import { Router } from 'express'
import { readFileSync, writeFileSync, existsSync } from 'fs'
import { join, dirname } from 'path'
import { fileURLToPath } from 'url'
import { Mutex } from 'async-mutex'
import { newsletterLimiter } from '../middleware/rateLimiter.js'
import { antiSpam } from '../middleware/antiSpam.js'
import { createToken, reserveToken, completeToken, releaseToken } from '../services/confirmationToken.js'
import { sendConfirmationEmail, MailerNotReadyError } from '../services/mailer.js'

const __dirname = dirname(fileURLToPath(import.meta.url))
const SUBS_FILE = join(__dirname, '..', 'data', 'subscribers.json')
const subsMutex = new Mutex()

function loadSubscribers() {
  if (!existsSync(SUBS_FILE)) return []
  try { return JSON.parse(readFileSync(SUBS_FILE, 'utf-8')) }
  catch { return [] }
}

function saveSubscribers(subs) {
  writeFileSync(SUBS_FILE, JSON.stringify(subs, null, 2), 'utf-8')
}

const router = Router()

router.post('/', newsletterLimiter, antiSpam, async (req, res) => {
  const { email } = req.body
  let token
  if (!email || !/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(email)) {
    return res.status(400).json({ errors: { email: 'Gültige E-Mail erforderlich.' } })
  }

  const subs = loadSubscribers()
  if (subs.find(s => s.email === email && s.active)) {
    return res.status(409).json({ error: 'Diese E-Mail ist bereits abonniert.' })
  }

  try {
    token = await createToken('newsletter', { email }, 48)
    await sendConfirmationEmail(email, 'newsletter', token)
    res.status(201).json({ ok: true, message: 'Bestätigungs-E-Mail gesendet.' })
  } catch (error) {
    if (token) await completeToken(token)
    res.status(error instanceof MailerNotReadyError ? 503 : 502).json({ error: 'Die Anfrage konnte derzeit nicht versendet werden.' })
  }
})

router.get('/confirm/:token', async (req, res) => {
  const baseUrl = (process.env.BASE_URL || '').replace(/\/+$/, '')
  const entry = await reserveToken(req.params.token)
  if (!entry) return res.redirect(baseUrl + '/bestaetigung?status=error')

  try {
    await subsMutex.runExclusive(async () => {
      const subs = loadSubscribers()
      if (!subs.find(s => s.email === entry.data.email && s.active)) {
        subs.push({
          email: entry.data.email,
          subscribedAt: new Date().toISOString(),
          active: true,
        })
        saveSubscribers(subs)
      }
    })
    await completeToken(req.params.token)
    res.redirect(baseUrl + '/bestaetigung?status=success')
  } catch {
    await releaseToken(req.params.token)
    res.redirect(baseUrl + '/bestaetigung?status=error')
  }
})

export default router