<template>
  <div>
    <canvas id="time_line" width="1200" height="27"></canvas>
  </div>
</template>

<script>
export default {
  name: 'pathwaytrack',
  data() {
    return {
      screenWidth: document.body.clientWidth
    }
  },
  mounted() {
    let that = this
    that.carveTimeScale(1200, 1, 10, 0, 10)
    let canvasColor = '#999999'
    let initTime = 12000
    setInterval(() => {
      initTime += 1000
      that.carveTimeScale(1200, 1, 10, initTime, 10)
    }, 1000);
  },
  methods: {
    /**
     * 分割像素刻度
     * width: 寬度 ms：一個(gè)小刻度的毫秒數(shù) pxMs：10像素一個(gè)小刻度 pageShowStartTime：初始時(shí)間（毫秒） 一大段間隔時(shí)長(秒）
     */
    carveTimeScale(width, ms, pxMs, pageShowStartTime, intervalTime) {
      let canvasId = document.getElementById('time_line')
      let ctx = canvasId.getContext('2d')
      ctx.clearRect(0, 0, 1200, 60)
      ctx.fillStyle = '#999999'
      // 為防止蘋果屏幕2X顯示不正常
      // 為防止蘋果屏幕2X顯示不正常
      var getPixelRatio = function (context) {
        var backingStore = context.backingStorePixelRatio ||
          context.webkitBackingStorePixelRatio ||
          context.mozBackingStorePixelRatio ||
          context.msBackingStorePixelRatio ||
          context.oBackingStorePixelRatio ||
          context.backingStorePixelRatio || 1
        return (window.devicePixelRatio || 1) / backingStore
      }
      let ratio = getPixelRatio(ctx)
      let msOffset = this.startOffsetTime(pageShowStartTime, ms) // 開始的偏移時(shí)間 ms
      let pxOffset = msOffset / 1000 * pxMs // 開始的偏移距離 px
      let leftDistance = 0 // 到左側(cè)的距離
      let leftDistanceTime = 0 // 到左側(cè)的時(shí)間
      let beginX = 0
      let beginY = 0
      for (let i = 0; i < width / (ms * pxMs); i++) {
        leftDistance = pxOffset + i * (ms * pxMs) // 距離 = 開始的偏移距離 + 格數(shù) * px/格
        leftDistanceTime = pageShowStartTime + msOffset + i * ms // 時(shí)間 = 左側(cè)開始時(shí)間 + 偏移時(shí)間 + 格數(shù) * ms
        beginX = pxOffset + i * (ms * pxMs)
        let canvasColor
        let showTime = pageShowStartTime + beginX / pxMs * 1000
        if (showTime % (intervalTime * 1000) === 0) {
          beginY = 0
          ctx.font = '12px Arial'
          ctx.fillText(this.changeTime(showTime, 1), beginX + 10, 22)
          canvasColor = '#999999'
          ctx.fillStyle = '#B1B1B1'
          this.drawLine(leftDistance, beginY, leftDistance, 20, canvasColor, 1)
        } else if (showTime % intervalTime == 0) {
          beginY = 0
          canvasColor = '#999999'
          this.drawLine(leftDistance, beginY, leftDistance, 10, canvasColor, 1)
        }
      }
    },
    /**
     * 根據(jù)傳入?yún)?shù)畫線
     */
    drawLine(beginX, beginY, endX, endY, color, width) {
      let canvasId = document.getElementById('time_line');
      let ctx = canvasId.getContext('2d');
      ctx.beginPath();
      ctx.moveTo(beginX, beginY);
      ctx.lineTo(endX, endY);
      ctx.strokeStyle = color;
      ctx.lineWidth = width;
      ctx.stroke();
    },
    /**
     * 左側(cè)開始時(shí)間的偏移，返回單位ms
     */
    startOffsetTime(timestamp, step) {
      let remainder = timestamp % step
      return remainder ? step - remainder : 0
    },
    /**
     * 返回時(shí)間
     */
    changeTime(time, num) {
      let hour = 0
      let minute = 0
      let second = 0
      second = time / 1000
      if (second >= 3600) {
        minute = (second - (second % 60)) / 60
        hour = parseInt((minute / 60).toString())
        minute = minute % 60
        /* eslint-disable */
        hour >= 10 ? hour : hour = '0' + hour
        minute >= 10 ? minute : minute = '0' + minute
        second = second % 60
        second >= 10 ? second : second = '0' + second
        /* eslint-enable */
        return hour + ':' + minute + ':' + second
      }
      if (second < 3600 && second >= 60) {
        hour = '00'
        minute = parseInt((second / 60).toString())
        /* eslint-disable */
        minute >= 10 ? minute : minute = '0' + minute
        second = second % 60
        second >= 10 ? second : second = '0' + second
        /* eslint-enable */
        return hour + ':' + minute + ':' + second
      }
      if (second < 60) {
        hour = '00'
        minute = '00'
        second = parseInt(second)
        /* eslint-disable */
        second >= 10 ? second : second = '0' + second
        /* eslint-enable */
        return hour + ':' + minute + ':' + second
      }
    }
  }
}
</script>

<style lang="less" scoped>
  canvas {
    background: black;
  }
</style>