feat: add rollLoot and Chests.new

src/chests.lua

@@ -0,0 +1,182 @@
+-- Lockable loot containers scattered through the dungeon: an unlocked chest
+-- yields its hoard the instant it is opened, a locked one demands either a
+-- spent key (Items.KEY, the same key a locked door already consumes) or a
+-- lockpick gamble (Items.LOCKPICK) that risks springing the chest's own trap
+-- on a failed pick - a second, riskier route into the same treasure rather
+-- than a strictly worse one, since a lockpick is commoner floor loot than a
+-- key. Only a locked chest can be trapped at all: there is no lock to punish
+-- fumbling with on one that was never going to resist in the first place.
+-- A chest never moves and never decays; once opened it stays on the map as
+-- an emptied husk exactly like a corpse past its last butchering, so a
+-- second visit finds nothing left to take. Chests are plain data on
+-- level.chests, exactly like level.corpses and level.nodes, so they
+-- serialize with no special save-format handling.
+
+local Items = require("items")
+local Affixes = require("affixes")
+local Status = require("status")
+
+local Chests = {}
+
+Chests.LOCK_CHANCE_NUMERATOR = 1
+Chests.LOCK_CHANCE_DENOMINATOR = 2
+
+Chests.TRAP_CHANCE_NUMERATOR = 1
+Chests.TRAP_CHANCE_DENOMINATOR = 3
+
+Chests.PICK_BASE_NUMERATOR = 1
+Chests.PICK_BASE_DENOMINATOR = 2
+Chests.PICK_LEVEL_BONUS_DIVISOR = 5
+
+Chests.TRAP_DART_MIN = 2
+Chests.TRAP_DART_MAX = 5
+
+Chests.GOLD_MIN_BONUS = 0
+Chests.GOLD_MAX_BONUS = 10
+Chests.GOLD_BASE = 10
+Chests.GOLD_PER_DEPTH = 6
+
+local chestWeapons = {
+  { name = "ornate rapier", power = 4 },
+  { name = "gilded axe",    power = 5 },
+}
+local chestArmors = {
+  { name = "banded mail", power = 3 },
+}
+
+-- One chest's hoard: always some gold plus a coin flip between a lightly
+-- affixed weapon or armor piece (see affixes.lua) and, half the time on top
+-- of that, a spare healing potion. Richer on average than a single floor
+-- drop (builder.lua's rollItem), since reaching it costs a key or a
+-- lockpick gamble rather than a free step onto its tile.
+local function rollLoot(rng, depth)
+  local loot = { Items.gold(Chests.GOLD_BASE + depth * Chests.GOLD_PER_DEPTH
+    + rng:range(Chests.GOLD_MIN_BONUS, Chests.GOLD_MAX_BONUS)) }
+  if rng:chance(1, 2) then
+    local base = chestWeapons[rng:range(1, #chestWeapons)]
+    loot[#loot + 1] = Affixes.decorate(Items.weapon(base.name, base.power + depth // 4), Affixes.rollWeapon(rng))
+  else
+    local base = chestArmors[rng:range(1, #chestArmors)]
+    loot[#loot + 1] = Affixes.decorate(Items.armor(base.name, base.power + depth // 4), Affixes.rollArmor(rng))
+  end
+  if rng:chance(1, 2) then
+    loot[#loot + 1] = Items.potionOf("heal")
+  end
+  return loot
+end
+
+-- A freshly rolled chest at (unassigned) x/y, exactly like Nodes.new -
+-- builder.lua stamps x/y directly onto the returned table once it finds a
+-- free cell for it. Trapped is only ever rolled for a locked chest (see
+-- above), so the rng stream is never touched by the trap roll at all on an
+-- unlocked one.
+function Chests.new(rng, depth)
+  local locked = rng:chance(Chests.LOCK_CHANCE_NUMERATOR, Chests.LOCK_CHANCE_DENOMINATOR)
+  local trapped = locked and rng:chance(Chests.TRAP_CHANCE_NUMERATOR, Chests.TRAP_CHANCE_DENOMINATOR)
+  return {
+    locked = locked,
+    trapped = trapped,
+    opened = false,
+    loot = rollLoot(rng, depth),
+  }
+end
+
+-- A chest still worth forcing: locked and not already emptied. An opened
+-- chest reports unlocked regardless of its own `locked` flag, since nothing
+-- is left inside to gate.
