name: Create Cherrypick PR

on:
  pull_request:
      types:
        - closed
      branches:
        # TODO: Extract this to an env variable?
        - 'master'

env:
  # TODO: Add a way to handle multiple potential cherrypick targets.
  TARGET_BRANCH: '4.3'
  USERNAME: 'Godot Organization'
  EMAIL: 'noreply@godotengine.org'

jobs:
  Create-cherrypick-PR:
    # The cherrypick label is hardcoded because `contains()` doesn't seem to be able to use an environment variable as a second argument.
    if: ${{ github.event.pull_request.merged == true && contains( github.event.pull_request.labels.*.name, 'cherrypick:4.3' ) }}
    runs-on: ubuntu-24.04
    timeout-minutes: 10
    env:
      # "Ternary" hack featured in the official docs.
      # When using "Squash and merge", the commit hash is the last merge commit of the pull request merge branch.
      # When using "Merge", the commit hash is the last commit to the head branch of the pull request.
      # This is mildly error-prone, since in theory we could merge multiple commits without squashing.
      # We are relying on human review of the generated PRs to catch that.
      COMMIT_HASH: ${{ github.event.pull_request.commits > 1 && github.sha || github.event.pull_request.head.sha }}
      PR_NUMBER: ${{ github.event.number }}

    permissions:
      contents: write
      pull-requests: write

    steps:
    - name: Checkout
      uses: actions/checkout@v5
      with:
        ref: ${{ env.TARGET_BRANCH }}

    - name: Cherrypick Commit
      id: cherrypick_commit
      continue-on-error: true
      # TODO: Maybe only fetch some branches?
      run: |
        git config user.name "${{ env.USERNAME }}"
        git config user.email "${{ env.EMAIL }}"
        git fetch
        git cherry-pick -m 1 ${{ env.COMMIT_HASH }}

    - name: Create Pull Request
      if: steps.cherrypick_commit.outcome == 'success'
      uses: peter-evans/create-pull-request@v8
      with:
        commit-message: 'Cherrypick to ${{ env.TARGET_BRANCH }}'
        branch: 'cherrypick-${{ env.PR_NUMBER }}-${{ env.TARGET_BRANCH }}'
        delete-branch: true

        # Configure the commit author.
        author: '${{ env.USERNAME }} <${{ env.EMAIL }}>'
        committer: '${{ env.USERNAME }} <${{ env.EMAIL }}>'

        # Configure the pull request.
        title: 'Cherrypick ${{ env.PR_NUMBER }} to ${{ env.TARGET_BRANCH }}'
        body: 'Cherrypick #${{ env.PR_NUMBER }} to ${{ env.TARGET_BRANCH }}.'
        # TODO: Only add the bug or enhancement label, depending on which the original PR uses.
        labels: 'bug,enhancement'

    - name: Handle failure
      if: steps.cherrypick_commit.outcome == 'failure'
      run: |
        echo "Can't automatically cherrypick. Potential causes:"
        echo "- PR has multiple commits. Did you squash and merge?"
        echo "- Cherrypick did not apply cleanly and can't be auto-merged."