const _cache = {}
const _loading = {}

async function simulateFetch(url) {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve(`Response from ${url}`)
    }, 1000) // 模拟延迟1秒的请求
  })
}

async function fetchWithCache(url) {
  if (url in _cache)
    return _cache[url]

  if (!_loading[url]) {
    _loading[url] = true
    const request = simulateFetch(url)
      .then((text) => {
        _cache[url] = text
        delete _loading[url]
        return text
      })
    _cache[url] = request
  }

  return _cache[url]
}

let requestStatus = 'idle'

async function getUser(userId) {
  requestStatus = 'loading'

  const cachedRequest = _cache[`/user/${userId}`]

  if (cachedRequest)
    return await cachedRequest

  const profile = await fetchWithCache(`/user/${userId}`)
  requestStatus = 'success'
  return profile
}

// 测试
getUser('123')
  .then((data) => {
    console.log(data) // 第一次请求
  })

getUser('123')
  .then((data) => {
    console.log(data) // 第二次请求，应该从缓存中获取
  })