// 根據(jù)請求生成對應(yīng)的key
function generateReqKey(config, hash) {
    const { method, url, params, data } = config;
    return [method, url, JSON.stringify(params), JSON.stringify(data), hash].join("&");
}

import axios from "axios"

let instance = axios.create({
    baseURL: "/api/"
})

// 發(fā)布訂閱
class EventEmitter {
    constructor() {
        this.event = {}
    }
    on(type, cbres, cbrej) {
        if (!this.event[type]) {
            this.event[type] = [[cbres, cbrej]]
        } else {
            this.event[type].push([cbres, cbrej])
        }
    }

    emit(type, res, ansType) {
        if (!this.event[type]) return
        else {
            this.event[type].forEach(cbArr => {
                if(ansType === 'resolve') {
                    cbArr[0](res)
                }else{
                    cbArr[1](res)
                }
            });
        }
    }
}


// 根據(jù)請求生成對應(yīng)的key
function generateReqKey(config, hash) {
    const { method, url, params, data } = config;
    return [method, url, JSON.stringify(params), JSON.stringify(data), hash].join("&");
}

// 存儲(chǔ)已發(fā)送但未響應(yīng)的請求
const pendingRequest = new Set();
// 發(fā)布訂閱容器
const ev = new EventEmitter()

// 添加請求攔截器
instance.interceptors.request.use(async (config) => {
    let hash = location.hash
    // 生成請求Key
    let reqKey = generateReqKey(config, hash)
    
    if(pendingRequest.has(reqKey)) {
        // 如果是相同請求,在這里將請求掛起，通過發(fā)布訂閱來為該請求返回結(jié)果
        // 這里需注意，拿到結(jié)果后，無論成功與否，都需要return Promise.reject()來中斷這次請求，否則請求會(huì)正常發(fā)送至服務(wù)器
        let res = null
        try {
            // 接口成功響應(yīng)
          res = await new Promise((resolve, reject) => {
                    ev.on(reqKey, resolve, reject)
                })
          return Promise.reject({
                    type: 'limiteResSuccess',
                    val: res
                })
        }catch(limitFunErr) {
            // 接口報(bào)錯(cuò)
            return Promise.reject({
                        type: 'limiteResError',
                        val: limitFunErr
                    })
        }
    }else{
        // 將請求的key保存在config
        config.pendKey = reqKey
        pendingRequest.add(reqKey)
    }

    return config;
  }, function (error) {
    return Promise.reject(error);
  });

// 添加響應(yīng)攔截器
instance.interceptors.response.use(function (response) {
    // 將拿到的結(jié)果發(fā)布給其他相同的接口
    handleSuccessResponse_limit(response)
    return response;
  }, function (error) {
    return handleErrorResponse_limit(error)
  });

// 接口響應(yīng)成功
function handleSuccessResponse_limit(response) {
      const reqKey = response.config.pendKey
    if(pendingRequest.has(reqKey)) {
      let x = null
      try {
        x = JSON.parse(JSON.stringify(response))
      }catch(e) {
        x = response
      }
      pendingRequest.delete(reqKey)
      ev.emit(reqKey, x, 'resolve')
      delete ev.reqKey
    }
}

// 接口走失敗響應(yīng)
function handleErrorResponse_limit(error) {
    if(error.type && error.type === 'limiteResSuccess') {
      return Promise.resolve(error.val)
    }else if(error.type && error.type === 'limiteResError') {
      return Promise.reject(error.val);
    }else{
      const reqKey = error.config.pendKey
      if(pendingRequest.has(reqKey)) {
        let x = null
        try {
          x = JSON.parse(JSON.stringify(error))
        }catch(e) {
          x = error
        }
        pendingRequest.delete(reqKey)
        ev.emit(reqKey, x, 'reject')
        delete ev.reqKey
      }
    }
      return Promise.reject(error);
}

export default instance;

function isFileUploadApi(config) {
  return Object.prototype.toString.call(config.data) === "[object FormData]"
}