LDtk.lua

-- version 1.07
--
-- Copyright 2022-2023 Nic Magnier
-- 
-- Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
--
-- The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
--
-- THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
--
-- Read levels made with LDtk level editor
-- More information about LDtk: https://ldtk.io/
--
-- Load the levels at the beginning of the game
--	LDtk.load( "levels/world.ldtk" )
--	tilemap = LDtk.create_tilemap( "Level_0" )
--
-- To get collision information, in LDtk create an enum for tiles (Wall, Water, Ladder etc.)
-- Use the enum in the tileset and tag tiles with the desired property
-- In your code:
-- 	playdate.graphics.sprite.addWallSprites( game.tilemap, LDtk.get_empty_tileIDs( "Level_0", "Solid") )

-- Tilsets
-- It is recommended to save the tileset image in the same folder (or in a sub folder) as the ldtk file
-- The tileset needs to be an image table so the filename should have the format: mytileset-table-w-h.format
-- If a tilemap use flipped tiles, you need to create an additional tileset image that includes mirrored version of the tiles
-- Original tileset: mytileset-table-8-8.png
-- Additional tileset filename: flipped-mytileset-table-8-8.png
-- Original tiles
--	(=\
-- Flipped tiles (image is 100% larger width and height, right side is flipped horozontally, bottom side is flipped vertically)
--	(=\/=)
--	(=/\=)

-- External levels
-- LDtk has an option to save each level in seperate files.
-- That allows you to load and unload levels when you need it instead of having the whole world in memory.
-- 	LDtk.load_level( "Level_1" )
--	LDtk.release_level( "Level_0" )
-- Note: release_level() is freeing the tileset so it is better to release a level after loading the next level if they use the same tilesets.

-- Fast loading
-- Parsing json can be long especially when running on the playdate
-- to speed up loading there is an option to load directly lua files
-- in the simulator call LDtk.export_to_lua_files() after a LDtl file is loaded to save the exported lua files in the save folder
-- copy the LDtk_lua_levels/ next to your .ldtk file in your project directory

LDtk = {}

local _ldtk_filepath = nil
local _ldtk_folder = nil
local _ldtk_filename = nil
local _ldtk_folder_table = nil
local _ldtk_lua_folder = nil

local _ldtk_lua_foldername = "LDtk_lua_levels"

local _level_files = {}
local _levels = {}
local _level_names = {} -- uids to name
local _level_rects = {}
local _tilesets = {}
local _imageTables = {}

local _use_external_files = false
local _use_lua_levels = false

local _ = {} -- for private functions

-- @use_lua_levels(optional)
--	true: will load lua precomputed levels
--	false: will load .ldtk files (slower)
--	nil: will load lua files if they exist
function LDtk.load( ldtk_file, use_lua_levels )
	if not ldtk_file then
		error("LDtk Importer Error: LDtk.load() is called without a path to a ldtk file.")
		return
	end

	_ldtk_filepath = ldtk_file
	_ldtk_folder, _ldtk_filename = _.get_folder_and_filename( ldtk_file )
	_ldtk_folder_table = _.get_folder_table( _ldtk_folder )
	_ldtk_lua_folder = _ldtk_folder.._ldtk_lua_foldername

	local lua_filename = _ldtk_lua_folder.."/".._ldtk_filename..".pdz"

	-- check if we should load the lua files instead of the json files
	_use_lua_levels = use_lua_levels
	if _use_lua_levels then
		if not playdate.file.exists( lua_filename ) then
			_use_lua_levels = false
			print("LDtk Importer Error: cannot load lua file (compiled as .pdz) because it does not exist.", lua_filename)
		end
	end

	-- simply load the level from the precomputed lua file
	if _use_lua_levels then
		print("LDtk Importer will use lua precomputed levels.")
		local data = playdate.file.run( lua_filename )

		_tilesets = data.tilesets
		_level_files = data.level_files
		_level_names = data.level_names
		_level_rects = data.level_rects
		_levels = data.levels
		_use_external_files = data.use_external_files

		if not _use_external_files then
			for level_name in pairs(_levels) do
				_.load_tileset( level_name )
			end
		end
		return
	end

	local data = json.decodeFile(ldtk_file)
	if not data then
		if playdate.file.exists(ldtk_file) then
			error("LDtk Importer Error: The LDtk file could not be decoded. Is it a valid LDtk file?")
		else
			print("LDtk Importer Error: The LDtk file does not exist. ", ldtk_file)
		end

		return
	end

	_use_external_files = data.externalLevels

	-- handle the tilesets
	for tileset_index, tileset_data in ipairs(data.defs.tilesets) do
		local tileset = {}

