import { randomUUID } from 'node:crypto'
import { Resend } from 'resend'
import { requireAdminAuth } from '../auth.js'
import { escapeHtml, splitName, buildAbsoluteUrl } from '../helpers.js'
import {
  MAX_CONTACT_SUBMISSIONS,
  MAX_QUESTIONS,
  USE_RESEND_AUTOMATION_WELCOME,
  DEFAULT_SEO,
  DATA_FILE,
} from '../config.js'
import { state } from '../state.js'
import {
  queueContactSubmissionsWrite,
  queueQuestionsWrite,
  queueDraftQuestionsWrite,
  normalizeContactEmailStatus,
  normalizeMessageType,
  fireWebhooks,
  loadSiteContentFile,
} from '../data.js'
import {
  noteContactEmailCooldown,
  extractTagValue,
  mapResendEventToStatus,
  extractResendMessageId,
} from '../study-helpers.js'
import {
  getResendFromAddress,
  getResendReplyToAddress,
  getResendInboxAddress,
  buildContactWelcomeEmailTemplate,
  buildContactAdminNotificationTemplate,
  sendResendEmailWithRetry,
  syncContactToResend,
  resendRetry,
} from '../email.js'

// RFC 5322 msg-id: "<" printable-ASCII-no-whitespace ">"
const MESSAGE_ID_RE = /^<[\x21-\x7E]+>$/

function upsertContactEmailStatus(submissionId, stream, patch) {
  if (!submissionId || typeof submissionId !== 'string') return
  if (!stream || typeof stream !== 'string') return
  const at = typeof patch?.lastEventAt === 'string' ? patch.lastEventAt : new Date().toISOString()
  let updated = false

  state.contactSubmissions = state.contactSubmissions.map(submission => {
    if (submission.id !== submissionId) return submission
    const next = normalizeContactEmailStatus(submission.emailStatus, submission.subscribe === true)
    const current = next[stream] ?? { status: 'pending', lastEventAt: null, lastEventType: null, resendEmailId: null, error: null }
    next[stream] = { ...current, ...patch, lastEventAt: at }
    updated = true
    return { ...submission, emailStatus: next }
  })

  if (updated) queueContactSubmissionsWrite()
}

function registerResendMessageForSubmission(submissionId, stream, sendResult) {
  const resendMessageId = extractResendMessageId(sendResult)
  if (!resendMessageId || !submissionId || !stream) return
  state.resendEmailSubmissionIndex.set(resendMessageId, { submissionId, stream })
  // Trim the index when it grows large; oldest entries are least likely to receive webhooks
  if (state.resendEmailSubmissionIndex.size > 2000) {
    const firstKey = state.resendEmailSubmissionIndex.keys().next().value
    state.resendEmailSubmissionIndex.delete(firstKey)
  }
  upsertContactEmailStatus(submissionId, stream, { resendEmailId: resendMessageId })
}

function shouldSendWelcomeEmail({ subscribe }) {
  return subscribe === true
}

const contactHits = new Map()

function contactRateLimit(req, res, next) {
  const ip = req.ip ?? 'unknown'
  const now = Date.now()
  const windowMs = 10 * 60 * 1000
  const entry = contactHits.get(ip) ?? { count: 0, start: now }
  if (now - entry.start > windowMs) { entry.count = 0; entry.start = now }
  entry.count += 1
  contactHits.set(ip, entry)
  // Prune stale entries to prevent unbounded growth
  if (contactHits.size > 5000) {
    const cutoff = now - windowMs
    for (const [k, v] of contactHits) { if (v.start < cutoff) contactHits.delete(k) }
  }
  if (entry.count > 5) {
    res.status(429).json({ message: 'Too many messages. Please wait a few minutes.' })
    return
  }
  next()
}

export function register(app) {
  app.post('/api/contact', contactRateLimit, async (req, res) => {
    try {
      const { firstName, lastName, email, message, messageType, subscribe, notifyOnAnswer, _honey } = req.body ?? {}

      if (_honey) { res.json({ ok: true }); return }

      if (!firstName || typeof firstName !== 'string' || firstName.trim().length < 1 || firstName.trim().length > 100) {
        res.status(400).json({ message: 'First name is required.' }); return
      }
      if (lastName !== undefined && lastName !== null && (typeof lastName !== 'string' || lastName.trim().length > 100)) {
        res.status(400).json({ message: 'Last name is too long.' }); return
      }
      if (!email || typeof email !== 'string' || !/^[a-zA-Z0-9._%+\-]{1,64}@[a-zA-Z0-9.\-]{1,253}\.[a-zA-Z]{2,}$/.test(email.trim())) {
        res.status(400).json({ message: 'A valid email address is required.' }); return
      }
      if (!message || typeof message !== 'string' || message.trim().length < 5 || message.trim().length > 3000) {
        res.status(400).json({ message: 'Message must be between 5 and 3000 characters.' }); return
      }

