<template>
  <view class="cu-dialog">
    <view class="cu-bar bg-white justify-end">
      <view class="content">签名</view>
      <view class="action" @tap="_cancel">
        <text class="cuIcon-close text-red"></text>
      </view>
    </view>
    <view>
      <view class="wrapper">
        <view class="handCenter">
          <canvas
              class="handWriting"
              :disable-scroll="true"
              @touchstart="uploadScaleStart"
              @touchmove="uploadScaleMove"
              @touchend="uploadScaleEnd"
              canvas-id="handWriting"
          ></canvas>
        </view>
      </view>
    </view>
    <view class="cu-bar bg-white justify-end">
      <view class="action">
        <button class="cu-btn line-green text-green" @click="retDraw">重写</button>
        <button class="cu-btn bg-green margin-left"  @click="confirm" >完成</button>
      </view>
    </view>
  </view>
</template>

<script>
export default {
  props: {
    imgList: {
      type: Array,
      default: function () {
        return []
      }
    }
  },
  data() {
    return {
      //手写板
      canvasName: 'handWriting',
      ctx: '',
      canvasWidth: 0,
      canvasHeight: 0,
      transparent: 1, // 透明度
      selectColor: 'black',
      lineColor: '#1A1A1A', // 颜色
      lineSize: 1.5, // 笔记倍数
      lineMin: 0.5, // 最小笔画半径
      lineMax: 4, // 最大笔画半径
      pressure: 1, // 默认压力
      smoothness: 60, //顺滑度，用60的距离来计算速度
      currentPoint: {},
      currentLine: [], // 当前线条
      firstTouch: true, // 第一次触发
      radius: 1, //画圆的半径
      cutArea: { top: 0, right: 0, bottom: 0, left: 0 }, //裁剪区域
      bethelPoint: [], //保存所有线条 生成的贝塞尔点；
      lastPoint: 0,
      chirography: [], //笔迹
      currentChirography: {}, //当前笔迹
      linePrack: [], //划线轨迹 , 生成线条的实际点
    }
  },
  created(){
    //手写板
    let canvasName = this.canvasName;
    let ctx = uni.createCanvasContext(canvasName,this);

    this.ctx = ctx;
    var query = uni.createSelectorQuery().in(this);
    query
        .select('.handCenter')
        .boundingClientRect(rect => {
          if (rect) {
            if (rect.width) this.canvasWidth = rect.width;
            if (rect.height) this.canvasHeight = rect.height;
          }

          /* 将canvas背景设置为 白底，不设置  导出的canvas的背景为透明 */
          this.setCanvasBg('#fff');
        })
        .exec();
  },
  methods: {
    // 笔迹开始
    uploadScaleStart(e) {
      if (e.type != 'touchstart') return false;
      let ctx = this.ctx;
      ctx.setFillStyle(this.lineColor); // 初始线条设置颜色
      ctx.setGlobalAlpha(this.transparent); // 设置半透明
      let currentPoint = {
        x: e.touches[0].x,
        y: e.touches[0].y
      };
      let currentLine = this.currentLine;
      currentLine.unshift({
        time: new Date().getTime(),
        dis: 0,
        x: currentPoint.x,
        y: currentPoint.y
      });
      this.currentPoint = currentPoint;
      // currentLine
      if (this.firstTouch) {
        this.cutArea = { top: currentPoint.y, right: currentPoint.x, bottom: currentPoint.y, left: currentPoint.x };
        this.firstTouch = false;
      }
      this.pointToLine(currentLine);
    },
    // 笔迹移动
    uploadScaleMove(e) {
      if (e.type != 'touchmove') return false;
      if (e.cancelable) {
        // 判断默认行为是否已经被禁用
        if (!e.defaultPrevented) {
          e.preventDefault();
        }
      }
      let point = {
        x: e.touches[0].x,
        y: e.touches[0].y
      };

