name: Remove Unused Labels
on:
  workflow_dispatch:

jobs:
  cleanup:
    runs-on: ubuntu-latest
    permissions:
      issues: write
      pull-requests: write
      contents: read
    steps:
      - name: Checkout Repository
        uses: actions/checkout@v4

      - name: Fetch All Issues and PRs
        id: fetch_issues_prs
        uses: actions/github-script@v7.0.1
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          script: |
            const issues = await github.paginate(github.rest.issues.listForRepo, {
              owner: context.repo.owner,
              repo: context.repo.repo,
              state: 'all',
              per_page: 100
            });

            const labelsInUse = new Set();
            issues.forEach(issue => {
              issue.labels.forEach(label => {
                labelsInUse.add(label.name);
              });
            });

            return JSON.stringify(Array.from(labelsInUse));
          result-encoding: string

      - name: Fetch All Labels
        id: fetch_labels
        uses: actions/github-script@v7.0.1
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          script: |
            const labels = await github.paginate(github.rest.issues.listLabelsForRepo, {
              owner: context.repo.owner,
              repo: context.repo.repo,
              per_page: 100
            });

            return JSON.stringify(labels.map(label => label.name));
          result-encoding: string

      - name: Remove Unused Labels
        uses: actions/github-script@v7.0.1
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          script: |
            const labelsInUse = new Set(JSON.parse(process.env.LABELS_IN_USE));
            const allLabels = JSON.parse(process.env.ALL_LABELS);

            const unusedLabels = allLabels.filter(label => !labelsInUse.has(label));

            for (const label of unusedLabels) {
              await github.rest.issues.deleteLabel({
                owner: context.repo.owner,
                repo: context.repo.repo,
                name: label
              });
              console.log(`Deleted label: ${label}`);
            }
        env:
          LABELS_IN_USE: ${{ steps.fetch_issues_prs.outputs.result }}
          ALL_LABELS: ${{ steps.fetch_labels.outputs.result }}