/**
 * Shader for the Region highlight.
 * @internal
 * @ignore
 */
class HighlightRegionShader extends RegionShader {

  /** @override */
  static vertexShader = `\
    precision ${PIXI.settings.PRECISION_VERTEX} float;

    ${this.CONSTANTS}

    attribute vec2 aVertexPosition;

    uniform mat3 translationMatrix;
    uniform mat3 projectionMatrix;
    uniform vec2 canvasDimensions;
    uniform vec4 sceneDimensions;
    uniform vec2 screenDimensions;
    uniform mediump float hatchThickness;

    varying vec2 vCanvasCoord; // normalized canvas coordinates
    varying vec2 vSceneCoord; // normalized scene coordinates
    varying vec2 vScreenCoord; // normalized screen coordinates
    varying float vHatchOffset;

    void main() {
      vec2 pixelCoord = aVertexPosition;
      vCanvasCoord = pixelCoord / canvasDimensions;
      vSceneCoord = (pixelCoord - sceneDimensions.xy) / sceneDimensions.zw;
      vec3 tPos = translationMatrix * vec3(aVertexPosition, 1.0);
      vScreenCoord = tPos.xy / screenDimensions;
      gl_Position = vec4((projectionMatrix * tPos).xy, 0.0, 1.0);
      vHatchOffset = (pixelCoord.x + pixelCoord.y) / (SQRT2 * 2.0 * hatchThickness);
    }
  `;

  /* ---------------------------------------- */

  /** @override */
  static fragmentShader = `\
    precision ${PIXI.settings.PRECISION_FRAGMENT} float;

    varying float vHatchOffset;

    uniform vec4 tintAlpha;
    uniform float resolution;
    uniform bool hatchEnabled;
    uniform mediump float hatchThickness;

    void main() {
      gl_FragColor = tintAlpha;
      if ( !hatchEnabled ) return;
      float x = abs(vHatchOffset - floor(vHatchOffset + 0.5)) * 2.0;
      float s = hatchThickness * resolution;
      float y0 = clamp((x + 0.5) * s + 0.5, 0.0, 1.0);
      float y1 = clamp((x - 0.5) * s + 0.5, 0.0, 1.0);
      gl_FragColor *= mix(0.3333, 1.0, y0 - y1);
    }
  `;

  /* ---------------------------------------- */

  /** @inheritDoc */
  static defaultUniforms = {
    ...super.defaultUniforms,
    resolution: 1,
    hatchEnabled: false,
    hatchThickness: 1
  };

  /** @inheritDoc */
  _preRender(mesh, renderer) {
    super._preRender(mesh, renderer);
    const uniforms = this.uniforms;
    uniforms.resolution = (renderer.renderTexture.current ?? renderer).resolution * mesh.worldTransform.a;
    const projection = renderer.projection.transform;
    if ( projection ) {
      const {a, b} = projection;
      uniforms.resolution *= Math.sqrt((a * a) + (b * b));
    }
  }
}