presubmit-python.yml

---
name: Presubmit (Python)

on: # yamllint disable-line rule:truthy
  pull_request:
    branches: ["main"]

jobs:
  build-python:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        python-version: ["3.10"]

    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0 # Fetch full history for git diff

      - name: Detect changed Python files
        id: detect-changes
        run: |
          # Get list of changed files
          if [ "${{ github.event_name }}" = "pull_request" ]; then
            # For PR, compare with base branch
            CHANGED_FILES=$(git diff --name-only \
              ${{ github.event.pull_request.base.sha }}..HEAD)
          else
            # For push, compare with previous commit
            if [ "${{ github.event.before }}" = \
              "0000000000000000000000000000000000000000" ]; then
              # First commit in repo
              CHANGED_FILES=$(git diff --name-only --diff-filter=A HEAD)
            else
              CHANGED_FILES=$(git diff --name-only \
                ${{ github.event.before }}..HEAD)
            fi
          fi

          echo "All changed files:"
          echo "$CHANGED_FILES"

          # Filter for Python files only
          CHANGED_PYTHON_FILES=$(echo "$CHANGED_FILES" | \
            grep '\.py$' || true)

          # Filter for Python files specifically in the problems directory
          CHANGED_PYTHON_PROBLEMS_FILES=$(echo "$CHANGED_PYTHON_FILES" | \
            grep -E '^problems/' || true)

          # Extract unique problem directories from changed Python files
          CHANGED_PROBLEMS=$(echo "$CHANGED_PYTHON_PROBLEMS_FILES" | \
            grep -E '^problems/[^/]+/' | cut -d'/' -f2 | \
            sort -u | tr '\n' ' ' || true)

          # Check if requirements.txt or Python-related config files changed
          PYTHON_CONFIG_CHANGES=$(echo "$CHANGED_FILES" | \
            grep -E '(requirements\.txt|setup\.py|pyproject\.toml)$' || true)

          echo "Changed Python files:"
          echo "$CHANGED_PYTHON_FILES"
          echo "Changed Python files in problems/:"
          echo "$CHANGED_PYTHON_PROBLEMS_FILES"
          echo "Changed problems: $CHANGED_PROBLEMS"
          echo "Python config changes: $PYTHON_CONFIG_CHANGES"

          # Set outputs
          echo "changed_problems=$CHANGED_PROBLEMS" >> $GITHUB_OUTPUT
          echo "has_python_changes=$([ -n "$CHANGED_PYTHON_PROBLEMS_FILES" ] && \
            echo 'true' || echo 'false')" >> $GITHUB_OUTPUT
          echo "has_python_config_changes=$([ -n "$PYTHON_CONFIG_CHANGES" ] && \
            echo 'true' || echo 'false')" >> $GITHUB_OUTPUT
          echo "should_run_all_tests=$([ -n "$PYTHON_CONFIG_CHANGES" ] && \
            echo 'true' || echo 'false')" >> $GITHUB_OUTPUT

      - name: Set up Python ${{ matrix.python-version }}
        if: >
          steps.detect-changes.outputs.has_python_changes == 'true' ||
          steps.detect-changes.outputs.has_python_config_changes == 'true'
        uses: actions/setup-python@v5
        with:
          python-version: ${{ matrix.python-version }}
          cache: "pip"

      - name: Install dependencies
        if: >
          steps.detect-changes.outputs.has_python_changes == 'true' ||
          steps.detect-changes.outputs.has_python_config_changes == 'true'
        run: |
          python -m pip install --upgrade pip
          pip install -r requirements.txt

      - name: Lint Python code
        if: steps.detect-changes.outputs.has_python_changes == 'true'
        run: make lint-py

      - name: Run Python tests for changed problems
        if: >
          steps.detect-changes.outputs.changed_problems != '' &&
          steps.detect-changes.outputs.should_run_all_tests == 'false'
        run: |
          PROBLEMS="${{ steps.detect-changes.outputs.changed_problems }}"
          echo "Running tests for changed problems: $PROBLEMS"

          for problem in $PROBLEMS; do
            echo "Testing problem: $problem"
            # Convert snake_case to kebab-case for make target
            kebab_case=$(echo "$problem" | sed 's/_/-/g')
            make test-py:$kebab_case || exit 1
          done

      - name: Run all Python tests (dependencies changed)
        if: steps.detect-changes.outputs.should_run_all_tests == 'true'
        run: |
          echo "Running all tests due to Python configuration changes"
          make test-py:all

      - name: Summary
        if: always()
        run: |
          echo "## Test Summary" >> $GITHUB_STEP_SUMMARY

          if [ "${{ steps.detect-changes.outputs.has_python_changes }}" = \
            "false" ] && \
            [ "${{ steps.detect-changes.outputs.has_python_config_changes }}" \
            = "false" ]; then
            echo "- No Python files in problems/ changed - skipped all tasks" >> \
            $GITHUB_STEP_SUMMARY
          elif [ "${{ steps.detect-changes.outputs.should_run_all_tests }}" = \
            "true" ]; then
            echo "- Ran all tests due to config changes" >> $GITHUB_STEP_SUMMARY
          elif [ "${{ steps.detect-changes.outputs.changed_problems }}" != \
            "" ]; then
            problems="${{ steps.detect-changes.outputs.changed_problems }}"
            echo "- Ran targeted tests for: $problems" >> \
            $GITHUB_STEP_SUMMARY
          else
            echo "- No tests needed (no problem files changed)" >> \
            $GITHUB_STEP_SUMMARY
          fi