import 'dart:io';

import 'package:device_info_plus/device_info_plus.dart';
import 'package:permission_handler/permission_handler.dart';

/// Outcome of a Bluetooth permission check or request.
enum BleAccess {
  /// Everything granted. Bluetooth adapter state is checked separately.
  granted,

  /// The user declined but can be asked again.
  denied,

  /// The user declined with "don't ask again" (Android) or in Settings (iOS).
  /// Only the system settings screen can fix this.
  permanentlyDenied,

  /// The platform reported Bluetooth as unavailable.
  unsupported,
}

/// Requests the runtime permissions OpenMotion needs to scan and connect.
///
/// Android 12+ (API 31): BLUETOOTH_SCAN and BLUETOOTH_CONNECT, shown to the
/// user as "Nearby devices". Android 11 and below: legacy BLE scanning needs
/// location while in use. iOS: the single Bluetooth permission, which the OS
/// prompts for the first time CoreBluetooth is touched.
class BlePermissions {
  BlePermissions._();

  static int? _androidSdk;

  static Future<int> androidSdk() async {
    if (!Platform.isAndroid) return 0;
    return _androidSdk ??= (await DeviceInfoPlugin().androidInfo).version.sdkInt;
  }

  static Future<List<Permission>> _needed() async {
    if (Platform.isAndroid) {
      final sdk = await androidSdk();
      return sdk >= 31
          ? const [Permission.bluetoothScan, Permission.bluetoothConnect]
          : const [Permission.locationWhenInUse];
    }
    if (Platform.isIOS || Platform.isMacOS) return const [Permission.bluetooth];
    return const [];
  }

  /// Checks without prompting.
  static Future<BleAccess> status() async {
    final statuses = <PermissionStatus>[];
    for (final p in await _needed()) {
      statuses.add(await p.status);
    }
    return _combine(statuses);
  }

  /// Prompts for anything not yet granted.
  static Future<BleAccess> request() async {
    final needed = await _needed();
    if (needed.isEmpty) return BleAccess.granted;
    final results = await needed.request();
    return _combine(results.values.toList());
  }

  static BleAccess _combine(List<PermissionStatus> statuses) {
    if (statuses.any((s) => s.isPermanentlyDenied || s.isRestricted)) {
      return BleAccess.permanentlyDenied;
    }
    if (statuses.any((s) => s.isDenied)) return BleAccess.denied;
    return BleAccess.granted;
  }

  static Future<bool> openSettings() => openAppSettings();
}