feat: add Shrines.costFor and Shrines.curseChance

src/shrines.lua

@@ -0,0 +1,111 @@
+-- Wayside altars the player can pray at for a permanent boon at a gold price.
+-- A shrine's favor wears thin with use: each prayer at the same altar is more
+-- likely to backfire into a curse than the last, so greedily re-praying at a
+-- single shrine is a real risk rather than a free stat pump. Shrines are plain
+-- data on level.shrines, keyed by position, so they serialize like traps and
+-- hazards do with no special save-format handling.
+
+local Status = require("status")
+local Curses = require("curses")
+
+local Shrines = {}
+
+Shrines.WAR = "war"
+Shrines.VITALITY = "vitality"
+Shrines.WISDOM = "wisdom"
+Shrines.FORTUNE = "fortune"
+
+-- Fixed order so a given rng draw always names the same kind.
+Shrines.order = { Shrines.WAR, Shrines.VITALITY, Shrines.WISDOM, Shrines.FORTUNE }
+
+Shrines.names = {
+  [Shrines.WAR] = "shrine of war",
+  [Shrines.VITALITY] = "shrine of vitality",
+  [Shrines.WISDOM] = "shrine of wisdom",
+  [Shrines.FORTUNE] = "shrine of fortune",
+}
+
+local BASE_COST = 20
+local COST_STEP = 10
+
+-- Prayer cost climbs with prior use at this specific altar, the same shape as
+-- its rising curse risk: the shrine asks more and gives worse odds once its
+-- patience with the petitioner is spent.
+function Shrines.costFor(shrine)
+  return BASE_COST + shrine.uses * COST_STEP
+end
+
+-- Numerator over a denominator of 6: the first prayer risks 1-in-6, climbing
+-- by one for every prior use, capped at a certainty of 6-in-6.
+function Shrines.curseChance(shrine)
+  return math.min(shrine.uses + 1, 6), 6
+end
+
+local function grantBlessing(player, kind)
+  if kind == Shrines.WAR then
+    player.attack = player.attack + 1
+    player.baseAttack = player.baseAttack + 1
+    return "your grip tightens with martial favor"
+  elseif kind == Shrines.VITALITY then
+    player.maxHp = player.maxHp + 5
+    player.hp = player.hp + 5
+    return "vigor floods through you"
+  elseif kind == Shrines.WISDOM then
+    player.maxMana = player.maxMana + 3
+    player.mana = player.maxMana
+    return "arcane insight fills your mind"
+  else
+    local cleansed = false
+    local kept = {}
+    for _, active in ipairs(player.statuses) do
+      if active.kind == Status.POISON or active.kind == Status.BURNING
+        or active.kind == Status.WEAKEN or active.kind == Status.SLOW then
+        cleansed = true
+      else
+        kept[#kept + 1] = active
+      end
+    end
+    player.statuses = kept
+    Status.apply(player, Status.SHIELD, 10, 1)
+    if Curses.cleanseWorn(player) > 0 then cleansed = true end
+    if cleansed then
+      return "fortune cleanses your ailments and wards you"
+    end
+    return "fortune wards you against harm"
+  end
+end
+
+local function inflictCurse(player)
+  Status.apply(player, Status.WEAKEN, 8, 1)
+  Status.apply(player, Status.SLOW, 8, 1)
+  return "the shrine's favor turns against you"
+end
+
+-- Attempts a prayer at `shrine` for `game.player`. When the price cannot be
+-- met nothing is spent and this returns (false, lines). Otherwise the gold is
+-- always spent, the shrine's use count always advances (so its price and
+-- curse odds keep climbing), and this returns (true, lines) describing
+-- whichever of a blessing or a curse landed.
+function Shrines.pray(game, shrine)
+  local player = game.player
+  local cost = Shrines.costFor(shrine)
+  if player.gold < cost then
+    return false, { "you cannot afford " .. Shrines.names[shrine.kind] .. "'s price" }
+  end
+  player.gold = player.gold - cost
+  local numerator, denominator = Shrines.curseChance(shrine)
+  local cursed = game.rng:chance(numerator, denominator)
+  shrine.uses = shrine.uses + 1
+  local line
+  if cursed then
+    line = inflictCurse(player)
+  else
+    line = grantBlessing(player, shrine.kind)
+  end
+  return true, {
+    string.format("you pray at the %s for %d gold", Shrines.names[shrine.kind], cost),
+    line,
+  }
+end
+
+return Shrines