import { EmailTemplate } from 'email-templates'
import path from 'path'
import nodemailer from 'nodemailer'

import config from '../../scripts/load-config'

// TEMPORARY FIX FOR NODE v9.2.0
import tls from 'tls'
tls.DEFAULT_ECDH_CURVE = 'auto'

const templateDir = path.join(__dirname, '../../', 'templates')

const templateCache = {}
let transporter

// Send an email to `email` with `headers`
async function sendMail (email, headers) {
  return new Promise(function (resolve, reject) {
    if (!transporter) return reject(new Error('No transporter present!'))

    transporter.sendMail(Object.assign({
      from: config.email.admin,
      to: email
    }, headers), (error, info) => {
      if (error) {
        return reject(error)
      }

      resolve(info)
    })
  })
}

// Send an email to `email` using `template` rendered with variables from `context`
async function pushMail (template, email, context) {
  if (!transporter) return null
  let templ = null

  if (!templateCache[template]) {
    templ = templateCache[template] = new EmailTemplate(path.join(templateDir, template))
  } else {
    templ = templateCache[template]
  }

  const result = await templ.render(context)

  console.debug('Mail being sent: %s to %s', template, email)

  return sendMail(email, result)
}

// Transporter initialization
async function init () {
  if (!config.email || config.email.enabled === false) return
  transporter = nodemailer.createTransport(config.email.transport)

  console.debug('Setting up mail transporter')

  try {
    await transporter.verify()
    console.debug('Mail transporter initialized')
  } catch (e) {
    console.error('Email server verification failed')
    console.error(e)
    transporter = null
  }
}

module.exports = {
  sendMail: sendMail,
  pushMail: pushMail,
  init: init
}