Introduction to CI/CD

# .github/workflows/ci.yml
name: CI

on:
  push:
    branches: [main, develop]
  pull_request:
    branches: [main]

jobs:
  test:
    runs-on: ubuntu-latest

    steps:
      - name: Checkout code
        uses: actions/checkout@v4

      - name: Set up Python
        uses: actions/setup-python@v5
        with:
          python-version: '3.12'

      - name: Cache pip packages
        uses: actions/cache@v4
        with:
          path: ~/.cache/pip
          key: ${{ runner.os }}-pip-${{ hashFiles('requirements.txt') }}

      - name: Install dependencies
        run: pip install -r requirements.txt

      - name: Run linter
        run: ruff check .

      - name: Run tests with coverage
        run: pytest --cov=. --cov-report=xml

      - name: Upload coverage
        uses: codecov/codecov-action@v4

# Add to the same file — deploy job runs after test passes
  deploy:
    needs: test        # only run if test job passes
    runs-on: ubuntu-latest
    if: github.ref == 'refs/heads/main'  # only deploy from main

    steps:
      - uses: actions/checkout@v4

      - name: Build Docker image
        run: |
          docker build -t myapp:${{ github.sha }} .
          docker tag myapp:${{ github.sha }} myapp:latest

      - name: Push to registry
        run: |
          echo ${{ secrets.DOCKER_PASSWORD }} | docker login -u ${{ secrets.DOCKER_USERNAME }} --password-stdin
          docker push myapp:${{ github.sha }}
          docker push myapp:latest

      - name: Deploy to staging
        run: |
          # SSH to server and pull new image
          ssh -o StrictHostKeyChecking=no deploy@${{ secrets.STAGING_HOST }} \
            "docker pull myapp:latest && docker compose up -d"