sharee.bike-App/LockItBLE/Services/BluetoothLock/BLE/LockItBase.cs

using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using Plugin.BLE.Abstractions;
using Plugin.BLE.Abstractions.Contracts;
using Plugin.BLE.Abstractions.Exceptions;
using Polly;
using Polly.Retry;
using Serilog;
using TINK.Model.Connector;
using TINK.Model.Device;
using TINK.Services.BluetoothLock.Crypto;
using TINK.Services.BluetoothLock.Exception;
using TINK.Services.BluetoothLock.Tdo;
using Xamarin.Essentials;

namespace TINK.Services.BluetoothLock.BLE
{
	/// <summary> Manages a single lock.</summary>
	public abstract class LockItBase : ILockService
	{
		/// <summary> Lenght of seed in bytes.</summary>
		private const int SEEDLENGTH = 16;

		/// <summary> Timeout for open/ close operations.</summary>
		protected const int OPEN_CLOSE_TIMEOUT_MS = 30000;

		/// <summary> Timeout for get service operations.</summary>
		private const int GETSERVICE_TIMEOUT_MS = 3000;

		/// <summary> Timeout for read operations.</summary>
		private const int READ_TIMEOUT_MS = 3000;

		protected LockItBase(IDevice device, IAdapter adapter, ICipher cipher)
		{
			Device = device ?? throw new ArgumentException(nameof(device));
			Cipher = cipher ?? throw new ArgumentException(nameof(cipher));
			Adapter = adapter ?? throw new ArgumentException(nameof(adapter));

			_retryPollicy = Policy<byte[]>
				.Handle<CharacteristicReadException>()
				.WaitAndRetryAsync(2, index => TimeSpan.FromMilliseconds(100));

			GetGuid();
			GetName();

			if (InvalidatedSeed.ContainsKey(Guid))
			{
				// Lock was already connected. No need to add entry.
				return;
			}

			InvalidatedSeed.Add(Guid, new List<string>());
		}

		private static readonly Dictionary<Guid, List<string>> InvalidatedSeed = new Dictionary<Guid, List<string>>();

		/// <summary> Count of write- actions to activate lock characteristic..</summary>
		protected int ActivateLockWriteCounter { get; private set; }

		protected ICipher Cipher { get; }

		protected IAdapter Adapter { get; }

		protected IDevice Device { get; }

		private IService LockControl { get; set; }

		private IService BatteryControl { get; set; }

		private ICharacteristic ActivateLockCharacteristic { get; set; }

		private ICharacteristic AlarmCharacteristic { get; set; }

		private ICharacteristic AlarmSettingsCharacteristic { get; set; }

		private ICharacteristic AuthCharacteristic { get; set; }

		private ICharacteristic StateCharacteristic { get; set; }

		private ICharacteristic SoundCharacteristic { get; set; }

		private ICharacteristic BatteryCharacteristic { get; set; }

		private ICharacteristic FirmwareVersionCharacteristic { get; set; }

		private readonly AsyncRetryPolicy<byte[]> _retryPollicy;

		/// <summary> Gets the lock control service.</summary>
		private async Task<IService> GetLockControlService()
		{
			if (LockControl != null) return LockControl;

			LockControl = null;

			Log.ForContext<LockItBase>().Debug("Request to get lock control service.");

			var cts = new CancellationTokenSource();
			cts.CancelAfter(GETSERVICE_TIMEOUT_MS);
			try
			{
				LockControl = await Device.GetServiceAsync(new Guid("0000f00d-1212-efde-1523-785fef13d123"), cts.Token);
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Getting lock control service failed. {Exception}", exception);
				throw new System.Exception($"Can not get lock control service. {exception.Message}", exception);
			}
			finally
			{
				cts.Dispose();
			}

			Log.ForContext<LockItBase>().Debug("Getting lock control service succeeded.");
			return LockControl;
		}

		/// <summary> Gets battery service.</summary>
		private async Task<IService> GetBatteryService()
		{
			if (BatteryControl != null) return BatteryControl;

			BatteryControl = null;

			Log.ForContext<LockItBase>().Debug("Request to get battery control service.");

			var cts = new CancellationTokenSource();
			cts.CancelAfter(GETSERVICE_TIMEOUT_MS);
			try
			{
				BatteryControl = await Device.GetServiceAsync(new Guid("0000180F-0000-1000-8000-00805f9b34fb"), cts.Token);
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Getting battery service failed. {Exception}", exception);
				throw new System.Exception($"Can not get battery service. {exception.Message}", exception);
			}
			finally
			{
				cts.Dispose();
			}

