Merge branch 'mon-pick'

The behaviour should be preserved exactly or almost exactly, only the code
changes from totally, utterly unreadable to merely hard to read.

Actual differences:
* strong OODs in shallow branches would degenerate into picking a monster
  randomly from the whole branch, now they pick from the bottom level (or
  so-called OOD cap of Elf:7, Tomb:5, D:31 and Vaults:15).
* Zot no longer replaces requests for Zot:5 by Zot:4, and proper hells,
  $(HELL):4-7 by $(HELL):3.
  * this means hell monster sets need fixing!
* zombie size doesn't affect their spawning
* zombie selection obeys the depth passed
  * which makes zombie sets pretty limited -- needs review/redesign?

The new format is:
{  9, 19,  826, SEMI, MONS_YAK },
which means: yaks can spawn on D:9-19, with _linear_ rarity 826 in the
middle of the range.  A "SEMI" distribution means that at the edges,
D:9 and D:19, the effective rarity is half that, 413.

Distributions:
FLAT   100% 100% 100%
SEMI    50% 100%  50%
PEAK     0% 100%   0%
UP       0%  50% 100%
DOWN   100%  50%   0%

That "0%" doesn't mean the monster won't spawn on the top/bottom level
(D:9 and D:19 for yaks), the range is fudged so D:8 receives 0% chance,
D:9 16.6%, linearly up to 100% on D:14.

Yes, this sounds and is complex, but at least the complexity is not strewn
around obscure code anymore, and a number of limitations have been lifted.

ZotDef still uses the old code via an emulation layer.

1 files changed, 20 insertions, 22 deletions

diff --git a/crawl-ref/source/zotdef.cc b/crawl-ref/source/zotdef.cc
index 5729d734f1..1d622606d7 100644
--- a/crawl-ref/source/zotdef.cc
+++ b/crawl-ref/source/zotdef.cc
@@ -43,7 +43,7 @@
 
 static monster_type _pick_unique(int level);
 
-static int _fuzz_mons_level(int level)
+static int _fuzz_mons_depth(int level)
 {
     if (level > 1 && one_chance_in(7))
     {
@@ -138,17 +138,10 @@ static int _mon_strength(monster_type mon_type)
     // Fix for skeletons and zombies
     switch (mon_type)
     {
-        case MONS_SKELETON_SMALL:
-        case MONS_ZOMBIE_SMALL:
+        case MONS_SKELETON:
+        case MONS_ZOMBIE:
             strength += 3;
             break;
-        case MONS_SKELETON_LARGE:
-        case MONS_ZOMBIE_LARGE:
-            strength += 4;
-            break;
-        case MONS_PANDEMONIUM_LORD: // base init has 4HD (!)
-            strength = 30;
-            break;
         default:
             break;
     }
@@ -559,19 +552,19 @@ static monster_type _get_zotdef_monster(level_id &place, int power)
     monster_type mon_type;
     for (int i = 0; i <= 10000; ++i)
     {
-        int count = 0;
         int rarity;
 
-        do
+        if (place.branch == NUM_BRANCHES)
         {
-            mon_type = static_cast<monster_type>(random2(NUM_MONSTERS));
-            count++;
-            rarity = (place.branch == NUM_BRANCHES) ? 30 : mons_rarity(mon_type, place);
+            mon_type = static_cast<monster_type>(random2(NUM_MONSTERS - 1) + 1);
+            rarity = 30;
+        }
+        else
+        {
+            mon_type = pick_monster_no_rarity(place.branch);
+            rarity = mons_rarity(mon_type, place.branch);
+            ASSERT(rarity > 0);
         }
-        while (rarity == 0 && count < 2000);
-
-        if (rarity == 0)
-            return MONS_PROGRAM_BUG;
 
         // Calculate strength
         const monsterentry *mentry = get_monster_data(mon_type);
@@ -595,7 +588,7 @@ static monster_type _get_zotdef_monster(level_id &place, int power)
         // get default level
         int lev_mons = (place.branch == NUM_BRANCHES)
                        ? ((strength * 3) / 2)
-                       : mons_level(mon_type, place)
+                       : mons_depth(mon_type, place.branch)
                          + absdungeon_depth(place.branch, 0);
 
         // if >50, bail out - these are special flags
@@ -656,7 +649,7 @@ static void _zotdef_set_random_branch_wave(int power)
     for (int i = 0; i < NSLOTS; i++)
     {
         level_id l(_zotdef_random_branch(), -1);
-        env.mons_alloc[i] = _get_zotdef_monster(l, _fuzz_mons_level(power));
+        env.mons_alloc[i] = _get_zotdef_monster(l, _fuzz_mons_depth(power));
     }
     level_id l(_zotdef_random_branch(), -1);
     env.mons_alloc[BOSS_SLOT] = _get_zotdef_monster(l,
@@ -671,7 +664,7 @@ static void _zotdef_set_branch_wave(branch_type b, int power)
          (b == NUM_BRANCHES) ? "RANDOM" : branches[b].shortname);
     wave_name(buf);
     for (int i = 0; i < NSLOTS; i++)
-        env.mons_alloc[i] = _get_zotdef_monster(l, _fuzz_mons_level(power));
+        env.mons_alloc[i] = _get_zotdef_monster(l, _fuzz_mons_depth(power));
     env.mons_alloc[BOSS_SLOT] = _get_zotdef_monster(l,
                                     power + ZOTDEF_BOSS_EXTRA_POWER);
 }
@@ -792,6 +785,11 @@ monster* zotdef_spawn(bool boss)
     mg.proximity = PROX_NEAR_STAIRS;
     mg.flags |= MG_PERMIT_BANDS;
 
+    // Hack: emulate old mg.power
+    mg.place = level_id(BRANCH_MAIN_DUNGEON, you.num_turns / (ZOTDEF_CYCLE_LENGTH * 3) + 1);
+    // but only for item generation/etc, not for actual monster selection.
+    ASSERT(mt != RANDOM_MONSTER);
+
     monster *mon  = mons_place(mg);
 
     // Boss monsters which aren't uniques are named, and beefed a bit further