feat: privacy-respecting analytics

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

server/src/engine/analytics.ts

@@ -0,0 +1,67 @@
+import { sqlite } from '../db/index.js'
+
+function today(): string {
+  return new Date().toISOString().slice(0, 10)
+}
+
+const incrementStmt = sqlite.prepare(
+  `INSERT INTO analytics (date, metric, value) VALUES (?, ?, 1)
+   ON CONFLICT(date, metric) DO UPDATE SET value = value + 1`
+)
+
+const incrementByStmt = sqlite.prepare(
+  `INSERT INTO analytics (date, metric, value) VALUES (?, ?, ?)
+   ON CONFLICT(date, metric) DO UPDATE SET value = value + ?`
+)
+
+/** Increment a metric counter for today */
+export function trackMetric(metric: string): void {
+  try { incrementStmt.run(today(), metric) } catch { /* best-effort */ }
+}
+
+/** Increment a metric by a specific amount */
+export function trackMetricBy(metric: string, amount: number): void {
+  try { incrementByStmt.run(today(), metric, amount, amount) } catch { /* best-effort */ }
+}
+
+/** Record a fight completion with aggregate counters */
+export function trackFightCompleted(opts: {
+  satsWagered: number
+  durationRounds: number
+  mode: 'free' | 'ranked'
+}): void {
+  trackMetric('fights')
+  trackMetric(`fights_${opts.mode}`)
+  if (opts.satsWagered > 0) {
+    trackMetricBy('sats_wagered', opts.satsWagered)
+  }
+  trackMetricBy('total_rounds', opts.durationRounds)
+}
+
+/** Track a unique bot that fought today */
+export function trackBotActive(botId: string): void {
+  const key = `${today()}:${botId}`
+  if (seenBots.has(key)) return
+  seenBots.add(key)
+  trackMetric('unique_bots')
+
+  // Prune old entries (keep only today's)
+  const todayPrefix = today() + ':'
+  for (const k of seenBots) {
+    if (!k.startsWith(todayPrefix)) seenBots.delete(k)
+  }
+}
+
+const seenBots = new Set<string>()
+
+/** Get aggregate stats for the last N days */
+export function getPublicStats(days: number = 30): Array<{ date: string; metric: string; value: number }> {
+  const cutoff = new Date()
+  cutoff.setDate(cutoff.getDate() - days)
+  const cutoffStr = cutoff.toISOString().slice(0, 10)
+
+  const stmt = sqlite.prepare(
+    'SELECT date, metric, value FROM analytics WHERE date >= ? ORDER BY date DESC, metric'
+  )
+  return stmt.all(cutoffStr) as Array<{ date: string; metric: string; value: number }>
+}

server/src/engine/orchestrator.ts

@@ -15,6 +15,7 @@ import { settleBets, lockBets } from './betting.js'
 import { publishFightResult } from './nostr-publish.js'
 import { getCurrentSeason } from './seasons.js'
 import { onFightFinished as onTournamentFightFinished } from './tournaments.js'
+import { trackFightCompleted, trackBotActive, trackMetric } from './analytics.js'
 
 interface BotRecord {
   id: string
@@ -514,6 +515,18 @@ async function executeFightRounds(fightId: string, botA: BotRecord, botB: BotRec
 
   finalize()
 
+  // Track aggregate analytics (no PII)
+  trackBotActive(botA.id)
+  trackBotActive(botB.id)
+  trackFightCompleted({
+    satsWagered: mode === 'ranked' ? ENTRY_FEE_SATS * 2 : 0,
+    durationRounds: lastRound,
+    mode,
+  })
+  for (const ct of usedTypes) {
+    trackMetric(`challenge_${ct}`)
+  }
+
   // Advance tournament bracket if this was a tournament match
   try { onTournamentFightFinished(fightId, winnerId ?? null) } catch { /* not a tournament fight */ }