		_tilesets[ tileset_data.uid ] = tileset

		tileset.imageTable_filename = _.convert_relative_folder( tileset_data.relPath )
		tileset.imageWidth = tileset_data.pxWid
		tileset.imageHeight = tileset_data.pxHei

		-- Tile IDs list
		local gsize = tileset_data.tileGridSize
		local cw, ch = tileset_data.__cWid, tileset_data.__cHei
		local cw2, ch2 = cw*2, ch*2

		tileset.tileIDs = {}
		tileset.tileIDs_empty = {}
		tileset.tileIDs_flipped = {}
		tileset.tileIDs_flipped_empty = {}
		for index, enum_def in ipairs(tileset_data.enumTags) do
			local tileIDs = {}
			local tileIDs_flipped = {}

			local registered_tileIDs = {}
			local registered_tileIDs_flipped = {}

			for i, tileID in ipairs( enum_def.tileIds ) do
				-- normal tileset
				table.insert( tileIDs, 1+tileID)
				registered_tileIDs[ 1+tileID ] = true

				-- flipped tileset
				local cy = tileID//cw
				local cx = tileID - cy*cw
				local tileID_flip_no = 1 + cy*cw2 + cx
				local tileID_flip_x = 1 + cy*cw2 + (cw2-cx-1)
				local tileID_flip_y = 1 + (ch2-cy-1)*cw2 + cx
				local tileID_flip_xy = 1 + (ch2-cy-1)*cw2 + (cw2-cx-1)

				table.insert( tileIDs_flipped, tileID_flip_no)
				table.insert( tileIDs_flipped, tileID_flip_x)
				table.insert( tileIDs_flipped, tileID_flip_y)
				table.insert( tileIDs_flipped, tileID_flip_xy)

				registered_tileIDs_flipped[ tileID_flip_no ] = true
				registered_tileIDs_flipped[ tileID_flip_x ] = true
				registered_tileIDs_flipped[ tileID_flip_y ] = true
				registered_tileIDs_flipped[ tileID_flip_xy ] = true
			end

			-- empty versions
			local tileIDs_empty = {}
			for tileID = 1, cw*ch do
				if not registered_tileIDs[tileID] then
					table.insert( tileIDs_empty, tileID )
				end
			end

			-- flipped empty version
			local tileIDs_flipped_empty = {}
			for tileID = 1, cw2*ch2 do
				if not registered_tileIDs_flipped[tileID] then
					table.insert( tileIDs_flipped_empty, tileID )
				end
			end

			tileset.tileIDs[ enum_def.enumValueId ] = tileIDs
			tileset.tileIDs_empty[ enum_def.enumValueId ] = tileIDs_empty
			tileset.tileIDs_flipped[ enum_def.enumValueId ] = tileIDs_flipped
			tileset.tileIDs_flipped_empty[ enum_def.enumValueId ] = tileIDs_flipped_empty
		end

	end

	-- we list the level names (the complete list needs to be ready before calling LDtk.load_level())
	for level_index, level_data in ipairs(data.levels) do
		_level_names[ level_data.iid ] = level_data.identifier
		_level_rects[ level_data.identifier ] = { x=level_data.worldX, y=level_data.worldY, width=level_data.pxWid, height=level_data.pxHei }
	end

	-- we load the levels
	for level_index, level_data in ipairs(data.levels) do
		local level_name = level_data.identifier

		if level_data.externalRelPath then
			_level_files[ level_name ] = _.convert_relative_folder( level_data.externalRelPath )
		else
			_levels[ level_name ] = _.process_level_data( level_data )
			_.load_tileset( level_name )
		end
	end
end

-- Call this function to save the LDtk level in lua files to improve loading performance
-- The files will be saved in the aave folder of the game (PlaydateSDK/Disk/Data)
function LDtk.export_to_lua_files()
	if _use_lua_levels then
		print("LDtk Importer Error: Cannot export level in lua. The system had loaded lua files instead of .ldtk")
		return
	end

	local folder = _ldtk_lua_foldername.."/"
	playdate.file.mkdir(_ldtk_lua_foldername)

	local lua_level_files = {}
	for level_name, level_file in pairs(_level_files) do
		local filename = _.get_filename(level_file)
		lua_level_files[ level_name ] = _ldtk_lua_folder.."/"..filename..".pdz"
	end

	print("LDtk Importer: Export LDtk world...")
	_.export_lua_table( folder.._ldtk_filename..".lua", {
		tilesets = _tilesets,
		level_files = lua_level_files,
		level_names = _level_names,
		level_rects = _level_rects,
		levels = _levels,
		use_external_files = _use_external_files
	})

	for level_name, level_file in pairs(_level_files) do
		print("LDtk Importer: Export LDtk level", level_name)

