import { BatchQueue } from './batch-queue';
import { getDeviceData, type CollectedDeviceData } from './device-collector';
import { captureAttribution, type StoredAttribution } from './utm-extractor';
import { CrossDomainLinker, type CrossDomainConfig } from './cross-domain';

import type {
  AnalyticsConfig,
  AttributionData,
  BatchedEvent,
  ViewEventData,
  EngagementEventData,
  InteractionEvent,
  InteractionEventPayload,
} from './types';

// Type declarations for browser APIs (allows compilation in Node.js environments)
declare const window: {
  addEventListener: (event: string, handler: () => void) => void;
  location: { hostname: string; href: string };
} | undefined;
declare const localStorage: { getItem: (key: string) => string | null; setItem: (key: string, value: string) => void } | undefined;

export class AnalyticsClient {
  private config: Required<AnalyticsConfig>;
  private queue: BatchQueue;
  private sessionId: string;
  private interactionQueue: InteractionEventPayload[] = [];
  private interactionFlushTimer: ReturnType<typeof setInterval> | null = null;
  private deviceData: CollectedDeviceData | null = null;
  private attribution: StoredAttribution | null = null;
  private crossDomainLinker: CrossDomainLinker | null = null;

  constructor(config: AnalyticsConfig) {
    this.config = {
      batchSize: 10,
      batchInterval: 5000,
      enableDebugLogging: false,
      sessionIdKey: 'analytics_session_id',
      enabled: true,
      scrollTracking: { enabled: false },
      trackResizes: false,
      resizeDebounceMs: 1000,
      crossDomainEnabled: false,
      allowedDomains: [],
      currentDomain: typeof window !== 'undefined' ? window.location.hostname : '',
      ...config,
    };

    // Skip initialization if analytics is disabled
    if (!this.config.enabled) {
      this.sessionId = '';
      this.queue = null as unknown as BatchQueue;
      if (this.config.enableDebugLogging) {
        console.log('[Analytics] Disabled via config');
      }
      return;
    }

    this.sessionId = this.getOrCreateSessionId();
    this.deviceData = getDeviceData(); // Collect device data once per session
    this.attribution = captureAttribution(); // Capture UTM params on first load
    this.queue = new BatchQueue(
      this.config.batchSize,
      this.config.batchInterval,
      this.flushBatch.bind(this),
      this.config.enableDebugLogging,
    );

    // Initialize cross-domain linker if enabled
    if (this.config.crossDomainEnabled) {
      this.initCrossDomain();
    }

    // Flush on page unload
    if (typeof window !== 'undefined') {
      window.addEventListener('beforeunload', () => {
        this.flush();
      });
    }

    // Set up periodic interaction flush
    this.interactionFlushTimer = setInterval(() => {
      this.flushInteractions();
    }, this.config.batchInterval);
  }

  /**
   * Initialize cross-domain session linking.
   */
  private async initCrossDomain(): Promise<void> {
    const crossDomainConfig: CrossDomainConfig = {
      apiBaseUrl: this.config.apiBaseUrl,
      sessionId: this.sessionId,
      domain: this.config.currentDomain,
      allowedDomains: this.config.allowedDomains,
      enableDebugLogging: this.config.enableDebugLogging,
    };

    this.crossDomainLinker = new CrossDomainLinker(crossDomainConfig);

    // Check for pending cross-domain token
    const pendingToken = CrossDomainLinker.getPendingToken();
    if (pendingToken) {
      if (this.config.enableDebugLogging) {
        console.log('[Analytics] Found cross-domain token, adopting session');
      }
      await this.crossDomainLinker.adoptSession(pendingToken, this.sessionId);
    }
  }

  /**
   * Get cross-domain linker for generating tokens for outbound links.
   */
  getCrossDomainLinker(): CrossDomainLinker | null {
    return this.crossDomainLinker;
  }

  /**
   * Generate a cross-domain URL with token appended.
   * Returns original URL if cross-domain is not enabled.
   */
  async getCrossDomainUrl(targetUrl: string): Promise<string> {
    if (!this.crossDomainLinker) {
      return targetUrl;
    }
    return this.crossDomainLinker.appendTokenToUrl(targetUrl);
  }

