 100;

    return div_rand_round(100, speed);
}

void reveal_secret_door(const coord_def& p)
{
    ASSERT(grd(p) == DNGN_SECRET_DOOR);

    dungeon_feature_type door = grid_secret_door_appearance(p);
    // Former secret doors become known but are still hidden to monsters
    // until opened.
    grd(p) = feat_is_opaque(door) ? DNGN_DETECTED_SECRET_DOOR
                                  : DNGN_OPEN_DOOR;
    viewwindow(false);
    learned_something_new(TUT_SEEN_SECRET_DOOR, p);

    // If a transparent secret door was forced open to preserve LOS,
    // check if it had an opening prompt.
    if (grd(p) == DNGN_OPEN_DOOR)
    {
        std::string door_open_prompt =
            env.markers.property_at(p, MAT_ANY, "door_open_prompt");

        if (!door_open_prompt.empty())
        {
            mprf("That secret door had a prompt on it:", MSGCH_PROMPT);
            mprf(MSGCH_PROMPT, "%s", door_open_prompt.c_str());

            if (!is_exclude_root(p))
            {
                if (yesno("Put travel exclusion on door? (Y/n)", true, 'y'))
                    // Zero radius exclusion right on top of door.
                    set_exclude(p, 0);
            }
        }
    }
}

// A feeble attempt at Nethack-like completeness for cute messages.
std::string your_hand(bool plural)
{
    std::string result;

    switch (you.attribute[ATTR_TRANSFORMATION])
    {
    default:
        mpr("ERROR: unknown transformation in your_hand() (spells4.cc)",
            MSGCH_ERROR);
    case TRAN_NONE:
    case TRAN_STATUE:
    case TRAN_LICH:
        result = (you.has_usable_claws()) ? "claw" : "hand";
        break;
    case TRAN_ICE_BEAST:
        result = "hand";
        break;
    case TRAN_SPIDER:
    case TRAN_PIG:
        result = "front leg";
        break;
    case TRAN_DRAGON:
    case TRAN_BAT:
        result = "foreclaw";
        break;
    case TRAN_BLADE_HANDS:
        result = "scythe-like blade";
        break;
    }

    if (plural)
        result += 's';

    return result;
}

bool stop_attack_prompt(const monsters *mon, bool beam_attack,
                        coord_def beam_target)
{
    ASSERT(!crawl_state.arena);

    if (you.confused() || !you.can_see(mon))
        return (false);

    bool retval = false;
    bool prompt = false;

    const bool mon_target    = (beam_target == mon->pos());
    const bool inSanctuary   = (is_sanctuary(you.pos())
                                || is_sanctuary(mon->pos()));
    const bool wontAttack    = mon->wont_attack();
    const bool isFriendly    = mon->friendly();
    const bool isNeutral     = mon->neutral();
    const bool isUnchivalric = is_unchivalric_attack(&you, mon);
    const bool isHoly        = mon->is_holy()
                                   && (mon->attitude != ATT_HOSTILE
                                       || testbits(mon->flags, MF_NO_REWARD)
                                       || testbits(mon->flags, MF_WAS_NEUTRAL));

    if (isFriendly)
    {
        // Listed in the form: "your rat", "Blork the orc".
        std::string verb = "";
        bool need_mon_name = true;
        if (beam_attack)
        {
            verb = "fire ";
            if (mon_target)
                verb += "at ";
            else if (you.pos() < beam_target && beam_target < mon->pos()
                     || you.pos() > beam_target && beam_target > mon->pos())
            {
                verb += "in " + mon->name(DESC_NOCAP_THE) + "'s direction";
                need_mon_name = false;
            }
            else
                verb += "through ";
        }
        else
            verb = "attack ";

        if (need_mon_name)
            verb += mon->name(DESC_NOCAP_THE);

        snprintf(info, INFO_SIZE, "Really %s%s?",
                 verb.c_str(),
                 (inSanctuary) ? ", despite your sanctuary" : "");

        prompt = true;
    }
    else if (inSanctuary || wontAttack
             || (you.religion == GOD_JIYVA && mons_is_slime(mon))
             || (isNeutral || isHoly) && is_good_god(you.religion)
             || isUnchivalric
                && you.religion == GOD_SHINING_ONE
                && !tso_unchivalric_attack_safe_monster(mon))
    {
        snprintf(info, INFO_SIZE, "Really %s the %s%s%s%s%s?",
                 (beam_attack) ? (mon_target) ? "fire at"
                                              : "fire through"
                               : "attack",
                 (isUnchivalric) ? "helpless "
                                 : "",
                 (isFriendly)    ? "friendly " :
                 (wontAttack)    ? "non-hostile " :
                 (isNeutral)     ? "neutral "
                                 : "",
                 (isHoly)        ? "holy "
                                 : "",
                 mon->name(DESC_PLAIN).c_str(),
                 (inSanctuary)   ? ", despite your sanctuary"
                                 : "");

