<!-- msw.svelte -->
<div class="msw-container">
  <div on:click|stopPropagation={showModal}
       bind:this={btnDOM}
       class="msw-show">MSW</div>
</div>
<script>
  import { onMount } from "svelte";
  // 區(qū)分當(dāng)前是PC端，還是移動(dòng)端，來設(shè)置 mouse 事件 或 touch 事件
  function getModels() {
    let userAgentInfo = navigator.userAgent;
    let mobileAgents = ["Android", "iPhone", "SymbianOS", "Windows Phone", "iPad", "iPod"];
    return mobileAgents.reduce((prev, ua)=>{
      return userAgentInfo.includes(ua) || prev
    }, false)
  };
  const MSW_BTN_POSITION = '__MSW_BTN_POSITION__'
  let show = false;
  let btnDOM = null;
  let isDrop = false;
  let isMoving = false;
  let offset = {
    x: 0,
    y: 0,
  };
  let offsetDown = {};
  let dropTimer = null;
  let isMobile = getModels();
  let btnW = 0;
  let btnH = 0;
  let clientW = 0;
  let clientH = 0;
  let eventType = isMobile ? 'touchstart' : 'mousedown';
  // DOM 掛載后執(zhí)行
  onMount(async () => {
    // 初始化，獲取按鈕、視口寬高、計(jì)算邊界值
    initClientData();
    return () => {
      // component 卸載后，解除事件綁定
      btnDOM.removeEventListener(eventType, btnMousedown)
    }
  });
  function initClientData() {
    // 按鈕位置保存在本地，可以記住位置，避免每次去拖拽
    let local = localStorage.getItem(MSW_BTN_POSITION)
    if (local) {
      offset = JSON.parse(local)
      btnMove()
    }
    let w = window.innerWidth || document.documentElement.clientWidth || document.body.clientWidth
    clientW = isMobile ? w : document.body.clientWidth
    clientH = window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight
    btnW = btnDOM.offsetWidth
    btnH = btnDOM.offsetHeight
    // 給按鈕綁定 mousedown 或 touchstart 事件
    btnDOM.addEventListener(eventType, btnMousedown)
  }
  function eventHandle (type) {
    if (isMobile) {
      document[`${type}EventListener`]('touchmove', mousemove);
      document[`${type}EventListener`]('touchend', mouseup);
    } else {
      document[`${type}EventListener`]('mousemove', mousemove);
      document[`${type}EventListener`]('mouseup', mouseup);
    }
  }
  function showModal () {
    if (!isMoving) {
      show = true;
    }
  }
  function btnMousedown(e) {
    e = e || window.event
    isDrop = true
    offsetDown = {
      ...getOffset(e)
    };
    eventHandle('add')
  }
  function mousemove(e) {
    e = e || window.event
    if (isDrop) {
      let data = getOffset(e);
      // 判斷是否移動(dòng)了
      isMoving = !(offsetDown.x === data.x && offsetDown.y === data.y)
      let x = data.x - btnW / 2;
      let y = data.y - btnH / 2;
      if (x > 5 && x < (clientW-btnW - 5)) {
        offset.x = x;
      }
      if (y > 5 &&  y < (clientH-btnH - 5)) {
        offset.y = y;
      }
      if (isMoving) {
        btnMove()
      }
      clearTimeout(dropTimer);
      dropTimer = setTimeout(()=>{
        isMoving = false;
        clearTimeout(dropTimer);
        dropTimer = null;
      }, 300);
    }
  }
  function mouseup() {
    if (isDrop) {
      window.localStorage.setItem(MSW_BTN_POSITION, JSON.stringify(offset))
      eventHandle('remove')
    }
    isDrop = false
    // console.log('mouseup')
  }
  function btnMove (){
    btnDOM.style.cssText = `
    left: ${offset.x}px;
    top: ${offset.y}px;
    right: auto;
    bottom: auto;
    `
  }
  function getOffset(e) {
    return isMobile ? {
      x: e.targetTouches[0].clientX,
      y: e.targetTouches[0].clientY,
    } : {
      x: e.clientX,
      y: e.clientY,
    }
  }
</script>
<style lang="scss" type="text/scss">
  @import "index";
</style>