      if (!process.env.RESEND_API_KEY) {
        console.error('[contact] RESEND_API_KEY env var not set')
        res.status(503).json({ message: 'The contact form is not yet configured on the server.' }); return
      }

      const trimmedName = [firstName.trim(), typeof lastName === 'string' ? lastName.trim() : ''].filter(Boolean).join(' ')
      const trimmedEmail = email.trim()
      const trimmedMessage = message.trim()
      const normalizedMessageType = normalizeMessageType(messageType)
      const cooldown = noteContactEmailCooldown(trimmedEmail)
      if (!cooldown.ok) {
        const retryAfterSeconds = Math.max(1, Math.ceil(cooldown.retryAfterMs / 1000))
        res.status(429).json({ message: `Please wait ${retryAfterSeconds}s before sending another message from this email.` }); return
      }

      const submittedAt = new Date().toLocaleString('en-US', { dateStyle: 'medium', timeStyle: 'short' })
      const shouldSendWelcome = shouldSendWelcomeEmail({ subscribe })

      const submission = {
        id: randomUUID(),
        submittedAt: new Date().toISOString(),
        name: trimmedName,
        email: trimmedEmail,
        message: trimmedMessage,
        messageType: normalizedMessageType,
        subscribe: shouldSendWelcome,
        archived: false,
        emailStatus: normalizeContactEmailStatus(null, shouldSendWelcome),
      }
      state.contactSubmissions.unshift(submission)
      state.contactSubmissions = state.contactSubmissions.slice(0, MAX_CONTACT_SUBMISSIONS)
      queueContactSubmissionsWrite()
      fireWebhooks('contact.new', { name: trimmedName, email: trimmedEmail, message: trimmedMessage, messageType: normalizedMessageType, submittedAt: submission.submittedAt })

      if (normalizedMessageType === 'question') {
        const question = {
          id: randomUUID(),
          submittedAt: new Date().toISOString(),
          firstName: splitName(trimmedName).firstName,
          email: trimmedEmail,
          question: trimmedMessage,
          answer: '',
          answeredAt: null,
          isApproved: false,
          approvedAt: null,
          notifyOnAnswer: notifyOnAnswer === true,
        }
        state.questions.unshift(question)
        state.questions = state.questions.slice(0, MAX_QUESTIONS)
        if (state.draftQuestions !== null) {
          state.draftQuestions.unshift(question)
          state.draftQuestions = state.draftQuestions.slice(0, MAX_QUESTIONS)
          queueDraftQuestionsWrite()
        }
        queueQuestionsWrite()
      }

      const resend = new Resend(process.env.RESEND_API_KEY)
      const adminInbox = getResendInboxAddress()
      const replyToAddress = getResendReplyToAddress()
      const fromAddress = getResendFromAddress()
      const safeMessageTypeTag = normalizedMessageType.replace(/[^a-z0-9_-]/gi, '-').toLowerCase()
      const adminTemplate = buildContactAdminNotificationTemplate({ normalizedMessageType, trimmedName, trimmedEmail, submittedAt, trimmedMessage })
      let welcomeSent = false

      if (subscribe === true) {
        await syncContactToResend(trimmedName, trimmedEmail)
      }

      if (shouldSendWelcome && !USE_RESEND_AUTOMATION_WELCOME) {
        const greetingName = splitName(trimmedName).firstName?.trim() ?? ''
        let publishedSiteContent = state.cachedSiteContent
        if (!publishedSiteContent) {
          try {
            const published = await loadSiteContentFile(DATA_FILE)
            publishedSiteContent = published?.siteContent ?? null
          } catch { publishedSiteContent = null }
        }

