lgtm-cat-github-app

A GitHub App that automatically posts a cat LGTM image when a pull request is approved.

Install

Install GitHub App

Features

• Automatic: Just approve a PR - no manual action needed
• Random images: A different cat LGTM image every time from lgtmeow.com
• No duplicates: Posts only once per PR, even with multiple approvals

How it works

Local Development Setup

Prerequisites

• Node.js >= 22
• npm
• GitHub account

1. Install dependencies

npm install

2. Set up smee.io

1. Go to https://smee.io
2. Click "Start a new channel"
3. Copy the generated URL

3. Create a GitHub App

1. Go to GitHub Settings > Developer settings > GitHub Apps
2. Click "New GitHub App"
3. Configure:
   • App name: lgtm-cat-local-dev (or any unique name)
   • Homepage URL: https://github.com/nekochans/lgtm-cat-github-app
   • Webhook URL: Your smee.io URL
   • Webhook secret: development
   • Permissions:
     • Pull requests: Read & write
   • Subscribe to events:
     • Pull request review
4. After creation:
   • Note the App ID
   • Generate and download a Private Key
5. Install the app on a test repository

4. Configure environment variables

cp .env.example .env

Edit .env:

APP_ID=<your-app-id>
PRIVATE_KEY_PATH=./private-key.pem
WEBHOOK_SECRET=development
WEBHOOK_PROXY_URL=<your-smee-url>
LGTMEOW_BASE_URL=https://api.lgtmeow.com

Place the downloaded private key file as private-key.pem in the project root.

5. Build and run

npm run build
npm start

6. Test

1. Create a PR in the repository where the app is installed
2. Approve the PR
3. Check the terminal logs for the pull_request_review.submitted event

Scripts

• npm run build - Compile TypeScript
• npm start - Start the app
• npm run dev - Build and start
• npm run lint - Run linter
• npm run fix - Auto-fix lint and format issues

Code Quality

This project uses ultracite for linting and formatting.

# Check for lint issues
npm run lint

# Auto-fix issues
npm run fix

Production Deployment (Fly.io)

Prerequisites

• Fly.io CLI
• Fly.io account

1. Login to Fly.io

fly auth login

2. Create the app

fly apps create lgtm-cat-bot

3. Set secrets

fly secrets set APP_ID="your-github-app-id"
fly secrets set PRIVATE_KEY="$(cat ./private-key.pem)"
fly secrets set WEBHOOK_SECRET="your-webhook-secret"

4. Deploy

fly deploy

5. Update GitHub App Webhook URL

Update your GitHub App settings:

• Webhook URL: https://lgtm-cat-bot.fly.dev/api/github/webhooks

Useful commands

# Check app status
fly status

# View logs
fly logs

# SSH into the machine
fly ssh console