/**
 * QUIXZOOM Replay Engine
 *
 * Spelar upp händelsekedjor i efterhand för debugging och utveckling.
 *
 * Exempel:
 *   08:13:01 Zoomer börjar filma
 *   08:13:07 Street Lamp observeras
 *   08:13:08 Identity Engine hittar objekt
 *   08:13:08 Evidence läggs till
 *   08:13:09 AI ser kunskapsgap
 *   08:13:10 Mission Generator skapar uppdrag
 *   08:13:11 Telefonen får instruktion: "Gå två meter närmare."
 *
 * Användning:
 * - Felsökning: Spela upp exakt vad som hände
 * - Regressionstest: Kör om samma events med ny kod
 * - Algoritm-jämförelse: Jämför resultat mellan versioner
 * - Demo: Visa hur systemet fungerar i realtid
 */

class ReplayEngine {
  constructor(options = {}) {
    this.speed = options.speed || 1.0; // 1.0 = realtid, 2.0 = dubbel hastighet
    this.events = [];
    this.handlers = new Map();
    this.state = 'idle'; // idle, playing, paused, stopped
    this.currentIndex = 0;
    this.startTime = null;
    this.pauseTime = null;
    this.results = [];
  }

  /**
   * ============================================================
   * REGISTRERA HANDLERS
   * ============================================================
   */

  registerHandler(eventType, handler) {
    this.handlers.set(eventType, handler);
    console.log(`[REPLAY] Registered handler for: ${eventType}`);
  }

  /**
   * ============================================================
   * LADDA EVENTS
   * ============================================================
   */

  loadEvents(events) {
    // Sortera efter timestamp
    this.events = events.sort((a, b) => a.timestamp - b.timestamp);
    this.currentIndex = 0;
    console.log(`[REPLAY] Loaded ${events.length} events`);
  }

  loadFromEventStore(eventStore, filter = {}) {
    // Ladda från Event Store med filter
    const events = eventStore.getEvents(filter);
    this.loadEvents(events);
  }

  /**
   * ============================================================
   * SPELA UPP
   * ============================================================
   */

  async play() {
    if (this.state === 'playing') {
      console.log('[REPLAY] Already playing');
      return;
    }

    if (this.state === 'paused') {
      // Återuppta
      const pausedDuration = Date.now() - this.pauseTime;
      this.startTime += pausedDuration;
      this.state = 'playing';
      console.log('[REPLAY] Resumed');
    } else {
      // Ny uppspelning
      this.startTime = Date.now();
      this.state = 'playing';
      this.currentIndex = 0;
      this.results = [];
      console.log('[REPLAY] Started');
    }

    // Spela upp events
    while (this.currentIndex < this.events.length && this.state === 'playing') {
      const event = this.events[this.currentIndex];
      const eventTime = this.getEventTime(event);

      // Vänta tills det är dags
      const now = Date.now();
      const elapsed = (now - this.startTime) * this.speed;
      const waitTime = eventTime - elapsed;

      if (waitTime > 0) {
        await this.sleep(waitTime / this.speed);
      }

      if (this.state !== 'playing') break;

      // Kör event
      await this.executeEvent(event);
      this.currentIndex++;
    }

    if (this.currentIndex >= this.events.length) {
      this.state = 'completed';
      console.log('[REPLAY] Completed');
    }
  }

  pause() {
    if (this.state === 'playing') {
      this.state = 'paused';
      this.pauseTime = Date.now();
      console.log('[REPLAY] Paused');
    }
  }

  stop() {
    this.state = 'stopped';
    console.log('[REPLAY] Stopped');
  }

  /**
   * ============================================================
   * EXECUTE EVENT
   * ============================================================
   */

  async executeEvent(event) {
    const handler = this.handlers.get(event.type);

    const context = {
      event,
      index: this.currentIndex,
      total: this.events.length,
      elapsed: Date.now() - this.startTime,
      results: this.results,
    };

    console.log(`[REPLAY] [${this.formatTime(event.timestamp)}] ${event.type}`);

    if (handler) {
      try {
        const result = await handler(event.payload, context);
        this.results.push({
          eventId: event.id,
          type: event.type,
          timestamp: event.timestamp,
          result,
          success: true,
        });
        return result;
      } catch (error) {
        console.error(`[REPLAY] Error executing ${event.type}:`, error.message);
        this.results.push({
          eventId: event.id,
          type: event.type,
          timestamp: event.timestamp,
          error: error.message,
          success: false,
        });
        throw error;
      }
    } else {
      console.log(`[REPLAY] No handler for: ${event.type}`);
      this.results.push({
        eventId: event.id,
        type: event.type,
        timestamp: event.timestamp,
        result: null,
        success: true,
      });
    }
  }

  /**
   * ============================================================
   * JÄMFÖR VERSIONER
   * ============================================================
   */

  async compareVersions(events, versionAHandlers, versionBHandlers) {
    console.log('[REPLAY] Comparing versions...');

    // Kör version A
    const engineA = new ReplayEngine({ speed: 100 }); // Snabb uppspelning
    for (const [type, handler] of versionAHandlers) {
      engineA.registerHandler(type, handler);
    }
    engineA.loadEvents(events);
    await engineA.play();

    // Kör version B
    const engineB = new ReplayEngine({ speed: 100 });
    for (const [type, handler] of versionBHandlers) {
      engineB.registerHandler(type, handler);
    }
    engineB.loadEvents(events);
    await engineB.play();

