-- Voxel world mode: resolve every tile of a tileset to an extrusion shape.
--
-- Reads the hand-authored groups in data/voxel_heights.lua and fills the
-- gaps from data the ROM extractor already emits. Resolution happens at two
-- granularities, and the order matters:
--
--   per tile   1. a group named in data/voxel_heights.lua  (hand-authored)
--   per CELL   2. the cell is water                        -> "water"
--              3. the cell is walkable                     -> "ground"
--   per tile   4. tile-level fallback: the map's water set -> "water",
--                 its walkable set -> "ground", else       -> "wall"
--
-- The cell steps (TileShape.at) are the load-bearing part. Collision in
-- this engine -- like the GB original -- is defined per 16x16 CELL, judged
-- by the cell's bottom-left 8x8 tile alone. The other three tiles of a
-- cell carry no collision meaning, and treating their walkable-list
-- membership as one (which is what a pure per-tile lookup does) misfiles
-- every decorative tile: flowers become 16px pillars, the gap tiles of a
-- fence row become wall, grass tufts extrude. A tile in a walkable cell is
-- ground the player is standing on, whatever the walkable list says about
-- it; hand-authoring (rule 1) is the only thing that overrides that.
--
-- Rule 4 covers positions whose cell IS blocked: there, walkable-listed
-- tiles (the gaps between fence posts) stay ground and the rest rise.
--
-- Every class also carries an ART mode, which is what the mesher renders:
--
--   flat     ground/water/void: a single quad, no box.
--   top      ledge/roof: a box with its art on the TOP face -- things
--            whose 2D art depicts a surface seen from above.
--   upright  wall/tree/fence/sign: a box whose SOUTH face reconstructs
--            the 2D artwork standing up (the mesher's fold-up rule) --
--            things whose 2D art depicts a surface seen face-on, which is
--            most of Gen 1: interior walls, furniture, tree canopies,
--            building facades.
--
-- Purely presentational: a shape decides how a tile DRAWS in voxel mode
-- and nothing else. Collision still reads the same walkable list it
-- always did.

-- the mod namespace (see main.lua): V.data loads a shipped data file
local V = ...

local TileShape = {}

-- class -> height fallbacks, used when data/voxel_heights.lua is missing
-- or omits a class. Same numbers the shipped file carries; a cell is 16x16.
local FALLBACK_HEIGHTS = {
  ground = 0,
  water = -2,
  void = 0,
  ledge = 6,
  fence = 10,
  sign = 12,
  wall = 16,
  tree = 16,
  roof = 28,
  cylinder = 16,
  billboard = 16,
  signpost = 16,
  post = 16,
  grass = 0,
  flower = 0,
  -- interior furniture: face-on drawings the detector would otherwise
  -- raise to wall height (or merge into the wall).  A bed is drawn from
  -- above and lies low; tables and desks are boxes at their real height;
  -- stairs become stepped geometry rising toward the named side.
  bed = 7,
  stool = 8,
  counter = 8,
  table = 12,
  desk = 24,
  prop = 16,
  cutout = 16,
  relief = 3,
  bookcase = 32,
  stair_e = 16,
  stair_w = 16,
  stair_down_e = 16,
  stair_down_w = 16,
}

-- class -> how the mesher draws it (see the header). The last three are
-- profile archetypes Structures.lua builds special geometry for:
--   cylinder   round-drawn cells (tree canopies) become voxel hulls cut
--              from the art's darkest-pixel outline, round in depth
--   billboard  signs, props: the art stands as a thin per-pixel voxel
--              slab, transparency respected
--   post       fence posts: the same thin per-pixel slab, but every CELL
--              stands alone in its own depth band -- a north-south fence
--              line is a march of separate posts, not one tall drawing
--              (which is what a shared cluster would make of it)
--   grass      tall grass: flat ground PLUS two thin standing rows of
--              tufts per tile (the art's top and bottom halves), each at
--              its drawn depth -- the player walks between them
local ART = {
  ground = "flat",
  water = "flat",
  void = "flat",
  ledge = "top",
  roof = "top",
  wall = "upright",
  tree = "upright",
  fence = "upright",
  sign = "upright",
  cylinder = "cylinder",
  billboard = "billboard",
  -- signposts share the billboard treatment but as their own pool at a
  -- 2-voxel depth: a sign is a thin plate on a stick, and the standard
  -- 10px standee body reads as a chunk of furniture outdoors
  signpost = "billboard",
  post = "post",
  grass = "grass",
  -- animated flowers: flat synthesized ground PLUS a standing cutout of
  -- the drawing's darkest tones, one voxel deep (see Structures'
  -- buildFlowers). Height 0 so a build with no pixel access degrades to
  -- the flat tile it always drew, not a box
  flower = "flower",
  -- furniture: a bed's art depicts its top surface; tables and desks are
  -- boxes whose fronts fold up (the mesher's authored-fold rule).
  -- Stools, `prop` and `cutout` are standee pools alongside `billboard`
  -- -- same per-pixel cutout, different thickness (see Structures'
  -- PINNED_DEPTH), and separate pools cluster separately so touching
  -- drawings never stack; a stool keeps its 8px height so a character
  -- standing on its (walkable) cell sits at seat height.  Stairs are a
  -- profile archetype Structures builds real steps for -- rising flights
  -- for stairs leading up, sunken stairwells for stairs leading down
  bed = "top",
  stool = "billboard",
  -- half-cell furniture: a service counter, a low couch.  One 8px band,
  -- so exactly the drawing's bottom row stands up as the front and
  -- every row above it rides the top face in drawn order -- which is
  -- also the only way to place a figure drawn INTO the furniture (the
  -- Center's seated man) without repeating him, since a taller box
  -- folds two rows upright and then repeats its north row across the
  -- top.  Reads as something you lean on rather than a wall stub
  counter = "upright",
  table = "upright",
  desk = "upright",
  prop = "billboard",
  cutout = "billboard",
  relief = "relief",
  -- free-standing shelves: the drawing is TALL, not deep -- Structures
  -- collapses each drawn rank onto a one-cell-deep box at full height
  bookcase = "bookcase",
  stair_e = "stair",
  stair_w = "stair",
  stair_down_e = "stair",
  stair_down_w = "stair",
}

local spec = nil          -- the loaded data file, or false when absent
local cache = {}          -- tileset id -> resolved shape list

