name: Flag new top-level entries

# BCQuality keeps a deliberately small repository root. New top-level folders
# or files are almost always unintended — a stray export, a tool's scratch
# directory, or content that meant to land inside an existing layer (e.g.
# /community/knowledge/). PR #55 leaked exactly this kind of stray folder.
#
# Unlike the custom-layer guard, this workflow does NOT close the PR. It only
# posts a single advisory comment so a maintainer (and the author) can eyeball
# the addition. It reads the PR's file LIST via the API and never checks out or
# runs PR code.

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

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

jobs:
  flag:
    if: github.repository == 'microsoft/BCQuality'
    runs-on: ubuntu-latest
    steps:
      - name: Check out repository
        uses: actions/checkout@v4
        with:
          sparse-checkout: |
            .github/new-top-level-flag.md
          sparse-checkout-cone-mode: false

      - name: Flag unexpected new top-level entries
        uses: actions/github-script@v7
        with:
          script: |
            const fs = require('fs');

            // Known, intended repository root. Anything else added at the root
            // is flagged for a human to eyeball.
            const ALLOWED_DIRS = new Set([
              '.claude-plugin', '.github', 'community', 'custom', 'microsoft', 'skills', 'tools',
            ]);
            const ALLOWED_FILES = new Set([
              '.gitignore', 'CODEOWNERS', 'LICENSE', 'README.md',
              'SECURITY.md', 'agent-consumption.md',
            ]);

            const MARKER = '<!-- guard:new-top-level -->';
            const { owner, repo } = context.repo;
            const prNumber = context.payload.pull_request.number;

            const files = await github.paginate(github.rest.pulls.listFiles, {
              owner, repo, pull_number: prNumber, per_page: 100,
            });

            // Only consider newly-added paths — a new top-level entry can only
            // appear via an added file.
            const added = files
              .filter((f) => f.status === 'added')
              .map((f) => f.filename);

            const newDirs = new Set();
            const newFiles = new Set();
            for (const p of added) {
              const slash = p.indexOf('/');
              if (slash === -1) {
                // Top-level file.
                if (!ALLOWED_FILES.has(p)) newFiles.add(p);
              } else {
                // Top-level directory.
                const dir = p.slice(0, slash);
                if (!ALLOWED_DIRS.has(dir)) newDirs.add(dir);
              }
            }

            if (newDirs.size === 0 && newFiles.size === 0) {
              core.info('No unexpected new top-level entries. Nothing to flag.');
              return;
            }

            // Idempotency: don't re-flag on every synchronize.
            const comments = await github.paginate(github.rest.issues.listComments, {
              owner, repo, issue_number: prNumber, per_page: 100,
            });
            if (comments.some((c) => c.body && c.body.includes(MARKER))) {
              core.info('Already flagged on this PR. Skipping duplicate comment.');
              return;
            }

            const lines = [];
            for (const d of [...newDirs].sort()) lines.push(`- 📁 \`${d}/\` (new top-level folder)`);
            for (const f of [...newFiles].sort()) lines.push(`- 📄 \`${f}\` (new top-level file)`);
            const entries = lines.join('\n');

            core.warning(`Unexpected new top-level entries: ${[...newDirs, ...newFiles].join(', ')}`);

            let body = fs.readFileSync('.github/new-top-level-flag.md', 'utf8');
            body = body
              .replace(/{{AUTHOR}}/g, context.payload.pull_request.user.login)
              .replace(/{{ENTRIES}}/g, entries);

            await github.rest.issues.createComment({
              owner, repo, issue_number: prNumber, body,
            });

            core.info(`Flagged PR #${prNumber}.`);