import { CompareFunction, Engine, Material, Matrix, Shader } from "oasis-engine";

export class BgMaterialIos extends Material {
  constructor(engine: Engine) {
    const yuv_vs = `
    attribute vec3 POSITION;
    attribute vec2 TEXCOORD_0;

    uniform mat4 u_proMatrix;
    uniform mat4 u_scaleMatrix;
    varying vec2 v_uv;

    void main() {
      v_uv = (u_proMatrix * vec4(TEXCOORD_0.x, 1.0 - TEXCOORD_0.y, 1.0, 1.0)).xy;
      vec4 position = u_scaleMatrix * vec4( POSITION.xy, 1.0, 1.0);
      position.z = position.w;
      gl_Position = position;
    }
    `;

    const yuv_fs = `
    precision highp float;

    uniform sampler2D u_frameY;
    uniform sampler2D u_frameUV;
    varying vec2 v_uv;

    void main() {
      // float y = texture2D(u_frameY, v_uv).a;
      // vec4 uvColor = texture2D(u_frameUV, v_uv);
      // float u = uvColor.r - 0.5;
      // float v = uvColor.a - 0.5;

      // float r = y + 1.04 * v;
      // float g = y - 0.343 * u - 0.711 * v;
      // float b = y + 1.765 * u;

      // gl_FragColor = vec4(r, g, b, 1.0);

      vec2 cbcr = texture2D(u_frameUV, v_uv).ra - vec2(0.5, 0.5);
      vec3 ycbcr = vec3(texture2D(u_frameY, v_uv).a, cbcr);
      vec3 rgb = mat3(1, 1, 1, 0, -0.344, 1.772, 1.402, -0.714, 0) * ycbcr;
      gl_FragColor = vec4(rgb, 1.0);
    }
    `;

    const shader = Shader.create("ar-background", yuv_vs, yuv_fs);
    super(engine, shader);
    this.shaderData.setMatrix("u_scaleMatrix", new Matrix());
    this.renderState.depthState.compareFunction = CompareFunction.LessEqual;
  }
}