class App extends Component {
  state = {
    url: ""
  }

  componentDidMount() {
    this.setState({ url: getImage() })
  }

  onReload = () => {
    this.setState({ url: getImage() })
  }
  render() {
    return (
      <div>
        <ImageCode
          imageUrl={this.state.url}
          onReload={this.onReload}
          onMatch={() => {
            console.log("code is match")
          }}
        />
      </div>
    )
  }
}

// index.js
/**
 * @name ImageCode
 * @desc 滑动拼图验证
 * @author darcrand
 * @version 2019-02-26
 *
 * @param {String} imageUrl 图片的路径
 * @param {Number} imageWidth 展示图片的宽带
 * @param {Number} imageHeight 展示图片的高带
 * @param {Number} fragmentSize 滑动图片的尺寸
 * @param {Function} onReload 当点击'重新验证'时执行的函数
 * @param {Function} onMath 匹配成功时执行的函数
 * @param {Function} onError 匹配失败时执行的函数
 */

import React from "react"

import "./styles.css"

const icoSuccess = require("./icons/success.png")
const icoError = require("./icons/error.png")
const icoReload = require("./icons/reload.png")
const icoSlider = require("./icons/slider.png")

const STATUS_LOADING = 0 // 还没有图片
const STATUS_READY = 1 // 图片渲染完成,可以开始滑动
const STATUS_MATCH = 2 // 图片位置匹配成功
const STATUS_ERROR = 3 // 图片位置匹配失败

const arrTips = [{ ico: icoSuccess, text: "匹配成功" }, { ico: icoError, text: "匹配失败" }]

// 生成裁剪路径
function createClipPath(ctx, size = 100, styleIndex = 0) {
  const styles = [
    [0, 0, 0, 0],
    [0, 0, 0, 1],
    [0, 0, 1, 0],
    [0, 0, 1, 1],
    [0, 1, 0, 0],
    [0, 1, 0, 1],
    [0, 1, 1, 0],
    [0, 1, 1, 1],
    [1, 0, 0, 0],
    [1, 0, 0, 1],
    [1, 0, 1, 0],
    [1, 0, 1, 1],
    [1, 1, 0, 0],
    [1, 1, 0, 1],
    [1, 1, 1, 0],
    [1, 1, 1, 1]
  ]
  const style = styles[styleIndex]

  const r = 0.1 * size
  ctx.save()
  ctx.beginPath()
  // left
  ctx.moveTo(r, r)
  ctx.lineTo(r, 0.5 * size - r)
  ctx.arc(r, 0.5 * size, r, 1.5 * Math.PI, 0.5 * Math.PI, style[0])
  ctx.lineTo(r, size - r)
  // bottom
  ctx.lineTo(0.5 * size - r, size - r)
  ctx.arc(0.5 * size, size - r, r, Math.PI, 0, style[1])
  ctx.lineTo(size - r, size - r)
  // right
  ctx.lineTo(size - r, 0.5 * size + r)
  ctx.arc(size - r, 0.5 * size, r, 0.5 * Math.PI, 1.5 * Math.PI, style[2])
  ctx.lineTo(size - r, r)
  // top
  ctx.lineTo(0.5 * size + r, r)
  ctx.arc(0.5 * size, r, r, 0, Math.PI, style[3])
  ctx.lineTo(r, r)

  ctx.clip()
  ctx.closePath()
}

class ImageCode extends React.Component {
  static defaultProps = {
    imageUrl: "",
    imageWidth: 500,
    imageHeight: 300,
    fragmentSize: 80,
    onReload: () => {},
    onMatch: () => {},
    onError: () => {}
  }

  state = {
    isMovable: false,
    offsetX: 0, //图片截取的x
    offsetY: 0, //图片截取的y
    startX: 0, // 开始滑动的 x
    oldX: 0,
    currX: 0, // 滑块当前 x,
    status: STATUS_LOADING,
    showTips: false,
    tipsIndex: 0
  }

  componentDidUpdate(prevProps) {
    // 当父组件传入新的图片后，开始渲染
    if (!!this.props.imageUrl && prevProps.imageUrl !== this.props.imageUrl) {
      this.renderImage()
    }
  }

  renderImage = () => {
    // 初始化状态
    this.setState({ status: STATUS_LOADING })

    // 创建一个图片对象，主要用于canvas.context.drawImage()
    const objImage = new Image()

    objImage.addEventListener("load", () => {
      const { imageWidth, imageHeight, fragmentSize } = this.props

      // 先获取两个ctx
      const ctxShadow = this.refs.shadowCanvas.getContext("2d")
      const ctxFragment = this.refs.fragmentCanvas.getContext("2d")

      // 让两个ctx拥有同样的裁剪路径(可滑动小块的轮廓)
      const styleIndex = Math.floor(Math.random() * 16)
      createClipPath(ctxShadow, fragmentSize, styleIndex)
      createClipPath(ctxFragment, fragmentSize, styleIndex)

      // 随机生成裁剪图片的开始坐标
      const clipX = Math.floor(fragmentSize + (imageWidth - 2 * fragmentSize) * Math.random())
      const clipY = Math.floor((imageHeight - fragmentSize) * Math.random())