			Log.ForContext<LockItBase>().Debug("Getting battery service succeeded.");
			return BatteryControl;
		}

		/// <summary> Gets the state characteristic.</summary>
		private async Task<ICharacteristic> GetActivateLockCharacteristicAsync()
		{
			if (ActivateLockCharacteristic != null) return ActivateLockCharacteristic;

			ActivateLockCharacteristic = null;

			Log.ForContext<LockItBase>().Debug("Request to get activate lock characteristic.");

			try
			{
				ActivateLockCharacteristic = await (await GetLockControlService())?.GetCharacteristicAsync(new Guid("0000beee-1212-efde-1523-785fef13d123"));
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Getting activate lock charcteristic failed. {Exception}", exception);
				throw new System.Exception($"Can not get activate characteristic. {exception.Message}", exception);
			}

			Log.ForContext<LockItBase>().Debug("Activate lock characteristic retrieved successfully.");

			return ActivateLockCharacteristic;
		}

		/// <summary> Gets the alarm characteristic.</summary>
		private async Task<ICharacteristic> GetAlarmCharacteristicAsync()
		{
			if (AlarmCharacteristic != null) return AlarmCharacteristic;

			AlarmCharacteristic = null;

			Log.ForContext<LockItBase>().Debug("Request to get alarm characteristic.");

			try
			{
				AlarmCharacteristic = await (await GetLockControlService())?.GetCharacteristicAsync(new Guid("0000BFFF-1212-efde-1523-785fef13d123"));
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Getting alarm-charcteristic failed. {Exception}", exception);
				throw new System.Exception($"Can not get alarm characteristic. {exception.Message}", exception);
			}

			Log.ForContext<LockItBase>().Debug("Get alarm characteristic retrieved successfully.");
			return AlarmCharacteristic;
		}

		/// <summary> Gets the alarm settings characteristic.</summary>
		private async Task<ICharacteristic> GetAlarmSettingsCharacteristicAsync()
		{
			if (AlarmSettingsCharacteristic != null) return AlarmSettingsCharacteristic;

			AlarmSettingsCharacteristic = null;

			Log.ForContext<LockItBase>().Debug("Request to get alarm settings characteristic.");

			try
			{
				AlarmSettingsCharacteristic = await (await GetLockControlService())?.GetCharacteristicAsync(new Guid("0000BFFE-1212-efde-1523-785fef13d123"));
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Getting alarm settings charcteristic failed. {Exception}", exception);
				throw new System.Exception($"Can not get alarm settings characteristic. {exception.Message}", exception);
			}

			Log.ForContext<LockItBase>().Debug("Get alarm settings characteristic retrieved successfully.");
			return AlarmSettingsCharacteristic;
		}

		/// <summary> Gets the auth characteristic.</summary>
		private async Task<ICharacteristic> GetAuthCharacteristicAsync()
		{
			if (AuthCharacteristic != null) return AuthCharacteristic;

			AuthCharacteristic = null;

			Log.ForContext<LockItBase>().Debug("Request to get auth characteristic.");
			try
			{
				AuthCharacteristic = await (await GetLockControlService())?.GetCharacteristicAsync(new Guid("0000baab-1212-efde-1523-785fef13d123"));
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Getting auth-charcteristic failed. {Exception}", exception);
				throw new System.Exception(string.Format("Can not get auth characteristic. {0}", exception.Message), exception);
			}

			Log.ForContext<LockItBase>().Debug("Get auth characteristic retrieved successfully.");
			return AuthCharacteristic;
		}

		/// <summary> Gets the state characteristic.</summary>
		protected async Task<ICharacteristic> GetStateCharacteristicAsync()
		{
			if (StateCharacteristic != null) return StateCharacteristic;

			StateCharacteristic = null;

			Log.ForContext<LockItBase>().Debug("Request to get lock state characteristic.");
			try
			{
				StateCharacteristic = await (await GetLockControlService())?.GetCharacteristicAsync(new Guid("0000baaa-1212-efde-1523-785fef13d123"));
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Getting state charcteristic failed. {Exception}", exception);
				throw new System.Exception(string.Format("Can not get state characteristic. {0}", exception.Message), exception);
			}

