# Telegram Client Library

This library (`telegram-client.js`) enables programmatic interaction with Telegram via the user client API (not bot API).

## Features

- Authentication with Telegram (including 2FA support)
- Session management (automatic reuse of existing sessions)
- Retrieving chats/dialogs (with caching)
- Fetching messages from specific chats (using cached IDs)
- Filtering messages by pattern (e.g., regex)

## Usage

```javascript
// Example using the client library (see client.js for a more complete example)
import TelegramClient from "./telegram-client.js";
import dotenv from "dotenv";

dotenv.config();

async function main() {
  // Create a new client instance
  const client = new TelegramClient(
    process.env.TELEGRAM_API_ID,
    process.env.TELEGRAM_API_HASH,
    process.env.TELEGRAM_PHONE_NUMBER
    // Optional: specify session path, default is './data/session.json'
  );

  // Login to Telegram (will prompt for code/password if needed)
  await client.login();

  // Load dialog cache (optional, but recommended for performance)
  // Or use getAllDialogs() to fetch and populate the cache
  await client.loadDialogCache(); // Default path: './data/dialog_cache.json'
  if (client.dialogCache.size === 0) {
    console.log("Cache empty, fetching all dialogs to build cache...");
    await client.getAllDialogs(); // Fetches all dialogs and populates cache
    await client.saveDialogCache(); // Save cache for next time
  }

  // Get dialogs from the cache
  const dialogs = Array.from(client.dialogCache.values());

  // Print all cached chats
  dialogs.forEach((chat) => {
    if (chat.title) {
      console.log(`Chat: ${chat.title} (ID: ${chat.id})`);
    }
  });

  // Example: Get messages (replace 'your_channel_id' with an actual ID from the cache)
  // const messages = await client.getMessagesByChannelId('your_channel_id', 50);
  // console.log(messages);
}

main().catch(console.error);
```

Run the standalone client example:

```bash
node client.js
```

## API Reference

### TelegramClient

#### Constructor

```javascript
const client = new TelegramClient(apiId, apiHash, phoneNumber, sessionPath);
```

- `apiId`: Your Telegram API ID
- `apiHash`: Your Telegram API Hash
- `phoneNumber`: Your phone number in international format
- `sessionPath`: (Optional) Path to save the session file (default: './data/session.json')

#### Methods

- `login()`: Authenticates with Telegram (handles new logins, 2FA, and session reuse).
- `hasSession()`: Checks if a valid session file exists.
- `getDialogs(limit, offset)`: Gets a batch of dialogs (chats) directly from Telegram API.
- `getAllDialogs(batchSize)`: Fetches all dialogs progressively, populating the internal cache (`dialogCache`).
- `_updateDialogCache(chats)`: Internal method to update the cache.
- `getPeerInputById(id)`: Gets the necessary `InputPeer` object from the cache for API calls.
- `getChatMessages(chatObject, limit)`: Gets messages from a specific chat _object_ (less commonly used now).
- `getMessagesByChannelId(channelId, limit)`: Gets messages from a specific chat/channel using its ID (uses cached peer info).
- `filterMessagesByPattern(messages, pattern)`: Filters an array of message _strings_ by a regex pattern.
- `saveDialogCache(cachePath)`: Saves the internal `dialogCache` Map to a JSON file (default: `./data/dialog_cache.json`).
- `loadDialogCache(cachePath)`: Loads the `dialogCache` Map from a JSON file.