import { ChildProcess, fork } from 'child_process'
import { randomInt } from '../../core-utils/miscs/miscs'
import { parallelTests } from '../server/servers'

class MockSmtpServer {

  private static instance: MockSmtpServer
  private started = false
  private emailChildProcess: ChildProcess
  private emails: object[]

  private constructor () {
    this.emailChildProcess = fork(`${__dirname}/email-child-process`, [])

    this.emailChildProcess.on('message', (msg) => {
      if (msg.email) {
        return this.emails.push(msg.email)
      }
    })

    process.on('exit', () => this.kill())
  }

  collectEmails (emailsCollection: object[]) {
    return new Promise<number>((res, rej) => {
      const port = parallelTests() ? randomInt(1000, 2000) : 1025

      if (this.started) {
        this.emails = emailsCollection
        return res()
      }

      // ensure maildev isn't started until
      // unexpected exit can be reported to test runner
      this.emailChildProcess.send({ start: true, port })
      this.emailChildProcess.on('exit', () => {
        return rej(new Error('maildev exited unexpectedly, confirm port not in use'))
      })
      this.emailChildProcess.on('message', (msg) => {
        if (msg.err) {
          return rej(new Error(msg.err))
        }
        this.started = true
        this.emails = emailsCollection
        return res(port)
      })
    })
  }

  kill () {
    if (!this.emailChildProcess) return

    process.kill(this.emailChildProcess.pid)

    this.emailChildProcess = null
    MockSmtpServer.instance = null
  }

  static get Instance () {
    return this.instance || (this.instance = new this())
  }
}

// ---------------------------------------------------------------------------

export {
  MockSmtpServer
}