<script setup lang="ts">
  import { ref, onMounted } from 'vue'
  
  let width = ref(600) // 地圖默認寬度
  let height = ref(400) // 地圖默認高度
  let canvas: any = null // canvas 對象
  let ctx: any = null // canvas 渲染上下文對象
  let snakeList = [[0, 100], [10, 100],] // 蛇的點位坐標
  let direction = 'right' // top | down | left | right // 當前方向
  let elementWidth = 10 // 元素尺寸
  let step = 10 // 速度
  let store = ref(0) // 分數(shù)
  let status = ref('start') // unStart | start | pause ｜ over | success(通關) // 狀態(tài)
  let foodCoordinate: any = [
    ((Math.random() * width.value) / 10) | 0,
    ((Math.random() * height.value) / 10) | 0,
  ] // 食物坐標
  let process: any = null // 定時器 Id
</script>

function handleInit() {
  canvas = document.getElementById('canvas')

  if (canvas?.getContext) {
    ctx = canvas?.getContext('2d')

    canvas.addEventListener('mousemove', e => {
      ctx.clearRect(10, height.value - 20, 120, 40)
      ctx.fillText(`當前鼠標位置：${e.offsetX}, ${e.offsetY}`, 10, height.value - 10)
    })

    document.addEventListener('keydown', e => {
      e.preventDefault()

      if (Direction[e.keyCode]) {
        direction = Direction[e.keyCode]
      }
    })

    process = setInterval(handleRenderSnake, 150)
    handleRenderFood()
    // window.requestAnimationFrame(handleRenderSnake)
  } else {
    alert('您的瀏覽器不支持 canvas')
  }
}

// 繪制食物
function handleRenderFood() {
  ctx.clearRect(foodCoordinate[0], foodCoordinate[1], 10, 10)
  foodCoordinate = [(Math.random() * width.value) | 0, (Math.random() * height.value) | 0]
  ctx.fillStyle = '#eb2f96'
  ctx.fillRect(foodCoordinate[0], foodCoordinate[1], 10, 10)
}

function handleRenderSnake() {
  switch (direction) {
    case 'top':
      if (snakeList.slice(-1)[0][1] <= 0) {
        status.value = 'over'
        return
      }

      snakeList.push([
        snakeList[snakeList.length - 1][0],
        snakeList[snakeList.length - 1][1] - step,
      ])
      handleUpdateVerify()
      break
    case 'down':
      if (snakeList.slice(-1)[0][1] >= height.value - 1) {
        status.value = 'over'
        return
      }

      snakeList.push([
        snakeList[snakeList.length - 1][0],
        snakeList[snakeList.length - 1][1] + step,
      ])
      handleUpdateVerify()

      break
      ...

// 更新校驗
function handleUpdateVerify() {
  if (status.value === 'pause') {
    clearInterval(process)
  }

  if (store.value >= 100) {
    status.value = 'success'
    return
  }

  for (let i of snakeList) {
    ctx.clearRect(i[0], i[1], elementWidth, elementWidth)
  }

  let currentSnake = snakeList.slice(-1)[0]
  if (
    Math.abs(currentSnake[0] - foodCoordinate[0]) < 10 &&
    Math.abs(currentSnake[1] - foodCoordinate[1]) < 10
  ) {
    store.value++
    handleRenderFood()
  } else {
    snakeList.shift()
  }
}