      //测试裁剪
      if (point.y < this.cutArea.top) {
        this.cutArea.top = point.y;
      }
      if (point.y < 0) this.cutArea.top = 0;

      if (point.x > this.cutArea.right) {
        this.cutArea.right = point.x;
      }
      if (this.canvasWidth - point.x <= 0) {
        this.cutArea.right = this.canvasWidth;
      }
      if (point.y > this.cutArea.bottom) {
        this.cutArea.bottom = point.y;
      }
      if (this.canvasHeight - point.y <= 0) {
        this.cutArea.bottom = this.canvasHeight;
      }
      if (point.x < this.cutArea.left) {
        this.cutArea.left = point.x;
      }
      if (point.x < 0) this.cutArea.left = 0;

      this.lastPoint = this.currentPoint;
      this.currentPoint = point;

      let currentLine = this.currentLine;
      currentLine.unshift({
        time: new Date().getTime(),
        dis: this.distance(this.currentPoint, this.lastPoint),
        x: point.x,
        y: point.y
      });

      this.pointToLine(currentLine);
    },
    // 笔迹结束
    uploadScaleEnd(e) {
      if (e.type != 'touchend') return 0;
      let point = {
        x: e.changedTouches[0].x,
        y: e.changedTouches[0].y
      };
      this.lastPoint = this.currentPoint;
      this.currentPoint = point;

      let currentLine = this.currentLine;
      currentLine.unshift({
        time: new Date().getTime(),
        dis: this.distance(this.currentPoint, this.lastPoint),
        x: point.x,
        y: point.y
      });

      if (currentLine.length > 2) {
        var info = (currentLine[0].time - currentLine[currentLine.length - 1].time) / currentLine.length;
        //$("#info").text(info.toFixed(2));
      }
      //一笔结束，保存笔迹的坐标点，清空，当前笔迹
      //增加判断是否在手写区域；
      this.pointToLine(currentLine);
      var currentChirography = {
        lineSize: this.lineSize,
        lineColor: this.lineColor
      };
      var chirography = this.chirography;
      chirography.unshift(currentChirography);
      this.chirography = chirography;

      var linePrack = this.linePrack;
      linePrack.unshift(this.currentLine);
      this.linePrack = linePrack;
      this.currentLine = [];
    },
    retDraw() {
      this.ctx.clearRect(0, 0, 700, 730);
      this.ctx.draw();

      //设置canvas背景
      this.setCanvasBg('#fff');
    },
    //画两点之间的线条；参数为:line，会绘制最近的开始的两个点；
    pointToLine(line) {
      this.calcBethelLine(line);
      return;
    },
    //计算插值的方式；
    calcBethelLine(line) {
      if (line.length <= 1) {
        line[0].r = this.radius;
        return;
      }
      let x0,
          x1,
          x2,
          y0,
          y1,
          y2,
          r0,
          r1,
          r2,
          len,
          lastRadius,
          dis = 0,
          time = 0,
          curveValue = 0.5;
      if (line.length <= 2) {
        x0 = line[1].x;
        y0 = line[1].y;
        x2 = line[1].x + (line[0].x - line[1].x) * curveValue;
        y2 = line[1].y + (line[0].y - line[1].y) * curveValue;
        //x2 = line[1].x;
        //y2 = line[1].y;
        x1 = x0 + (x2 - x0) * curveValue;
        y1 = y0 + (y2 - y0) * curveValue;
      } else {
        x0 = line[2].x + (line[1].x - line[2].x) * curveValue;
        y0 = line[2].y + (line[1].y - line[2].y) * curveValue;
        x1 = line[1].x;
        y1 = line[1].y;
        x2 = x1 + (line[0].x - x1) * curveValue;
        y2 = y1 + (line[0].y - y1) * curveValue;
      }
      //从计算公式看，三个点分别是(x0,y0),(x1,y1),(x2,y2) ；(x1,y1)这个是控制点，控制点不会落在曲线上；实际上，这个点还会手写获取的实际点，却落在曲线上
      len = this.distance({ x: x2, y: y2 }, { x: x0, y: y0 });
      lastRadius = this.radius;
      for (let n = 0; n < line.length - 1; n++) {
        dis += line[n].dis;
        time += line[n].time - line[n + 1].time;
        if (dis > this.smoothness) break;
      }