			Log.ForContext<LockItBase>().Debug("Get state characteristic retrieved successfully.");
			return StateCharacteristic;
		}

		/// <summary> Gets the sound characteristic.</summary>
		private async Task<ICharacteristic> GetSoundCharacteristicAsync()
		{
			if (SoundCharacteristic != null) return SoundCharacteristic;

			SoundCharacteristic = null;

			Log.ForContext<LockItBase>().Debug("Request to get sound characteristic.");
			try
			{
				SoundCharacteristic = await (await GetLockControlService())?.GetCharacteristicAsync(new Guid("0000BAAE-1212-efde-1523-785fef13d123"));
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Getting sound charcteristic failed. {Exception}", exception);
				throw new System.Exception($"Can not get sound characteristic. {exception.Message}", exception);
			}

			Log.ForContext<LockItBase>().Debug("Get sound characteristic retrieved successfully.");
			return SoundCharacteristic;
		}

		/// <summary> Gets the battery characteristic.</summary>
		protected async Task<ICharacteristic> GetBatteryCharacteristicAsync()
		{
			if (BatteryCharacteristic != null) return BatteryCharacteristic;

			BatteryCharacteristic = null;

			Log.ForContext<LockItBase>().Debug("Request to get battery characteristic.");
			try
			{
				BatteryCharacteristic = await (await GetBatteryService())?.GetCharacteristicAsync(new Guid("00002a19-0000-1000-8000-00805f9b34fb"));
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Getting battery charcteristic failed. {Exception}", exception);
				throw new System.Exception($"Can not get battery characteristic. {exception.Message}", exception);
			}

			Log.ForContext<LockItBase>().Debug("Get battery characteristic retrieved successfully.");
			return BatteryCharacteristic;
		}

		/// <summary> Gets the versions info characteristic.</summary>
		protected async Task<ICharacteristic> GetVersionsCharacteristicAsync()
		{
			if (FirmwareVersionCharacteristic  != null) return FirmwareVersionCharacteristic ;

			FirmwareVersionCharacteristic  = null;

			Log.ForContext<LockItBase>().Debug("Request to get versions info characteristic.");
			try
			{
				FirmwareVersionCharacteristic  = await (await GetLockControlService())?.GetCharacteristicAsync(new Guid("0000baad-1212-efde-1523-785fef13d123"));
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Getting versions info charcteristic failed. {Exception}", exception);
				throw new System.Exception(string.Format("Can not get versions info characteristic. {0}", exception.Message), exception);
			}

			Log.ForContext<LockItBase>().Debug("Get versions info characteristic retrieved successfully.");
			return FirmwareVersionCharacteristic ;
		}
		/// <summary> Query name of lock.</summary>
		private void GetName()
		{
			if (!string.IsNullOrEmpty(Name))
			{
				// Prevent valid name to be queried more than twice because Name does not change.
				return;
			}

			Log.ForContext<LockItBase>().Debug("Query name of lock.");
			try
			{
				Name = Device.Name ?? string.Empty;
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Retrieving bluetooth name failed . {Exception}", exception);
				throw new System.Exception($"Can not get name of lock. {exception.Message}", exception);
			}

			Log.ForContext<LockItBase>().Debug($"Lock name is {Name}.");
			Id = Name.GetBluetoothLockId();
			return;
		}

		/// <summary> Full idvertisement name.</summary>
		public string Name { get; private set; } = string.Empty;

		/// <summary> Id part of idvertisement name.</summary>
		public int Id { get; private set; }

		/// <summary> Query GUID of lock.</summary>
		private void GetGuid()
		{
			if (Guid != TextToLockItTypeHelper.INVALIDLOCKGUID)
			{
				// Prevent valid GUID to be queried more than twice because GUID does not change.
			}

			Log.ForContext<LockItBase>().Debug("Query name of lock.");
			try
			{
				Guid = Device.Id;
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Retrieving bluetooth guid failed. {Exception}", exception);
				throw new System.Exception($"Can not get guid of lock. {exception.Message}", exception);
			}

			Log.ForContext<LockItBase>().Debug($"Lock GUID is {Guid}.");
		}

		/// <summary> GUID.</summary>
		public Guid Guid { get; private set; } = TextToLockItTypeHelper.INVALIDLOCKGUID;

		private byte[] CopriKey { get; set; } = new byte[0];