        const emailConfig = publishedSiteContent ?? {}
        const welcomeBaseUrl = typeof emailConfig?.seo?.canonicalUrl === 'string' && emailConfig.seo.canonicalUrl.trim()
          ? emailConfig.seo.canonicalUrl.trim()
          : DEFAULT_SEO.canonicalUrl
        const welcomeSubject = process.env.RESEND_WELCOME_SUBJECT ?? emailConfig.welcomeEmailSubject ?? 'Welcome to Verse by Verse with Nate'
        const welcomeGreetingPrefix = emailConfig.welcomeEmailGreetingPrefix?.trim() || "Glad you're here"
        const welcomeTemplate = buildContactWelcomeEmailTemplate({
          greetingName,
          welcomeGreetingPrefix,
          welcomeIntro: emailConfig.welcomeEmailIntro?.trim() || 'Thanks for subscribing to Verse by Verse with Nate - a Bible teaching podcast where we slow down, dig into the text, and pull out the nuggets God has for us word by word.',
          welcomeCurrentSeries: emailConfig.welcomeEmailCurrentSeries?.trim() || "Right now we're working through the book of Titus - a short letter packed with practical wisdom about grace, godliness, and what the Christian life looks like when it's rooted in sound doctrine.",
          welcomeStartHereTitle: emailConfig.welcomeEmailStartHereTitle?.trim() || 'Episode 1 - Introduction to Titus',
          welcomeStartHereSummary: emailConfig.welcomeEmailStartHereSummary?.trim() || 'Who wrote it, who received it, and why it still matters.',
          welcomeExpect1: emailConfig.welcomeEmailWhatToExpect1?.trim() || 'Verse-by-verse teaching - we go slow and let the text speak for itself.',
          welcomeExpect2: emailConfig.welcomeEmailWhatToExpect2?.trim() || 'Greek word studies - the kind that open up meaning without being a lecture.',
          welcomeExpect3: emailConfig.welcomeEmailWhatToExpect3?.trim() || 'New episodes + study notes delivered right to your inbox.',
          welcomeScripture: emailConfig.welcomeEmailScripture?.trim() || 'For the grace of God has appeared, bringing salvation to all people.',
          welcomeScriptureRef: emailConfig.welcomeEmailScriptureRef?.trim() || 'Titus 2:11 - BSB',
          welcomeSignoff: emailConfig.welcomeEmailSignoff?.trim() || 'Grace and peace,\nNate',
          welcomeSpotifyUrl: buildAbsoluteUrl(welcomeBaseUrl, process.env.RESEND_WELCOME_SPOTIFY_URL ?? emailConfig.welcomeEmailSpotifyUrl ?? '/spotify'),
          welcomeAppleUrl: buildAbsoluteUrl(welcomeBaseUrl, process.env.RESEND_WELCOME_APPLE_URL ?? emailConfig.welcomeEmailAppleUrl ?? '/apple'),
          welcomeAmazonUrl: buildAbsoluteUrl(welcomeBaseUrl, process.env.RESEND_WELCOME_AMAZON_URL ?? emailConfig.welcomeEmailAmazonUrl ?? '/amazon'),
          welcomeWebsiteUrl: buildAbsoluteUrl(welcomeBaseUrl, process.env.RESEND_WELCOME_WEBSITE_URL ?? emailConfig.welcomeEmailWebsiteUrl ?? '/'),
          welcomeEpisodeUrl: buildAbsoluteUrl(welcomeBaseUrl, process.env.RESEND_WELCOME_EPISODE_URL ?? emailConfig.welcomeEmailStartHereUrl ?? '/start-here'),
          welcomeImageUrl: buildAbsoluteUrl(welcomeBaseUrl, process.env.RESEND_WELCOME_IMAGE_URL ?? emailConfig.welcomeEmailImageUrl ?? '/images/podcast-art.jpeg'),
          welcomeSpotifyBtnLabel: emailConfig.welcomeEmailSpotifyBtnLabel?.trim() || 'Listen on Spotify',
          welcomeAppleBtnLabel: emailConfig.welcomeEmailAppleBtnLabel?.trim() || 'Apple Podcasts',
          welcomeStartHereLinkLabel: emailConfig.welcomeEmailStartHereLinkLabel?.trim() || 'Open Start Here page',
        })

        try {
          const welcomeSendResult = await sendResendEmailWithRetry({
            resend,
            context: 'contact-welcome',
            payload: {
              from: fromAddress,
              to: [trimmedEmail],
              replyTo: replyToAddress,
              subject: welcomeSubject,
              tags: [
                { name: 'flow', value: 'contact-welcome' },
                { name: 'message_type', value: safeMessageTypeTag },
                { name: 'submission_id', value: submission.id },
              ],
              headers: {
                'List-Unsubscribe': `<mailto:${replyToAddress}?subject=Unsubscribe>`,
                'X-Contact-Submission-Id': submission.id,
              },
              text: welcomeTemplate.text,
              html: welcomeTemplate.html,
            },
          })
          registerResendMessageForSubmission(submission.id, 'welcome', welcomeSendResult)
          upsertContactEmailStatus(submission.id, 'welcome', { status: 'sent', lastEventType: 'email.sent', error: null })
          welcomeSent = true
        } catch (welcomeErr) {
          upsertContactEmailStatus(submission.id, 'welcome', {
            status: 'failed',
            lastEventType: 'email.failed',
            error: String(welcomeErr?.message ?? welcomeErr ?? 'unknown error').slice(0, 600),
          })
          console.error('[contact] welcome email failed:', welcomeErr)
          // Submission is already saved — don't 500 the user; fall through to admin notification.
        }
      } else if (shouldSendWelcome && USE_RESEND_AUTOMATION_WELCOME) {
        upsertContactEmailStatus(submission.id, 'welcome', { status: 'automation-enabled', lastEventType: 'email.automation.enabled', error: null })
      }

