import 'dart:io';
import 'package:path/path.dart' as p;

/// Operator-managed gRPC bearer token used to authenticate
/// Studio against a hub that has `auth.tokens:` configured
/// (RBAC Level 2). Stored at `~/.fai/hub-auth-token` (mode
/// 0600 on Unix). Sister of [RegistryToken] — same on-disk
/// hygiene, different secret.
///
/// When the file is present and non-empty Studio constructs
/// `HubClient(authToken: ...)`, which attaches
/// `Authorization: Bearer <token>` to every gRPC and
/// gRPC-Web call. When the file is missing Studio stays in
/// anonymous mode; the hub then either accepts or rejects
/// based on its own `auth.tokens:` config.
class HubAuthToken {
  static String _faiHome() {
    final home = Platform.environment['HOME'] ??
        Platform.environment['USERPROFILE'];
    if (home == null || home.isEmpty) {
      throw StateError(
        'Cannot resolve home directory (no HOME / USERPROFILE)',
      );
    }
    return p.join(home, '.fai');
  }

  /// Absolute path to the token file.
  static String get path => p.join(_faiHome(), 'hub-auth-token');

  /// True iff the file exists with a non-empty trimmed body.
  static Future<bool> isConfigured() async {
    final f = File(path);
    if (!await f.exists()) return false;
    final content = await f.readAsString();
    return content.trim().isNotEmpty;
  }

  /// Length of the trimmed token, or null when the file is
  /// missing / empty. Used for status display ("Configured
  /// (40 chars)") without ever surfacing the secret.
  static Future<int?> charCount() async {
    final f = File(path);
    if (!await f.exists()) return null;
    final content = await f.readAsString();
    final trimmed = content.trim();
    return trimmed.isEmpty ? null : trimmed.length;
  }

  /// Read the trimmed token, or `null` when missing/empty.
  /// Studio calls this at startup so [HubService] can supply
  /// it to the underlying gRPC client.
  static Future<String?> read() async {
    final f = File(path);
    if (!await f.exists()) return null;
    final content = (await f.readAsString()).trim();
    return content.isEmpty ? null : content;
  }

  /// Persist [token] to disk, creating `~/.fai/` if needed.
  /// On Unix the file is chmod-ed to 0600. Windows leaves the
  /// default user-ACL alone.
  static Future<void> write(String token) async {
    final f = File(path);
    await f.parent.create(recursive: true);
    await f.writeAsString(token.trim(), flush: true);
    if (Platform.isLinux || Platform.isMacOS) {
      try {
        await Process.run('chmod', ['600', f.path]);
      } catch (_) {
        // best-effort; default perms still confine to the
        // operator's machine.
      }
    }
  }

  /// Remove the token file. Returns true iff the file existed
  /// before deletion.
  static Future<bool> clear() async {
    final f = File(path);
    if (!await f.exists()) return false;
    await f.delete();
    return true;
  }
}