import { randomUUID } from 'node:crypto';
import { MongoServerError, type Db } from 'mongodb';
import { ACTIVE_WINDOW_MS, RETENTION_MS, VISIT_SESSION_MS } from '../../constants/analytics.js';
import type { AnalyticsEvent, Presence, VisitMetadata, VisitSession } from '../shared/analytics-types.js';
import type { PlayerDocument } from './stats-store.js';
import { kstDay } from './analytics-report.js';
export interface AnalyticsStore {
  db: Db;
  touch(playerId: string, now: Date, visible: boolean, metadata: VisitMetadata, metadataFinal?: boolean): Promise<VisitSession>;
  insert(event: AnalyticsEvent): Promise<void>;
  sample(now: Date, presence: Presence, environment: string, quality?: { restartedAt: Date; failures: number; dropped: number; rateLimited: number }): Promise<void>;
  cleanup(now: Date): Promise<void>;
}
export async function createAnalyticsStore(db: Db): Promise<AnalyticsStore> {
  const players = db.collection<PlayerDocument & { visit?: VisitSession }>('players');
  const sessions = db.collection<VisitSession & { _id: string }>('analytics_sessions');
  const events = db.collection<AnalyticsEvent>('analytics_events');
  const samples = db.collection('analytics_presence_samples');
  for (const collection of [sessions, events, samples]) await collection.createIndex({ expiresAt: 1 }, { expireAfterSeconds: 0 });
  await sessions.createIndex({ playerId: 1, lastAt: -1 });
  await sessions.createIndex({ sessionId: 1 }, { unique: true });
  for (const field of ['eventType', 'playerId', 'sessionId']) await events.createIndex({ [field]: 1, occurredAt: 1 });
  await samples.createIndex({ occurredAt: 1 });
  await players.createIndex({ 'visit.expiresAt': 1 });
  const cleanup = async (now: Date) => { await players.updateMany({ 'visit.expiresAt': { $lte: now } }, { $unset: { visit: '' } }); };
  await cleanup(new Date());
  return {
    db,
    cleanup,
    async touch(playerId, now, visible, metadata, metadataFinal = false) {
      // The single player document atomically decides the session ID and activity delta.
      // Snapshot writes to analytics_sessions never decide or increment counters independently.
      const expired = { $or: [{ $eq: [{ $type: '$visit' }, 'missing'] }, { $lte: ['$visit.lastAt', new Date(+now - VISIT_SESSION_MS)] }] };
      const fresh: VisitSession = { sessionId: randomUUID(), playerId, startedAt: now, lastAt: now, lastSignalAt: now, visible,
        activeMs: 0, activeDays: visible ? [kstDay(now)] : [], metadata, metadataReady: metadataFinal, expiresAt: new Date(+now + RETENTION_MS) };
      const delta = { $cond: [{ $and: [visible, '$visit.visible', { $lte: [{ $subtract: [now, '$visit.lastSignalAt'] }, ACTIVE_WINDOW_MS] }, { $gte: [now, '$visit.lastSignalAt'] }] }, { $subtract: [now, '$visit.lastSignalAt'] }, 0] };
      const doc = await players.findOneAndUpdate({ _id: playerId }, [{ $set: {
        visit: { $cond: [expired, { $literal: fresh }, { $mergeObjects: ['$visit', {
          visible, lastSignalAt: now, lastAt: visible ? now : '$visit.lastAt',
          activeMs: { $add: ['$visit.activeMs', delta] }, expiresAt: new Date(+now + RETENTION_MS),
          activeDays: { $setUnion: [{ $filter: { input: { $ifNull: ['$visit.activeDays', []] }, as: 'day', cond: { $gte: ['$$day', kstDay(new Date(+now - RETENTION_MS))] } } }, visible ? [kstDay(now)] : []] },
          metadata: { $cond: [{ $and: [metadataFinal, { $ne: ['$visit.metadataReady', true] }] }, { $literal: metadata }, '$visit.metadata'] },
          metadataReady: { $or: [metadataFinal, { $eq: ['$visit.metadataReady', true] }] },
        }] }] },
      } }], { returnDocument: 'after' });
      if (!doc?.visit) throw new Error('UNKNOWN_PLAYER');
      const visit = doc.visit;
      await sessions.updateOne({ _id: visit.sessionId }, {
        $setOnInsert: { sessionId: visit.sessionId, playerId, startedAt: visit.startedAt, ...(!visit.metadataReady ? { metadata: visit.metadata } : {}) },
        $max: { lastAt: visit.lastAt, lastSignalAt: visit.lastSignalAt, activeMs: visit.activeMs, expiresAt: visit.expiresAt },
        $set: { visible: visit.visible, ...(visit.metadataReady ? { metadata: visit.metadata, metadataReady: true } : {}) },
        $addToSet: { activeDays: { $each: visit.activeDays } },
      }, { upsert: true });
      return visit;
    },
    async insert(event) {
      try { await events.insertOne({ ...event, expiresAt: new Date(+event.occurredAt + RETENTION_MS) }); }
      catch (error) { if (!(error instanceof MongoServerError) || error.code !== 11000) throw error; }
      await db.collection<{ _id: string; firstCollectedAt: Date }>('analytics_metadata').updateOne({ _id: event.environment }, { $min: { firstCollectedAt: event.occurredAt } }, { upsert: true });
      if (event.eventType === 'page_view' && event.playerId) await players.updateOne({ _id: event.playerId }, { $min: { firstVisitAt: event.occurredAt } });
    },
    async sample(now, presence, environment, quality) { await samples.insertOne({ occurredAt: now, active: presence.active, source: presence.source, environment, ...(quality ?? {}), expiresAt: new Date(+now + RETENTION_MS) }); },
  };
}