/**
 * @fileoverview A centralized service for managing client-side storage.
 * This service uses IndexedDB for persistent message storage, ensuring
 * chats are saved locally on the user's device.
 */

import type { Message, Contact, Group } from '@/lib/types';
import { openDB, IDBPDatabase, DBSchema } from 'idb';

const DB_NAME = 'WhisperLinkDB_v2'; 
const DB_VERSION = 4; // Incremented version to add new stores
const MESSAGES_STORE = 'messages';
const CONTACTS_STORE = 'contacts';
const GROUPS_STORE = 'groups';
const SYNC_STORE = 'syncInfo';
const MEDIA_CACHE_STORE = 'media-cache';
const DATA_CACHE_STORE = 'data-cache';

// Define the database schema for type safety with the idb library
interface WhisperLinkDBSchema extends DBSchema {
  [MESSAGES_STORE]: {
    key: string;
    value: Message & { chatId: string }; // Ensure chatId is part of the value
    indexes: { 'chatId': string };
  };
   [CONTACTS_STORE]: {
    key: string; // uid
    value: Contact;
  };
  [GROUPS_STORE]: {
    key: string; // id
    value: Group;
  };
  [SYNC_STORE]: {
    key: string;
    value: { chatId: string; timestamp: number };
  };
  [MEDIA_CACHE_STORE]: {
    key: string; // The fileKey from R2
    value: {
        fileKey: string;
        blob: Blob;
        timestamp: number;
    };
  };
  [DATA_CACHE_STORE]: {
      key: string;
      value: any;
  }
}

class StorageService {
  private isBrowser: boolean;
  private dbPromise: Promise<IDBPDatabase<WhisperLinkDBSchema>> | null = null;

  constructor() {
    this.isBrowser = typeof window !== 'undefined';
  }

  private getDB(): Promise<IDBPDatabase<WhisperLinkDBSchema>> {
    if (!this.isBrowser) {
        return Promise.reject(new Error("IndexedDB is not available in this environment."));
    }
    if (!this.dbPromise) {
      this.dbPromise = openDB<WhisperLinkDBSchema>(DB_NAME, DB_VERSION, {
        upgrade(db, oldVersion, newVersion, transaction) {
          console.log(`Upgrading IndexedDB from version ${oldVersion} to ${newVersion}...`);
          
          if (!db.objectStoreNames.contains(MESSAGES_STORE)) {
            const messageStore = db.createObjectStore(MESSAGES_STORE, { keyPath: 'id' });
            messageStore.createIndex('chatId', 'chatId', { unique: false });
             console.log(`Created object store: ${MESSAGES_STORE} with index 'chatId'.`);
          }
           if (!db.objectStoreNames.contains(CONTACTS_STORE)) {
            db.createObjectStore(CONTACTS_STORE, { keyPath: 'uid' });
            console.log(`Created object store: ${CONTACTS_STORE}.`);
          }
           if (!db.objectStoreNames.contains(GROUPS_STORE)) {
            db.createObjectStore(GROUPS_STORE, { keyPath: 'id' });
            console.log(`Created object store: ${GROUPS_STORE}.`);
          }
          if (!db.objectStoreNames.contains(SYNC_STORE)) {
            db.createObjectStore(SYNC_STORE, { keyPath: 'chatId' });
             console.log(`Created object store: ${SYNC_STORE}.`);
          }
          if (!db.objectStoreNames.contains(MEDIA_CACHE_STORE)) {
            db.createObjectStore(MEDIA_CACHE_STORE, { keyPath: 'fileKey' });
            console.log(`Created object store: ${MEDIA_CACHE_STORE}.`);
          }
          if (!db.objectStoreNames.contains(DATA_CACHE_STORE)) {
            db.createObjectStore(DATA_CACHE_STORE, { keyPath: 'key' });
            console.log(`Created object store: ${DATA_CACHE_STORE}.`);
          }
        },
      });
    }
    return this.dbPromise;
  }

  // --- LocalStorage Methods ---

  setItem<T>(key: string, value: T): void {
    if (!this.isBrowser) return;
    try {
      window.localStorage.setItem(key, JSON.stringify(value));
    } catch (error) {
      console.error(`Error setting localStorage key "${key}":`, error);
    }
  }

  getItem<T>(key: string): T | null {
    if (!this.isBrowser) return null;
    try {
      const item = window.localStorage.getItem(key);
      return item ? JSON.parse(item) : null;
    } catch (error) {
      console.error(`Error reading localStorage key "${key}":`, error);
      return null;
    }
  }

  removeItem(key: string): void {
    if (!this.isBrowser) return;
    try {
      window.localStorage.removeItem(key);
    } catch (error) {
      console.error(`Error removing localStorage key "${key}":`, error);
    }
  }

