DESCO Prepaid Balance Notification Worker

A production-ready Cloudflare Worker that automatically checks DESCO prepaid electricity meter balances daily and sends notifications via Telegram.

Features

• ✅ Automated Daily Checks: Runs every day at 1:00 AM (Asia/Dhaka timezone)
• ✅ Multiple Accounts: Supports checking multiple DESCO account numbers
• ✅ Telegram Notifications: Sends formatted balance updates to your Telegram chat
• ✅ Retry Logic: Implements exponential backoff for API failures
• ✅ Manual Trigger: Test anytime via /run endpoint
• ✅ Error Handling: Robust error handling with detailed logging
• ✅ Zero Dependencies: Uses only Cloudflare Workers runtime
• ✅ Multiple Account Support: You Can get balance notification for multiple accounts

Example Telegram Message Output

🔌 DESCO Prepaid Balance Update  
🕐 20 Oct 2025, 1:00 AM (Asia/Dhaka)

• Account 12345511 → 374.04 ৳  
• Account 12345512 → 250.32 ৳

💰 Total Balance: 624.36 ৳

Prerequisites

• Node.js (v18 or later)
• npm or yarn
• Cloudflare account (free tier works)
• Telegram bot token and chat ID

Setup Instructions

1. Clone and Install Dependencies

cd ./desco-balance-notification
npm install

2. Create a Telegram Bot

1. Open Telegram and search for @BotFather
2. Send /newbot and follow the instructions
3. Save the bot token (looks like 123456789:ABCdefGHIjklMNOpqrsTUVwxyz)
4. Start a chat with your new bot and send any message
5. Get your chat ID by visiting:

   https://api.telegram.org/bot<YOUR_BOT_TOKEN>/getUpdates
   

   Look for "chat":{"id":123456789} in the response

3. Configure Environment Secrets

Set your secrets using the Wrangler CLI:

# Set Telegram Bot Token
wrangler secret put TELEGRAM_BOT_TOKEN
# When prompted, paste your bot token

# Set Telegram Chat ID
wrangler secret put TELEGRAM_CHAT_ID
# When prompted, paste your chat ID (e.g., 123456789)

# Set Account Numbers (comma-separated)
wrangler secret put ACCOUNT_NUMBERS
# When prompted, enter: 12345511,12345512,12345513
# Or as JSON array: ["12345511","12345512","12345513"]

Alternative: Use npm scripts

npm run secret:telegram-token
npm run secret:chat-id
npm run secret:accounts

4. Test Locally (Optional)

# Start local development server
npm run dev

# In another terminal, test the endpoint
curl http://localhost:8787/run

5. Deploy to Cloudflare

npm run deploy

After deployment, you'll get a URL like:

https://desco-balance-notification.<your-subdomain>.workers.dev

Usage

Automatic Daily Checks

The worker runs automatically every day at 1:00 AM Asia/Dhaka time (19:00 UTC).

Manual Trigger

Test the worker anytime by visiting:

https://desco-balance-notification.<your-subdomain>.workers.dev/run

Or use curl:

curl https://desco-balance-notification.<your-subdomain>.workers.dev/run

Health Check

curl https://desco-balance-notification.<your-subdomain>.workers.dev/health

Configuration

Cron Schedule

The cron trigger is configured in wrangler.toml:

[triggers]
crons = ["0 19 * * *"]  # 1:00 AM Asia/Dhaka (UTC+6)

To change the schedule, modify the cron expression:

• 0 19 * * * = 1:00 AM Dhaka
• 0 13 * * * = 7:00 PM Dhaka
• 0 0 * * * = 6:00 AM Dhaka

Multiple Accounts

You can specify account numbers in two formats:

Comma-separated:

12345511,12345512,12345513

JSON array:

["12345511","12345512","12345513"]

Project Structure

desco-balance-notification/
├── src/
│   └── index.ts           # Main worker code
├── wrangler.toml          # Cloudflare Workers configuration
├── package.json           # Dependencies and scripts
├── tsconfig.json          # TypeScript configuration
├── .gitignore            # Git ignore rules
└── README.md             # This file

API Details

DESCO API Endpoint

GET https://prepaid.desco.org.bd/api/unified/customer/getBalance?accountNo=12345511

Response:

{
  "code": 200,
  "desc": "OK",
  "data": {
    "accountNo": "12345511",
    "meterNo": "1234556025",
    "balance": 374.04,
    "currentMonthConsumption": null,
    "readingTime": "2025-10-20"
  }
}

Telegram API

POST https://api.telegram.org/bot<token>/sendMessage

Monitoring

View Logs

# Stream real-time logs
npm run tail

# Or directly with wrangler
wrangler tail

Check Cron Triggers

Visit the Cloudflare Dashboard:

1. Go to Workers & Pages
2. Select your worker
3. Click on "Triggers" tab
4. View cron trigger history

Troubleshooting

Worker not sending messages?

1. Check secrets are set correctly:

   wrangler secret list

2. Verify bot token and chat ID:

   curl "https://api.telegram.org/bot<YOUR_TOKEN>/getMe"

3. Check worker logs:

   npm run tail

API timeout errors?

The worker implements retry logic with exponential backoff. If DESCO API is slow:

• Default timeout: 10 seconds
• Retries: 3 attempts
• Backoff: 1s, 2s, 3s

Cron not triggering?

• Cron triggers only work on deployed workers (not local dev)
• Check the Cloudflare dashboard for trigger history
• Verify the cron expression in wrangler.toml

Security Notes

• ✅ Secrets are stored securely in Cloudflare's encrypted storage
• ✅ Never commit secrets to git
• ✅ Account numbers are treated as sensitive data
• ✅ Use Telegram bot tokens, not user tokens

Cost

Cloudflare Workers Free Tier includes:

• 100,000 requests/day
• 10ms CPU time per request

This worker uses:

• 1 cron trigger/day
• ~2-5ms CPU time per run
• Well within free tier limits

License

MIT

Support

For issues or questions:

1. Check the Cloudflare Workers docs
2. Review the worker logs with wrangler tail
3. Test the DESCO API directly to verify it's working

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