      try {
        const adminSendResult = await sendResendEmailWithRetry({
          resend,
          context: 'contact-admin-notification',
          payload: {
            from: fromAddress,
            to: [adminInbox],
            replyTo: trimmedEmail,
            subject: adminTemplate.subject,
            tags: [
              { name: 'flow', value: 'contact-admin' },
              { name: 'message_type', value: safeMessageTypeTag },
              { name: 'submission_id', value: submission.id },
            ],
            headers: { 'X-Contact-Submission-Id': submission.id },
            text: adminTemplate.text,
            html: adminTemplate.html,
          },
        })
        registerResendMessageForSubmission(submission.id, 'adminNotification', adminSendResult)
        upsertContactEmailStatus(submission.id, 'adminNotification', { status: 'sent', lastEventType: 'email.sent', error: null })
      } catch (adminSendErr) {
        upsertContactEmailStatus(submission.id, 'adminNotification', {
          status: 'failed',
          lastEventType: 'email.failed',
          error: String(adminSendErr?.message ?? adminSendErr ?? 'unknown error').slice(0, 600),
        })
        console.error('[contact] admin notification email failed:', adminSendErr)
        // Submission is already saved — don't 500 the user.
      }

      res.json({ ok: true, welcomeSent, welcomeHandledByAutomation: shouldSendWelcome && USE_RESEND_AUTOMATION_WELCOME })
    } catch (err) {
      console.error('[contact] send error:', err)
      res.status(500).json({ message: 'Failed to send your message. Please try again or email us directly.' })
    }
  })

  app.post('/api/resend/webhook', (req, res) => {
    const expectedToken = typeof process.env.RESEND_WEBHOOK_TOKEN === 'string' ? process.env.RESEND_WEBHOOK_TOKEN.trim() : ''
    if (!expectedToken) {
      res.status(503).json({ message: 'Webhook token is not configured.' }); return
    }

    const providedToken = (req.get('x-webhook-token') || '').trim()
      || (req.get('x-resend-webhook-token') || '').trim()
      || String(req.query?.token || '').trim()
      || (req.get('authorization') || '').replace(/^Bearer\s+/i, '').trim()

    if (!providedToken || providedToken !== expectedToken) {
      res.status(401).json({ message: 'Unauthorized webhook.' }); return
    }

    const body = req.body && typeof req.body === 'object' ? req.body : {}
    const eventType = typeof body.type === 'string' ? body.type.trim() : ''
    const data = body.data && typeof body.data === 'object' ? body.data : {}
    const tags = Array.isArray(data.tags) ? data.tags : []

    const resendMessageId = (
      typeof data.email_id === 'string' && data.email_id.trim()
        ? data.email_id.trim()
        : (typeof data.emailId === 'string' && data.emailId.trim()
          ? data.emailId.trim()
          : (typeof data.id === 'string' && data.id.trim() ? data.id.trim() : ''))
    )

    const indexed = resendMessageId ? state.resendEmailSubmissionIndex.get(resendMessageId) : null
    const taggedSubmissionId = extractTagValue(tags, 'submission_id')
    const submissionId = indexed?.submissionId || taggedSubmissionId

    const flow = extractTagValue(tags, 'flow')
    const stream = indexed?.stream
      || (flow === 'contact-welcome' ? 'welcome' : '')
      || (flow === 'contact-admin' ? 'adminNotification' : '')
      || (flow === 'admin-reply' ? 'adminReply' : '')

    if (!submissionId || !stream) {
      res.json({ ok: true, ignored: true }); return
    }

    upsertContactEmailStatus(submissionId, stream, {
      status: mapResendEventToStatus(eventType),
      lastEventType: eventType || 'webhook.event',
      resendEmailId: resendMessageId || null,
      error: typeof data?.message === 'string' ? data.message.slice(0, 600) : null,
    })

    res.json({ ok: true })
  })


  app.get('/api/admin-contact-submissions', requireAdminAuth, (_req, res) => {
    res.json({ submissions: state.contactSubmissions })
  })

  app.patch('/api/admin-contact-submissions/:id', requireAdminAuth, (req, res) => {
    const { id } = req.params
    const { archived, read } = req.body ?? {}
    if (typeof archived !== 'boolean' && typeof read !== 'boolean') {
      res.status(400).json({ message: 'archived or read must be a boolean.' }); return
    }
    const idx = state.contactSubmissions.findIndex(s => s.id === id)
    if (idx === -1) {
      res.status(404).json({ message: 'Submission not found.' }); return
    }
    const patch = {}
    if (typeof archived === 'boolean') patch.archived = archived
    if (typeof read === 'boolean') patch.read = read
    state.contactSubmissions[idx] = { ...state.contactSubmissions[idx], ...patch }
    queueContactSubmissionsWrite()
    res.json({ ok: true, submission: state.contactSubmissions[idx] })
  })