		LDtk.load_level( level_name )
		_.export_lua_table( folder.._.get_filename(level_file)..".lua", _levels[ level_name ])
		LDtk.release_level( level_name )
	end
end

-- load the level in memory
-- only necessary to call if the ldtk file is saved in multiple files
function LDtk.load_level( level_name )
	-- check if the level was already loaded
	if _levels[ level_name ] then
		return
	end

	-- load the level as recompiled lua file or the ldtk json file
	if _use_lua_levels then
		_levels[ level_name ] = playdate.file.run( _level_files[ level_name ] )
	else
		_levels[ level_name ] = _.process_level_data( json.decodeFile( _level_files[ level_name ] ) )
	end

	_.load_tileset( level_name )
end

-- free the level from the memory
-- the tileset is also freed if no other level is using it
function LDtk.release_level( level_name )
	if not _use_external_files then
		print("LDtk Importer Warning: file doesn't use external files. No need to load/release individual levels.")
		return
	end

	local level = _levels[level_name]
	if not level then return end

	-- release image table tilesets
	for layer_name, layer in pairs(level.layers) do
		_.release_tileset_imagetable( layer.tileset_file, layer.has_flipped_tiles)
	end

	_levels[level_name] = nil
end

-- get a list of entities
-- @layer_name is optional, if nil then it will return all the entities
-- entities format
-- 	.name : name of the entity class
-- 	.position : position of the entity
--	.center : alignment of the sprite around the position. can be used with sprite:setCenter()
--	.size :  width and height of the entity
--	.zIndex : layer index
-- 	.fields : all the custom fields data entered in the LDtk editor
function LDtk.get_entities( level_name, layer_name )
	local level = _levels[level_name]
	if not level then return end

	if not layer_name then
		local all_entities = {}
		for layer_name, layer in pairs(level.layers) do
			for entity_index, entity in pairs(layer.entities or {}) do
				table.insert( all_entities, entity)
			end
		end

		return all_entities
	end

	local layer = level.layers[ layer_name ]
	if not layer then return end

	return layer.entities or {}
end

-- return a tilemap for the level
-- @layer_name is optional, if nil then will return the first layer with tiles
function LDtk.create_tilemap( level_name, layer_name )
	local layer = _.get_tile_layer( level_name, layer_name )
	if not layer then return end

	local tilemap = playdate.graphics.tilemap.new()
	tilemap:setImageTable( layer.tileset_image )
	tilemap:setTiles( layer.tiles, layer.tilemap_width)

	return tilemap
end

-- return a table with all the adjacent levels
-- @direction is optional: values can be "east", "west", "north", "south", "back", "front", "northwest", "northeast", "southwest", "southeast"
function LDtk.get_neighbours( level_name, direction )
	local level = _levels[level_name]
	if not level then return end

	if not direction then
		return level.neighbours
	end

	return level.neighbours[ direction ]
end

-- return the position and site of the level in the world
-- always available, the level doesn't need to be loaded
function LDtk.get_rect( level_name )
	return _level_rects[ level_name ]
end

-- return custom data for the specified level
-- @field_name is optional, if nil then it will return all the fields as a table
function LDtk.get_custom_data( level_name, field_name )
	local level = _levels[ level_name ]
	if not level then
		return nil
	end

	local custom_data = level.custom_data
	if not custom_data then
		return nil
	end

	if field_name then
		return custom_data[ field_name ]
	end

	return custom_data
end

-- return all the tileIDs tagged in LDtk with tileset_enum_value
-- LDtk.get_tileIDs( "Level_0", "Solid" )
function LDtk.get_tileIDs( level_name, tileset_enum_value, layer_name )
	local layer = _.get_tile_layer( level_name, layer_name )
	if not layer then return end

	local tileset = _tilesets[ layer.tileset_uid ]
	if not tileset then return end

	if layer.has_flipped_tiles then
		return tileset.tileIDs_flipped[ tileset_enum_value ]
	end