		/// <summary> Gets the device state.</summary>
		public DeviceState? GetDeviceState()
		{
			if (DeviceInfo.Platform != DevicePlatform.Unknown && MainThread.IsMainThread == false)
			{
				throw new System.Exception("Can not get device state. Platform must not be unknown and bluetooth code must be run on main thread.");
			}

			DeviceState? state;
			Log.ForContext<LockItBase>().Debug("Request to get connection state.");
			try
			{
				state = Device?.State.GetDeviceState()
					?? throw new System.Exception("Can not get bluetooth device state. State must not be null.");
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Retrieving bluetooth state failed. {Exception}", exception);
				throw new System.Exception($"Can not get bluetooth state. {exception.Message}", exception);
			}

			Log.ForContext<LockItBase>().Debug($"Connection state is {state}.");
			return state;
		}

		/// <summary> Reconnects to device. </summary>
		/// <remarks> Consists of a bluetooth connect plus invocation of an authentication sequence. </remarks>
		/// <param name="authInfo">Info required to connect.</param>
		/// <param name="connectTimeout">Timeout to apply when connecting to bluetooth lock.</param>
		/// <returns>True if connecting succeeded, false if not.</returns>
		public abstract Task ReconnectAsync(
			LockInfoAuthTdo authInfo,
			TimeSpan connectTimeout);

		/// <summary> Reconnects to device. </summary>
		/// <remarks> Consists of a bluetooth connect plus invocation of an authentication sequence. </remarks>
		/// <param name="authInfo">Info required to connect.</param>
		/// <param name="connectTimeout">Timeout to apply when connecting to bluetooth lock.</param>
		/// <returns>True if connecting succeeded, false if not.</returns>
		protected async Task ReconnectAsync(
		LockInfoAuthTdo authInfo,
		TimeSpan connectTimeout,
		Func<LockItBase> factory)
		{
			if (DeviceInfo.Platform != DevicePlatform.Unknown && MainThread.IsMainThread == false)
			{
				throw new System.Exception("Can not reconnect to lock. Platform must not be unknown and bluetooth code must be run on main thread.");
			}

			// Check if key is available.
			if (authInfo == null)
			{
				Log.ForContext<LockItBase>().Error($"Can not authenticate. No auth info available.");
				throw new AuthKeyException($"Can not authenticate. No auth info available.");
			}

			if (authInfo.K_seed.Length != SEEDLENGTH
				|| authInfo.K_u.Length <= 0)
			{
				throw new AuthKeyException($"Can not authenticate. Invalid seed-/ k-user-lenght {authInfo.K_seed.Length}/ {authInfo.K_u.Length} detected.");
			}

			if (Device.State == Plugin.BLE.Abstractions.DeviceState.Connected)
			{
				throw new AlreadyConnectedException();
			}

			// Reset all references to characteristics.
			LockControl = null;
			ActivateLockCharacteristic = null;
			AlarmCharacteristic = null;
			AlarmSettingsCharacteristic = null;
			AuthCharacteristic = null;
			StateCharacteristic = null;
			SoundCharacteristic = null;
			ActivateLockWriteCounter = 0;

			var cts = new CancellationTokenSource(connectTimeout);

			// Connect to device and authenticate.
			Log.ForContext<LockItBase>().Debug($"Request connect to device {Device.Name}. Connect state is {Device.State}.");
			try
			{
				await Adapter.ConnectToDeviceAsync(
					Device,
					new ConnectParameters(forceBleTransport: true /* Force BLE transport */),
					cts.Token);
			}
			catch (System.Exception exception)
			{
				if (exception is TaskCanceledException)
				{
					// A timeout occurred.
					throw new System.Exception($"Can not reconnect.\r\nTimeout of {connectTimeout.TotalMilliseconds} [ms] elapsed.", exception);
				}

				Log.ForContext<LockItBase>().Error("Can not reconnect. {Exception}", exception);
				throw new System.Exception($"Can not Reconnect. {exception.Message}", exception);
			}

			Log.ForContext<LockItBase>().Debug($"Connecting to device succeeded. Starting auth sequence...");

			var lockIt = await Authenticate(Device, authInfo, Adapter, Cipher, factory);
			CopriKey = lockIt.CopriKey;
		}

