export class OutlinePipeline extends Phaser.Renderer.WebGL.Pipelines.TextureTintPipeline
{

    // the unique id of this pipeline
    public static readonly KEY = 'Outline';

    /**
     * @param {Phaser.Game} game - the controller of the game instance
     */
    constructor(game: Phaser.Game)
    {
        super({
            game: game,
            renderer: game.renderer,
            fragShader: `
        precision mediump float;

        uniform sampler2D uMainSampler;
        uniform vec2 uTextureSize;

        varying vec2 outTexCoord;
        varying float outTintEffect;
        varying vec4 outTint;

        void main(void) 
        {
          vec4 texture = texture2D(uMainSampler, outTexCoord);
          vec4 texel = vec4(outTint.rgb * outTint.a, outTint.a);
          vec4 color = texture;

          if (outTintEffect == 0.0)
          {
            color = texture * texel;
          }
          else if (outTintEffect == 1.0)
          {
            color.rgb = mix(texture.rgb, outTint.rgb * outTint.a, texture.a);
            color.a = texture.a * texel.a;
          }
          else if (outTintEffect == 2.0)
          {
            color = texel;
          }

          vec2 onePixel = vec2(1.0, 1.0) / uTextureSize;
          float upAlpha = texture2D(uMainSampler, outTexCoord + vec2(0.0, onePixel.y)).a;
          float leftAlpha = texture2D(uMainSampler, outTexCoord + vec2(-onePixel.x, 0.0)).a;
          float downAlpha = texture2D(uMainSampler, outTexCoord + vec2(0.0, -onePixel.y)).a;
          float rightAlpha = texture2D(uMainSampler, outTexCoord + vec2(onePixel.x, 0.0)).a;

          if (texture.a == 0.0 && max(max(upAlpha, downAlpha), max(leftAlpha, rightAlpha)) == 1.0) 
          {
            color = vec4(1.0, 1.0, 0.0, 1.0);
          }

          gl_FragColor = color;
        }
      `
        });
    }
}