Add study user re-engagement reminder emails; v1.1.19

Sends 7/14/30-day inactivity emails to study users who haven't logged in,
with one-click HMAC-signed unsubscribe and automatic re-arm on next login.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/data.js

@@ -1307,6 +1307,7 @@ export function sanitizeStudyUsers(value) {
       createdAt: typeof item?.createdAt === 'string' ? item.createdAt : null,
       updatedAt: typeof item?.updatedAt === 'string' ? item.updatedAt : null,
       lastLoginAt: typeof item?.lastLoginAt === 'string' ? item.lastLoginAt : null,
+      reengagementSentAt: typeof item?.reengagementSentAt === 'object' && item.reengagementSentAt !== null && !Array.isArray(item.reengagementSentAt) ? item.reengagementSentAt : {},
       pendingEmailChange,
       twoFaMethod: item?.twoFaMethod === 'app' || item?.twoFaMethod === 'email' ? item.twoFaMethod : null,
       totpSecret: typeof item?.totpSecret === 'string' && item.totpSecret ? item.totpSecret : null,

server/email.js

@@ -584,3 +584,61 @@ export async function sendStudyReminderEmail(email, displayName, studyTitle, sec
     console.error('[study-reminder] send exception:', err)
   }
 }
+
+const REENGAGEMENT_COPY = {
+  '7d': {
+    subject: 'Your study is waiting for you',
+    eyebrow: 'Come Back',
+    headline: 'Pick up where you left off',
+    body: "It's been a week — your progress is saved and your next lesson is ready whenever you are.",
+    cta: 'Continue Studying',
+  },
+  '14d': {
+    subject: "Don't lose your momentum",
+    eyebrow: 'Still With You',
+    headline: 'Your spot is still saved',
+    body: 'Two weeks have passed, but every note and completed lesson is still right there. A little each day adds up.',
+    cta: 'Return to Your Study',
+  },
+  '30d': {
+    subject: 'Your progress is still here',
+    eyebrow: 'We Saved Your Spot',
+    headline: "It's been a month — come back anytime",
+    body: 'Your study progress is still intact and waiting. There\'s no deadline — come back whenever you\'re ready.',
+    cta: 'Open Your Study',
+  },
+}
+
+export async function sendStudyReengagementEmail(email, displayName, studyTitle, studyUrl, tier, unsubUrl) {
+  if (!process.env.RESEND_API_KEY) return
+  const copy = REENGAGEMENT_COPY[tier]
+  if (!copy) return
+  try {
+    const resend = new Resend(process.env.RESEND_API_KEY)
+    const namePart = typeof displayName === 'string' && displayName.trim() ? displayName.trim() : 'friend'
+    const subject = `${copy.subject}${studyTitle ? ` — ${studyTitle}` : ''}`
+    const bodyHtml = (
+      `<p style="margin:0 0 16px;">Hi <strong style="color:#f0ead8;">${escapeHtml(namePart)}</strong>,</p>` +
+      `<p style="margin:0 0 16px;">${escapeHtml(copy.body)}${studyTitle ? ` Your current study: <strong style="color:#f0ead8;">${escapeHtml(studyTitle)}</strong>.` : ''}</p>`
+    )
+    const unsubLine = unsubUrl ? `<p style="margin:16px 0 0;font-size:11px;color:#7a7060;">Not interested? <a href="${escapeHtml(unsubUrl)}" style="color:#7a7060;">Unsubscribe from these reminders.</a></p>` : ''
+    const footerHtml = `<p style="margin:0;font-family:Georgia,serif;font-size:12px;font-weight:300;color:#7a7060;line-height:1.6;">Grace and peace,<br/>Verse by Verse with Nate</p>${unsubLine}`
+    const { error } = await resend.emails.send({
+      from: process.env.RESEND_FROM ?? DEFAULT_RESEND_FROM,
+      to: [email],
+      subject,
+      text: `Hi ${namePart},\n\n${copy.body}${studyTitle ? ` Your current study: ${studyTitle}.` : ''}\n\n${studyUrl}\n\nGrace and peace,\nVerse by Verse with Nate${unsubUrl ? `\n\nUnsubscribe: ${unsubUrl}` : ''}`,
+      html: buildBrandedEmailHtml({
+        title: copy.headline,
+        eyebrow: copy.eyebrow,
+        bodyHtml,
+        ctaLabel: copy.cta,
+        ctaUrl: studyUrl,
+        footerHtml,
+      }),
+    })
+    if (error) console.error('[study-reengagement] send error:', error)
+  } catch (err) {
+    console.error('[study-reengagement] send exception:', err)
+  }
+}

server/routes/study-auth.js

@@ -1,4 +1,4 @@
-import { createHash, randomUUID, timingSafeEqual } from 'node:crypto'
+import { createHash, createHmac, randomUUID, timingSafeEqual } from 'node:crypto'
 import rateLimit from 'express-rate-limit'
 import qrcode from 'qrcode'
 import {
@@ -174,6 +174,7 @@ export function register(app) {
 
     user.lastLoginAt = new Date().toISOString()
     user.updatedAt = user.lastLoginAt
+    user.reengagementSentAt = {}
     queueStudyUsersWrite()
 