  app.post('/api/admin-contact-submissions/bulk', requireAdminAuth, (req, res) => {
    const { ids, action } = req.body ?? {}
    const actions = ['archive', 'unarchive', 'read', 'unread', 'delete']
    if (!Array.isArray(ids) || ids.length === 0 || ids.length > 500 || !ids.every(id => typeof id === 'string') || !actions.includes(action)) {
      res.status(400).json({ message: 'Provide ids (1-500) and a valid action.' }); return
    }
    const idSet = new Set(ids)
    let count = 0
    if (action === 'delete') {
      const before = state.contactSubmissions.length
      state.contactSubmissions = state.contactSubmissions.filter(s => !idSet.has(s.id))
      count = before - state.contactSubmissions.length
    } else {
      state.contactSubmissions = state.contactSubmissions.map(s => {
        if (!idSet.has(s.id)) return s
        count += 1
        if (action === 'archive') return { ...s, archived: true }
        if (action === 'unarchive') return { ...s, archived: false }
        return { ...s, read: action === 'read' }
      })
    }
    queueContactSubmissionsWrite()
    res.json({ ok: true, count })
  })

  app.get('/api/admin-subscribers', requireAdminAuth, (_req, res) => {
    const seen = new Set()
    const subscribers = state.contactSubmissions
      .filter(entry => entry.subscribe === true && entry.email && !seen.has(entry.email) && seen.add(entry.email))
      .map(entry => ({
        name: entry.name,
        email: entry.email,
        subscribedAt: entry.submittedAt,
        source: entry.source === 'resend-import' ? 'resend-import' : entry.message?.startsWith('Requested') ? 'download' : 'contact-form',
      }))
      .sort((a, b) => new Date(b.subscribedAt).getTime() - new Date(a.subscribedAt).getTime())
    res.json({ subscribers, total: subscribers.length })
  })

  app.post('/api/admin-subscribers/export', requireAdminAuth, (_req, res) => {
    const seen = new Set()
    const rows = [['Name', 'Email', 'Subscribed At', 'Source']]
    state.contactSubmissions
      .filter(entry => entry.subscribe === true && entry.email && !seen.has(entry.email) && seen.add(entry.email))
      .sort((a, b) => new Date(b.submittedAt).getTime() - new Date(a.submittedAt).getTime())
      .forEach(entry => {
        const source = entry.message?.startsWith('Requested') ? 'download' : 'contact-form'
        rows.push([entry.name, entry.email, entry.submittedAt, source])
      })
    const csv = rows.map(row => row.map(cell => `"${String(cell ?? '').replace(/"/g, '""')}"`).join(',')).join('\n')
    res.setHeader('Content-Type', 'text/csv')
    res.setHeader('Content-Disposition', `attachment; filename="subscribers-${new Date().toISOString().slice(0, 10)}.csv"`)
    res.send(csv)
  })

  // ── Subscribers ⇄ Resend comparison ─────────────────────────────────────────
  const sleep = ms => new Promise(resolve => setTimeout(resolve, ms))

  function getAppSubscribers() {
    const byEmail = new Map()
    for (const entry of state.contactSubmissions) {
      if (entry.subscribe !== true || !entry.email) continue
      const email = String(entry.email).trim().toLowerCase()
      if (!byEmail.has(email)) byEmail.set(email, { name: entry.name ?? '', email })
    }
    return byEmail
  }

  async function listAllResendContacts(resend, segmentId) {
    const out = []
    let after
    for (let page = 0; page < 50; page += 1) {
      const { data, error } = await resendRetry(() => resend.contacts.list({ limit: 100, ...(segmentId ? { segmentId } : {}), ...(after ? { after } : {}) }))
      if (error) throw new Error(error.message || 'Resend contacts.list failed')
      const rows = data?.data ?? []
      out.push(...rows)
      if (!data?.has_more || rows.length === 0) break
      after = rows[rows.length - 1].id
      await sleep(550) // Resend allows ~2 requests/second
    }
    return out
  }

  async function buildResendComparison() {
    const resend = new Resend(process.env.RESEND_CONTACTS_API_KEY ?? process.env.RESEND_API_KEY)
    const segmentId = process.env.RESEND_SEGMENT_ID || null
    const appSubs = getAppSubscribers()
    const resendContacts = await listAllResendContacts(resend)
    let segmentEmails = null
    if (segmentId) {
      await sleep(550)
      segmentEmails = new Set((await listAllResendContacts(resend, segmentId)).map(c => String(c.email).toLowerCase()))
    }

    const resendByEmail = new Map(resendContacts.map(c => [String(c.email).toLowerCase(), c]))
    const nameOf = c => [c.first_name, c.last_name].filter(Boolean).join(' ')