	return tileset.tileIDs[ tileset_enum_value ]
end


-- return all the tileIDs NOT tagged in LDtk with tileset_enum_value
-- playdate functions usually require this function (getCollisionRects(emptyIDs), addWallSprites() )
function LDtk.get_empty_tileIDs( level_name, tileset_enum_value, layer_name )
	local layer = _.get_tile_layer( level_name, layer_name )
	if not layer then return end

	local tileset = _tilesets[ layer.tileset_uid ]
	if not tileset then return end

	if layer.has_flipped_tiles then
		return tileset.tileIDs_flipped_empty[ tileset_enum_value ]
	end

	return tileset.tileIDs_empty[ tileset_enum_value ]
end

-- return all layers from a level
function LDtk.get_layers(level_name)
	local level = _levels[level_name]

	if not level then return end
	return level.layers
end

-- return the name of a level bsed on their Strind IID
function LDtk.get_level_name(levelIid)
	return _level_names[levelIid]
end

-- Generate an image from a section of a tileset
-- https://ldtk.io/json/#ldtk-TilesetRect
-- You can use it as custom property
function LDtk.generate_image_from_tileset_rect( tileset_rect )
	if not tileset_rect then
		return nil
	end

	-- Load tileset
	local tileset = _tilesets[ tileset_rect.tilesetUid ]
	if not tileset then
		return nil
	end
	local cells = _.load_tileset_imagetable( tileset.imageTable_filename )
	if not cells then
		return nil
	end

	local cell_width, cell_height = cells[1]:getSize()
	local x_count = math.ceil( tileset_rect.w/cell_width )
	local y_count = math.ceil( tileset_rect.h/cell_height )

	local entity_image = playdate.graphics.image.new(tileset_rect.w, tileset_rect.h)

	playdate.graphics.lockFocus( entity_image )
		for y = 0, y_count-1 do
			for x = 0, x_count-1 do
				cells:getImage( 1 + (tileset_rect.x//cell_width) + x, 1 + (tileset_rect.y//cell_height) + y ):draw( x*cell_width, y*cell_height )
			end
		end
	playdate.graphics.unlockFocus()

	_.release_tileset_imagetable( tileset.imageTable_filename )

	return entity_image
end

-- Generate an image of an entity
-- The entity needs to have the 'Editor Visual' property set to a tileset in LDtk
function LDtk.generate_image_from_entity( entity )
	if not entity then
		return nil
	end

	if not entity.tileset_rect then
		print("LDtk Importer Error: Cannot generate entity image. No tileset assigned to it.")
		return
	end

	return LDtk.generate_image_from_tileset_rect( entity.tileset_rect )
end

--
-- internal functions
--

function _.get_folder_and_filename( filepath )
	local folder, filename, extension = filepath:match("(.-)([^/.]-).([^.]+)$")
	return folder, filename
end

function _.get_filename( filepath )
	local folder, filename = _.get_folder_and_filename( filepath )
	return filename
end

function _.get_folder( filepath )
	local folder, filename = _.get_folder_and_filename( filepath )
	return folder
end


function _.get_folder_table( path )
	local delimiter = '/'
	local result = {}
	local string_index = 1
	local folder

	if not path then
		return result
	end

	local found_start, found_end = string.find( path, delimiter, string_index)
	while found_start do
		folder = string.sub( path, string_index , found_start-1 )
		if type(folder)=="string" and string.len(folder)>0 then
			table.insert(result, folder)
		end

		string_index = found_end + 1
		found_start, found_end = string.find( path, delimiter, string_index)
	end

	folder = string.sub( path, string_index)
	if type(folder)=="string" and string.len(folder)>0 then
		table.insert(result, folder)
	end

	return result
end

function _.convert_relative_folder( filepath )
	if not filepath then
		return nil
	end

	local ldtk_folder_end = #_ldtk_folder_table
	local relative_path_start = 1

	local relative_path_table = _.get_folder_table( filepath )
	for index, relative_folder in ipairs(relative_path_table) do
		if relative_folder==".." then
			ldtk_folder_end = ldtk_folder_end - 1
		elseif relative_folder~="." then
			goto skip_folders
		end

		relative_path_start = relative_path_start + 1
	end
	::skip_folders::

	if ldtk_folder_end<0 then
		error( "LDtk Importer Error: Cannot access the following path because it is outside the project folder: "..filepath)
	end

