/**
 * Notification reader service - detects new notifications in IndexedDB
 * This service is separate from the Service Worker that populates notifications
 */

import { notificationService } from './notificationService'
import type { Notification } from './notificationService'

class NotificationReader {
  private lastReadTime: number = 0
  private subscribers: Array<(notifications: Notification[]) => void> = []

  /**
   * Subscribe to notification updates
   */
  subscribe(callback: (notifications: Notification[]) => void): () => void {
    this.subscribers.push(callback)

    // Return unsubscribe function
    return () => {
      const index = this.subscribers.indexOf(callback)
      if (index > -1) {
        this.subscribers.splice(index, 1)
      }
    }
  }

  /**
   * Notify subscribers of new notifications
   */
  private notifySubscribers(notifications: Notification[]): void {
    this.subscribers.forEach((callback) => {
      try {
        callback(notifications)
      } catch (error) {
        console.error('[NotificationReader] Error in subscriber callback:', error)
      }
    })
  }

  /**
   * Read notifications from IndexedDB
   */
  async readNotifications(limit: number = 100): Promise<Notification[]> {
    try {
      const notifications = await notificationService.getAllNotifications(limit)
      this.lastReadTime = Date.now()
      this.notifySubscribers(notifications)
      return notifications
    } catch (error) {
      console.error('[NotificationReader] Error reading notifications:', error)
      return []
    }
  }

  /**
   * Get unread notifications count
   */
  async getUnreadCount(): Promise<number> {
    try {
      return await notificationService.getUnreadCount()
    } catch (error) {
      console.error('[NotificationReader] Error getting unread count:', error)
      return 0
    }
  }

  /**
   * Get new notifications since last read
   */
  async getNewNotifications(since: number = this.lastReadTime): Promise<Notification[]> {
    try {
      const allNotifications = await notificationService.getAllNotifications(1000)
      return allNotifications.filter((n) => n.timestamp > since)
    } catch (error) {
      console.error('[NotificationReader] Error getting new notifications:', error)
      return []
    }
  }
}

export const notificationReader = new NotificationReader()