    const onlyInApp = []
    const unsubscribedInResend = []
    const notInSegment = []
    let matched = 0
    for (const sub of appSubs.values()) {
      const contact = resendByEmail.get(sub.email)
      if (!contact) { onlyInApp.push(sub); continue }
      if (contact.unsubscribed) { unsubscribedInResend.push(sub); continue }
      if (segmentEmails && !segmentEmails.has(sub.email)) { notInSegment.push(sub); continue }
      matched += 1
    }
    const onlyInResend = resendContacts
      .filter(c => !appSubs.has(String(c.email).toLowerCase()) && !c.unsubscribed)
      .map(c => ({ name: nameOf(c), email: String(c.email).toLowerCase() }))

    return {
      appCount: appSubs.size,
      resendCount: resendContacts.length,
      resendUnsubscribedCount: resendContacts.filter(c => c.unsubscribed).length,
      segmentConfigured: Boolean(segmentId),
      segmentCount: segmentEmails ? segmentEmails.size : null,
      matched,
      onlyInApp,
      onlyInResend,
      unsubscribedInResend,
      notInSegment,
    }
  }

  app.get('/api/admin-subscribers/resend-compare', requireAdminAuth, async (_req, res) => {
    if (!process.env.RESEND_API_KEY) {
      res.status(500).json({ message: 'RESEND_API_KEY is not configured.' }); return
    }
    try {
      res.json(await buildResendComparison())
    } catch (err) {
      console.error('[subscribers] resend compare failed:', err)
      res.status(502).json({ message: 'Could not read contacts from Resend. Try again in a moment.' })
    }
  })

  app.post('/api/admin-subscribers/resend-sync', requireAdminAuth, async (req, res) => {
    const { action } = req.body ?? {}
    if (!['add-to-resend', 'add-to-segment', 'apply-unsubscribes'].includes(action)) {
      res.status(400).json({ message: 'Unknown action.' }); return
    }
    if (!process.env.RESEND_API_KEY) {
      res.status(500).json({ message: 'RESEND_API_KEY is not configured.' }); return
    }
    try {
      const diff = await buildResendComparison()

      if (action === 'apply-unsubscribes') {
        const emails = new Set(diff.unsubscribedInResend.map(s => s.email))
        let changed = 0
        state.contactSubmissions = state.contactSubmissions.map(entry => {
          if (entry.subscribe === true && emails.has(String(entry.email ?? '').trim().toLowerCase())) {
            changed += 1
            return { ...entry, subscribe: false }
          }
          return entry
        })
        if (changed > 0) queueContactSubmissionsWrite()
        res.json({ ok: true, done: emails.size, failed: 0 }); return
      }

      const resend = new Resend(process.env.RESEND_CONTACTS_API_KEY ?? process.env.RESEND_API_KEY)
      const segmentId = process.env.RESEND_SEGMENT_ID || null
      const targets = (action === 'add-to-resend' ? diff.onlyInApp : diff.notInSegment).slice(0, 100)
      if (action === 'add-to-segment' && !segmentId) {
        res.status(400).json({ message: 'RESEND_SEGMENT_ID is not configured.' }); return
      }

      let done = 0
      let failed = 0
      for (const target of targets) {
        try {
          if (action === 'add-to-resend') {
            const { firstName, lastName } = splitName(target.name)
            const { error } = await resendRetry(() => resend.contacts.create({
              email: target.email, firstName, lastName, unsubscribed: false,
              ...(segmentId ? { segments: [{ id: segmentId }] } : {}),
            }))
            if (error) throw new Error(error.message)
          } else {
            const { error } = await resendRetry(() => resend.contacts.segments.add({ email: target.email, segmentId }))
            if (error) throw new Error(error.message)
          }
          done += 1
        } catch (err) {
          failed += 1
          console.error(`[subscribers] resend sync failed for ${target.email}:`, err?.message ?? err)
        }
        await sleep(550)
      }
      const total = action === 'add-to-resend' ? diff.onlyInApp.length : diff.notInSegment.length
      res.json({ ok: true, done, failed, remaining: Math.max(total - targets.length, 0) })
    } catch (err) {
      console.error('[subscribers] resend sync failed:', err)
      res.status(502).json({ message: 'Resend sync failed. Try again in a moment.' })
    }
  })

  app.get('/api/admin-broadcast/templates', requireAdminAuth, async (_req, res) => {
    if (!process.env.RESEND_API_KEY) {
      res.status(500).json({ message: 'RESEND_API_KEY is not configured.' }); return
    }
    try {
      const resend = new Resend(process.env.RESEND_API_KEY)
      const templates = []
      let after
      for (let page = 0; page < 5; page += 1) {
        const { data, error } = await resendRetry(() => resend.templates.list({ limit: 100, ...(after ? { after } : {}) }))
        if (error) throw new Error(error.message)
        templates.push(...(data?.data ?? []))
        if (!data?.has_more || !data.data?.length) break
        after = data.data[data.data.length - 1].id
      }
      res.json({
        templates: templates
          .map(t => ({ id: t.id, name: t.name, status: t.status, updatedAt: t.updated_at, publishedAt: t.published_at }))
          .sort((a, b) => String(b.updatedAt ?? '').localeCompare(String(a.updatedAt ?? ''))),
      })
    } catch (err) {
      console.error('[admin-broadcast] template list failed:', err)
      res.status(502).json({ message: 'Could not load templates from Resend.' })
    }
  })

