From d0fe4c5b3544058f0998aaf5b61db21b186017a6 Mon Sep 17 00:00:00 2001
From: William Valentin <william.valentin.info@gmail.com>
Date: Mon, 2 Feb 2026 20:59:17 -0800
Subject: [PATCH] feat: add Telegram bot frontend with message handling

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
---
 src/frontends/telegram/bot.ts           | 96 +++++++++++++++++++++++++
 src/frontends/telegram/handlers.test.ts | 29 ++++++++
 src/frontends/telegram/handlers.ts      | 17 +++++
 src/frontends/telegram/index.ts         |  2 +
 4 files changed, 144 insertions(+)
 create mode 100644 src/frontends/telegram/bot.ts
 create mode 100644 src/frontends/telegram/handlers.test.ts
 create mode 100644 src/frontends/telegram/handlers.ts
 create mode 100644 src/frontends/telegram/index.ts

diff --git a/src/frontends/telegram/bot.ts b/src/frontends/telegram/bot.ts
new file mode 100644
index 0000000..c1f1199
--- /dev/null
+++ b/src/frontends/telegram/bot.ts
@@ -0,0 +1,96 @@
+import { Bot, Context } from 'grammy';
+import type { NativeAgent } from '../../backends/index.js';
+import type { TelegramConfig } from '../../config/index.js';
+import { isAllowedChat, createMessageHandler, createResetHandler } from './handlers.js';
+
+export interface TelegramBotConfig {
+  telegram: TelegramConfig;
+  agent: NativeAgent;
+}
+
+export function createTelegramBot(config: TelegramBotConfig): Bot {
+  const bot = new Bot(config.telegram.bot_token);
+  const handleMessage = createMessageHandler(config.agent);
+  const handleReset = createResetHandler(config.agent);
+  const allowedChatIds = config.telegram.allowed_chat_ids;
+
+  // Middleware to check chat ID
+  bot.use(async (ctx, next) => {
+    const chatId = ctx.chat?.id;
+    if (chatId === undefined || !isAllowedChat(chatId, allowedChatIds)) {
+      console.log(`Rejected message from unauthorized chat: ${chatId}`);
+      return;
+    }
+    await next();
+  });
+
+  // Command handlers
+  bot.command('start', async (ctx) => {
+    await ctx.reply('Flynn is ready. Send me a message!');
+  });
+
+  bot.command('reset', async (ctx) => {
+    handleReset();
+    await ctx.reply('Conversation reset.');
+  });
+
+  bot.command('status', async (ctx) => {
+    await ctx.reply('Flynn is running.');
+  });
+
+  // Message handler
+  bot.on('message:text', async (ctx) => {
+    const text = ctx.message.text;
+
+    // Show typing indicator
+    await ctx.replyWithChatAction('typing');
+
+    try {
+      const response = await handleMessage(text);
+
+      // Telegram has a 4096 character limit per message
+      if (response.length <= 4096) {
+        await ctx.reply(response, { parse_mode: 'Markdown' });
+      } else {
+        // Split into chunks
+        const chunks = splitMessage(response, 4096);
+        for (const chunk of chunks) {
+          await ctx.reply(chunk, { parse_mode: 'Markdown' });
+        }
+      }
+    } catch (error) {
+      console.error('Error processing message:', error);
+      await ctx.reply('Sorry, an error occurred while processing your message.');
+    }
+  });
+
+  return bot;
+}
+
+function splitMessage(text: string, maxLength: number): string[] {
+  const chunks: string[] = [];
+  let remaining = text;
+
+  while (remaining.length > 0) {
+    if (remaining.length <= maxLength) {
+      chunks.push(remaining);
+      break;
+    }
+
+    // Try to split at a newline
+    let splitIndex = remaining.lastIndexOf('\n', maxLength);
+    if (splitIndex === -1 || splitIndex < maxLength / 2) {
+      // Fall back to splitting at space
+      splitIndex = remaining.lastIndexOf(' ', maxLength);
+    }
+    if (splitIndex === -1 || splitIndex < maxLength / 2) {
+      // Hard split
+      splitIndex = maxLength;
+    }
+
+    chunks.push(remaining.slice(0, splitIndex));
+    remaining = remaining.slice(splitIndex).trimStart();
+  }
+
+  return chunks;
+}
diff --git a/src/frontends/telegram/handlers.test.ts b/src/frontends/telegram/handlers.test.ts
new file mode 100644
index 0000000..8bff60c
--- /dev/null
+++ b/src/frontends/telegram/handlers.test.ts
@@ -0,0 +1,29 @@
+import { describe, it, expect, vi } from 'vitest';
+import { createMessageHandler, isAllowedChat } from './handlers.js';
+import type { NativeAgent } from '../../backends/native/agent.js';
+
+describe('isAllowedChat', () => {
+  it('returns true for allowed chat ID', () => {
+    expect(isAllowedChat(123, [123, 456])).toBe(true);
+  });
+
+  it('returns false for disallowed chat ID', () => {
+    expect(isAllowedChat(789, [123, 456])).toBe(false);
+  });
+});
+
+describe('createMessageHandler', () => {
+  it('processes message and returns response', async () => {
+    const mockAgent: NativeAgent = {
+      process: vi.fn().mockResolvedValue('Agent response'),
+      reset: vi.fn(),
+      getHistory: vi.fn(),
+    } as unknown as NativeAgent;
+
+    const handler = createMessageHandler(mockAgent);
+    const response = await handler('Hello');
+
+    expect(response).toBe('Agent response');
+    expect(mockAgent.process).toHaveBeenCalledWith('Hello');
+  });
+});
diff --git a/src/frontends/telegram/handlers.ts b/src/frontends/telegram/handlers.ts
new file mode 100644
index 0000000..8115458
--- /dev/null
+++ b/src/frontends/telegram/handlers.ts
@@ -0,0 +1,17 @@
+import type { NativeAgent } from '../../backends/index.js';
+
+export function isAllowedChat(chatId: number, allowedIds: number[]): boolean {
+  return allowedIds.includes(chatId);
+}
+
+export function createMessageHandler(agent: NativeAgent): (text: string) => Promise<string> {
+  return async (text: string): Promise<string> => {
+    return agent.process(text);
+  };
+}
+
+export function createResetHandler(agent: NativeAgent): () => void {
+  return (): void => {
+    agent.reset();
+  };
+}
diff --git a/src/frontends/telegram/index.ts b/src/frontends/telegram/index.ts
new file mode 100644
index 0000000..fcec8bf
--- /dev/null
+++ b/src/frontends/telegram/index.ts
@@ -0,0 +1,2 @@
+export { createTelegramBot, type TelegramBotConfig } from './bot.js';
+export { isAllowedChat, createMessageHandler, createResetHandler } from './handlers.js';