name: PR title labels

on:
  pull_request_target:
    types: [opened, edited, reopened]

permissions:
  pull-requests: write

jobs:
  label:
    runs-on: ubuntu-latest
    timeout-minutes: 5
    steps:
      # Run only this trusted script; never check out or execute PR head code.
      - uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8
        with:
          script: |
            if (context.payload.action === 'edited' && !context.payload.changes?.title) return;

            // Fetch current metadata so delayed events do not use an outdated title or labels.
            const { data: pr } = await github.rest.pulls.get({
              ...context.repo,
              pull_number: context.issue.number,
            });
            const match = /^(fix|bug|docs|feat|feature)(?:\([^()\r\n]+\))?[:：]/i.exec(pr.title.trim());
            if (!match) return;

            const label = {
              fix: 'bug', bug: 'bug', docs: 'documentation', feat: 'enhancement', feature: 'enhancement',
            }[match[1].toLowerCase()];
            if (pr.labels.some(({ name }) => name.toLowerCase() === label)) return;

            // Only use labels already defined in this repository.
            try {
              await github.rest.issues.getLabel({ ...context.repo, name: label });
            } catch (error) {
              if (error.status !== 404) throw error;
              core.info(`Skipping missing repository label: ${label}`);
              return;
            }
            await github.rest.issues.addLabels({
              ...context.repo,
              issue_number: context.issue.number,
              labels: [label],
            });