      this.radius = Math.min((time / len) * this.pressure + this.lineMin, this.lineMax) * this.lineSize;
      line[0].r = this.radius;
      //计算笔迹半径；
      if (line.length <= 2) {
        r0 = (lastRadius + this.radius) / 2;
        r1 = r0;
        r2 = r1;
        //return;
      } else {
        r0 = (line[2].r + line[1].r) / 2;
        r1 = line[1].r;
        r2 = (line[1].r + line[0].r) / 2;
      }
      let n = 5;
      let point = [];
      for (let i = 0; i < n; i++) {
        let t = i / (n - 1);
        let x = (1 - t) * (1 - t) * x0 + 2 * t * (1 - t) * x1 + t * t * x2;
        let y = (1 - t) * (1 - t) * y0 + 2 * t * (1 - t) * y1 + t * t * y2;
        let r = lastRadius + ((this.radius - lastRadius) / n) * i;
        point.push({ x: x, y: y, r: r });
        if (point.length == 3) {
          let a = this.ctaCalc(point[0].x, point[0].y, point[0].r, point[1].x, point[1].y, point[1].r, point[2].x, point[2].y, point[2].r);
          a[0].color = this.lineColor;
          // let bethelPoint = this.bethelPoint;
          // bethelPoint = bethelPoint.push(a);
          this.bethelDraw(a, 1);
          point = [{ x: x, y: y, r: r }];
        }
      }
      this.currentLine = line;
    },
    //求两点之间距离
    distance(a, b) {
      let x = b.x - a.x;
      let y = b.y - a.y;
      return Math.sqrt(x * x + y * y);
    },
    ctaCalc(x0, y0, r0, x1, y1, r1, x2, y2, r2) {
      let a = [],
          vx01,
          vy01,
          norm,
          n_x0,
          n_y0,
          vx21,
          vy21,
          n_x2,
          n_y2;
      vx01 = x1 - x0;
      vy01 = y1 - y0;
      norm = Math.sqrt(vx01 * vx01 + vy01 * vy01 + 0.0001) * 2;
      vx01 = (vx01 / norm) * r0;
      vy01 = (vy01 / norm) * r0;
      n_x0 = vy01;
      n_y0 = -vx01;
      vx21 = x1 - x2;
      vy21 = y1 - y2;
      norm = Math.sqrt(vx21 * vx21 + vy21 * vy21 + 0.0001) * 2;
      vx21 = (vx21 / norm) * r2;
      vy21 = (vy21 / norm) * r2;
      n_x2 = -vy21;
      n_y2 = vx21;
      a.push({ mx: x0 + n_x0, my: y0 + n_y0, color: '#1A1A1A' });
      a.push({ c1x: x1 + n_x0, c1y: y1 + n_y0, c2x: x1 + n_x2, c2y: y1 + n_y2, ex: x2 + n_x2, ey: y2 + n_y2 });
      a.push({ c1x: x2 + n_x2 - vx21, c1y: y2 + n_y2 - vy21, c2x: x2 - n_x2 - vx21, c2y: y2 - n_y2 - vy21, ex: x2 - n_x2, ey: y2 - n_y2 });
      a.push({ c1x: x1 - n_x2, c1y: y1 - n_y2, c2x: x1 - n_x0, c2y: y1 - n_y0, ex: x0 - n_x0, ey: y0 - n_y0 });
      a.push({ c1x: x0 - n_x0 - vx01, c1y: y0 - n_y0 - vy01, c2x: x0 + n_x0 - vx01, c2y: y0 + n_y0 - vy01, ex: x0 + n_x0, ey: y0 + n_y0 });
      a[0].mx = a[0].mx.toFixed(1);
      a[0].mx = parseFloat(a[0].mx);
      a[0].my = a[0].my.toFixed(1);
      a[0].my = parseFloat(a[0].my);
      for (let i = 1; i < a.length; i++) {
        a[i].c1x = a[i].c1x.toFixed(1);
        a[i].c1x = parseFloat(a[i].c1x);
        a[i].c1y = a[i].c1y.toFixed(1);
        a[i].c1y = parseFloat(a[i].c1y);
        a[i].c2x = a[i].c2x.toFixed(1);
