/**
 * @created by pan
 * @updated by helin3 2019-04-08
 * @description Mock Express 热更新注册
 */
const chokidar = require('chokidar')
const bodyParser = require('body-parser')
const chalk = require('chalk')
const path = require('path')

const mockDir = path.join(process.cwd(), 'mocks')
const mockEnable = process.env.VUE_APP_MOCK_ENABLE === 'true' // Mock是否启用
const mockMode = process.env.VUE_APP_MOCK_MODE === 'true' // 模拟模式，true真实express服务，false XHR拦截方式

/**
 * 通过express 路由方式注册mocks api
 * @param {*} app express实例
 * @returns {object}
 *  mockStartIndex mock路由开始索引位置
 *  mockRoutesLength  路由长度mocks api
 */
function registerRoutes(app) {
  let mockLastIndex
  // 读取注册路由
  const { default: mocks } = require('./index.js')
  console.log('\n Mocks Server Register Routes : \n')
  for (const mock of mocks) {
    let url = mock.url ? (mock.url.source || mock.url): ''
    url = url.replace(/\\\//g, '/')
    console.log(' - ' + mock.type + ' - ' + url)
    app[mock.type](mock.url, mock.response)
  }
  mockLastIndex = app._router.stack.length
  const mockRoutesLength = Object.keys(mocks).length
  return {
    mockStartIndex: mockLastIndex - mockRoutesLength,
    mockRoutesLength: Object.keys(mocks).length
  }
}

/**
 * 清除/mocks目录require缓存
 * TODO: 待调试
 */
function unregisterRoutes() {
  Object.keys(require.cache).forEach(i => {
    // 清除/mocks目录require缓存
    if (i.includes(mockDir)) {
      delete require.cache[require.resolve(i)]
    }
  })
}

module.exports = app => {
  // es6 polyfill
  require('@babel/register')

  // Mock启用，则在开发模式添加mock api拦截
  // 此处必须得是字符串方式判断，因其不在浏览器中
  if (!mockEnable || !mockMode) {
    return
  }
  // 开发模式，没有统一前缀，如何区分API是Mock服务
  app.all('*', function(req, res, next) {
    res.header("X-Mock-Api", "xyMock")
    next()
  })
  // parse app.body
  // https://expressjs.com/en/4x/api.html#req.body
  app.use(bodyParser.json())
  app.use(bodyParser.urlencoded({
    extended: true
  }))
  
  let lastRegReturn = registerRoutes(app)
  let mockRoutesLength = lastRegReturn.mockRoutesLength
  let mockStartIndex = lastRegReturn.mockStartIndex

  // 监听/mocks文件（忽略/mocks/mocks-server.js)，热加载Mocks Server
  chokidar.watch(mockDir, {
    ignored: /mocks-server/,
    ignoreInitial: true
  }).on('all', (event, path) => {
    if (event === 'change' || event === 'add') {
      // 移除 mock api Express路由堆栈
      app._router.stack.splice(mockStartIndex, mockRoutesLength)
      // 清除路由文件缓存
      unregisterRoutes()
      // 重新注册Mocks api路由
      lastRegReturn = registerRoutes(app)
      mockRoutesLength = lastRegReturn.mockRoutesLength
      mockStartIndex = lastRegReturn.mockStartIndex
      
      console.log(chalk.magentaBright(`\n > Mocks Server hot reload success! changed ${path}`))
    }
  })
}