  // --- IndexedDB Methods for Messages, Contacts, Groups ---

  async saveMessages(chatId: string, messages: Message[]): Promise<void> {
    if (!this.isBrowser) return;
    try {
        const db = await this.getDB();
        const tx = db.transaction(MESSAGES_STORE, 'readwrite');
        await Promise.all(messages.map(message => tx.store.put({ ...message, chatId })));
        await tx.done;
    } catch (error) {
        console.error("Failed to save messages to IndexedDB:", error);
    }
  }

  async getMessages(chatId: string): Promise<Message[]> {
    if (!this.isBrowser) return [];
    const db = await this.getDB();
    const messages = await db.getAllFromIndex(MESSAGES_STORE, 'chatId', chatId);
    return messages.sort((a, b) => a.timestamp - b.timestamp);
  }

  async updateMessage(chatId: string, messageId: string, updates: Partial<Message>): Promise<void> {
    if (!this.isBrowser) return;
    const db = await this.getDB();
    const message = await db.get(MESSAGES_STORE, messageId);
    if (message) {
        const updatedMessage = { ...message, ...updates };
        await db.put(MESSAGES_STORE, updatedMessage);
    }
  }
  
  async deleteMessage(chatId: string, messageId: string): Promise<void> {
    if (!this.isBrowser) return;
    const db = await this.getDB();
    await db.delete(MESSAGES_STORE, messageId);
  }


  async clearMessages(chatId: string): Promise<void> {
    if (!this.isBrowser) return;
    const db = await this.getDB();
    const tx = db.transaction(MESSAGES_STORE, 'readwrite');
    const index = tx.store.index('chatId');
    for await (const cursor of index.iterate(chatId)) {
      await cursor.delete();
    }
    await tx.done;
  }
  
  async saveContacts(contacts: Contact[]): Promise<void> {
    if (!this.isBrowser) return;
    const db = await this.getDB();
    const tx = db.transaction(CONTACTS_STORE, 'readwrite');
    await Promise.all(contacts.map(contact => tx.store.put(contact)));
    await tx.done;
  }

  async getContacts(): Promise<Contact[]> {
      if (!this.isBrowser) return [];
      const db = await this.getDB();
      return await db.getAll(CONTACTS_STORE);
  }

  async saveGroups(groups: Group[]): Promise<void> {
    if (!this.isBrowser) return;
    const db = await this.getDB();
    const tx = db.transaction(GROUPS_STORE, 'readwrite');
    await Promise.all(groups.map(group => tx.store.put(group)));
    await tx.done;
  }

  async getGroups(): Promise<Group[]> {
      if (!this.isBrowser) return [];
      const db = await this.getDB();
      return await db.getAll(GROUPS_STORE);
  }


  // --- Media Caching Methods ---

  async cacheMedia(fileKey: string, blob: Blob): Promise<void> {
    if (!this.isBrowser) return;
    const db = await this.getDB();
    await db.put(MEDIA_CACHE_STORE, { fileKey, blob, timestamp: Date.now() });
  }

  async getCachedMedia(fileKey: string): Promise<Blob | null> {
    if (!this.isBrowser) return null;
    try {
        const db = await this.getDB();
        const record = await db.get(MEDIA_CACHE_STORE, fileKey);
        return record?.blob || null;
    } catch (error) {
        console.error(`Failed to get cached media for key ${fileKey}:`, error);
        return null;
    }
  }

    // --- General Data Caching ---
  
  async saveCachedData(key: string, data: any): Promise<void> {
    if (!this.isBrowser) return;
    try {
      const db = await this.getDB();
      await db.put(DATA_CACHE_STORE, { key, data });
    } catch (error) {
      console.error(`Failed to save data to cache with key ${key}:`, error);
    }
  }

  async getCachedData<T>(key: string): Promise<T | null> {
    if (!this.isBrowser) return null;
    try {
      const db = await this.getDB();
      const result = await db.get(DATA_CACHE_STORE, key);
      return result?.data || null;
    } catch (error) {
      console.error(`Failed to retrieve cached data with key ${key}:`, error);
      return null;
    }
  }
  
  // --- Sync Info Management ---

  async updateLastSync(chatId: string, timestamp: number): Promise<void> {
    if (!this.isBrowser) return;
    const db = await this.getDB();
    await db.put(SYNC_STORE, { chatId, timestamp });
  }

  async getLastSync(chatId: string): Promise<number> {
    if (!this.isBrowser) return 0;
    const db = await this.getDB();
    const syncInfo = await db.get(SYNC_STORE, chatId);
    return syncInfo?.timestamp || 0;
  }
}

// Export a singleton instance of the service
export const storageService = new StorageService();