-- Tilemap entity, it dynamically rebuilds its draw cache thingy
-- You just need to worry not and use the tile getting/setting functions

TILESIZE = 16
function new_tilemap(width, height)
  local map = new_entity()
  add_comp(map, "Tilemap", width, height)

  return map
end

function AUTO_ID(tl, tr, bl, br)
  return tl + 2 * tr + 4 * bl + 8 * br
end

local AUTOTILE_TBL = {
  ["0001"] = { 0, 0 },
  ["0010"] = { 1, 0 },
  ["0101"] = { 2, 0 },
  ["1010"] = { 3, 0 },
  ["0100"] = { 0, 1 },
  ["1000"] = { 1, 1 },
  ["0011"] = { 2, 1 },
  ["1100"] = { 3, 1 },
  ["1110"] = { 0, 2 },
  ["1101"] = { 1, 2 },
  ["0110"] = { 2, 2 },
  ["1001"] = { 3, 2 },
  ["1011"] = { 0, 3 },
  ["0111"] = { 1, 3 },
  ["1111"] = { 2, 3 },
  ["0000"] = {}
}

local function ID(map, x, y)
  return x + y * map.width + 1
end

-- local function POS(map, id)
--   id = id - 1
--   return id % map.width, math.floor(id / map.width)
-- end

register_comp("Tilemap", function(tilemap, width, height)
  tilemap.tiledata = {}
  for i = 1, width * height do
    tilemap.tiledata[i] = 0
  end
  tilemap.width = width
  tilemap.height = height
  tilemap.cache = {}
  tilemap.cachesize = 0
  tilemap.needs_rebuild = false
end)

function AUTOTILE_CODE(map, x, y)
  local typ

  local tl = get_tile(map, x, y)
  if tl ~= 0 then
    typ = tl
    tl = 1
  end

  local tr = get_tile(map, x + 1, y)
  if tr ~= 0 then
    typ = tr
    tr = 1
  end

  local bl = get_tile(map, x, y + 1)
  if bl ~= 0 then
    typ = bl
    bl = 1
  end

  local br = get_tile(map, x + 1, y + 1)
  if br ~= 0 then
    typ = br
    br = 1
  end
  return tl .. tr .. bl .. br, typ
end

function rebuild_tilemap(map)
  map.cache = {}
  map.cachesize = 0

  for x = -1, map.width do
    for y = -1, map.height do
      local code, typ = AUTOTILE_CODE(map, x, y)
      local tex_x, tex_y = unpack(AUTOTILE_TBL[code])

      if typ then
        -- Adjust for tile type fr
        tex_y = tex_y + (typ - 1) * 4

        map.cachesize = map.cachesize + 1
        map.cache[map.cachesize] = {
          x = x * TILESIZE + TILESIZE/2,
          y = y * TILESIZE + TILESIZE/2,
          tex_x = tex_x * TILESIZE,
          tex_y = tex_y * TILESIZE,
        }
      end
    end
  end
end

TILE_TEX = get_tex("res/img/tilesets.png")
local TILE_QUAD = lg.newQuad(
  0, 0,
  TILESIZE, TILESIZE,
  TILE_TEX:getWidth(), TILE_TEX:getHeight())

function tilemap_draw_sys(tilemap)
  if tilemap.needs_rebuild then
    rebuild_tilemap(tilemap)
    tilemap.needs_rebuild = false
  end

  for i = 1, tilemap.cachesize do
    local tile = tilemap.cache[i]
    TILE_QUAD:setViewport(tile.tex_x, tile.tex_y, TILESIZE, TILESIZE)
    lg.draw(TILE_TEX, TILE_QUAD, tile.x, tile.y)
  end
end

function get_tile(map, x, y)
  if x < 0 or x >= map.width or y < 0 or y >= map.height then
    return 0
  end
  return map.tiledata[ID(map, x, y)]
end

function has_tile(map, x, y)
  if x < 0 or x >= map.width or y < 0 or y >= map.height then
    return false
  end
  return map.tiledata[ID(map, x, y)] ~= 0
end

function queue_tilemap_rebuild(tilemap)
  tilemap.needs_rebuild = true
end

function set_tile(map, x, y, tileid)
  map.tiledata[ID(map, x, y)] = tileid
  map.needs_rebuild = true
end

function to_tile_coords(x, y)
  return math.floor(x / TILESIZE), math.floor(y / TILESIZE)
end

function remove_tile(map, x, y)
  map.tiledata[ID(map, x, y)] = 0
  map.needs_rebuild = true
end

function get_tileset_quad(tileset)
  local start_y = (tileset - 1) * 4 * TILESIZE
  return lg.newQuad(
    0, start_y,
    4 * TILESIZE, 4 * TILESIZE,
    TILE_TEX:getDimensions()
  )
end

function get_tileset_count()
  return TILE_TEX:getHeight() / (4 * TILESIZE)
end