        a[i].c2x = parseFloat(a[i].c2x);
        a[i].c2y = a[i].c2y.toFixed(1);
        a[i].c2y = parseFloat(a[i].c2y);
        a[i].ex = a[i].ex.toFixed(1);
        a[i].ex = parseFloat(a[i].ex);
        a[i].ey = a[i].ey.toFixed(1);
        a[i].ey = parseFloat(a[i].ey);
      }
      return a;
    },
    bethelDraw(point, is_fill, color) {
      let ctx = this.ctx;
      ctx.beginPath();
      ctx.moveTo(point[0].mx, point[0].my);
      if (undefined != color) {
        ctx.setFillStyle(color);
        ctx.setStrokeStyle(color);
      } else {
        ctx.setFillStyle(point[0].color);
        ctx.setStrokeStyle(point[0].color);
      }
      for (let i = 1; i < point.length; i++) {
        ctx.bezierCurveTo(point[i].c1x, point[i].c1y, point[i].c2x, point[i].c2y, point[i].ex, point[i].ey);
      }
      ctx.stroke();
      if (undefined != is_fill) {
        ctx.fill(); //填充图形 ( 后绘制的图形会覆盖前面的图形, 绘制时注意先后顺序 )
      }
      ctx.draw(true);
    },
    selectColorEvent(str,color) {
      this.selectColor = str;
      this.lineColor = color;
    },
    //完成
    confirm() {
      var _this = this;
      let img={};
      this.ctx.draw(true, () => {
        uni.canvasToTempFilePath({
          canvasId: 'handWriting',
          fileType: 'jpg',
          quality: 1, //图片质量
          destWidth:900,
          destHeight:435,
          success(res) {
            img.id='';
            img.filePath=res.tempFilePath;
            _this.retDraw();
            _this.$emit("confirm", img);
          }
        });
      });
    },
    //保存到相册
    saveCanvasAsImg() {
      uni.canvasToTempFilePath({
        canvasId: 'handWriting',
        fileType: 'png',
        quality: 1, //图片质量
        success(res) {
          // console.log(res.tempFilePath, 'canvas生成图片地址');
          uni.saveImageToPhotosAlbum({
            filePath: res.tempFilePath,
            success(res) {
              uni.showToast({
                title: '已保存到相册',
                duration: 2000
              });
            }
          });
        }
      });
    },
    //设置canvas背景色  不设置  导出的canvas的背景为透明
    //@params：字符串  color
    setCanvasBg(color) {

      /* 将canvas背景设置为 白底，不设置  导出的canvas的背景为透明 */
      //rect() 参数说明  矩形路径左上角的横坐标，左上角的纵坐标, 矩形路径的宽度, 矩形路径的高度
      //这里是 canvasHeight - 4 是因为下边盖住边框了，所以手动减了写
      this.ctx.rect(0, 0, this.canvasWidth, this.canvasHeight - 4);
      // ctx.setFillStyle('red')
      this.ctx.setFillStyle(color);
      this.ctx.fill(); //设置填充
      this.ctx.draw(); //开画
    },
    _cancel() {
      this.$emit("cancel", '');
    },
  }
}
</script>

<style scoped>
.wrapper {
  width: 100%;
  height: 24vh;
  margin: 0;
  overflow: hidden;
  display: flex;
  align-content: center;
  flex-direction: row;
  justify-content: center;
  font-size: 28upx;
}
.handWriting {
  background: #fff;
  width: 100%;
  height: 100%;
}
.handCenter {
  border: 4upx dashed #e9e9e9;
  flex: 5;
  overflow: hidden;
  box-sizing: border-box;
}
</style>