		/// <summary> Connects to device. </summary>
		/// <param name="authInfo">Info required to connect.</param>
		/// <param name="device">Device with must be connected.</param>
		/// <returns>True if connecting succeeded, false if not.</returns>
		protected static async Task<LockItBase> Authenticate(
			IDevice device,
			LockInfoAuthTdo authInfo,
			IAdapter adapter,
			ICipher cipher,
			Func<LockItBase> factory)
		{
			if (DeviceInfo.Platform != DevicePlatform.Unknown && MainThread.IsMainThread == false)
			{
				throw new System.Exception("Can not authenticate. Platform must not be unknown and bluetooth code must be run on main thread.");
			}

			if (device == null)
				throw new ArgumentException(nameof(device));

			if (cipher == null)
				throw new ArgumentException(nameof(cipher));

			if (adapter == null)
				throw new ArgumentException(nameof(adapter));

			// Check if connect is required.
			DeviceState deviceState;
			Log.ForContext<LockItBase>().Debug("Retrieving connection state is in context of auth.");
			try
			{
				deviceState = device?.State.GetDeviceState()
					?? throw new System.Exception("Can not get bluetooth device state. State must not be null.");
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Can not authenticate. Retrieving bluetooth state failed. {Exception}", exception);
				throw new System.Exception(string.Format("Can not authenticate. Getting bluetooth state failed. {0}", exception.Message), exception);
			}

			switch (deviceState)
			{
				case DeviceState.Disconnected:
					throw new BluetoothDisconnectedException();

				case DeviceState.Connected:
					break;

				default:
					// Can not get state if device is not connected.
					Log.ForContext<LockItBase>().Error($"Can not authenticate. Unexpected lock state {deviceState} detected.");
					throw new System.Exception(string.Format("Can not authenticate. Unexpected bluetooth state {0} detected.", deviceState));
			}

			// Check if key is available.
			if (authInfo == null)
			{
				Log.ForContext<LockItBase>().Error($"Can not authenticate. No auth info available.");
				throw new AuthKeyException($"Can not authenticate. No auth info available.");
			}

			if (authInfo.K_seed.Length != SEEDLENGTH
				|| authInfo.K_u.Length <= 0)
			{
				throw new AuthKeyException($"Can not authenticate. Invalid seed-/ k-user-lenght {authInfo.K_seed.Length}/ {authInfo.K_u.Length} detected.");
			}

			Log.ForContext<LockItBase>().Debug($"Connection state is {deviceState} in context of auth.");

			var lockIt = factory();

			if (InvalidatedSeed[lockIt.Guid].Contains(string.Join(",", authInfo.K_seed)))
			{
				throw new AuthKeyException($"Can not authenticate. Seed {string.Join(",", authInfo.K_seed)} was already used.");
			}

			InvalidatedSeed[lockIt.Guid].Add(string.Join(",", authInfo.K_seed));

			// Connect to device and authenticate.
			try
			{
				await AuthenticateAsync(
					lockIt,
					authInfo,
				   lockIt.Cipher);
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Authentication failed. {Exception}", exception);
				try
				{
					// Disconnect from device if auth did not succeed.
					await lockIt.Adapter.DisconnectDeviceAsync(lockIt.Device);
				}
				catch (System.Exception exceptionInner)
				{
					Log.ForContext<LockItBase>().Error("Authentication failed. Disconnect throw an exception. {Exception}", exceptionInner);
				}

				Log.ForContext<LockItBase>().Error($"Auth failed for device name={lockIt.Name}, GUID={lockIt.Guid}.");

				throw;
			}

			lockIt.CopriKey = authInfo.K_u;

			Log.ForContext<LockItBase>().Debug($"Auth succeeded for device name={lockIt.Name}, GUID={lockIt.Guid}, state={lockIt.GetDeviceState()}.");
			return lockIt;
		}

		/// <summary> Performs an authentication.</summary>
		private static async Task AuthenticateAsync(
			LockItBase lockIt,
			LockInfoAuthTdo lockInfo,
			ICipher cipher)
		{
			Log.ForContext<LockItBase>().Debug($"Request to autenticate for {lockIt.Name}.");

			var authCharacteristic = await lockIt.GetAuthCharacteristicAsync();
			if (authCharacteristic == null)
			{
				Log.ForContext<LockItBase>().Debug("Getting auth-charcteristic failed.");
				throw new CoundntGetCharacteristicException("Authentication failed. Auth characteristic must not be null.");
			}

			bool success;