+function Chests.isLocked(chest)
+  return chest.locked and not chest.opened
+end
+
+-- Odds of a lockpick attempt succeeding: a flat coin flip that improves
+-- slightly with player level, capped a point shy of the denominator so a
+-- pick attempt is never a sure thing no matter how experienced the player
+-- gets - mirrors disarm.lua's Disarm.oddsFor.
+function Chests.oddsFor(player)
+  local numerator = Chests.PICK_BASE_NUMERATOR + player.level // Chests.PICK_LEVEL_BONUS_DIVISOR
+  if numerator > Chests.PICK_BASE_DENOMINATOR - 1 then
+    numerator = Chests.PICK_BASE_DENOMINATOR - 1
+  end
+  return numerator, Chests.PICK_BASE_DENOMINATOR
+end
+
+-- Pours every item in `chest`'s hoard into `player`'s inventory and marks
+-- the chest spent for good.
+local function grant(player, chest)
+  for _, item in ipairs(chest.loot) do
+    player.inventory[#player.inventory + 1] = item
+  end
+  chest.opened = true
+  chest.loot = {}
+end
+
+-- Opens an already-unlocked (or never-locked) chest outright. Refuses with
+-- (false, line) and no state change against one still locked or already
+-- emptied - the caller (Game:openChest) routes a locked chest through
+-- Chests.unlockWithKey or Chests.pick instead.
+function Chests.open(player, chest)
+  if chest.opened then return false, "this chest is already empty" end
+  if Chests.isLocked(chest) then return false, "the chest is locked" end
+  grant(player, chest)
+  return true, "you open the chest and take its hoard"
+end
+
+-- Spends a key from `player`'s inventory to force the lock outright, no
+-- roll involved - the same certain trade a locked door already makes for
+-- one of Items.KEY. Returns (false, line) with nothing spent if the player
+-- is not carrying one, or against a chest that is not actually locked.
+function Chests.unlockWithKey(player, chest)
+  if not Chests.isLocked(chest) then return false, "this chest has no lock to open" end
+  for i, item in ipairs(player.inventory) do
+    if item.kind == Items.KEY then
+      table.remove(player.inventory, i)
+      chest.locked = false
+      grant(player, chest)
+      return true, "you unlock the chest with your key"
+    end
+  end
+  return false, "you have no key"
+end
+
+-- A trapped chest's punishment for a failed pick: a dart to the ribs or a
+-- dose of poison, the same two effects a floor trap can spring (see
+-- game.lua's Game:springTrap) but resolved locally since a chest is not a
+-- level.traps entry. Spends the trap the instant it springs - a chest only
+-- ever bites back once.
+function Chests.springTrap(game, chest)
+  chest.trapped = false
+  local player = game.player
+  if game.rng:chance(1, 2) then
+    local dealt = game.rng:range(Chests.TRAP_DART_MIN, Chests.TRAP_DART_MAX)
+    player.hp = player.hp - dealt
+    return string.format("a needle trap jabs you for %d", dealt)
+  end
+  Status.apply(player, Status.POISON, 5, 2)
+  return "a cloud of poison bursts from the lock"
+end
+
+-- Gambles a lockpick against `chest`'s lock. Always spends the pick, win or
+-- lose, once one is found. On success the chest opens exactly like
+-- Chests.unlockWithKey; on failure a trapped chest springs on the player
+-- (Chests.springTrap) while an untrapped one merely wastes the pick, the
+-- lock still standing for a later key or another pick.
+function Chests.pick(game, chest)
+  local player = game.player
+  if not Chests.isLocked(chest) then return false, "this chest has no lock to pick" end
+  local pickIndex
+  for i, item in ipairs(player.inventory) do
+    if item.kind == Items.LOCKPICK then pickIndex = i; break end
+  end
+  if not pickIndex then return false, "you have no lockpicks" end
+  table.remove(player.inventory, pickIndex)
+  local numerator, denominator = Chests.oddsFor(player)
+  if not game.rng:chance(numerator, denominator) then
+    if chest.trapped then return false, Chests.springTrap(game, chest) end
+    return false, "your lockpick slips and the lock holds"
+  end
+  chest.locked = false
+  grant(player, chest)
+  return true, "your lockpick clicks the lock open"
+end
+
+return Chests