import { IndexedDBService, IQueueOperation } from './IndexedDBService';

/**
 * Operation Queue Manager
 * Handles FIFO queue of pending sync operations
 */
export class OperationQueue {
  private indexedDB: IndexedDBService;

  constructor(indexedDB: IndexedDBService) {
    this.indexedDB = indexedDB;
  }

  /**
   * Add operation to the end of the queue
   */
  async enqueue(operation: Omit<IQueueOperation, 'id'>): Promise<void> {
    await this.indexedDB.addToQueue(operation);
  }

  /**
   * Get the first operation from the queue (without removing it)
   * Returns null if queue is empty
   */
  async peek(): Promise<IQueueOperation | null> {
    const queue = await this.indexedDB.getQueue();
    return queue.length > 0 ? queue[0] : null;
  }

  /**
   * Get all operations in the queue (sorted by timestamp FIFO)
   */
  async getAll(): Promise<IQueueOperation[]> {
    return await this.indexedDB.getQueue();
  }

  /**
   * Remove a specific operation from the queue
   */
  async remove(operationId: string): Promise<void> {
    await this.indexedDB.removeFromQueue(operationId);
  }

  /**
   * Remove the first operation from the queue and return it
   * Returns null if queue is empty
   */
  async dequeue(): Promise<IQueueOperation | null> {
    const operation = await this.peek();
    if (operation) {
      await this.remove(operation.id);
    }
    return operation;
  }

  /**
   * Clear all operations from the queue
   */
  async clear(): Promise<void> {
    await this.indexedDB.clearQueue();
  }

  /**
   * Get the number of operations in the queue
   */
  async size(): Promise<number> {
    const queue = await this.getAll();
    return queue.length;
  }

  /**
   * Check if queue is empty
   */
  async isEmpty(): Promise<boolean> {
    const size = await this.size();
    return size === 0;
  }

  /**
   * Get operations for a specific event ID
   */
  async getOperationsForEvent(eventId: string): Promise<IQueueOperation[]> {
    const queue = await this.getAll();
    return queue.filter(op => op.eventId === eventId);
  }

  /**
   * Remove all operations for a specific event ID
   */
  async removeOperationsForEvent(eventId: string): Promise<void> {
    const operations = await this.getOperationsForEvent(eventId);
    for (const op of operations) {
      await this.remove(op.id);
    }
  }

  /**
   * Update retry count for an operation
   */
  async incrementRetryCount(operationId: string): Promise<void> {
    const queue = await this.getAll();
    const operation = queue.find(op => op.id === operationId);

    if (operation) {
      operation.retryCount++;
      // Re-add to queue with updated retry count
      await this.remove(operationId);
      await this.enqueue(operation);
    }
  }
}