			try
			{
				success = await authCharacteristic.WriteAsync(lockInfo.K_seed);
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Writing copri seed failed.{AuthCharacteristic}{CommandWritten}{Exception}", ToSerilogString(authCharacteristic), ToSerilogString(lockInfo.K_seed), exception);
				throw new System.Exception(string.Format("Can not authenticate. Writing copri seed failed. {0}", exception.Message), exception);
			}
			if (!success)
			{
				Log.ForContext<LockItBase>().Debug("Writing copri seed failed.{AuthCharacteristic}{CommandWritten}", ToSerilogString(authCharacteristic), ToSerilogString(lockInfo.K_seed));
				throw new System.Exception("Can not authenticate. Writing copri seed did not succeed.");
			}

			Log.ForContext<LockItBase>().Debug("Copri seed written successfully.{AuthCharacteristic}{CommandWritten}.", ToSerilogString(authCharacteristic), ToSerilogString(lockInfo.K_seed));

			byte[] seedLockEncrypted;
			var cts = new CancellationTokenSource();
			cts.CancelAfter(READ_TIMEOUT_MS);
			try
			{
				seedLockEncrypted = await authCharacteristic.ReadAsync(cts.Token); // encrypted seed value (random value) from lock to decypt using k_user
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Retrieveing encrypted random value from lock (seed)(ReadAsync-call) failed.{ReadCharacteristic}{Exception}", ToSerilogString(authCharacteristic), exception);
				throw new System.Exception(string.Format("Can not authenticate. Reading encrypted seed failed. {0}", exception.Message), exception);
			}
			finally
			{
				cts.Dispose();
			}

			Log.ForContext<LockItBase>().Debug("Retrieveing encrypted random value from lock (seed)(ReadAsync-call) succeeded.{ReadCharacteristic}{Reading}", ToSerilogString(authCharacteristic), "***");

			var crypto = new AuthCryptoHelper(
				seedLockEncrypted,
				lockInfo.K_u,
				cipher);

			byte[] accessKeyEncrypted;
			try
			{
				accessKeyEncrypted = crypto.GetAccessKeyEncrypted();
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Error getting encrypted access key. {Exception}", exception);
				throw new System.Exception(string.Format("Can not authenticate. Getting access key failed. {0}", exception.Message), exception);
			}

			try
			{
				success = await authCharacteristic.WriteAsync(accessKeyEncrypted);
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Writing encrypted access key failed.{Key}{Seed}{AuthCharacteristic}{CommandWritten}{Exception}", ToSerilogString(crypto.KeyCopri), ToSerilogString(lockInfo.K_seed), ToSerilogString(authCharacteristic), ToSerilogString(accessKeyEncrypted), exception);
				throw new System.Exception(string.Format("Can not authenticate. Writing access key failed. {0}", exception.Message), exception);
			}
			if (!success)
			{
				Log.ForContext<LockItBase>().Debug("Writing encrypted access key failed.{Key}{Seed}{AuthCharacteristic}{CommandWritten}", ToSerilogString(crypto.KeyCopri), ToSerilogString(lockInfo.K_seed), ToSerilogString(authCharacteristic), "***");
				throw new System.Exception(string.Format("Can not authenticate. Writing access key did not succeed."));
			}

			Log.ForContext<LockItBase>().Debug("Encrypted access key written successfully.{Key}{Seed}{AuthCharacteristic}{CommandWritten}", ToSerilogString(crypto.KeyCopri), ToSerilogString(lockInfo.K_seed), ToSerilogString(authCharacteristic), "***");
		}

		/// <summary> Gets the lock state like locking state (open/ close). </summary>
		/// <param name="doWaitRetry">True if to wait and retry in case of failures. </param>
		/// <remarks> 
		/// Lock state is first byte of of value read from state characteristic ("0000baaa-1212-efde-1523-785fef13d123").
		/// Values are as follows
		/// Open = 0x00,
		/// Closed = 0x01,
		/// Unknown = 0x02,
		/// CouldntCloseMoving = 0x03,
		/// CouldntOpenBoldBlocked = 0x04,
		/// CouldntCloseBoldBlocked = 0x05
		/// TINK.Services.BluetoothLock.Tdo.LockitLockingState.
		/// </remarks>
		/// <returns> Lock state.</returns>
		/// <exception cref="BluetoothDisconnectedException">App is not connected to lock.</exception>
		/// <exception cref="CoundntGetCharacteristicException">Getting state characteristic to read from failed.</exception>
		/// <exception cref="Exception">
		/// Call not from main thread or unkonwn platform detected or
		/// query device state (connected, disconnected, ....) failed for an unknown reason or returned an unexpected value or
		/// reading state characteristic failed or reading from characteristic was empty.
		/// </exception>
		/// <exception> Exceptions thrown by PluginBle::ICharacteristic.ReasAsync.</exception>
		public async Task<LockInfoTdo> GetLockStateAsync(bool doWaitRetry = false)
		{
			if (DeviceInfo.Platform != DevicePlatform.Unknown && MainThread.IsMainThread == false)
			{
				throw new System.Exception("Can not get lock state. Platform must not be unknown and bluetooth code must be run on main thread.");
			}

