/**
 * Chat Storage Service
 * Manages chat list in localStorage for widget persistence
 */

import { ChatListItem } from '../types/api';

const STORAGE_KEY = 'bcx_chat_list';
const MAX_CHATS = 50; // Maximum number of chats to store

export class ChatStorageService {
  /**
   * Get all chats from localStorage
   */
  static getChats(): ChatListItem[] {
    try {
      const stored = localStorage.getItem(STORAGE_KEY);
      if (!stored) {
        return [];
      }
      const chats = JSON.parse(stored) as ChatListItem[];
      // Sort by timestamp (newest first)
      return chats.sort((a, b) => new Date(b.lastMessageTimestamp).getTime() - new Date(a.lastMessageTimestamp).getTime());
    } catch (error) {
      console.error('[ChatStorage] Error reading chats from localStorage:', error);
      return [];
    }
  }

  /**
   * Save or update a chat in localStorage
   */
  static saveChat(chatId: string, lastMessage: string, lastMessageTimestamp: string): void {
    try {
      const chats = this.getChats();

      // Find existing chat
      const existingIndex = chats.findIndex(chat => chat.chatId === chatId);

      const chatItem: ChatListItem = {
        chatId,
        lastMessage,
        lastMessageTimestamp,
      };

      if (existingIndex >= 0) {
        // Update existing chat
        chats[existingIndex] = chatItem;
      } else {
        // Add new chat at the beginning
        chats.unshift(chatItem);
      }

      // Limit to MAX_CHATS
      if (chats.length > MAX_CHATS) {
        chats.splice(MAX_CHATS);
      }

      // Sort by timestamp (newest first)
      chats.sort((a, b) => new Date(b.lastMessageTimestamp).getTime() - new Date(a.lastMessageTimestamp).getTime());

      localStorage.setItem(STORAGE_KEY, JSON.stringify(chats));
    } catch (error) {
      console.error('[ChatStorage] Error saving chat to localStorage:', error);
    }
  }

  /**
   * Get a specific chat by ID
   */
  static getChat(chatId: string): ChatListItem | null {
    const chats = this.getChats();
    return chats.find(chat => chat.chatId === chatId) || null;
  }

  /**
   * Remove a chat from localStorage
   */
  static removeChat(chatId: string): void {
    try {
      const chats = this.getChats();
      const filtered = chats.filter(chat => chat.chatId !== chatId);
      localStorage.setItem(STORAGE_KEY, JSON.stringify(filtered));
    } catch (error) {
      console.error('[ChatStorage] Error removing chat from localStorage:', error);
    }
  }

  /**
   * Clear all chats from localStorage
   */
  static clearAll(): void {
    try {
      localStorage.removeItem(STORAGE_KEY);
    } catch (error) {
      console.error('[ChatStorage] Error clearing chats from localStorage:', error);
    }
  }
}