name: PR Labels

on:
  pull_request_target:
    types:
      - opened
      - edited
      - synchronize
      - labeled
      - unlabeled
      - reopened
      - ready_for_review
    branches:
      - main

permissions:
  pull-requests: write

jobs:
  apply_label:
    name: Apply
    runs-on: ubuntu-latest
    if: github.event.pull_request.user.type != 'Bot'
    steps:
      - name: 🏷 Apply label from PR description checkbox
        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3
        with:
          script: |
            const known = [
              'breaking-change', 'bugfix', 'refactor',
              'new-feature', 'enhancement', 'maintenance',
              'ci', 'dependencies', 'documentation',
            ];

            const { owner, repo } = context.repo;
            const issue_number = context.payload.pull_request.number;
            const current = (context.payload.pull_request.labels || [])
              .map(l => l.name);

            const alreadyLabelled = current.filter(n => known.includes(n));
            if (alreadyLabelled.length === 1) {
              core.info(
                `Skipping: PR already labelled '${alreadyLabelled[0]}'.`
              );
              return;
            }

            const body = context.payload.pull_request.body || '';
            const re = /^\s*-\s*\[x\][^`\n]*`([^`]+)`/gim;
            const ticked = [];
            for (const m of body.matchAll(re)) {
              const name = m[1];
              if (known.includes(name) && !ticked.includes(name)) {
                ticked.push(name);
              }
            }

            if (ticked.length === 0) {
              core.setFailed(
                'No "Types of changes" checkbox is ticked in the PR ' +
                'description. Edit the description and tick exactly ' +
                'one box so this PR can be release-noted.'
              );
              return;
            }
            if (ticked.length > 1) {
              core.setFailed(
                `Multiple "Types of changes" checkboxes are ticked ` +
                `(${ticked.join(', ')}). Tick exactly one.`
              );
              return;
            }

            const desired = ticked[0];

            for (const name of current) {
              if (known.includes(name) && name !== desired) {
                await github.rest.issues.removeLabel({
                  owner, repo, issue_number, name,
                }).catch(() => {});
              }
            }
            if (!current.includes(desired)) {
              await github.rest.issues.addLabels({
                owner, repo, issue_number, labels: [desired],
              });
            }