const request = require('superagent')
const cheerio = require('cheerio')
// 簡(jiǎn)單封裝下請(qǐng)求,其他的類似

function getHTML(url) {
// 一些操作,比如設(shè)置一下請(qǐng)求頭信息
return superagent.get(url).set('referer', referer).set('user-agent', userAgent)
}
// 下面就請(qǐng)求一張圖片
async function imageCrawler(url) {
  let res = await getHTML(url)
  let html = res.text
  let $ = cheerio.load(html)
  let $img = $(selector)[0]
  let href = $img.attribs.src
  res = await getImage(href)
  retrun res.body
}
async function handler(url) {
  let img = await imageCrawler(url)
  console.log(img) // buffer 格式的數(shù)據(jù)
  // 處理圖片
}
handler(url)

 async function infoCrawler(url, name) {
    let [schoolAdr, homeAdr] = await Promise.all([getSchoolAdr(name), getHomeAdr(name)])
    let info = await getInfo(url + `?schoolAdr=${schoolAdr}&homeAdr=${homeAdr}`)
    return info
  }

let imageUrls = ['href1', 'href2', 'href3']
async function saveImages(imageUrls) {
  await Promise.all(imageUrls.map(async imageUrl => {
  let img = await getImage(imageUrl)
  return await saveImage(img)
}))
  console.log('done')
}

// 如果我們連存儲(chǔ)是否全部完成也不關(guān)心,也可以這么寫

let imageUrls = ['href1', 'href2', 'href3']
// saveImages() 連 async 都省了
function saveImages(imageUrls) {
  imageUrls.forEach(async imageUrl => {
  let img = await getImage(imageUrl)
  saveImage(img)
  })
}

async function imageCrawler(url) {
  try {
    let img = await getImage(url)
    return img
  } catch (error) {
    console.log(error)
  }
}

// imageCrawler 返回的是一個(gè) promise 可以這樣處理

async function imageCrawler(url) {
  let img = await getImage(url)
  return img
}
imageCrawler(url).catch(err => {
  console.log(err)
})

async function ctx(next) {
  try {
    await next()
  } catch (error) {
    console.log(error)
  }
}

function timeOut(delay) {

return new Promise((resolve, reject) => {
  setTimeout(() => {
  reject(new Error('不用等了,別傻了'))
  }, delay)
})
}

async function imageCrawler(url,delay) {

try {
  let img = await Promise.race([getImage(url), timeOut(delay)])
  return img
} catch (error) {
  console.log(error)
}
}

async function getImages(urls, limit) {
  let running = 0
  let r
  let p = new Promise((resolve, reject) => {
  r = resolve
  })
  function run() {
    if (running < limit && urls.length > 0) {
      running++
      let url = urls.shift();
      (async () => {
        let img = await getImage(url)
        running--
        console.log(img)
        if (urls.length === 0 && running === 0) {
          console.log('done')
          return r('done')
        } else {
          run()
        }
      })()
      run() // 立即到并發(fā)上限
    }
  }
  run()
  return await p
}

function delay(time) {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve(time)
    }, time)
  })
}
function *createTime() {
  let time1 = yield delay(1000)
  let time2 = yield delay(2000)
  let time3 = yield delay(3000)
  console.log(time1, time2, time3)
}
let iterator = createTime()
console.log(iterator.next())
console.log(iterator.next(1000))
console.log(iterator.next(2000))
console.log(iterator.next(3000))
// 輸出

{ value: Promise { <pending> }, done: false } 

{ value: Promise { <pending> }, done: false }

 { value: Promise { <pending> }, done: false } 

1000 2000 3000 

{ value: undefined, done: true }

function run(createTime) {
  let iterator = createTime()
  let result = iterator.next()
  function autoRun() {
    if (!result.done) {
      Promise.resolve(result.value).then(time => {
      result = iterator.next(time)
      autoRun()
    }).catch(err => {
      result = iterator.throw(err)
      autoRun()
      })
    }
  }
  autoRun()
}
run(createTime)

function delay(time) {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      if (time == 2000) {
      reject('2000錯(cuò)誤')
    }
      resolve(time)
    }, time)
  })
}
function *createTime() {
  let time1 = yield delay(1000)
  let time2
  try {
    time2 = yield delay(2000)
  } catch (error) {
    time2 = error
  }
  let time3 = yield delay(3000)
  console.log(time1, time2, time3)
}

async function createTime() {
  let time1 = await delay(1000)
  let time2
  try {
    time2 = await delay(2000)
  } catch (error) {
    time2 = error
  }
  let time3 = await delay(3000)
  console.log(time1, time2, time3)
}

function transform(async) {
 let str = async.toString()
 str = str.replace(/async\s+(function)\s+/, '$1 *').replace(/await/g, 'yield')
 return str
}