  app.get('/api/admin-broadcast/templates/:id', requireAdminAuth, async (req, res) => {
    if (!process.env.RESEND_API_KEY) {
      res.status(500).json({ message: 'RESEND_API_KEY is not configured.' }); return
    }
    try {
      const resend = new Resend(process.env.RESEND_API_KEY)
      const { data, error } = await resendRetry(() => resend.templates.get(req.params.id))
      if (error || !data) {
        res.status(404).json({ message: error?.message || 'Template not found.' }); return
      }
      // Resend variables look like {{{KEY}}}; fill in their saved fallback values, but keep name for per-subscriber personalization.
      let html = data.html ?? ''
      for (const v of data.variables ?? []) {
        if (/^(first_?name|name)$/i.test(v.key)) continue
        if (v.fallback_value === null || v.fallback_value === undefined) continue
        html = html.replace(new RegExp(`\\{\\{\\{\\s*${v.key.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')}\\s*\\}\\}\\}`, 'g'), escapeHtml(String(v.fallback_value)))
      }
      res.json({
        id: data.id,
        name: data.name,
        subject: data.subject ?? '',
        html,
        hasUnsubscribeLink: /\{\{\{\s*RESEND_UNSUBSCRIBE_URL\s*\}\}\}/i.test(html),
        unresolved: [...new Set([...html.matchAll(/\{\{\{\s*([A-Za-z0-9_]+)\s*\}\}\}/g)].map(m => m[1]))]
          .filter(k => !/^(RESEND_UNSUBSCRIBE_URL|first_?name|name)$/i.test(k)),
      })
    } catch (err) {
      console.error('[admin-broadcast] template get failed:', err)
      res.status(502).json({ message: 'Could not load that template from Resend.' })
    }
  })

  // Import chosen Resend-only contacts into the app's subscriber list (explicit, per-person opt-in by the admin).
  app.post('/api/admin-subscribers/import-from-resend', requireAdminAuth, async (req, res) => {
    const { emails } = req.body ?? {}
    if (!Array.isArray(emails) || emails.length === 0 || emails.length > 200 || !emails.every(e => typeof e === 'string')) {
      res.status(400).json({ message: 'Choose between 1 and 200 contacts to import.' }); return
    }
    if (!process.env.RESEND_API_KEY) {
      res.status(500).json({ message: 'RESEND_API_KEY is not configured.' }); return
    }
    try {
      const diff = await buildResendComparison()
      const allowed = new Map(diff.onlyInResend.map(c => [c.email, c]))
      const now = new Date().toISOString()
      const created = []
      for (const raw of emails) {
        const email = raw.trim().toLowerCase()
        const contact = allowed.get(email)
        if (!contact) continue // not active in Resend, or already a subscriber here
        created.push({
          id: randomUUID(),
          submittedAt: now,
          name: contact.name || email,
          email,
          message: 'Imported from Resend audience',
          messageType: 'general',
          subscribe: true,
          archived: true,
          read: true,
          source: 'resend-import',
        })
      }
      if (created.length > 0) {
        state.contactSubmissions = [...created, ...state.contactSubmissions]
        queueContactSubmissionsWrite()
      }
      res.json({ ok: true, imported: created.length, skipped: emails.length - created.length })
    } catch (err) {
      console.error('[subscribers] import from resend failed:', err)
      res.status(502).json({ message: 'Import failed. Try again in a moment.' })
    }
  })

  // ── Broadcast Email: sent as a real Resend Broadcast to the Resend segment ──────
  const UNSUB_FOOTER = '<p style="margin:32px 0 0;font-size:12px;color:#888;text-align:center;"><a href="{{{RESEND_UNSUBSCRIBE_URL}}}" style="color:#888;">Unsubscribe</a></p>'

  // App-side {{name}} becomes Resend's per-contact variable; guarantee an unsubscribe link exists.
  function toResendBroadcastHtml(html) {
    let out = html.replace(/\{\{\{?\s*(?:first_?name|name)\s*\}?\}\}/gi, '{{{FIRST_NAME|Friend}}}')
    if (!/RESEND_UNSUBSCRIBE_URL/i.test(out)) {
      out = /<\/body>/i.test(out) ? out.replace(/<\/body>/i, `${UNSUB_FOOTER}</body>`) : `${out}\n${UNSUB_FOOTER}`
    }
    return out
  }

