name: PR check
on:
  # pull_request_target so the check can label PRs from forks. It never checks out
  # or runs PR code: it only reads the PR title and description.
  pull_request_target:
    types: [opened, edited, reopened, ready_for_review]

permissions:
  issues: write
  pull-requests: write

concurrency:
  group: pr-check-${{ github.event.pull_request.number }}
  cancel-in-progress: true

jobs:
  check:
    if: github.event.pull_request.user.type != 'Bot' && !github.event.pull_request.draft
    runs-on: ubuntu-latest
    steps:
      - uses: actions/github-script@v8
        with:
          script: |
            const pr = context.payload.pull_request;
            const LABEL = 'needs-info';
            const MARKER = '<!-- pr-check -->';
            const body = (pr.body || '').replace(/<!--[\s\S]*?-->/g, '');
            const problems = [];

            const verified = body.match(/^##+\s*How it was verified\s*$([\s\S]*?)(?=^##+\s|(?![\s\S]))/im);
            if (!verified || !verified[1].trim()) {
              problems.push('Fill in **How it was verified**: the commands you ran and their results. UI changes need before/after screenshots.');
            }

            const { owner, repo } = context.repo;
            const issue_number = pr.number;
            const comments = await github.paginate(github.rest.issues.listComments, { owner, repo, issue_number });
            const existing = comments.find(c => c.user.type === 'Bot' && c.body.includes(MARKER));
            const labeled = pr.labels.some(l => l.name === LABEL);

            if (problems.length) {
              const text = `${MARKER}\nThanks for the PR. Before review, please update the description (see [CONTRIBUTING.md](https://github.com/${owner}/${repo}/blob/main/CONTRIBUTING.md)):\n\n${problems.map(p => `- ${p}`).join('\n')}\n\nThis check reruns when you edit the description.`;
              if (existing) {
                await github.rest.issues.updateComment({ owner, repo, comment_id: existing.id, body: text });
              } else {
                await github.rest.issues.createComment({ owner, repo, issue_number, body: text });
              }
              if (!labeled) {
                await github.rest.issues.addLabels({ owner, repo, issue_number, labels: [LABEL] });
              }
              return;
            }

            // Only undo what this check did: the label is cleared only when our comment exists.
            if (existing) {
              await github.rest.issues.deleteComment({ owner, repo, comment_id: existing.id });
              if (labeled) {
                await github.rest.issues.removeLabel({ owner, repo, issue_number, name: LABEL }).catch(() => {});
              }
            }