const app = getApp()

Page({
  data: {
    translateX: 0, // 位移x坐标 单位px
    translateY: 0, // 位移y坐标 单位px
    distance: 0, // 双指接触点距离
    scale: 1, // 缩放倍数
    rotate: 0, // 旋转角度
    oldRotate: 0, // 上一次旋转停止后的角度
    startMove: { // 起始位移距离
      x: 0,
      y: 0,
    },
    startTouches: [] // 起始点touch数组
  },
  touchStart(e) {
    const touches = e.touches
    const { translateX, translateY } = this.data
    const { pageX, pageY } = touches[0]
    this.data.startMove = {
      x: pageX - translateX,
      y: pageY - translateY
    }
    this.data.startTouches = touches
  },

  touchMove(e) {
    const touches = e.touches
    const { pageX: onePageX, pageY: onePageY } = touches[0]
    const { startMove, scale, distance: oldDistance, startTouches, oldRotate } = this.data
    if (touches.length === 2 && startTouches.length === 2) {
      const { pageX: twoPageX, pageY: twoPageY } = touches[1]
      const distance = Math.sqrt((twoPageX - onePageX) ** 2 + (twoPageY - onePageY) ** 2)
      let rotate = this.getAngle(touches[0], touches[1]) - this.getAngle(startTouches[0], startTouches[1]) + oldRotate
      rotate = rotate > 360 ? rotate - 360 : rotate
      this.data.distance = distance
      this.setData({
        scale: scale * (distance / (oldDistance || distance)),
        rotate
      })
    } else if (startTouches.length !== 2) {
      this.setData({
        translateX: onePageX - startMove.x,
        translateY: onePageY - startMove.y
      })
    }
  },

  touchEnd() {
    this.data.oldRotate = this.data.rotate
  },

  getAngle(p1, p2) {
    const x = p1.pageX - p2.pageX
    const y = p1.pageY- p2.pageY
    return Math.atan2(y, x) * 180 / Math.PI
  }
})