name: Auto-generate PR Description

on:
  pull_request:
    types: [opened]
    branches:
      - main

jobs:
  update-pr-description:
    runs-on: ubuntu-latest
    # Only run for PRs from `dev` to `main`
    if: github.head_ref == 'dev' && github.base_ref == 'main'
    permissions:
      pull-requests: write
      contents: read
    steps:
      - name: Checkout
        uses: actions/checkout@v4
        with:
          # Fetch all history for all branches and tags to get the commit messages
          fetch-depth: 0

      - name: Generate PR Body
        id: generate_body
        run: |
          # Get commit messages from the PR's commits
          COMMITS=$(git log origin/${{ github.base_ref }}..origin/${{ github.head_ref }} --pretty=format:"* %s")
          # Set the multiline output for the next step
          {
            echo 'body<<EOF'
            echo "This PR includes the following changes:"
            echo ""
            echo "$COMMITS"
            echo 'EOF'
          } >> "$GITHUB_OUTPUT"

      - name: Update PR Title and Body
        uses: actions/github-script@v7
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          script: |
            github.rest.pulls.update({
              owner: context.repo.owner,
              repo: context.repo.repo,
              pull_number: context.issue.number,
              title: 'Sync `dev` to `main`',
              body: `${{ steps.generate_body.outputs.body }}`
            });