class TextureAtlas {

 final List<TextureAtlasFrame> _frames = new List<TextureAtlasFrame>();
 RenderTexture _renderTexture;

 //-------------------------------------------------------------------------------------------------

 static Future<TextureAtlas> load(String url, String textureAtlasFormat, [
     BitmapDataLoadOptions bitmapDataLoadOptions]) {

   Completer<TextureAtlas> completer = new Completer<TextureAtlas>();
   TextureAtlas textureAtlas = new TextureAtlas();

   switch(textureAtlasFormat) {

     case TextureAtlasFormat.JSON:
     case TextureAtlasFormat.JSONARRAY:

       HttpRequest.getString(url).then((textureAtlasJson) {

         var data = JSON.decode(textureAtlasJson);
         var frames = data["frames"];
         var meta = data["meta"];
         var imageUrl = _replaceFilename(url, meta["image"]);

         if (frames is List) {
           for(var frame in frames) {
             var frameMap = frame as Map;
             var fileName = frameMap["filename"] as String;
             var frameName = _getFilenameWithoutExtension(fileName);
             var taf = new TextureAtlasFrame.fromJson(textureAtlas, frameName, frameMap);
             textureAtlas._frames.add(taf);
           }
         }

         if (frames is Map) {
           for(String fileName in frames.keys) {
             var frameMap = frames[fileName] as Map;
             var frameName = _getFilenameWithoutExtension(fileName);
             var taf = new TextureAtlasFrame.fromJson(textureAtlas, frameName, frameMap);
             textureAtlas._frames.add(taf);
           }
         }

         if (bitmapDataLoadOptions == null) {
           bitmapDataLoadOptions = BitmapData.defaultLoadOptions;
         }

         var autoHiDpi = bitmapDataLoadOptions.autoHiDpi;
         var webpAvailable = bitmapDataLoadOptions.webp;
         var loader = RenderTexture.load(imageUrl, autoHiDpi, webpAvailable);

         loader.then((RenderTexture renderTexture) {
           textureAtlas._renderTexture = renderTexture;
           completer.complete(textureAtlas);
         }).catchError((error) {
           completer.completeError(new StateError("Failed to load image."));
         });

       }).catchError((error) {
         completer.completeError(new StateError("Failed to load json file."));
       });

       break;
   }

   return completer.future;
 }

 //-------------------------------------------------------------------------------------------------
 //-------------------------------------------------------------------------------------------------

 RenderTexture get renderTexture => _renderTexture;

 List<TextureAtlasFrame> get frames => _frames.toList(growable: false);
 List<String> get frameNames => _frames.map((f) => f.name).toList(growable: false);

 //-------------------------------------------------------------------------------------------------

 BitmapData getBitmapData(String name) {

   for(int i = 0; i < _frames.length; i++) {
     var frame = _frames[i];
     if (frame.name == name) return frame.getBitmapData();
   }

   throw new ArgumentError("TextureAtlasFrame not found: '$name'");
 }

 //-------------------------------------------------------------------------------------------------

 List<BitmapData> getBitmapDatas(String namePrefix) {

   var bitmapDataList = new List<BitmapData>();

   for(int i = 0; i < _frames.length; i++) {
     var frame = _frames[i];
     if (frame.name.startsWith(namePrefix)) {
       bitmapDataList.add(frame.getBitmapData());
     }
   }

   return bitmapDataList;
 }

}