# Remind release PR authors to use merge commit (not squash) so post-release
# develop sync can fast-forward and release PRs do not accumulate phantom commits.

name: release-pr-check

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

permissions:
  pull-requests: write
  contents: read

jobs:
  check:
    if: github.event.pull_request.head.ref == 'develop'
    runs-on: ubuntu-latest
    steps:
      - name: Checkout develop tip
        uses: actions/checkout@v4
        with:
          ref: ${{ github.event.pull_request.head.sha }}
          fetch-depth: 0

      - name: Measure delta vs master
        id: delta
        run: |
          set -euo pipefail
          git fetch origin master
          commits="$(git rev-list --count origin/master..HEAD)"
          echo "commits=${commits}" >> "$GITHUB_OUTPUT"
          echo "Commits on develop not in master: ${commits}"
          git diff origin/master...HEAD --stat | tail -1 || true

      - name: Post merge-method reminder
        uses: actions/github-script@v7
        with:
          script: |
            const marker = '<!-- release-pr-check -->';
            const commits = '${{ steps.delta.outputs.commits }}';
            const body = [
              marker,
              '## Release PR — merge method',
              '',
              `**Commits listed on this PR:** ${commits} (file diff may be smaller — that is normal when squash releases stacked up).`,
              '',
              '### Required',
              'Merge with **Create a merge commit**. Do **not** use **Squash and merge**.',
              '',
              '### Why',
              '- Squash on `master` creates new commit SHAs; `develop` keeps the original squash commits from feature PRs.',
              '- The next release PR then lists old fixes again even though `master` already has them.',
              '- **Merge commit** keeps the same SHAs on both branches; CI **fast-forwards** `develop` to `master` after `chore(release)` — no force-push, local `git pull` on `develop` still works.',
              '',
              '### One-time cleanup',
              'If this PR lists commits from earlier releases (2.0.4, 2.0.5, …), merge once with **merge commit**; post-release sync realigns `develop` with `master` automatically.',
            ].join('\n');

            const { data: comments } = await github.rest.issues.listComments({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: context.issue.number,
            });
            const existing = comments.find((c) => c.body?.includes(marker));
            if (existing) {
              await github.rest.issues.updateComment({
                owner: context.repo.owner,
                repo: context.repo.repo,
                comment_id: existing.id,
                body,
              });
            } else {
              await github.rest.issues.createComment({
                owner: context.repo.owner,
                repo: context.repo.repo,
                issue_number: context.issue.number,
                body,
              });
            }