// @flow

import http from 'http'
import express from 'express'

import Module from './Module'
import { ExtendedError } from './errorUtils'

import type { $Application } from 'express'

const { MODULE_NAME, log, warn, error, noteGauge, noteCount, trackOp } = new Module(__filename) // eslint-disable-line no-unused-vars

export default class ExpressApp {


  expressApp: $Application
  expressServer: ?Object


  constructor() {
    this.expressApp = express()
  }


  start = async (port: number) => {
    noteCount('ServerStart')

    await this.initExpress()

    // $FlowIgnore
    this.expressServer = await new Promise((res, rej) => {
      const server = http.createServer(this.expressApp)
      server.on('error', (err: Error) => {
        rej(new ExtendedError('Failed to start server', { err }))
      })
      server.on('listening', () => {
        log('Server started', { port: port })
        res(server)
      })
      server.listen(port, undefined);
    })

  }

  stop = async () => { // eslint-disable-line require-await
    if (this.expressServer) {
      // $FlowIgnore
      await new Promise((resp, rej) => this.expressServer.close((err) => err ? rej(err) : resp()))
      this.expressServer = null
    }
    noteCount('ServerStop')
    log('Server stopped')
  }

  initExpress = async () => { }
}