name: Require Linked Issue

# Ensure every pull request is linked to a REAL GitHub issue in this repo.
# A PR passes when it links an issue via any of:
#   * GitHub's "Development" sidebar (closing issue reference), or
#   * a closing keyword in the body/title (e.g. "Closes #123"), or
#   * a plain mention (#123 / owner/repo#123) or full issue URL.
# Any referenced number is verified against the API: it must resolve to an
# existing issue (not a pull request) in this repository.

on:
  pull_request:
    types: [opened, edited, reopened, synchronize, ready_for_review]

permissions:
  contents: read
  pull-requests: read
  issues: read

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

jobs:
  require-issue:
    name: Require Linked Issue
    runs-on: ubuntu-latest
    timeout-minutes: 5
    steps:
      - name: Check for a linked, existing issue
        uses: actions/github-script@v7
        with:
          script: |
            const pr = context.payload.pull_request;
            if (!pr) {
              core.info('No pull_request payload; skipping.');
              return;
            }

            const owner = context.repo.owner;
            const repo = context.repo.repo;
            const text = `${pr.title || ''}\n\n${pr.body || ''}`;

            // Collect candidate issue numbers that belong to THIS repo.
            const candidates = new Set();

            // Full issue URLs: https://github.com/owner/repo/issues/123
            const urlRe = /https?:\/\/github\.com\/([\w.-]+)\/([\w.-]+)\/issues\/(\d+)/gi;
            for (const m of text.matchAll(urlRe)) {
              if (m[1].toLowerCase() === owner.toLowerCase() &&
                  m[2].toLowerCase() === repo.toLowerCase()) {
                candidates.add(Number(m[3]));
              }
            }

            // owner/repo#123 or bare #123 (bare assumed to be this repo).
            const refRe = /(?:([\w.-]+)\/([\w.-]+))?#(\d+)/g;
            for (const m of text.matchAll(refRe)) {
              const refOwner = m[1];
              const refRepo = m[2];
              const num = Number(m[3]);
              if (!refOwner && !refRepo) {
                candidates.add(num); // bare #123 -> this repo
              } else if (refOwner?.toLowerCase() === owner.toLowerCase() &&
                         refRepo?.toLowerCase() === repo.toLowerCase()) {
                candidates.add(num);
              }
            }

            // Issues linked via the Development sidebar (closing references).
            try {
              const query = `query($owner:String!, $repo:String!, $number:Int!) {
                repository(owner:$owner, name:$repo) {
                  pullRequest(number:$number) {
                    closingIssuesReferences(first: 10) { nodes { number } }
                  }
                }
              }`;
              const result = await github.graphql(query, { owner, repo, number: pr.number });
              const nodes = result?.repository?.pullRequest?.closingIssuesReferences?.nodes || [];
              for (const n of nodes) candidates.add(Number(n.number));
            } catch (err) {
              core.warning(`Could not query closing issue references: ${err}`);
            }

            // Verify at least one candidate is a real issue (not a PR, not this PR).
            let linkedIssue = null;
            for (const num of candidates) {
              if (num === pr.number) continue;
              try {
                const { data } = await github.rest.issues.get({ owner, repo, issue_number: num });
                if (!data.pull_request) { // issues have no pull_request field
                  linkedIssue = num;
                  break;
                }
              } catch (err) {
                // 404 -> number doesn't exist; ignore and keep checking.
              }
            }

            if (!linkedIssue) {
              core.setFailed(
                'This PR must be linked to an existing GitHub issue in this repository. ' +
                  'Add a closing keyword (e.g. "Closes #123") to the PR description, link an ' +
                  'issue via the Development sidebar, or reference an existing issue number ' +
                  '(e.g. "#123"). If no issue exists yet, please open one first.'
              );
              return;
            }

            core.info(`Linked to existing issue #${linkedIssue}. ✅`);