/**
 * 贝塞尔平滑曲线 
 * @module zrender/shape/util/smoothBezier
 * @author pissang (https://www.github.com/pissang) 
 *         Kener (@Kener-林峰, kener.linfeng@gmail.com)
 *         errorrik (errorrik@gmail.com)
 */
module.exports = function (require) {
  var vector = require('../../tool/vector');
  /**
   * 贝塞尔平滑曲线
   * @alias module:zrender/shape/util/smoothBezier
   * @param {Array} points 线段顶点数组
   * @param {number} smooth 平滑等级, 0-1
   * @param {boolean} isLoop
   * @param {Array} constraint 将计算出来的控制点约束在一个包围盒内
   *                           比如 [[0, 0], [100, 100]], 这个包围盒会与
   *                           整个折线的包围盒做一个并集用来约束控制点。
   * @param {Array} 计算出来的控制点数组
   */


  return function (points, smooth, isLoop, constraint) {
    var cps = [];
    var v = [];
    var v1 = [];
    var v2 = [];
    var prevPoint;
    var nextPoint;
    var hasConstraint = !!constraint;
    var min, max;

    if (hasConstraint) {
      min = [Infinity, Infinity];
      max = [-Infinity, -Infinity];

      for (var i = 0, len = points.length; i < len; i++) {
        vector.min(min, min, points[i]);
        vector.max(max, max, points[i]);
      } // 与指定的包围盒做并集


      vector.min(min, min, constraint[0]);
      vector.max(max, max, constraint[1]);
    }

    for (var i = 0, len = points.length; i < len; i++) {
      var point = points[i];
      var prevPoint;
      var nextPoint;

      if (isLoop) {
        prevPoint = points[i ? i - 1 : len - 1];
        nextPoint = points[(i + 1) % len];
      } else {
        if (i === 0 || i === len - 1) {
          cps.push(vector.clone(points[i]));
          continue;
        } else {
          prevPoint = points[i - 1];
          nextPoint = points[i + 1];
        }
      }

      vector.sub(v, nextPoint, prevPoint); // use degree to scale the handle length

      vector.scale(v, v, smooth);
      var d0 = vector.distance(point, prevPoint);
      var d1 = vector.distance(point, nextPoint);
      var sum = d0 + d1;

      if (sum !== 0) {
        d0 /= sum;
        d1 /= sum;
      }

      vector.scale(v1, v, -d0);
      vector.scale(v2, v, d1);
      var cp0 = vector.add([], point, v1);
      var cp1 = vector.add([], point, v2);

      if (hasConstraint) {
        vector.max(cp0, cp0, min);
        vector.min(cp0, cp0, max);
        vector.max(cp1, cp1, min);
        vector.min(cp1, cp1, max);
      }

      cps.push(cp0);
      cps.push(cp1);
    }

    if (isLoop) {
      cps.push(vector.clone(cps.shift()));
    }

    return cps;
  };
}(require);