name: Issue area labeler

# Adds area labels to new/edited issues based on keyword regexes in
# .github/issue-labeler.yml. Additive only (addLabels never removes): it
# never touches a label a maintainer set by hand. Base bug/enhancement
# labels already come from the issue forms.
#
# Implemented with first-party actions/github-script (not a third-party
# labeler action) so every pattern is compiled as a JavaScript RegExp with
# the `i` flag applied centrally — inline `(?i)` groups are PCRE-only and
# threw `SyntaxError: Invalid group` on every issue (#764). A pattern that
# fails to compile now fails the run loudly instead of silently no-oping.

on:
  issues:
    types: [opened, edited]

permissions:
  contents: read

jobs:
  triage:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      issues: write
    steps:
      - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
      - uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
        with:
          script: |
            const fs = require('fs');
            const text = [context.payload.issue.title, context.payload.issue.body]
              .filter(Boolean).join('\n');
            const rules = [];
            const bad = [];
            // Config format: one rule per line — "label": 'regex' (see the
            // header comment in .github/issue-labeler.yml).
            for (const line of fs.readFileSync('.github/issue-labeler.yml', 'utf8').split('\n')) {
              const m = line.match(/^"([^"]+)":\s*'(.*)'\s*$/);
              if (!m) continue;
              try { rules.push({ label: m[1], re: new RegExp(m[2], 'i') }); }
              catch (e) { bad.push(`${m[1]}: ${e.message}`); }
            }
            if (rules.length === 0 && bad.length === 0) {
              core.setFailed('no labeling rules parsed from .github/issue-labeler.yml');
              return;
            }
            const labels = rules.filter(r => r.re.test(text)).map(r => r.label);
            if (labels.length) {
              await github.rest.issues.addLabels({
                owner: context.repo.owner,
                repo: context.repo.repo,
                issue_number: context.issue.number,
                labels,
              });
            }
            core.info(`matched: ${labels.join(', ') || '(none)'}`);
            if (bad.length) core.setFailed(`invalid label regex(es): ${bad.join('; ')}`);