feat(identify): add appearance-based item identification

src/identify.lua

@@ -0,0 +1,72 @@
+-- Item identification. At world creation each potion and scroll type is dealt a
+-- random appearance (a colour or a nonsense label) by shuffling fixed pools with
+-- the world rng. Until a type is known the player only sees its appearance; using
+-- an item, or reading a scroll of identify, reveals the type for good.
+
+local Items = require("items")
+
+local Identify = {}
+
+local potionLooks = {
+  "ruby", "azure", "cloudy", "fizzy", "smoky", "golden", "murky", "viscous",
+}
+local scrollLooks = {
+  "XYZZY", "ELBERETH", "ZELGO KAI", "JUYED AWK", "VE FORBRYDERNE",
+  "FOOBIE BLETCH", "GHOTI", "NR 9",
+}
+
+local function shuffled(pool, rng)
+  local copy = {}
+  for i = 1, #pool do copy[i] = pool[i] end
+  for i = #copy, 2, -1 do
+    local j = rng:range(1, i)
+    copy[i], copy[j] = copy[j], copy[i]
+  end
+  return copy
+end
+
+function Identify.new(rng)
+  local appearance = {}
+  local potionOrder = shuffled(potionLooks, rng)
+  for i, entry in ipairs(Items.potionTypes) do
+    appearance[Items.POTION .. "/" .. entry.effect] = potionOrder[i] .. " potion"
+  end
+  local scrollOrder = shuffled(scrollLooks, rng)
+  for i, entry in ipairs(Items.scrollTypes) do
+    appearance[Items.SCROLL .. "/" .. entry.effect] = "scroll labeled " .. scrollOrder[i]
+  end
+  return { appearance = appearance, known = {} }
+end
+
+function Identify.isConcealable(item)
+  return item.kind == Items.POTION or item.kind == Items.SCROLL
+end
+
+function Identify.reveal(state, item)
+  state.known[Items.typeId(item)] = true
+end
+
+function Identify.isKnown(state, item)
+  return state.known[Items.typeId(item)] == true
+end
+
+function Identify.label(state, item)
+  if not Identify.isConcealable(item) then return item.name end
+  local id = Items.typeId(item)
+  if state.known[id] then return item.name end
+  return state.appearance[id] or item.name
+end
+
+-- Reveals the first still-unknown concealable item in an inventory. Returns the
+-- item whose type became known, or nil when everything is already identified.
+function Identify.revealFirstUnknown(state, inventory)
+  for _, item in ipairs(inventory) do
+    if Identify.isConcealable(item) and not Identify.isKnown(state, item) then
+      Identify.reveal(state, item)
+      return item
+    end
+  end
+  return nil
+end
+
+return Identify