/**
 * Geometry colleting cloud points data
 * Points will move on a cubic curve path
 *
 * @module echarts-gl/chart/lines3D/CurveTrailGeometry
 * @author Yi Shen(http://github.com/pissang)
 */
import Geometry from 'claygl/src/Geometry';
import glmatrix from 'claygl/src/dep/glmatrix';
var vec3 = glmatrix.vec3;
/**
 * @constructor
 * @alias module:echarts-gl/chart/lines3D/CurveTrailGeometry
 * @extends clay.Geometry
 */

var CurveTrailGeometry = Geometry.derive(function () {
  return {
    attributes: {
      uv: new Geometry.Attribute('offset', 'float', 2),
      currT: new Geometry.Attribute('offset', 'float', 1),
      start: new Geometry.Attribute('offset', 'float', 1),
      prevT: new Geometry.Attribute('offset', 'float', 1),
      nextT: new Geometry.Attribute('offset', 'float', 1),
      offset: new Geometry.Attribute('offset', 'float', 1),
      color: new Geometry.Attribute('color', 'float', 4, 'COLOR')
    },
    mainAttribute: 'uv',
    scale: 1,
    trailLength: 0.3,
    _vertexOffset: 0,
    _triangleOffset: 0
  };
},
/** @lends module:echarts-gl/chart/lines3D/CurveTrailGeometry.prototype */
{
  reset: function () {
    this._vertexOffset = 0;
    this._triangleOffset = 0;
  },
  setVertexCount: function (vertexCount) {
    if (this.vertexCount !== vertexCount) {
      for (var name in this.attributes) {
        this.attributes[name].init(vertexCount);
      }

      if (vertexCount > 0xffff) {
        if (this.indices instanceof Uint16Array) {
          this.indices = new Uint32Array(this.indices);
        }
      } else {
        if (this.indices instanceof Uint32Array) {
          this.indices = new Uint16Array(this.indices);
        }
      }
    }
  },
  setTriangleCount: function (triangleCount) {
    if (this.triangleCount !== triangleCount) {
      if (triangleCount === 0) {
        this.indices = null;
      } else {
        this.indices = this.vertexCount > 0xffff ? new Uint32Array(triangleCount * 3) : new Uint16Array(triangleCount * 3);
      }
    }
  },

  /**
   * Get vertex count of cubic curve
   * @param {Array.<number>} p0
   * @param {Array.<number>} p1
   * @param {Array.<number>} p2
   * @param {Array.<number>} p3
   * @return number
   */
  getCurveVertexCount: function (p0, p1, p2, p3) {
    var len = (vec3.dist(p0, p1) + vec3.dist(p2, p1) + vec3.dist(p3, p2)) * this.trailLength; // TODO Remove magic number.

    var count = Math.max(Math.min(Math.round((len + 1) / this.scale * 500), 50), 5);
    return count * 2;
  },
  getCurveTriangleCount: function (p0, p1, p2, p3) {
    var segCount = this.getCurveVertexCount(p0, p1, p2, p3) / 2 - 1;
    return segCount * 2;
  },

  /**
   * Add a point
   * @param {Array.<number>} p0
   * @param {Array.<number>} p1
   * @param {Array.<number>} p2
   * @param {Array.<number>} p3
   * @param {number} size
   * @param {Array.<number>} color
   */
  addCurveTrail: function (p0, p1, p2, p3, uv, size, color) {
    var attributes = this.attributes;
    var start = Math.random();
    var t = 0;
    var prevT = 0;
    var nextT;
    var count = this.getCurveVertexCount(p0, p1, p2, p3) / 2;
    var offset = this._vertexOffset;
    var alpha = color[3];

    for (var i = 0; i < count; i++) {
      nextT = t - 1 / count * this.trailLength; // PENDING

      var fadeOutFactor = 1 - Math.pow(i / count, 2);
      color[3] = Math.max(alpha * fadeOutFactor, 0.0);

      for (var k = 0; k < 2; k++) {
        attributes.currT.set(offset, t);
        attributes.prevT.set(offset, prevT);
        attributes.offset.set(offset, (k * 2 - 1) * size / 2 * fadeOutFactor);
        attributes.color.set(offset, color);
        attributes.uv.set(offset, uv);
        attributes.start.set(offset, start);

        if (i < count - 1) {
          attributes.nextT.set(offset, nextT);
        } else {
          attributes.nextT.set(offset, t);
        }

        offset++;
      }

      prevT = t;
      t = nextT;

      if (i > 0) {
        var idx3 = this._triangleOffset * 3;
        var indices = this.indices; // 0-----2
        // 1-----3
        // 0->1->2, 1->3->2

        indices[idx3] = offset - 4;
        indices[idx3 + 1] = offset - 3;
        indices[idx3 + 2] = offset - 2;
        indices[idx3 + 3] = offset - 3;
        indices[idx3 + 4] = offset - 1;
        indices[idx3 + 5] = offset - 2;
        this._triangleOffset += 2;
      }
    }

    this._vertexOffset = offset;
  }
});
export default CurveTrailGeometry;