import 'dart:convert';
import 'dart:io' show Platform;
import 'dart:math';
import 'package:crypto/crypto.dart';
import 'package:device_info_plus/device_info_plus.dart';
import 'package:flutter/foundation.dart';
import 'package:shared_preferences/shared_preferences.dart';

/// Enterprise Real Device Fingerprint & Hardware Identity Service (Directorate Admin)
class DeviceFingerprintService {
  static final DeviceInfoPlugin _deviceInfoPlugin = DeviceInfoPlugin();
  static String? _cachedFingerprint;
  static Map<String, String>? _cachedMetadata;

  static const String _storageKeyDeviceId = 'saqel_admin_device_persistent_id';

  /// Returns the deterministic, physical/hardware-based device fingerprint.
  /// Format: saqel_{platform}_{sha256_hash_first_32_chars}
  static Future<String> getFingerprint() async {
    if (_cachedFingerprint != null && _cachedFingerprint!.isNotEmpty) {
      return _cachedFingerprint!;
    }

    final metadata = await getDeviceMetadata();
    _cachedFingerprint = metadata['device_fingerprint']!;
    return _cachedFingerprint!;
  }

  /// Extracts comprehensive physical/hardware metadata from the running platform.
  static Future<Map<String, String>> getDeviceMetadata() async {
    if (_cachedMetadata != null) {
      return _cachedMetadata!;
    }

    String platform = 'unknown';
    String hardwareId = '';
    String model = '';
    String brand = '';
    String osVersion = '';
    String deviceName = '';

    try {
      if (kIsWeb) {
        platform = 'web';
        final web = await _deviceInfoPlugin.webBrowserInfo;
        hardwareId = '${web.vendor}_${web.platform}_${web.hardwareConcurrency}';
        model = web.browserName.name;
        brand = web.vendor ?? 'Web';
        osVersion = web.userAgent ?? 'UnknownWeb';
        deviceName = 'Web Browser';
      } else if (Platform.isAndroid) {
        platform = 'android';
        final android = await _deviceInfoPlugin.androidInfo;
        hardwareId = android.id.isNotEmpty ? android.id : android.fingerprint;
        model = android.model;
        brand = android.brand;
        osVersion = 'Android ${android.version.release} (SDK ${android.version.sdkInt})';
        deviceName = '${android.brand} ${android.model}';
      } else if (Platform.isIOS) {
        platform = 'ios';
        final ios = await _deviceInfoPlugin.iosInfo;
        hardwareId = ios.identifierForVendor ?? '';
        model = ios.model;
        brand = 'Apple';
        osVersion = 'iOS ${ios.systemVersion}';
        deviceName = ios.name;
      } else if (Platform.isMacOS) {
        platform = 'macos';
        final mac = await _deviceInfoPlugin.macOsInfo;
        hardwareId = mac.systemGUID ?? '';
        model = mac.model;
        brand = 'Apple';
        osVersion = 'macOS ${mac.osRelease}';
        deviceName = mac.computerName;
      } else if (Platform.isWindows) {
        platform = 'windows';
        final win = await _deviceInfoPlugin.windowsInfo;
        hardwareId = win.deviceId;
        model = win.productName;
        brand = 'Microsoft';
        osVersion = 'Windows ${win.majorVersion}.${win.minorVersion}.${win.buildNumber}';
        deviceName = win.computerName;
      } else if (Platform.isLinux) {
        platform = 'linux';
        final linux = await _deviceInfoPlugin.linuxInfo;
        hardwareId = linux.machineId ?? '';
        model = linux.name;
        brand = linux.id;
        osVersion = linux.versionId ?? '';
        deviceName = linux.prettyName;
      }
    } catch (_) {
      platform = kIsWeb
          ? 'web'
          : (Platform.isAndroid
              ? 'android'
              : (Platform.isIOS ? 'ios' : 'desktop'));
    }

    final persistentId = await _getOrCreatePersistentInstallationId();

    final rawSeed =
        'saqel_hw:$platform:$hardwareId:$brand:$model:$osVersion:$persistentId';
    final hash = sha256.convert(utf8.encode(rawSeed)).toString();
    final fingerprint = 'saqel_${platform}_${hash.substring(0, 32)}';

    _cachedMetadata = {
      'device_fingerprint': fingerprint,
      'platform': platform,
      'hardware_id': hardwareId,
      'model': model,
      'brand': brand,
      'os_version': osVersion,
      'device_name': deviceName,
      'persistent_install_id': persistentId,
    };

    return _cachedMetadata!;
  }

  static Future<String> _getOrCreatePersistentInstallationId() async {
    try {
      final prefs = await SharedPreferences.getInstance();
      var id = prefs.getString(_storageKeyDeviceId);
      if (id != null && id.isNotEmpty) {
        return id;
      }

      final rand = Random.secure();
      final bytes = List<int>.generate(16, (_) => rand.nextInt(256));
      bytes[6] = (bytes[6] & 0x0f) | 0x40;
      bytes[8] = (bytes[8] & 0x3f) | 0x80;
      final hex = bytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();
      id =
          '${hex.substring(0, 8)}-${hex.substring(8, 12)}-${hex.substring(12, 16)}-${hex.substring(16, 20)}-${hex.substring(20)}';

      await prefs.setString(_storageKeyDeviceId, id);
      return id;
    } catch (_) {
      return 'fallback-${DateTime.now().millisecondsSinceEpoch}';
    }
  }

  static void resetCache() {
    _cachedFingerprint = null;
    _cachedMetadata = null;
  }
}