## Bot Architecture

### Stack Options
| Language | Library | Best For |
|----------|---------|----------|
| Node.js | telegraf | Most projects |
| Node.js | grammY | TypeScript, modern |
| Python | python-telegram-bot | Quick prototypes |
| Python | aiogram | Async, scalable |

### Basic Telegraf Setup
```javascript
import { Telegraf } from 'telegraf';

const bot = new Telegraf(process.env.BOT_TOKEN);

// Command handlers
bot.start((ctx) => ctx.reply('Welcome!'));
bot.help((ctx) => ctx.reply('How can I help?'));

// Text handler
bot.on('text', (ctx) => {
  ctx.reply(`You said: ${ctx.message.text}`);
});

// Launch
bot.launch();

// Graceful shutdown
process.once('SIGINT', () => bot.stop('SIGINT'));
process.once('SIGTERM', () => bot.stop('SIGTERM'));

telegram-bot/
├── src/
│   ├── bot.js           # Bot initialization
│   ├── commands/        # Command handlers
│   │   ├── start.js
│   │   ├── help.js
│   │   └── settings.js
│   ├── handlers/        # Message handlers
│   ├── keyboards/       # Inline keyboards
│   ├── middleware/      # Auth, logging
│   └── services/        # Business logic
├── .env
└── package.json

### Inline Keyboards

Interactive button interfaces

**When to use**: When building interactive bot flows

```python
## Inline Keyboards

### Basic Keyboard
```javascript
import { Markup } from 'telegraf';

bot.command('menu', (ctx) => {
  ctx.reply('Choose an option:', Markup.inlineKeyboard([
    [Markup.button.callback('Option 1', 'opt_1')],
    [Markup.button.callback('Option 2', 'opt_2')],
    [
      Markup.button.callback('Yes', 'yes'),
      Markup.button.callback('No', 'no'),
    ],
  ]));
});

// Handle button clicks
bot.action('opt_1', (ctx) => {
  ctx.answerCbQuery('You chose Option 1');
  ctx.editMessageText('You selected Option 1');
});

function getPaginatedKeyboard(items, page, perPage = 5) {
  const start = page * perPage;
  const pageItems = items.slice(start, start + perPage);

  const buttons = pageItems.map(item =>
    [Markup.button.callback(item.name, `item_${item.id}`)]
  );

  const nav = [];
  if (page > 0) nav.push(Markup.button.callback('◀️', `page_${page-1}`));
  if (start + perPage < items.length) nav.push(Markup.button.callback('▶️', `page_${page+1}`));

  return Markup.inlineKeyboard([...buttons, nav]);
}

### Bot Monetization

Making money from Telegram bots

**When to use**: When planning bot revenue

```javascript
## Bot Monetization

### Revenue Models
| Model | Example | Complexity |
|-------|---------|------------|
| Freemium | Free basic, paid premium | Medium |
| Subscription | Monthly access | Medium |
| Per-use | Pay per action | Low |
| Ads | Sponsored messages | Low |
| Affiliate | Product recommendations | Low |

### Telegram Payments
```javascript
// Create invoice
bot.command('buy', (ctx) => {
  ctx.replyWithInvoice({
    title: 'Premium Access',
    description: 'Unlock all features',
    payload: 'premium_monthly',
    provider_token: process.env.PAYMENT_TOKEN,
    currency: 'USD',
    prices: [{ label: 'Premium', amount: 999 }], // $9.99
  });
});

// Handle successful payment
bot.on('successful_payment', (ctx) => {
  const payment = ctx.message.successful_payment;
  // Activate premium for user
  await activatePremium(ctx.from.id);
  ctx.reply('🎉 Premium activated!');
});

Free tier:
- 10 uses per day
- Basic features
- Ads shown

Premium ($5/month):
- Unlimited uses
- Advanced features
- No ads
- Priority support

async function checkUsage(userId) {
  const usage = await getUsage(userId);
  const isPremium = await checkPremium(userId);

  if (!isPremium && usage >= 10) {
    return { allowed: false, message: 'Daily limit reached. Upgrade?' };
  }
  return { allowed: true };
}

## Anti-Patterns

### ❌ Blocking Operations

**Why bad**: Telegram has timeout limits.
Users think bot is dead.
Poor experience.
Requests pile up.

**Instead**: Acknowledge immediately.
Process in background.
Send update when done.
Use typing indicator.

### ❌ No Error Handling

**Why bad**: User