	local absolute_path
	for index = 1, ldtk_folder_end do
		if absolute_path then
			absolute_path = absolute_path.."/".._ldtk_folder_table[ index ]
		else
			absolute_path = _ldtk_folder_table[ index ]
		end
	end
	for index = relative_path_start, #relative_path_table do
		if absolute_path then
			absolute_path = absolute_path.."/"..relative_path_table[ index ]
		else
			absolute_path = relative_path_table[ index ]
		end
	end

	return absolute_path
end

function _.process_level_data( level_data )
	if not level_data then return end
	if not level_data.identifier then return end

	local level = {}

	-- set neighbours information
	level.neighbours = { east = {}, west = {}, north = {}, south = {}, back = {}, front = {}, northwest = {}, northeast = {}, southwest = {}, southeast = {} }
	local direction_table = {
		e = "east",
		w = "west",
		n = "north",
		s = "south",
		[">"] = "back",
		["<"] = "front",
		nw = "northwest",
		ne = "northeast",
		sw = "southwest",
		se = "southeast"
	}

	for index, neighbour_data in ipairs(level_data.__neighbours) do
    	local direction = direction_table[neighbour_data.dir]
   		if direction then
       		table.insert(level.neighbours[direction], _level_names[neighbour_data.levelIid])
    	end
	end

	-- load level's custom fields
	level.custom_data = {}
	for index, field_data in ipairs(level_data.fieldInstances) do
		level.custom_data[ field_data.__identifier ] = field_data.__value
	end

	-- handle layers
	level.layers = {}
	local layer_count = #level_data.layerInstances
	for layer_index, layer_data in ipairs(level_data.layerInstances) do

		local layer = {}
		level.layers[ layer_data.__identifier ] = layer

		local layer_type = layer_data.__type

		layer.grid_size = layer_data.__gridSize
		layer.zIndex = layer_count - layer_index
		layer.rect = {
			x = level_data.worldX + layer_data.__pxTotalOffsetX,
			y = level_data.worldY + layer_data.__pxTotalOffsetY,
			width = layer_data.__cWid * layer_data.__gridSize,
			height = layer_data.__cHei * layer_data.__gridSize
			}

		-- load tileset
		if layer_data.__tilesetRelPath then
			layer.tileset_file = _.convert_relative_folder( layer_data.__tilesetRelPath )
		end
		layer.has_flipped_tiles = false

		-- handle tiles
		local tiles_data = layer_data.gridTiles
		if #layer_data.autoLayerTiles>0 then
			tiles_data = layer_data.autoLayerTiles
		end
		if #tiles_data>0 then
			layer.tilemap_width = layer_data.__cWid
			layer.tileset_uid = layer_data.__tilesetDefUid

			layer.tiles = {}

			local gsize = layer.grid_size
			local tileset_data = _tilesets[ layer.tileset_uid ]
			local cw, ch = tileset_data.imageWidth/gsize, tileset_data.imageHeight/gsize

			-- check we we have any flipped tiles
			for tile_index, tile_data in ipairs(tiles_data) do
				if tile_data.f~=0 then
					layer.has_flipped_tiles = true
					cw = cw * 2
					ch = ch * 2
					goto finish_flip_search
				end
			end
			::finish_flip_search::

			local tiles_list = {}
			for tile_index, tile_data in ipairs(tiles_data) do
				local id = (tile_data.px[2]/gsize)*layer_data.__cWid + tile_data.px[1]/gsize

				if layer.has_flipped_tiles then
					local cx, cy = tile_data.src[1]/gsize, tile_data.src[2]/gsize

					if tile_data.f==0 then
						tiles_list[id] = 1 + cy*cw + cx
					elseif tile_data.f==1 then
						tiles_list[id] = 1 + cy*cw + (cw-cx-1)
					elseif tile_data.f==2 then
						tiles_list[id] = 1 + (ch-cy-1)*cw + cx
					else
						tiles_list[id] = 1 + (ch-cy-1)*cw + (cw-cx-1)
					end
				else
					tiles_list[id] = 1 + tile_data.t
				end
			end

			for y = 0, layer_data.__cHei-1 do
				for x = 0, layer_data.__cWid-1 do
					local id = y*layer_data.__cWid + x

					if tiles_list[id] then
						table.insert( layer.tiles, math.floor(tiles_list[id]) )
					else
						table.insert( layer.tiles, 0 )
					end
				end
			end
		end

		local entities_data = layer_data.entityInstances
		if #entities_data>0 then
			layer.entities = {}

