// From https://github.com/evanw/glfx.js
import { Vector2 } from 'three'
import DefaultShader from './default'

export default {
  uniforms: {
    tDiffuse: { value: null },
    blurRadius: { value: 0 },
    gradientRadius: { value: 0 },
    start: { value: new Vector2() },
    end: { value: new Vector2() },
    delta: { value: new Vector2() },
    texSize: { value: new Vector2() },
  },
  vertexShader: DefaultShader.vertexShader,
  fragmentShader: `
    uniform sampler2D tDiffuse;
    uniform float blurRadius;
    uniform float gradientRadius;
    uniform vec2 start;
    uniform vec2 end;
    uniform vec2 delta;
    uniform vec2 texSize;
    varying vec2 vUv;

    float random(vec3 scale, float seed) {
      /* use the fragment position for a different seed per-pixel */
      return fract(sin(dot(gl_FragCoord.xyz + seed, scale)) * 43758.5453 + seed);
    }

    void main() {
      vec4 color = vec4(0.0);
      float total = 0.0;

      /* randomize the lookup values to hide the fixed number of samples */
      float offset = random(vec3(12.9898, 78.233, 151.7182), 0.0);

      vec2 normal = normalize(vec2(start.y - end.y, end.x - start.x));
      float radius = smoothstep(0.0, 1.0, abs(dot(vUv * texSize - start, normal)) / gradientRadius) * blurRadius;
      for (float t = -30.0; t <= 30.0; t++) {
          float percent = (t + offset - 0.5) / 30.0;
          float weight = 1.0 - abs(percent);
          vec4 texel = texture2D(tDiffuse, vUv + delta / texSize * percent * radius);
          // vec4 texel2 = texture2D(tDiffuse, vUv + vec2(-delta.y, delta.x) / texSize * percent * radius);

          /* switch to pre-multiplied alpha to correctly blur transparent images */
          texel.rgb *= texel.a;
          // texel2.rgb *= texel2.a;

          color += texel * weight;
          total += 2.0 * weight;
      }

      gl_FragColor = color / total;

      /* switch back from pre-multiplied alpha */
      gl_FragColor.rgb /= gl_FragColor.a + 0.00001;
    }
  `,
}