name: Pre-Commit Checks

# Triggers on pull requests and pushes to master or main branches
on:
  pull_request:
  push:
    branches: [master, main]

jobs:
  pre-commit:
    runs-on: ubuntu-latest
    steps:
      # Fetches full Git history to enable branch comparison
      - name: Checkout code
        uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Set up Python
        uses: actions/setup-python@v5
        with:
          python-version: "3.x"

      - name: Install pre-commit
        run: pip install pre-commit

      # Identifies changed files using git diff
      - name: Get modified files
        id: modified_files
        shell: bash
        run: |
          if [ "${{ github.event_name }}" == "pull_request" ]; then
            BASE_BRANCH="${{ github.base_ref }}"
            git fetch origin "$BASE_BRANCH" --depth=1
            MODIFIED_FILES="$(git diff --name-only "origin/$BASE_BRANCH...HEAD" || echo "")"
          else
            MODIFIED_FILES="$(git diff --name-only "${{ github.event.before }}" "${{ github.sha }}" || echo "")"
          fi
          if [ -n "$MODIFIED_FILES" ]; then
            echo "Running pre-commit on changed files:"
            echo "$MODIFIED_FILES"
            echo "files=$(echo "$MODIFIED_FILES" | tr '\n' ' ')" >> "$GITHUB_OUTPUT"
            echo "has_files=true" >> "$GITHUB_OUTPUT"
          else
            echo "No modified files to check."
            echo "has_files=false" >> "$GITHUB_OUTPUT"
          fi
      - name: Run pre-commit on modified files
        if: steps.modified_files.outputs.has_files == 'true'
        run: pre-commit run --files ${{ steps.modified_files.outputs.files }}