// ============================================================
// ADMIN DOCS ROUTE — serves the project docs/ folder as a
// browseable, admin-only site inside the app.
//
// Endpoints (both require req.user.role === 'admin'):
//   GET /api/admin/docs/tree           — returns nested JSON of docs/
//   GET /api/admin/docs/file?path=X    — returns rendered HTML for one .md
//
// Path safety: every requested path is normalised + forced to live
// under /app/docs (or wherever DOCS_ROOT resolves). Any attempt to
// traverse out (../, absolute paths, symlinks pointing elsewhere) is
// rejected with 400.
// ============================================================

var express = require('express');
var router  = express.Router();
var fs      = require('fs');
var path    = require('path');
var { authMiddleware } = require('../middleware/auth');
var logger  = require('../utils/logger');
var { marked } = require('marked');

router.use(authMiddleware);

// Admin gate. Returns 403 with a generic message — does not leak
// whether the path exists or not.
function requireAdmin(req, res, next) {
  if (!req.user || req.user.role !== 'admin') {
    return res.status(403).json({ error: 'Admin only' });
  }
  next();
}

// Resolve the docs folder relative to the project root. server.js lives
// at the repo root and __dirname here is src/routes, so go up two.
var DOCS_ROOT = path.resolve(__dirname, '..', '..', 'docs');

// Resolve a user-supplied path safely. Returns null if the path tries
// to escape DOCS_ROOT or doesn't exist.
function safeResolve(relPath) {
  if (typeof relPath !== 'string' || !relPath) return null;
  // Strip any leading slashes so path.join can't be tricked into an
  // absolute path on POSIX.
  var trimmed = relPath.replace(/^[\/\\]+/, '');
  var abs = path.resolve(DOCS_ROOT, trimmed);
  // Must stay inside DOCS_ROOT after resolution (defends against
  // ../ traversal and on Windows backslash variants).
  if (abs !== DOCS_ROOT && !abs.startsWith(DOCS_ROOT + path.sep)) return null;
  if (!fs.existsSync(abs)) return null;
  return abs;
}

// Recursively walk DOCS_ROOT into a JSON tree the client can render
// as a sidebar. Skips dotfiles and non-.md files inside leaf nodes.
function buildTree(dir, baseRel) {
  var entries = fs.readdirSync(dir, { withFileTypes: true })
    .filter(function (d) { return !d.name.startsWith('.'); })
    .sort(function (a, b) {
      // README always first inside its folder so the index is the obvious landing.
      if (a.name.toLowerCase() === 'readme.md') return -1;
      if (b.name.toLowerCase() === 'readme.md') return  1;
      // Folders before files within the same level.
      if (a.isDirectory() && !b.isDirectory()) return -1;
      if (!a.isDirectory() && b.isDirectory()) return  1;
      return a.name.localeCompare(b.name);
    });
  var out = [];
  entries.forEach(function (e) {
    var rel = baseRel ? (baseRel + '/' + e.name) : e.name;
    if (e.isDirectory()) {
      out.push({
        type: 'dir',
        name: e.name,
        path: rel,
        children: buildTree(path.join(dir, e.name), rel)
      });
    } else if (/\.md$/i.test(e.name)) {
      out.push({
        type: 'file',
        name: e.name,
        path: rel
      });
    }
  });
  return out;
}

// ── GET /tree (mounted at /api/admin/docs) ─────────────────────────
router.get('/tree', requireAdmin, function (req, res) {
  try {
    if (!fs.existsSync(DOCS_ROOT)) {
      return res.json({ success: true, tree: [], root: 'docs' });
    }
    var tree = buildTree(DOCS_ROOT, '');
    res.json({ success: true, tree: tree, root: 'docs' });
  } catch (e) {
    logger.error('[adminDocs] tree failed', e.message);
    res.status(500).json({ error: 'Tree build failed' });
  }
});

// ── GET /file?path=X (mounted at /api/admin/docs) ──────────────────
router.get('/file', requireAdmin, function (req, res) {
  try {
    var raw = req.query.path;
    var abs = safeResolve(raw);
    if (!abs) return res.status(400).json({ error: 'Invalid path' });
    var stat = fs.statSync(abs);
    if (!stat.isFile()) return res.status(400).json({ error: 'Not a file' });
    if (!/\.md$/i.test(abs)) return res.status(400).json({ error: 'Only .md files served' });

    var src = fs.readFileSync(abs, 'utf8');
    // marked: GitHub-flavoured rendering with automatic line breaks off
    // (so authors can wrap prose without inserting <br> everywhere) and
    // header IDs on so the client can deep-link via #anchor.
    var html = marked.parse(src, { gfm: true, breaks: false, headerIds: true });
    res.json({ success: true, html: html, path: raw, bytes: stat.size });
  } catch (e) {
    logger.error('[adminDocs] file failed', e.message);
    res.status(500).json({ error: 'Read failed' });
  }
});

module.exports = router;