      // 让小块绘制出被裁剪的部分
      ctxFragment.drawImage(objImage, clipX, clipY, fragmentSize, fragmentSize, 0, 0, fragmentSize, fragmentSize)

      // 让阴影canvas带上阴影效果
      ctxShadow.fillStyle = "rgba(0, 0, 0, 0.5)"
      ctxShadow.fill()

      // 恢复画布状态
      ctxShadow.restore()
      ctxFragment.restore()

      // 设置裁剪小块的位置
      this.setState({ offsetX: clipX, offsetY: clipY })

      // 修改状态
      this.setState({ status: STATUS_READY })
    })

    objImage.src = this.props.imageUrl
  }

  onMoveStart = e => {
    if (this.state.status !== STATUS_READY) {
      return
    }

    // 记录滑动开始时的绝对坐标x
    this.setState({ isMovable: true, startX: e.clientX })
  }

  onMoving = e => {
    if (this.state.status !== STATUS_READY || !this.state.isMovable) {
      return
    }
    const distance = e.clientX - this.state.startX
    let currX = this.state.oldX + distance

    const minX = 0
    const maxX = this.props.imageWidth - this.props.fragmentSize
    currX = currX < minX "2d")
    const ctxFragment = this.refs.fragmentCanvas.getContext("2d")

    // 清空画布
    ctxShadow.clearRect(0, 0, this.props.fragmentSize, this.props.fragmentSize)
    ctxFragment.clearRect(0, 0, this.props.fragmentSize, this.props.fragmentSize)

    this.setState(
      {
        isMovable: false,
        offsetX: 0, //图片截取的x
        offsetY: 0, //图片截取的y
        startX: 0, // 开始滑动的 x
        oldX: 0,
        currX: 0, // 滑块当前 x,
        status: STATUS_LOADING
      },
      this.props.onReload
    )
  }

  onShowTips = () => {
    if (this.state.showTips) {
      return
    }

    const tipsIndex = this.state.status === STATUS_MATCH "image-code" style={{ width: imageWidth }}>
        <div className="image-container" style={{ height: imageHeight, backgroundImage: `url("${imageUrl}")` }}>
          <canvas
            ref="shadowCanvas"
            className="canvas"
            width={fragmentSize}
            height={fragmentSize}
            style={{ left: offsetX + "px", top: offsetY + "px" }}
          />
          <canvas
            ref="fragmentCanvas"
            className="canvas"
            width={fragmentSize}
            height={fragmentSize}
            style={{ top: offsetY + "px", left: currX + "px" }}
          />

          <div className={showTips "tips-container--active" : "tips-container"}>
            <i className="tips-ico" style={{ backgroundImage: `url("${tips.ico}")` }} />
            <span className="tips-text">{tips.text}</span>
          </div>
        </div>

        <div className="reload-container">
          <div className="reload-wrapper" onClick={this.onReload}>
            <i className="reload-ico" style={{ backgroundImage: `url("${icoReload}")` }} />
            <span className="reload-tips">刷新验证</span>
          </div>
        </div>

        <div className="slider-wrpper" onMouseMove={this.onMoving} onMouseLeave={this.onMoveEnd}>
          <div className="slider-bar">按住滑块，拖动完成拼图</div>
          <div
            className="slider-button"
            onMouseDown={this.onMoveStart}
            onMouseUp={this.onMoveEnd}
            style={{ left: currX + "px", backgroundImage: `url("${icoSlider}")` }}
          />
        </div>
      </div>
    )
  }
}

export default ImageCode

// styles.css

.image-code {
  padding: 10px;
  user-select: none;
}

.image-container {
  position: relative;
  background-color: #ddd;
}

.canvas {
  position: absolute;
  top: 0;
  left: 0;
}

.reload-container {
  margin: 20px 0;
}

.reload-wrapper {
  display: inline-flex;
  align-items: center;
  cursor: pointer;
}

.reload-ico {
  width: 20px;
  height: 20px;
  margin-right: 10px;
  background: center/cover no-repeat;
}

.reload-tips {
  font-size: 14px;
  color: #666;
}

.slider-wrpper {
  position: relative;
  margin: 10px 0;
}

.slider-bar {
  padding: 10px;
  font-size: 14px;
  text-align: center;
  color: #999;
  background-color: #ddd;
}

.slider-button {
  position: absolute;
  top: 50%;
  left: 0;
  width: 50px;
  height: 50px;
  border-radius: 25px;
  transform: translateY(-50%);
  cursor: pointer;
  background: #fff center/80% 80% no-repeat;
  box-shadow: 0 2px 10px 0 #333;
}

/* 提示信息 */
.tips-container,
.tips-container--active {
  position: absolute;
  top: 50%;
  left: 50%;
  display: flex;
  align-items: center;
  padding: 10px;
  transform: translate(-50%, -50%);
  transition: all 0.25s;
  background: #fff;
  border-radius: 5px;

  visibility: hidden;
  opacity: 0;
}

.tips-container--active {
  visibility: visible;
  opacity: 1;
}

.tips-ico {
  width: 20px;
  height: 20px;
  margin-right: 10px;
  background: center/cover no-repeat;
}

.tips-text {
  color: #666;
}