/*
 * @Description: 流动线
 */
function FlowLine() {
  class FlowLineMaterialProperty {
    constructor(options) {
      this._definitionChanged = new Cesium.Event();
      this._color = undefined;
      this._duration = undefined;
      this.color = new Cesium.Color.fromCssColorString(options.color || "rgba(255,255,255,1)");
      this.duration = options.duration || 10.0;
      this.lineBackAlpha = options.lineBackAlpha || 0.05;
    }

    get isConstant() {
      return false;
    }

    get definitionChanged() {
      return this._definitionChanged;
    }

    getType(time) {
      return Cesium.Material.FlowLineMaterialType;
    }

    getValue(time, result) {
      if (!Cesium.defined(result)) {
        result = {};
      }

      result.color = Cesium.Property.getValueOrDefault(
        this._color,
        time,
        Cesium.Color.RED,
        result.color
      );
      result.duration = Cesium.Property.getValueOrDefault(
        this._duration,
        time,
        10,
        result.duration
      );
      result.lineBackAlpha = this.lineBackAlpha;
      result.frameNumber = Cesium.getTimestamp();
      return result;
    }

    equals(other) {
      return (
        this === other ||
        (other instanceof FlowLineMaterialProperty &&
          Cesium.Property.equals(this._color, other._color) &&
          Cesium.Property.equals(this._duration, other.duration) &&
          Cesium.Property.equals(this.lineBackAlpha, other.lineBackAlpha))
      );
    }
  }

  Object.defineProperties(FlowLineMaterialProperty.prototype, {
    color: Cesium.createPropertyDescriptor("color"),
    duration: Cesium.createPropertyDescriptor("duration"),
    transparency: Cesium.createPropertyDescriptor("lineBackAlpha"),
  });

  Cesium.FlowLineMaterialProperty = FlowLineMaterialProperty;
  Cesium.Material.FlowLineMaterialProperty = "FlowLineMaterialProperty";
  Cesium.Material.FlowLineMaterialType = "FlowLineMaterialType";
  Cesium.Material.FlowLineMaterialSource = `
      uniform vec4 color;
      uniform float duration;
      uniform float lineBackAlpha;

      czm_material czm_getMaterial(czm_materialInput materialInput)
        {
            //生成默认的基础材质
            czm_material material = czm_getDefaultMaterial(materialInput);
            //获取st（uv）
            vec2 st = materialInput.st;
            //获取当前帧数，10秒内变化0-1
            float time = fract(czm_frameNumber / (60.0*duration));
            //长度1/10
            time = time * (1.0 + 0.1);
            //平滑过渡函数
            float alpha = smoothstep(time-0.1,time,st.s) * step(-time,-st.s);
            //光带轨迹（不会完全透明）
            alpha += lineBackAlpha;
            material.alpha = alpha;
            material.diffuse = color.rgb;
            return material;
        }
       `;

  Cesium.Material._materialCache.addMaterial(
    Cesium.Material.FlowLineMaterialType,
    {
      fabric: {
        type: Cesium.Material.FlowLineMaterialType,
        uniforms: {
          color: new Cesium.Color(1.0, 1.0, 1.0, 1.0),
          duration: 10.0,
          lineBackAlpha: 0.05,
        },
        source: Cesium.Material.FlowLineMaterialSource,
      },
      translucent: function (material) {
        return true;
      },
    }
  );
}

export { FlowLine }