import { ScraperRequest } from './types';
import { logger } from '../services/logger';
import crypto from 'crypto';

export class RequestScheduler {
  private queue: ScraperRequest[] = [];
  private inProgress: Set<string> = new Set();
  private seen: Set<string> = new Set();
  private deduplicationEnabled: boolean = true;

  constructor(deduplicationEnabled: boolean = true) {
    this.deduplicationEnabled = deduplicationEnabled;
  }

  /**
   * Generate fingerprint for request deduplication
   */
  private generateFingerprint(request: Partial<ScraperRequest>): string {
    if (request.fingerprint) {
      return request.fingerprint;
    }

    // Generate fingerprint based on URL and relevant metadata
    const data = {
      url: request.url,
      method: request.metadata?.method || 'GET',
      body: request.metadata?.body
    };

    return crypto.createHash('md5').update(JSON.stringify(data)).digest('hex');
  }

  /**
   * Add a request to the queue
   */
  enqueue(partialRequest: Partial<ScraperRequest>): boolean {
    if (!partialRequest.url) {
      logger.warn('scraper', 'Cannot enqueue request without URL');
      return false;
    }

    const fingerprint = this.generateFingerprint(partialRequest);

    // Check for duplicates
    if (this.deduplicationEnabled && this.seen.has(fingerprint)) {
      logger.debug('scraper', `Request already seen: ${partialRequest.url}`);
      return false;
    }

    // Create full request with defaults
    const request: ScraperRequest = {
      url: partialRequest.url,
      priority: partialRequest.priority ?? 0,
      retryCount: partialRequest.retryCount ?? 0,
      maxRetries: partialRequest.maxRetries ?? 3,
      metadata: partialRequest.metadata || {},
      callback: partialRequest.callback!,
      errorHandler: partialRequest.errorHandler,
      fingerprint
    };

    this.queue.push(request);
    this.seen.add(fingerprint);

    // Sort by priority (higher priority first)
    this.queue.sort((a, b) => b.priority - a.priority);

    logger.debug('scraper', `Enqueued: ${request.url} (priority: ${request.priority})`);
    return true;
  }

  /**
   * Get the next request from the queue
   */
  dequeue(): ScraperRequest | null {
    const request = this.queue.shift();

    if (request) {
      this.inProgress.add(request.fingerprint!);
    }

    return request || null;
  }

  /**
   * Mark a request as complete
   */
  markComplete(request: ScraperRequest): void {
    if (request.fingerprint) {
      this.inProgress.delete(request.fingerprint);
    }
  }

  /**
   * Requeue a failed request (for retry)
   */
  requeueForRetry(request: ScraperRequest): boolean {
    if (request.fingerprint) {
      this.inProgress.delete(request.fingerprint);
      this.seen.delete(request.fingerprint);
    }

    request.retryCount++;

    if (request.retryCount > request.maxRetries) {
      logger.warn('scraper', `Max retries exceeded for: ${request.url}`);
      return false;
    }

    // Decrease priority for retried requests
    request.priority = Math.max(0, request.priority - 1);

    return this.enqueue(request);
  }

  /**
   * Get queue stats
   */
  getStats(): {
    pending: number;
    inProgress: number;
    total: number;
  } {
    return {
      pending: this.queue.length,
      inProgress: this.inProgress.size,
      total: this.seen.size
    };
  }

  /**
   * Check if queue is empty
   */
  isEmpty(): boolean {
    return this.queue.length === 0 && this.inProgress.size === 0;
  }

  /**
   * Clear all queues
   */
  clear(): void {
    this.queue = [];
    this.inProgress.clear();
    this.seen.clear();
  }

  /**
   * Get pending requests count
   */
  getPendingCount(): number {
    return this.queue.length;
  }

  /**
   * Get in-progress count
   */
  getInProgressCount(): number {
    return this.inProgress.size;
  }
}