Add per-episode play tracking with bar chart in admin analytics

- POST /api/analytics/play records a play event (title + date) on first
  play per player mount, skipping admin sessions
- Plays persisted to data/episode-plays.json with total + byDay buckets
- Admin stats response includes episodePlays sorted by total plays
- AnalyticsPanel shows horizontal bar chart + summary cards for all
  episodes dynamically — new episodes appear automatically as played

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

server/config.js

@@ -37,6 +37,7 @@ export const STUDY_COMMENTS_FILE = path.join(DATA_DIR, 'study-section-comments.j
 export const STUDY_CERTIFICATES_FILE = path.join(DATA_DIR, 'study-certificates.json')
 export const EPISODE_SCRIPTS_FILE = path.join(DATA_DIR, 'episode-scripts.json')
 export const QR_CODES_FILE = path.join(DATA_DIR, 'qr-codes.json')
+export const EPISODE_PLAYS_FILE = path.join(DATA_DIR, 'episode-plays.json')
 export const MAX_EPISODE_SCRIPT_LENGTH = 200_000 // ~150k words, well beyond any sermon
 
 export const DIST_DIR = path.join(ROOT_DIR, 'dist')

server/data.js

@@ -28,6 +28,7 @@ import {
   UPLOADS_DIR,
   UPLOADS_META_FILE,
   DOWNLOAD_COUNTS_FILE,
+  EPISODE_PLAYS_FILE,
   EMPTY_HIT_STATS,
   EMPTY_VISITOR_STATS,
   DEFAULT_REPLY_TEMPLATES,
@@ -675,6 +676,40 @@ export function incrementDownloadCount(resourceKey) {
   queueDownloadCountsWrite()
 }
 
+// ── Episode play counts ────────────────────────────────────────────────────
+
+export function queueEpisodePlaysWrite() {
+  state.episodePlaysWritePromise = state.episodePlaysWritePromise
+    .then(async () => {
+      await mkdir(DATA_DIR, { recursive: true })
+      await writeFile(EPISODE_PLAYS_FILE, JSON.stringify(state.episodePlays, null, 2), 'utf8')
+    })
+    .catch(err => {
+      console.error('[episode-plays] failed to write:', err)
+    })
+}
+
+export function loadEpisodePlaysFromDisk() {
+  return readFile(EPISODE_PLAYS_FILE, 'utf8')
+    .then(raw => {
+      const parsed = JSON.parse(raw)
+      state.episodePlays = (parsed && typeof parsed === 'object' && !Array.isArray(parsed)) ? parsed : {}
+    })
+    .catch(() => {
+      state.episodePlays = {}
+    })
+}
+
+export function recordEpisodePlay(title) {
+  const today = new Date().toISOString().slice(0, 10)
+  if (!state.episodePlays[title]) {
+    state.episodePlays[title] = { total: 0, byDay: {} }
+  }
+  state.episodePlays[title].total += 1
+  state.episodePlays[title].byDay[today] = (state.episodePlays[title].byDay[today] ?? 0) + 1
+  queueEpisodePlaysWrite()
+}
+
 // ── Uploads ────────────────────────────────────────────────────────────────
 
 export async function readUploadsMetadata() {

server/routes/analytics.js

@@ -6,7 +6,7 @@ import {
   MAX_RECENT_VISITS,
 } from '../config.js'
 import { state } from '../state.js'
-import { queueVisitorStatsWrite, queueHitStatsWrite, normalizeMessageType } from '../data.js'
+import { queueVisitorStatsWrite, queueHitStatsWrite, normalizeMessageType, recordEpisodePlay } from '../data.js'
 import {
   detectBot,
   sanitizeUserAgent,
@@ -146,6 +146,14 @@ export function register(app) {
     res.json({ ok: true, consent })
   })
 
+  app.post('/api/analytics/play', (req, res) => {
+    if (isValidAdminSession(req)) { res.json({ ok: false, reason: 'admin' }); return }
+    const title = typeof req.body?.title === 'string' ? req.body.title.trim().slice(0, 200) : ''
+    if (!title) { res.status(400).json({ ok: false, reason: 'missing-title' }); return }
+    recordEpisodePlay(title)
+    res.json({ ok: true })
+  })
+
   app.post('/api/analytics/pageview', async (req, res) => {
     if (isValidAdminSession(req)) {
       res.json({ ok: false, reason: 'admin' }); return
@@ -324,6 +332,14 @@ export function register(app) {
         users,
         funnel: { signups: funnelSignups, firstVisit: funnelFirstVisit, firstCompletion: funnelFirstCompletion },
       },
+      episodePlays: Object.entries(state.episodePlays)
+        .map(([title, data]) => ({
+          title,
+          total: data.total ?? 0,
+          byDay: data.byDay ?? {},
+          last30Days: buildLastNDaysStats(30).map(item => ({ day: item.day, plays: data.byDay?.[item.day] ?? 0 })),
+        }))
+        .sort((a, b) => b.total - a.total),
     })
   })
 }

server/state.js

@@ -59,6 +59,10 @@ export const state = {
   downloadCounts: {},
   downloadCountsWritePromise: Promise.resolve(),
 
+  // episodePlays: { [title]: { total: number, byDay: { [YYYY-MM-DD]: number } } }
+  episodePlays: {},
+  episodePlaysWritePromise: Promise.resolve(),
+
   // qrCodes: Array<{ id, slug, label, destination, createdAt }>
   // qrScans: Array<{ id, qrId, slug, scannedAt, ip, userAgent }>
   qrCodes: [],