        prompt = true;
    }

    if (prompt)
        retval = !yesno(info, false, 'n');

    return (retval);
}

bool is_orckind(const actor *act)
{
    if (mons_genus(act->mons_species()) == MONS_ORC)
        return (true);

    if (act->atype() == ACT_MONSTER)
    {
        const monsters* mon = dynamic_cast<const monsters*>(act);
        if (mons_is_zombified(mon)
            && mons_genus(mon->base_monster) == MONS_ORC)
        {
            return (true);
        }
    }

    return (false);
}

bool is_dragonkind(const actor *act)
{
    if (mons_genus(act->mons_species()) == MONS_DRAGON
        || mons_genus(act->mons_species()) == MONS_DRACONIAN)
    {
        return (true);
    }

    if (act->atype() == ACT_PLAYER)
        return (you.attribute[ATTR_TRANSFORMATION] == TRAN_DRAGON);

    // Else the actor is a monster.
    const monsters* mon = dynamic_cast<const monsters*>(act);

    if (mon->type == MONS_SERPENT_OF_HELL)
        return (true);

    if (mons_is_zombified(mon)
        && (mons_genus(mon->base_monster) == MONS_DRAGON
            || mons_genus(mon->base_monster) == MONS_DRACONIAN))
    {
        return (true);
    }

    return (false);
}

// Make the player swap positions with a given monster.
void swap_with_monster(monsters *mon_to_swap)
{
    monsters& mon(*mon_to_swap);
    ASSERT(mon.alive());
    const coord_def newpos = mon.pos();

    // Be nice: no swapping into uninhabitable environments.
    if (!you.is_habitable(newpos) || !mon.is_habitable(you.pos()))
    {
        mpr("You spin around.");
        return;
    }

    const bool mon_caught = mon.caught();
    const bool you_caught = you.attribute[ATTR_HELD];

    // If it was submerged, it surfaces first.
    mon.del_ench(ENCH_SUBMERGED);

    mprf("You swap places with %s.", mon.name(DESC_NOCAP_THE).c_str());

    // Pick the monster up.
    mgrd(newpos) = NON_MONSTER;
    mon.moveto(you.pos());

    // Plunk it down.
    mgrd(mon.pos()) = mon_to_swap->mindex();

    if (you_caught)
    {
        check_net_will_hold_monster(&mon);
        if (!mon_caught)
            you.attribute[ATTR_HELD] = 0;
    }

    // Move you to its previous location.
    move_player_to_grid(newpos, false, true, true, false);

    if (mon_caught)
    {
        if (you.body_size(PSIZE_BODY) >= SIZE_GIANT)
        {
            mpr("The net rips apart!");
            you.attribute[ATTR_HELD] = 0;
            int net = get_trapping_net(you.pos());
            if (net != NON_ITEM)
                destroy_item(net);
        }
        else
        {
            you.attribute[ATTR_HELD] = 10;
            mpr("You become entangled in the net!");

            // Xom thinks this is hilarious if you trap yourself this way.
            if (you_caught)
                xom_is_stimulated(16);
            else
                xom_is_stimulated(255);
        }

        if (!you_caught)
            mon.del_ench(ENCH_HELD, true);
    }
}

// AutoID an equipped ring of teleport.
// Code copied from fire/ice in spl-cast.cc
void maybe_id_ring_TC()
{
    if (you.duration[DUR_CONTROL_TELEPORT]
        || player_mutation_level(MUT_TELEPORT_CONTROL))
    {
        return;
    }

    int num_unknown = 0;
    for (int i = EQ_LEFT_RING; i <= EQ_RIGHT_RING; ++i)
    {
        if (player_wearing_slot(i)
            && !item_ident(you.inv[you.equip[i]], ISFLAG_KNOW_PROPERTIES))
        {
            ++num_unknown;
        }
    }

    if (num_unknown != 1)
        return;

    for (int i = EQ_LEFT_RING; i <= EQ_RIGHT_RING; ++i)
        if (player_wearing_slot(i))
        {
            item_def& ring = you.inv[you.equip[i]];
            if (!item_ident(ring, ISFLAG_KNOW_PROPERTIES)
                && ring.sub_type == RING_TELEPORT_CONTROL)
            {
                set_ident_type( ring.base_type, ring.sub_type, ID_KNOWN_TYPE );
                set_ident_flags(ring, ISFLAG_KNOW_PROPERTIES);
                mprf("You are wearing: %s",
                     ring.name(DESC_INVENTORY_EQUIP).c_str());
            }
        }
}