readline.emitKeypressEvents(process.stdin) // 注册 keypress 事件

process.stdin.setRawMode(true) // 开启原始模式, 使输入的每个字符带上各种详细属性

process.stdin.on('keypress', (...args) => {
 console.log(args)
 // 按下方向键会输出
 // [
 //  undefined,
 //  {
 //   sequence: '\u001b[A',
 //   name: 'up',
 //   ctrl: false,
 //   meta: false,
 //   shift: false,
 //   code: '[A'
 //  }
 // ]
})

const ansiEscapes = require('ansi-escapes')

function clear(lines) {
 process.stdout.write(ansiEscapes.eraseLines(lines)) // 可以擦除指定行数的输出
}

let dots = []
for (let col = 0; col < wall.height; col++) {
 dots[col] = new Array(wall.width).fill(' ')
}

const SNAKE_HEAD = '@' // 头的符号
const SNAKE_BODY = '○' // 身体的符号

function drawFrame() {
 let dots = []
 for (let col = 0; col < wall.height; col++) {
  dots[col] = new Array(wall.width).fill(' ')
 }

 let nextBody = []
 let head = next(snake.body[0]) // next 方法传入当前点的 x, y 坐标, 返回向前进方向前进一个的 x, y 坐标
 nextBody.push(head)
 dots[head.y][head.x] = SNAKE_HEAD
 for (let i = 1; i < snake.length; i++) {
  let body = snake.body[i - 1]
  dots[body.y][body.x] = SNAKE_BODY
  nextBody.push(body)
 }
 
 screen.draw(dots) // 将二维数组中的点输出到命令行中
 
 // 更新蛇的状态
 snake.body = nextBody
 snake.head = snake.body[0]
}

function layAEgg() {
 let x = ~~(wall.width * Math.random())
 let y = ~~(wall.height * Math.random())
 return { x, y }
}

const SNAKE_HEAD = '@'
const SNAKE_BODY = '○'
const BIRD_EGG = '●'

function drawFrame() {
 let dots = []
 for (let col = 0; col < wall.height; col++) {
  dots[col] = new Array(wall.width).fill(' ')
 }

 let nextBody = []
 let head = next(snake.body[0])
 nextBody.push(head)
 dots[head.y][head.x] = SNAKE_HEAD
 for (let i = 1; i < snake.length; i++) {
  let body = snake.body[i - 1]
  dots[body.y][body.x] = SNAKE_BODY
  nextBody.push(body)
 }

 // 判断蛇头位置在上一帧中是否为鸟蛋位置, 为真视为蛇吃到鸟蛋
 if (prevDots && prevDots[head.y][head.x] === BIRD_EGG) {
  let body = snake.body[snake.length - 1]
  dots[body.y][body.x] = SNAKE_BODY
  nextBody.push(body)
  snake.length += 1
  egg = null
  prevDots = null
 }

 if (!egg) {
  egg = layAEgg()
  while (dots[egg.y][egg.x] !== ' ') {
   egg = layAEgg()
  }
 }
 dots[egg.y][egg.x] = BIRD_EGG

 prevDots = dots // 保存上一帧的数据, 用于下次绘制时判断逻辑

 screen.draw(dots)
 snake.body = nextBody
 snake.head = snake.body[0]
}