namespace TSE {
    
    const LEVEL: number = 0;
    const BORDER: number = 0;
    const TEMP_IMAGE_DATA: Uint8Array = new Uint8Array([255, 255, 255, 255]);
    
    export class Texture implements IMessageHanlder {
        
        private _name: string;
        private _handle: WebGLTexture;
        private _isLoaded: boolean = false;
        private _width: number;
        private _height: number;
        
        public constructor(name: string, width: number = 1, height: number = 1) {
            this._name = name;
            this._width = width;
            this._height = height;
            
            this._handle = gl.createTexture();
            
            Message.subscribe(MESSAGE_ASSET_LOADER_ASSET_LOADED + this._name, this);
            
            this.bind();

            gl.texImage2D(gl.TEXTURE_2D, LEVEL, gl.RGBA, 1, 1, BORDER, gl.RGBA, gl.UNSIGNED_BYTE, TEMP_IMAGE_DATA);

            let asset = AssetManager.getAsset(this._name) as ImageAsset;
            if (asset !== undefined) {
                this.loadTextureFromAsset(asset);
            }
        }

        public onMessage(message: Message): void {
            if (message.code === MESSAGE_ASSET_LOADER_ASSET_LOADED + this._name) {
                this.loadTextureFromAsset(message.context as ImageAsset);
            }
        }
        
        public get name(): string { return this._name; }
        public get isLoaded(): boolean { return this._isLoaded; }
        public get width(): number { return this._width; }
        public get height(): number { return this._height; }

        public activateAndBind(textureUnit: number = 0): void {
            gl.activeTexture(gl.TEXTURE0 + textureUnit);

            this.bind();
        }
        
        public bind(): void {
            gl.bindTexture(gl.TEXTURE_2D, this._handle);
        }

        public unbind(): void {
            gl.bindTexture(gl.TEXTURE_2D, undefined);
        }

        public destroy(): void {
            gl.deleteTexture(this._handle);
        }

        private loadTextureFromAsset(asset: ImageAsset): void {
            this._width = asset.width;
            this._height = asset.height;

            this.bind();

            gl.texImage2D(gl.TEXTURE_2D, LEVEL, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, asset.data);

            if (this.isPowerOf2()) {
                gl.generateMipmap(gl.TEXTURE_2D);
            } else {
                gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
                gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
            }

            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);

            this._isLoaded = true;
        }

        private isPowerOf2(): boolean {
            return (this.isValuePowerOf2(this.width) && this.isValuePowerOf2(this.height));
        }

        private isValuePowerOf2(value: number): boolean {
            return (value & (value - 1)) == 0;
        }
        
    }
    
}