'use strict';
const { Router } = require('express');
const fs   = require('fs');
const path = require('path');

const router = Router();

/** Return available drive letters on Windows. */
function getWindowsRoots() {
  const roots = [];
  for (let code = 65; code <= 90; code++) {
    const drive = `${String.fromCharCode(code)}:\\`;
    try { fs.accessSync(drive); roots.push({ name: drive, path: drive }); } catch { /* skip */ }
  }
  return roots;
}

router.get('/', (req, res) => {
  const reqPath = req.query.path ? String(req.query.path) : null;

  // No path → return filesystem roots
  if (!reqPath) {
    const isWindows = process.platform === 'win32';
    const dirs = isWindows ? getWindowsRoots() : [{ name: '/', path: '/' }];
    return res.json({ path: null, parent: null, dirs });
  }

  // Validate: must exist and be a directory
  let stat;
  try { stat = fs.statSync(reqPath); }
  catch { return res.status(400).json({ error: 'Path does not exist' }); }

  if (!stat.isDirectory()) {
    return res.status(400).json({ error: 'Path is not a directory' });
  }

  // List subdirectories, excluding hidden entries
  let dirs;
  try {
    dirs = fs.readdirSync(reqPath, { withFileTypes: true })
      .filter(e => e.isDirectory() && !e.name.startsWith('.'))
      .map(e => ({ name: e.name, path: path.join(reqPath, e.name) }))
      .sort((a, b) => a.name.localeCompare(b.name));
  } catch {
    return res.status(403).json({ error: 'Cannot read directory' });
  }

  // Compute parent; at a drive root on Windows dirname === reqPath
  const parent = path.dirname(reqPath);
  const atRoot = parent === reqPath;

  res.json({ path: reqPath, parent: atRoot ? null : parent, dirs });
});

module.exports = router;