  app.get('/api/admin-broadcast/audience', requireAdminAuth, async (_req, res) => {
    const segmentId = process.env.RESEND_SEGMENT_ID
    if (!process.env.RESEND_API_KEY || !segmentId) {
      res.json({ segmentConfigured: false, count: null }); return
    }
    try {
      const resend = new Resend(process.env.RESEND_CONTACTS_API_KEY ?? process.env.RESEND_API_KEY)
      const contacts = await listAllResendContacts(resend, segmentId)
      res.json({ segmentConfigured: true, count: contacts.filter(c => !c.unsubscribed).length })
    } catch (err) {
      console.error('[admin-broadcast] audience count failed:', err)
      res.status(502).json({ message: 'Could not read the Resend segment.' })
    }
  })

  app.post('/api/admin-broadcast/test', requireAdminAuth, async (req, res) => {
    const { subject, html, to } = req.body ?? {}
    if (typeof subject !== 'string' || !subject.trim() || typeof html !== 'string' || !html.trim()) {
      res.status(400).json({ message: 'Subject and body are required.' }); return
    }
    if (typeof to !== 'string' || !/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(to.trim())) {
      res.status(400).json({ message: 'Enter a valid test email address.' }); return
    }
    if (!process.env.RESEND_API_KEY) {
      res.status(500).json({ message: 'RESEND_API_KEY is not configured.' }); return
    }
    try {
      const preview = toResendBroadcastHtml(html)
        .replace(/\{\{\{\s*FIRST_NAME\s*\|\s*([^}]*?)\s*\}\}\}/gi, (_m, fallback) => escapeHtml(fallback || 'Friend'))
        .replace(/\{\{\{\s*RESEND_UNSUBSCRIBE_URL\s*\}\}\}/gi, '#')
      const resend = new Resend(process.env.RESEND_API_KEY)
      const { error } = await resend.emails.send({
        from: getResendFromAddress(),
        to: to.trim(),
        replyTo: getResendReplyToAddress(),
        subject: `[TEST] ${subject.trim()}`,
        html: preview,
      })
      if (error) throw new Error(error.message)
      res.json({ ok: true })
    } catch (err) {
      console.error('[admin-broadcast] test send failed:', err)
      res.status(502).json({ message: 'Test email failed to send.' })
    }
  })

  app.post('/api/admin-broadcast', requireAdminAuth, async (req, res) => {
    const { subject, html, previewText, tagNewEpisode, scheduledAt } = req.body ?? {}
    if (!subject || typeof subject !== 'string' || !subject.trim()) {
      res.status(400).json({ message: 'Subject is required.' }); return
    }
    if (!html || typeof html !== 'string' || !html.trim()) {
      res.status(400).json({ message: 'Email body is required.' }); return
    }
    if (!process.env.RESEND_API_KEY) {
      res.status(500).json({ message: 'RESEND_API_KEY is not configured.' }); return
    }
    const segmentId = process.env.RESEND_SEGMENT_ID
    if (!segmentId) {
      res.status(500).json({ message: 'RESEND_SEGMENT_ID is not configured, so there is no segment to send to.' }); return
    }
    let scheduled
    if (typeof scheduledAt === 'string' && scheduledAt.trim()) {
      const when = Date.parse(scheduledAt)
      if (!Number.isFinite(when) || when < Date.now() + 60 * 1000) {
        res.status(400).json({ message: 'Schedule time must be at least a minute in the future.' }); return
      }
      scheduled = new Date(when).toISOString()
    }

    try {
      const resend = new Resend(process.env.RESEND_API_KEY)

      let topicId
      if (tagNewEpisode === true) {
        const { data: topics, error: topicsError } = await resendRetry(() => resend.topics.list())
        if (topicsError) throw new Error(topicsError.message)
        topicId = (topics?.data ?? []).find(t => String(t.name || '').trim().toLowerCase() === 'new episode')?.id
        if (!topicId) {
          res.status(400).json({ message: 'No "New Episode" topic exists in Resend.' }); return
        }
      }

      const { data, error } = await resendRetry(() => resend.broadcasts.create({
        name: subject.trim().slice(0, 120),
        segmentId,
        from: getResendFromAddress(),
        replyTo: getResendReplyToAddress(),
        subject: subject.trim(),
        html: toResendBroadcastHtml(html),
        ...(typeof previewText === 'string' && previewText.trim() ? { previewText: previewText.trim().slice(0, 200) } : {}),
        ...(topicId ? { topicId } : {}),
        send: true,
        ...(scheduled ? { scheduledAt: scheduled } : {}),
      }))
      if (error || !data?.id) throw new Error(error?.message || 'Resend did not return a broadcast id.')

      console.log(`[admin-broadcast] ${scheduled ? 'scheduled' : 'sent'} Resend broadcast ${data.id}: ${subject.trim()}`)
      res.json({ ok: true, broadcastId: data.id, scheduledAt: scheduled ?? null })
    } catch (err) {
      console.error('[admin-broadcast] send failed:', err)
      res.status(502).json({ message: `Resend rejected the broadcast: ${err instanceof Error ? err.message : 'unknown error'}` })
    }
  })
}