     const sessionToken = createStudySession(user.id)
@@ -209,6 +210,7 @@ export function register(app) {
     function completeLogin(extra = {}) {
       user.lastLoginAt = new Date().toISOString()
       user.updatedAt = user.lastLoginAt
+      user.reengagementSentAt = {}
       queueStudyUsersWrite()
       const sessionToken = createStudySession(user.id)
       setStudySessionCookie(res, sessionToken)
@@ -359,4 +361,32 @@ export function register(app) {
     clearStudySessionCookie(res)
     res.json({ ok: true })
   })
+
+  // One-click unsubscribe from re-engagement emails (no login required)
+  app.get('/api/study-auth/unsubscribe-reminders', (req, res) => {
+    const { uid, token } = req.query ?? {}
+    if (typeof uid !== 'string' || typeof token !== 'string') {
+      res.status(400).send('Invalid unsubscribe link.')
+      return
+    }
+    const secret = process.env.RESEND_WEBHOOK_TOKEN ?? 'siteforge'
+    const expected = createHmac('sha256', secret).update(uid).digest('hex')
+    const expectedBuf = Buffer.from(expected, 'hex')
+    const actualBuf = Buffer.from(token.length === expected.length ? token : '', 'hex')
+    let valid = false
+    try { valid = timingSafeEqual(expectedBuf, actualBuf) } catch { valid = false }
+    if (!valid) {
+      res.status(400).send('Invalid or expired unsubscribe link.')
+      return
+    }
+    const user = state.studyUsers.find(u => u.id === uid)
+    if (!user) {
+      res.status(404).send('Account not found.')
+      return
+    }
+    user.studyRemindersEnabled = false
+    user.updatedAt = new Date().toISOString()
+    queueStudyUsersWrite()
+    res.send('<!doctype html><html><head><meta charset="utf-8"><title>Unsubscribed</title><style>body{font-family:system-ui,sans-serif;max-width:480px;margin:80px auto;padding:24px;text-align:center;color:#333}h1{font-size:1.4rem;margin-bottom:12px}p{color:#666;line-height:1.6}</style></head><body><h1>You\'ve been unsubscribed</h1><p>You will no longer receive re-engagement reminder emails. You can re-enable them anytime from your account settings.</p></body></html>')
+  })
 }

server/study-helpers.js

@@ -1,4 +1,4 @@
-import { createHash, randomUUID } from 'node:crypto'
+import { createHash, createHmac, randomUUID } from 'node:crypto'
 import path from 'node:path'
 import { parseCookies, cookieSecureFlag } from './helpers.js'
 import {
@@ -666,3 +666,67 @@ export async function scheduleStudyReminders(sendStudyReminderEmail) {
   state.studyReminders.updatedAt = new Date().toISOString()
   queueStudyRemindersWrite()
 }
+
+// ── Study re-engagement scheduler ─────────────────────────────────────────
+
+const REENGAGEMENT_TIERS = [
+  { key: '7d', days: 7 },
+  { key: '14d', days: 14 },
+  { key: '30d', days: 30 },
+]
+
+function makeUnsubUrl(userId) {
+  const secret = process.env.RESEND_WEBHOOK_TOKEN ?? 'siteforge'
+  const token = createHmac('sha256', secret).update(userId).digest('hex')
+  const canonical = state.cachedSiteContent?.seo?.canonicalUrl || 'https://versebyversewithnate.us/'
+  const base = canonical.endsWith('/') ? canonical.slice(0, -1) : canonical
+  return `${base}/api/study-auth/unsubscribe-reminders?uid=${encodeURIComponent(userId)}&token=${token}`
+}
+
+export async function scheduleReengagementEmails(sendStudyReengagementEmail) {
+  if (!state.cachedSiteContent) return
+  const now = new Date()
+  const nowMs = now.getTime()
+
+  for (const user of state.studyUsers) {
+    if (user.studyRemindersEnabled !== true) continue
+    if (!user.lastLoginAt) continue
+    const lastLogin = new Date(user.lastLoginAt)
+    if (isNaN(lastLogin.getTime())) continue
+    const daysSinceLogin = (nowMs - lastLogin.getTime()) / (1000 * 60 * 60 * 24)
+
+    const sent = typeof user.reengagementSentAt === 'object' && user.reengagementSentAt !== null ? user.reengagementSentAt : {}
+
+    const enrolledStudySlugs = Array.isArray(user.enrolledStudySlugs) ? user.enrolledStudySlugs : []
+    const studies = Array.isArray(state.cachedSiteContent.studies) ? state.cachedSiteContent.studies : []
+    const enrolledStudies = enrolledStudySlugs
+      .map(slug => studies.find(s => normalizeStudySlug(s?.slug) === slug))
+      .filter(Boolean)
+
+    if (enrolledStudies.length === 0) continue
+
+    const firstStudy = enrolledStudies[0]
+    const studyTitle = enrolledStudies.length === 1 ? firstStudy.title : null
+    const canonical = state.cachedSiteContent?.seo?.canonicalUrl || 'https://versebyversewithnate.us/'
+    const base = canonical.endsWith('/') ? canonical.slice(0, -1) : canonical
+    const studyUrl = enrolledStudies.length === 1
+      ? `${base}/study/${firstStudy.slug}`
+      : `${base}/study`
+
+    for (const tier of REENGAGEMENT_TIERS) {
+      if (daysSinceLogin < tier.days) continue
+      if (sent[tier.key]) continue
+
+      const unsubUrl = makeUnsubUrl(user.id)
+      try {
+        await sendStudyReengagementEmail(user.username, user.displayName || user.username, studyTitle, studyUrl, tier.key, unsubUrl)
+      } catch (err) {
+        console.error(`[study-reengagement] failed to send ${tier.key} to ${user.username}:`, err)
+        continue
+      }
+      user.reengagementSentAt = { ...sent, [tier.key]: new Date().toISOString() }
+      queueStudyUsersWrite()
+      break  // one tier per run so we don't spam if they've been gone >30 days
+    }
+  }
+}