			for entity_index, entity_data in ipairs(entities_data) do
				local properties = {}
				for field_index, field_data in ipairs(entity_data.fieldInstances) do
					properties[ field_data.__identifier ] = field_data.__value
				end

				local world_position
				if entity_data.__worldX and entity_data.__worldY then
					world_position = { x=entity_data.__worldX, y=entity_data.__worldY }
				end

				table.insert( layer.entities, {
					name = entity_data.__identifier,
					iid = entity_data.iid,
					tileset_rect = entity_data.__tile,
					position = { x=entity_data.px[1], y=entity_data.px[2] },
					world_position = world_position,
					center = { x=entity_data.__pivot[1], y=entity_data.__pivot[2] },
					size = { width=entity_data.width, height=entity_data.height },
					zIndex = layer.zIndex,
					fields = properties,
				})

			end
		end
	end

	return level
end

function _.load_tileset( level_name )
	local level = _levels[level_name]
	if not level then return end

	for layer_name, layer in pairs(level.layers) do
		if layer.tileset_file then
			layer.tileset_image = _.load_tileset_imagetable(layer.tileset_file, layer.has_flipped_tiles)
		end
	end
end

function _.load_tileset_imagetable(path, flipped)
	if not path then
		return
	end

	local id = path
	if flipped then
		id = id.."[flipped]"
	end

	if _imageTables[id] then
		_imageTables[id].count = _imageTables[id].count + 1
		return _imageTables[id].image
	end

	local image_filepath
	if flipped then
		local filename = path:match("^.+/(.+)$")
		local tileset_folder = path:sub(0, -#filename-1)
		image_filepath = tileset_folder.."flipped-"..filename
	else
		image_filepath = path
	end

	local image = playdate.graphics.imagetable.new(image_filepath)
	if not image then
		if flipped then
			error( "LDtk Importer Error: cannot load tileset "..image_filepath..". Tileset requires a flipped version of the image: flipped-filename-table-w-h.png", 3)
		else
			error( "LDtk Importer Error: cannot load tileset "..image_filepath..". Filename should have a image table format: name-table-w-h.png", 3)
		end

		return nil
	end

	_imageTables[id] = {
		count = 1,
		image = image
	}

	return image
end

function _.release_tileset_imagetable(path, flipped)
	if not path then return end

	local id = path
	if flipped then
		id = id.."[flipped]"
	end

	if not _imageTables[id] then
		print("LDtk Importer Warning: We release an image that was not loaded. Strange...")
		return
	end

	_imageTables[id].count = _imageTables[id].count - 1
	if _imageTables[id].count<=0 then
		_imageTables[id] = nil
	end
end

function _.get_tile_layer( level_name, layer_name )
	local level = _levels[level_name]
	if not level then return end

	if layer_name then
		return level.layers[ layer_name ]
	end

	for layer_name, layer in pairs(level.layers) do
		if layer.tiles then
			return layer
		end
	end
end

-- write the content of a table in a lua file
function _.export_lua_table( filepath, table_to_export )
	local function _isArray( t )
		if type(t[1])=="nil" then return false end

		local pairs_count = 0
		for key in pairs(t) do
			pairs_count = pairs_count + 1
			if type(key)~="number" then
				return false
			end
		end

		return pairs_count==#t
	end

	assert( filepath, "LDtk Importer Assert: export_lua_table(), filepath required")
	assert( table_to_export, "LDtk Importer Assert: export_lua_table(), table_to_export required")

	local file, file_error = playdate.file.open(filepath, playdate.file.kFileWrite)
	assert(file, "LDtk Importer Assert: export_lua_table(), Cannot open file",filepath," (",file_error,")")

	local _write_entry
	_write_entry = function( entry, name )
		local entry_type = type(entry)

		if entry_type=="table" then
			file:write("{")
			if _isArray( entry ) then
				for key, value in ipairs(entry) do
					_write_entry(value, key)
					file:write(",")
				end
			else
				for key, value in pairs(entry) do
					if type(key) == "number" then
						file:write("["..tostring(key).."]=")
					else
						file:write("[\""..tostring(key).."\"]=")
					end
					_write_entry(value, key)
					file:write(",")
				end
			end
			file:write("}")
		elseif entry_type=="string" then
			file:write("\""..tostring(entry).."\"")
		elseif entry_type=="boolean" or entry_type=="number" then
			file:write(tostring(entry))
		else
			file:write("nil")
		end
	end

	file:write("return ")
	_write_entry( table_to_export )

	file:close()
end