name: Enable auto-merge

on:
  pull_request:
    types: [opened, ready_for_review, reopened, synchronize]
    branches: [main]

concurrency:
  group: enable-auto-merge-${{ github.event.pull_request.number }}
  cancel-in-progress: true

permissions:
  contents: write
  pull-requests: write

jobs:
  enable:
    if: >-
      github.event.pull_request.draft == false
      && github.event.pull_request.head.repo.full_name == github.repository
      && github.event.pull_request.user.login != 'dependabot[bot]'
      && github.event.pull_request.user.login != 'renovate[bot]'
    runs-on: ubuntu-latest
    steps:
      - name: Enable squash auto-merge
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          PR: ${{ github.event.pull_request.number }}
          REPO: ${{ github.repository }}
        run: |
          set -euo pipefail
          method="$(gh pr view "$PR" --repo "$REPO" --json autoMergeRequest --jq '.autoMergeRequest.mergeMethod // empty')"
          # Merge queue requires squash. `gh pr merge --auto` with no method
          # records MERGE and never enqueues.
          if [ "$method" = "MERGE" ] || [ "$method" = "REBASE" ]; then
            gh pr merge "$PR" --repo "$REPO" --disable-auto
          fi
          if ! out=$(gh pr merge "$PR" --repo "$REPO" --squash --auto 2>&1); then
            echo "$out"
            if [ "$(gh pr view "$PR" --repo "$REPO" --json autoMergeRequest --jq '.autoMergeRequest.mergeMethod // empty')" = "SQUASH" ]; then
              echo "squash auto-merge already enabled"
              exit 0
            fi
            exit 1
          fi
          printf '%s\n' "$out"