  /**
   * Get current attribution data.
   */
  getAttribution(): AttributionData | null {
    if (!this.attribution) {
      return null;
    }
    return {
      utmSource: this.attribution.utmSource,
      utmMedium: this.attribution.utmMedium,
      utmCampaign: this.attribution.utmCampaign,
      utmContent: this.attribution.utmContent,
      utmTerm: this.attribution.utmTerm,
    };
  }

  trackView(data: Omit<ViewEventData, 'app' | 'sessionId'>): void {
    if (!this.config.enabled) {return;}

    // Include attribution on first view (or all views for completeness)
    const attribution = this.getAttribution();

    const event: BatchedEvent = {
      type: 'view',
      data: {
        ...data,
        app: this.config.appName,
        sessionId: this.sessionId,
        // Include client device data for server-side enrichment
        clientDevice: this.deviceData ?? undefined,
        // Include attribution data for first-touch tracking
        attribution: attribution ?? undefined,
      } as ViewEventData,
      timestamp: Date.now(),
    };

    this.queue.add(event);
  }

  trackEngagement(data: EngagementEventData): void {
    if (!this.config.enabled) {return;}

    const event: BatchedEvent = {
      type: 'engagement',
      data,
      timestamp: Date.now(),
    };

    this.queue.add(event);
  }

  trackInteraction(event: InteractionEvent): void {
    if (!this.config.enabled) {return;}

    const payload: InteractionEventPayload = {
      type: event.type,
      data: event.data,
      sessionId: this.sessionId,
      timestamp: Date.now(),
    };

    this.interactionQueue.push(payload);

    // Flush if batch size reached
    if (this.interactionQueue.length >= this.config.batchSize) {
      this.flushInteractions();
    }
  }

  async flush(): Promise<void> {
    if (!this.config.enabled) {return;}
    await Promise.all([
      this.queue.flush(),
      this.flushInteractions(),
    ]);
  }

  destroy(): void {
    if (!this.config.enabled) {return;}
    this.queue.destroy();
    if (this.interactionFlushTimer) {
      clearInterval(this.interactionFlushTimer);
      this.interactionFlushTimer = null;
    }
  }

  private async flushInteractions(): Promise<void> {
    if (this.interactionQueue.length === 0) {return;}

    const events = [...this.interactionQueue];
    this.interactionQueue = [];

    try {
      await fetch(`${this.config.apiBaseUrl}/analytics/track/interaction`, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ events }),
      });

      if (this.config.enableDebugLogging) {
        console.log(`[Analytics] Flushed ${events.length} interaction events`);
      }
    } catch (error) {
      // Re-queue on failure
      this.interactionQueue = [...events, ...this.interactionQueue];
      if (this.config.enableDebugLogging) {
        console.error('[Analytics] Failed to flush interactions:', error);
      }
    }
  }

  private async flushBatch(events: BatchedEvent[]): Promise<void> {
    const viewEvents = events
      .filter((e) => e.type === 'view')
      .map((e) => e.data as ViewEventData);

    const engagementEvents = events
      .filter((e) => e.type === 'engagement')
      .map((e) => e.data as EngagementEventData);

    const promises: Promise<void>[] = [];

    if (viewEvents.length > 0) {
      promises.push(this.sendViewEvents(viewEvents));
    }

    if (engagementEvents.length > 0) {
      promises.push(this.sendEngagementEvents(engagementEvents));
    }

    await Promise.all(promises);
  }

  private async sendViewEvents(events: ViewEventData[]): Promise<void> {
    for (const event of events) {
      await fetch(`${this.config.apiBaseUrl}/analytics/track/view`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
        },
        body: JSON.stringify(event),
      });
    }
  }

  private async sendEngagementEvents(
    events: EngagementEventData[],
  ): Promise<void> {
    for (const event of events) {
      await fetch(`${this.config.apiBaseUrl}/analytics/track/engagement`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
        },
        body: JSON.stringify(event),
      });
    }
  }

  private getOrCreateSessionId(): string {
    if (typeof window === 'undefined' || typeof localStorage === 'undefined') {
      return this.generateSessionId();
    }

    const stored = localStorage.getItem(this.config.sessionIdKey);
    if (stored) {
      return stored;
    }

    const newSessionId = this.generateSessionId();
    localStorage.setItem(this.config.sessionIdKey, newSessionId);
    return newSessionId;
  }

  private generateSessionId(): string {
    return `${Date.now()}-${Math.random().toString(36).substring(2, 15)}`;
  }
}