feat: add Corpses.leavesCorpse and nutritionFor

src/corpses.lua

@@ -0,0 +1,103 @@
+-- Raw meat left behind by a fallen wild monster - a second, turn-costed food
+-- source alongside a found or bought ration (see Items.food, shop.lua). A
+-- corpse decays over a fixed number of rounds whether or not the player is
+-- even on this floor to see it (Corpses.step runs off Game:endPlayerTurn
+-- exactly like hazards.lua's fire/gas and nodes.lua's vein cooldown); left
+-- alone past its rot threshold it still butchers in one stroke, but the
+-- reward turns from a meal into a bout of poisoning instead. Undead crumble
+-- to dust and leave nothing to carve (see factions.lua's UNDEAD tag), a mimic
+-- was never alive to begin with (mimics.lua), and a boss's fixed loot drop
+-- (bosses.lua) is reward enough on its own - none of the three spawn a
+-- corpse. Corpses are plain data on level.corpses, exactly like
+-- level.hazards and level.nodes, so they serialize with no special
+-- save-format handling.
+
+local Factions = require("factions")
+local Items = require("items")
+local Status = require("status")
+
+local Corpses = {}
+
+Corpses.DECAY_TURNS = 60
+Corpses.ROT_TURNS = 25
+
+Corpses.NUTRITION_MIN = 30
+Corpses.NUTRITION_MAX = 200
+Corpses.NUTRITION_PER_HP = 8
+
+-- Wild monster corpses only: the undead were already dead before the player
+-- got there, a mimic's "corpse" would just be its loot disguise falling
+-- apart, and a boss's own scripted drop already covers its reward.
+function Corpses.leavesCorpse(target)
+  return target.faction ~= Factions.UNDEAD and not target.mimic and not target.isBoss
+end
+
+-- Nutrition scales with how tough the felled species was (maxHp, itself
+-- depth-scaled per monsters.lua), clamped to a fixed band so a late-game
+-- dragon corpse never trivializes hunger outright.
+local function nutritionFor(maxHp)
+  local raw = maxHp * Corpses.NUTRITION_PER_HP
+  return math.max(Corpses.NUTRITION_MIN, math.min(Corpses.NUTRITION_MAX, raw))
+end
+
+function Corpses.new(target)
+  return {
+    x = target.x, y = target.y,
+    species = target.species, name = target.name,
+    nutrition = nutritionFor(target.maxHp),
+    decay = Corpses.DECAY_TURNS,
+  }
+end
+
+-- Appends a fresh corpse for `target` onto `level.corpses`, or does nothing
+-- for anything Corpses.leavesCorpse rules out.
+function Corpses.spawn(level, target)
+  if not Corpses.leavesCorpse(target) then return end
+  level.corpses[#level.corpses + 1] = Corpses.new(target)
+end
+
+function Corpses.isRotten(corpse)
+  return corpse.decay <= Corpses.ROT_TURNS
+end
+
+-- Advances every corpse on the level one round toward fully rotting away,
+-- exactly like hazards.step and nodes.step - called once per round, not per
+-- actor, so a seeded run always loses a given corpse on the identical turn
+-- regardless of how many actors acted that round.
+function Corpses.step(level)
+  for i = #level.corpses, 1, -1 do
+    local corpse = level.corpses[i]
+    corpse.decay = corpse.decay - 1
+    if corpse.decay <= 0 then table.remove(level.corpses, i) end
+  end
+end
+
+-- Drops `corpse` off level.corpses outright - shared by every way of
+-- spending one (see Corpses.butcher below and scavenging.lua's own harvest),
+-- so a corpse can never be carved twice over.
+function Corpses.remove(level, corpse)
+  for i, candidate in ipairs(level.corpses) do
+    if candidate == corpse then
+      table.remove(level.corpses, i)
+      return
+    end
+  end
+end
+
+-- Carves up `corpse` in one stroke, always spending it whether the meat is
+-- still good or not. A corpse still inside its rot threshold yields a fresh
+-- Items.food ration into the player's inventory, eaten later exactly like a
+-- found one; a corpse butchered past that threshold instead poisons the
+-- player outright - the corpse itself is just as gone either way.
+function Corpses.butcher(game, corpse)
+  Corpses.remove(game.level, corpse)
+  if Corpses.isRotten(corpse) then
+    Status.apply(game.player, Status.POISON, 5, 2)
+    return string.format("the %s corpse has rotted; you gag it down and immediately regret it", corpse.name)
+  end
+  local food = Items.food(corpse.name .. " meat", corpse.nutrition)
+  game.player.inventory[#game.player.inventory + 1] = food
+  return string.format("you carve %d nutrition worth of meat from the %s corpse", corpse.nutrition, corpse.name)
+end
+
+return Corpses