import Shader from '../../../shader/Shader';
import Program from '../../../shader/Program';

/**
 * This shader is used to draw simple primitive shapes for {@link PIXI.Graphics}.
 *
 * @class
 * @memberof PIXI
 * @extends PIXI.Shader
 */
export default class PrimitiveShader extends Shader
{
    /**
     * @param {WebGLRenderingContext} gl - The webgl shader manager this shader works for.
     */
    constructor()
    {
        const program = Program.from([
            'attribute vec2 aVertexPosition;',
            'attribute vec4 aColor;',

            'uniform mat3 translationMatrix;',
            'uniform mat3 projectionMatrix;',

            'uniform float alpha;',
            'uniform vec3 tint;',

            'varying vec4 vColor;',

            'void main(void){',
            '   gl_Position = vec4((projectionMatrix * translationMatrix * vec3(aVertexPosition, 1.0)).xy, 0.0, 1.0);',
            '   vColor = aColor * vec4(tint * alpha, alpha);',
            '}',
        ].join('\n'),
            // fragment shader
        [
            'varying vec4 vColor;',

            'void main(void){',
            '   gl_FragColor = vColor;',
            '}',
        ].join('\n'));

        super(program, {});
    }
}