feat: add statsFor and Reanimation.raise

src/reanimation.lua

@@ -0,0 +1,158 @@
+-- Necromancy: consumes a still-fresh corpse underfoot to raise it as a
+-- temporary skeletal thrall that fights beside the player until its
+-- borrowed animation runs out. Unlike companions.lua's charm-bonded ally,
+-- which persists across the whole run once bonded, a thrall is spent the
+-- instant it collapses - reduced to inert bones, nothing left to butcher a
+-- second time - and raising one costs the player a bite of sanity.lua's own
+-- meter, the same currency dread already drains, since bending a corpse
+-- back into motion is exactly the kind of wrongness that meter tracks.
+-- Only one thrall may walk at a time; raising a second dismisses the first
+-- outright, the same one-bond-at-a-time rule companions.lua keeps for its
+-- own charm. Thralls are plain entities on level.entities, exactly like
+-- companions, so they serialize with no special save-format handling
+-- beyond the one extra field (decay) entity.lua's toData whitelist adds.
+
+local Entity = require("entity")
+local Combat = require("combat")
+local Los = require("los")
+local Monsters = require("monsters")
+local Corpses = require("corpses")
+local Status = require("status")
+local Noise = require("noise")
+
+local Reanimation = {}
+
+Reanimation.LIFESPAN = 40
+Reanimation.SANITY_COST = 15
+Reanimation.HP_FRACTION = 0.6
+Reanimation.ATTACK_PENALTY = 1
+Reanimation.SIGHT = 6
+
+local ADJACENT = { { 1, 0 }, { -1, 0 }, { 0, 1 }, { 0, -1 }, { 1, 1 }, { 1, -1 }, { -1, 1 }, { -1, -1 } }
+
+-- Combat numbers for the thrall raised from a corpse of `speciesKey`: a
+-- fraction of the living species' own hp, attack blunted by one point for
+-- fighting with brittle bone instead of flesh, and defense and speed left
+-- exactly as they were - an animated skeleton is exactly as easy or hard to
+-- land a blow on, and exactly as quick underfoot, as the creature it once
+-- was. Falls back to a flat, unremarkable skeleton for any corpse whose
+-- species the bestiary no longer recognises (none today, but a save could
+-- in principle outlive a species removed from a later build).
+local function statsFor(speciesKey)
+  local spec = Monsters.byKey[speciesKey]
+  if not spec then return { hp = 8, attack = 2, defense = 0, speed = 100 } end
+  return {
+    hp = math.max(4, math.floor(spec.hp * Reanimation.HP_FRACTION)),
+    attack = math.max(1, spec.attack - Reanimation.ATTACK_PENALTY),
+    defense = spec.defense,
+    speed = spec.speed,
+  }
+end
+
+-- Raises `corpse` beside the player, retiring any earlier thrall first and
+-- spending the corpse and a bite of sanity outright. Returns the new
+-- thrall, or (nil, line) with nothing changed when the corpse has already
+-- rotted past use, the player's own mind cannot bear the cost, or every
+-- cell around the player is blocked.
+function Reanimation.raise(game, corpse)
+  if Corpses.isRotten(corpse) then
+    return nil, "this corpse has rotted too far to answer the call"
+  end
+  if game.player.sanity < Reanimation.SANITY_COST then
+    return nil, "your grip on your own mind is too frail for this"
+  end
+  local player = game.player
+  local x, y
+  for _, dir in ipairs(ADJACENT) do
+    local cx, cy = player.x + dir[1], player.y + dir[2]
+    if game.level.map:isWalkable(cx, cy) and not game.level:entityAt(cx, cy) then
+      x, y = cx, cy
+      break
+    end
+  end
+  if not x then
+    return nil, "there is nowhere for a thrall to rise"
+  end
+  for _, other in ipairs(game.level.entities) do
+    if other.kind == "thrall" and other:isAlive() then other.hp = 0 end
+  end
+  game:cleanupDead()
+  for i, candidate in ipairs(game.level.corpses) do
+    if candidate == corpse then
+      table.remove(game.level.corpses, i)
+      break
+    end
+  end
+  player.sanity = math.max(0, player.sanity - Reanimation.SANITY_COST)
+  local stats = statsFor(corpse.species)
+  local thrall = Entity.new({
+    id = game:nextMonsterId(), x = x, y = y,
+    glyph = "Z", name = corpse.name .. " thrall", kind = "thrall",
+    species = corpse.species, hp = stats.hp, attack = stats.attack, defense = stats.defense, speed = stats.speed,
+  })
+  thrall.decay = Reanimation.LIFESPAN
+  game.level.entities[#game.level.entities + 1] = thrall
+  return thrall
+end
+
+local function adjacent(a, b)
+  return math.max(math.abs(a.x - b.x), math.abs(a.y - b.y)) == 1
+end
+
+-- Nearest living monster the thrall can see within Reanimation.SIGHT, ties
+-- broken by ascending id for determinism - the same shape companions.lua's
+-- own nearestHostile follows, including its blind clamp (Game:canSeePlayer's
+-- own melee-range fallback for a blinded monster).
+local function nearestHostile(game, thrall)
+  local sight = Reanimation.SIGHT
+  if Status.has(thrall, Status.BLIND) then sight = math.min(sight, 1) end
+  local best, bestDist = nil, math.huge
+  for _, entity in ipairs(game.level.entities) do
+    if entity.kind == "monster" and entity:isAlive() then
+      local dist = math.max(math.abs(entity.x - thrall.x), math.abs(entity.y - thrall.y))
+      if dist <= sight and Los.clear(game.level.map, thrall.x, thrall.y, entity.x, entity.y) then
+        if dist < bestDist or (dist == bestDist and entity.id < best.id) then
+          best, bestDist = entity, dist
+        end
+      end
+    end
+  end
+  return best
+end
+
+-- The thrall's full turn: its borrowed animation runs out by one turn
+-- first, and once it hits zero the thrall collapses back into inert bones
+-- through the very same Game:onActorDeath path a slain one already falls
+-- through - called directly here, exactly like Game:checkTrapFor calls it
+-- directly for a trap kill mid-move, since nothing later in the caller's
+-- own takeMonsterTurn pipeline re-checks aliveness once dispatch returns.
+-- Otherwise it fights whatever hostile it can already reach, closes on one
+-- it can see but not yet reach, or shadows the player - the same
+-- three-branch shape as Companions.act, minus any tending since a thrall
+-- has nothing of its own to spare.
+function Reanimation.act(game, thrall)
+  thrall.decay = thrall.decay - 1
+  if thrall.decay <= 0 then
+    thrall.hp = 0
+    game:onActorDeath(thrall)
+    return
+  end
+  if game:allyActsConfused(thrall) then return end
+  local target = nearestHostile(game, thrall)
+  if target and adjacent(thrall, target) then
+    local outcome = Combat.attack(thrall, target)
+    game.log:add(string.format("your %s claws %s for %d", thrall.name, target.name, outcome.damage))
+    game:emitNoise(thrall.x, thrall.y, Noise.MELEE)
+    if outcome.killed then game:awardKill(target) end
+    return
+  end
+  if target then
+    game:stepMonsterToward(thrall, target.x, target.y)
+    return
+  end
+  if not adjacent(thrall, game.player) and not (thrall.x == game.player.x and thrall.y == game.player.y) then
+    game:stepMonsterToward(thrall, game.player.x, game.player.y)
+  end
+end
+
+return Reanimation