// @/components/Canvas.vue

<template>
  <div :style="{ height: waveAllHeight + 'px', background: bgColor }" class="wave">
    <canvas id="wave1"></canvas>
    <canvas id="wave2"></canvas>
    <canvas id="wave3"></canvas>
  </div>
</template>

<script>
export default {
  name: "Canvas",
  props: {
    bgColor: {
      default: "none",
    }, // 背景色
    waveAllHeight: { default: 160 }, // 波浪的整体高度
    waveCount: { default: 2 }, // 波峰个数
    waveHeight: { default: 50 }, // 波浪起伏高度
    // 波浪颜色
    waveColor: {
      default () {
        return [
          "#f3f3f3",
          "#f3f3f3",
          "#f3f3f3",
        ];
      },
    },
    // 波浪速率
    waveTime: {
      default () {
        return [4000, 4000, 4000];
      },
    },
  },
  data () {
    return {};
  },
  mounted () {
    this.wavePlay("wave1", 140, this.waveColor[0], this.waveTime[0]);
    this.wavePlay("wave2", 140, this.waveColor[1], this.waveTime[1]);
    this.wavePlay("wave3", 140, this.waveColor[2], this.waveTime[2]);
  },
  methods: {
    wavePlay ($canvasID, $progress, $maveColor, $time) {
      const that = this;
      let waveWidth = 3300, // 波浪长度
        offset = 0,
        waveHeight = that.waveHeight, // 波浪起伏高度
        waveCount = that.waveCount, // 波浪个数
        startX = -1200,
        startY = 212, // canvas 高度
        progress = $progress, // 波浪位置高度
        d2 = waveWidth / waveCount, // 单个波浪的宽度
        d = d2 / 2,
        hd = d / 2,
        c = document.getElementById($canvasID),
        ctx = c.getContext("2d");
      c.width = 1920; // 画布宽度
      c.height = that.waveAllHeight; // 画布高度
      function move () {
        offset -= 5;
        if (-1 * offset === d2) {
          offset = 0;
        }
        ctx.clearRect(0, 0, c.width, c.height);
        ctx.fillStyle = $maveColor; // 画布填充色
        ctx.beginPath();
        let offsetY = startY - progress;
        // 绘制贝塞尔曲线
        ctx.moveTo(startX - offset, offsetY); // 开始点
        for (let i = 0; i < waveCount; i++) {
          let dx = i * d2;
          let offsetX = dx + startX - offset;
          ctx.quadraticCurveTo(
            offsetX + hd,
            offsetY + waveHeight,
            offsetX + d,
            offsetY
          );
          ctx.quadraticCurveTo(
            offsetX + hd + d,
            offsetY - waveHeight,
            offsetX + d2,
            offsetY
          );
        }
        ctx.lineTo(startX + waveWidth, 3000);
        ctx.lineTo(startX, 0);
        ctx.fill();
        setTimeout(move, $time / 60); // 速度
      }

      move();
    },
  },
};
</script>

<style scoped lang="scss">
.wave {
  width: 100%;
  height: 100%;
  position: relative;
  top: 0;
  left: 0;
  margin-top: -8%;
  canvas {
    width: 100%;
    opacity: 1;
    position: absolute;
    top: 0;
    left: 0;
  }
}
@media (max-width: 900px) {
  .wave {
    display: none;
  }
}
</style>