    // Jämför resultat
    const comparison = this.compareResults(engineA.results, engineB.results);

    return {
      versionA: { results: engineA.results, stats: engineA.getStats() },
      versionB: { results: engineB.results, stats: engineB.getStats() },
      comparison,
    };
  }

  compareResults(resultsA, resultsB) {
    const differences = [];
    const minLength = Math.min(resultsA.length, resultsB.length);

    for (let i = 0; i < minLength; i++) {
      const a = resultsA[i];
      const b = resultsB[i];

      if (JSON.stringify(a.result) !== JSON.stringify(b.result)) {
        differences.push({
          index: i,
          eventId: a.eventId,
          type: a.type,
          versionA: a.result,
          versionB: b.result,
        });
      }
    }

    return {
      totalEvents: minLength,
      differences: differences.length,
      differenceRate: (differences.length / minLength * 100).toFixed(2) + '%',
      details: differences,
    };
  }

  /**
   * ============================================================
   * EXPORT/IMPORT
   * ============================================================
   */

  exportSession() {
    return {
      events: this.events,
      results: this.results,
      stats: this.getStats(),
      exportedAt: new Date().toISOString(),
    };
  }

  importSession(session) {
    this.loadEvents(session.events);
    this.results = session.results || [];
    console.log(`[REPLAY] Imported session with ${session.events.length} events`);
  }

  /**
   * ============================================================
   * STATISTIK
   * ============================================================
   */

  getStats() {
    const typeCounts = {};
    for (const event of this.events) {
      typeCounts[event.type] = (typeCounts[event.type] || 0) + 1;
    }

    const successCount = this.results.filter(r => r.success).length;
    const errorCount = this.results.filter(r => !r.success).length;

    return {
      totalEvents: this.events.length,
      playedEvents: this.currentIndex,
      remainingEvents: this.events.length - this.currentIndex,
      typeCounts,
      successCount,
      errorCount,
      state: this.state,
    };
  }

  /**
   * ============================================================
   * HJÄLPMETODER
   * ============================================================
   */

  getEventTime(event) {
    // Relativ tid från första eventet
    if (!this.firstEventTime) {
      this.firstEventTime = this.events[0]?.timestamp || Date.now();
    }
    return event.timestamp - this.firstEventTime;
  }

  formatTime(timestamp) {
    const date = new Date(timestamp);
    return date.toISOString().split('T')[1].split('.')[0];
  }

  sleep(ms) {
    return new Promise(resolve => setTimeout(resolve, ms));
  }
}

// Exportera
module.exports = ReplayEngine;

// Demo
if (require.main === module) {
  const engine = new ReplayEngine({ speed: 10 }); // 10x hastighet för demo

  console.log('=== REPLAY ENGINE DEMO ===\n');

  // Registrera handlers
  engine.registerHandler('zoomer_started', async (payload) => {
    console.log(`  → Zoomer ${payload.zoomerId} started recording`);
    return { status: 'recording' };
  });

  engine.registerHandler('observation_created', async (payload) => {
    console.log(`  → Object ${payload.objectType} observed`);
    return { objectId: payload.objectId, confidence: 0.92 };
  });

  engine.registerHandler('identity_matched', async (payload) => {
    console.log(`  → Matched to ${payload.objectId} (${(payload.confidence * 100).toFixed(0)}% confidence)`);
    return { matched: true, objectId: payload.objectId };
  });

  engine.registerHandler('evidence_added', async (payload) => {
    console.log(`  → Evidence added: ${payload.evidenceType}`);
    return { evidenceId: payload.evidenceId };
  });

  engine.registerHandler('knowledge_gap_detected', async (payload) => {
    console.log(`  → Knowledge gap: ${payload.gapType}`);
    return { gapId: payload.gapId, priority: payload.priority };
  });

  engine.registerHandler('mission_created', async (payload) => {
    console.log(`  → Mission created: ${payload.missionType}`);
    return { missionId: payload.missionId };
  });

  engine.registerHandler('instruction_sent', async (payload) => {
    console.log(`  → Instruction: "${payload.instruction}"`);
    return { sent: true };
  });

  // Skapa scenario
  const baseTime = Date.now();
  const events = [
    { id: 'evt_001', type: 'zoomer_started', timestamp: baseTime, payload: { zoomerId: 'zoomer_00001' } },
    { id: 'evt_002', type: 'observation_created', timestamp: baseTime + 6000, payload: { objectType: 'street_lamp', objectId: 'obj_001' } },
    { id: 'evt_003', type: 'identity_matched', timestamp: baseTime + 7000, payload: { objectId: 'street_lamp_000001', confidence: 0.94 } },
    { id: 'evt_004', type: 'evidence_added', timestamp: baseTime + 7000, payload: { evidenceType: 'image', evidenceId: 'ev_001' } },
    { id: 'evt_005', type: 'knowledge_gap_detected', timestamp: baseTime + 8000, payload: { gapType: 'angle', gapId: 'gap_001', priority: 'medium' } },
    { id: 'evt_006', type: 'mission_created', timestamp: baseTime + 9000, payload: { missionType: 'verify_angle', missionId: 'mission_001' } },
    { id: 'evt_007', type: 'instruction_sent', timestamp: baseTime + 10000, payload: { instruction: 'Gå två meter närmare' } },
  ];

  // Ladda och spela
  engine.loadEvents(events);

  console.log('Starting playback...\n');
  engine.play().then(() => {
    console.log('\n=== PLAYBACK COMPLETE ===');
    console.log('\nStats:', engine.getStats());
    console.log('\nResults:');
    for (const result of engine.results) {
      console.log(`  ${result.type}: ${result.success ? '✓' : '✗'} ${JSON.stringify(result.result)}`);
    }
  });
}