-- The shape profile ships with the mod (data/voxel_heights.lua) and is read
-- through the mod's own file loader rather than package.path: a mod's
-- directory is not on it, and may live inside a mounted .love archive that
-- plain require cannot reach either.  Absent or broken degrades to the
-- derived defaults, which is a rougher-looking world rather than no world.
local function load()
  if spec == nil then
    local ok, s = pcall(V.data, "voxel_heights")
    spec = (ok and type(s) == "table") and s or false
  end
  return spec or nil
end

function TileShape.heights()
  local s = load()
  local out = {}
  for class, h in pairs(FALLBACK_HEIGHTS) do out[class] = h end
  for class, h in pairs(s and s.heights or {}) do
    if type(h) == "number" and FALLBACK_HEIGHTS[class] then out[class] = h end
  end
  return out
end

-- tile id -> class, from the hand-authored groups for one tileset. Unknown
-- class names are dropped rather than trusted: a typo in the data file
-- should degrade to the derived default, not invent a zero-height class.
local function authoredGroups(tilesetId, heights)
  local s = load()
  local entry = s and s.tilesets and s.tilesets[tilesetId]
  local out = {}
  if not entry then return out end
  for class, tiles in pairs(entry) do
    if heights[class] and type(tiles) == "table" then
      for _, t in ipairs(tiles) do out[t] = class end
    end
  end
  return out
end

local function shapeFor(class, heights, authored)
  return { class = class, h = heights[class] or 0,
           art = ART[class] or "upright",
           -- grass and flowers draw a flat ground base like any walkable
           -- tile; the standing tufts and cutouts are additive geometry
           -- from Structures
           flat = ART[class] == "flat" or class == "grass"
                  or class == "flower",
           authored = authored or false }
end

-- Resolved TILE-LEVEL shapes for the tileset `map` uses: a list indexed by
-- tile id holding { class, h, art, flat, authored }, plus `classes`, one
-- canonical shape per class for the cell-level overrides in TileShape.at.
-- Cached per tileset id -- this table depends only on the tileset record
-- and the data file, both constant for a given id. The per-map part of
-- resolution (cell walkability) lives in TileShape.at, NOT here.
function TileShape.forMap(map)
  local tileset = map.tileset
  local id = tileset.id
  if cache[id] then return cache[id] end

  local heights = TileShape.heights()
  local authored = authoredGroups(id, heights)
  local count = math.floor((tileset.imageWidth or 128) / 8)
                * math.floor((tileset.imageHeight or 48) / 8)

  -- derived pin: a tile the tileset animates by FRAME REWRITE (the
  -- overworld's flower) is already named by its animation spec, so like
  -- tall grass it needs no profile entry anywhere. Hand-authoring still
  -- wins -- a mod animating a wall tile this way keeps its wall by
  -- listing it. Guarded because the spec seam is engine data a stub map
  -- may not carry.
  local flowerTiles = {}
  do
    local ok, declared = pcall(function()
      if tileset.animatedTiles then return tileset.animatedTiles end
      local TileRenderer = require("src.render.TileRenderer")
      return TileRenderer.defaultAnimatedTiles(tileset)
    end)
    if ok then
      for _, spec in ipairs(type(declared) == "table" and declared or {}) do
        if spec.kind == "frames" and spec.tile then
          flowerTiles[spec.tile] = true
        end
      end
    end
  end

  local shapes = { classes = {} }
  for class in pairs(FALLBACK_HEIGHTS) do
    shapes.classes[class] = shapeFor(class, heights)
  end
  for t = 0, count - 1 do
    local class = authored[t]
    if class then
      shapes[t] = shapeFor(class, heights, true)
    elseif t == tileset.grassTile then
      -- derived pin: every tileset already names its tall-grass tile, so
      -- the standing-tuft treatment needs no profile entry anywhere
      shapes[t] = shapeFor("grass", heights, true)
    elseif flowerTiles[t] then
      shapes[t] = shapeFor("flower", heights, true)
    elseif map.waterTiles and map.waterTiles[t] then
      shapes[t] = shapes.classes.water
    elseif map.walkable and map.walkable[t] then
      shapes[t] = shapes.classes.ground
    else
      shapes[t] = shapes.classes.wall
    end
  end
  shapes.count = count
  cache[id] = shapes
  return shapes
end

-- The shape of the tile at TILE coordinates (tx, ty) -- the full
-- resolution including the cell-granularity steps (see the header).
-- `shapes` is the table forMap returned for this map; `tile` is
-- map:tileAt(tx, ty), passed in because every caller already has it.
function TileShape.at(map, shapes, tile, tx, ty)
  local s = shapes[tile]
  if not s or s.authored then return s end
  local cx = math.floor(tx / 2)
  local cy = math.floor(ty / 2)
  if map:isWaterCell(cx, cy) then return shapes.classes.water end
  if map:isWalkableCell(cx, cy) then return shapes.classes.ground end
  return s
end

-- Drop the cache: a mod that shadows data/voxel_heights.lua or a tileset
-- record needs the next lookup to re-resolve (hot reload, mod toggle).
function TileShape.invalidate()
  spec = nil
  cache = {}
end

return TileShape