			DeviceState? deviceState;
			Log.ForContext<LockItBase>().Debug("Request to get connection state in context of getting locking state.");
			try
			{
				deviceState = Device?.State.GetDeviceState()
					?? throw new System.Exception("Can not get bluetooth device state. State must not be null.");
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Can not get lock state. Retrieving bluetooth state failed. {Exception}", exception);
				throw new System.Exception(string.Format("Can not get lock state. Getting bluetooth state failed. {0}", exception.Message), exception);
			}

			switch (deviceState)
			{
				case DeviceState.Disconnected:
					throw new BluetoothDisconnectedException();

				case DeviceState.Connected:
					break;

				default:
					// Can not get state if device is not connected.
					Log.ForContext<LockItBase>().Error($"Getting lock state failed. Unexpected lock state {deviceState} detected.");
					throw new System.Exception(string.Format("Can not get lock state. Unexpected bluetooth state {0} detected.", deviceState));
			}

			Log.ForContext<LockItBase>().Debug($"Connection state is {deviceState}.");

			var stateCharacteristic = await GetStateCharacteristicAsync();
			if (stateCharacteristic == null)
			{
				Log.ForContext<LockItBase>().Error($"Can not get lock state. State characteristic is not available.");
				throw new CoundntGetCharacteristicException("Can not get lock state. State characteristic must not be null.");
			}

			byte[] state;
			async Task<byte[]> readAsyncDelegate()
			{
				var cts = new CancellationTokenSource();
				cts.CancelAfter(READ_TIMEOUT_MS);
				try
				{
					return await stateCharacteristic.ReadAsync(cts.Token);
				}
				catch (System.Exception exception)
				{
					Log.ForContext<LockItBase>().Error("Retrieving lock state (ReadAsync-call) failed inside delegate.{StateCharacteristic}{Exception}", ToSerilogString(stateCharacteristic), exception);
					throw;
				}
				finally
				{
					cts.Dispose();
				}
			}

			try
			{
				state = doWaitRetry
					? await _retryPollicy.ExecuteAsync(async () => await readAsyncDelegate())
					: await readAsyncDelegate();
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Retrieving lock state (ReadAsync-call) failed.{StateCharacteristic}{Exception}", ToSerilogString(stateCharacteristic), exception);
				throw new System.Exception(string.Format("Can not get lock state. Reading data failed. {0}", exception.Message), exception);
			}
			if (state == null || state.Length <= 0)
			{
				Log.ForContext<LockItBase>().Debug("Retrieving lock state (ReadAsync-call) failed. Data read is null or empty.{StateCharacteristic}", ToSerilogString(stateCharacteristic));
				throw new System.Exception("Can not get lock state. No data read");
			}

			var lockInfoTdo = new LockInfoTdo.Builder
			{
				Id = Id,
				Guid = Guid,
				State = (LockitLockingState?)state[0]
			}.Build();

			Log.ForContext<LockItBase>().Debug("Retrieving lock state (ReadAsync-call) succeeded. {@LockInfoTdo}{StateCharacteristic}{Reading}",
				lockInfoTdo,
				ToSerilogString(stateCharacteristic),
				state);

			return lockInfoTdo;
		}

		/// <summary>Gets the battery percentage.</summary>
		public async Task<double> GetBatteryPercentageAsync()
		{
			if (DeviceInfo.Platform != DevicePlatform.Unknown && MainThread.IsMainThread == false)
			{
				throw new System.Exception("Can not get battery percentage. Platform must not be unknown and bluetooth code must be run on main thread.");
			}

			DeviceState? deviceState;
			Log.ForContext<LockItBase>().Debug("Request to get battery percentage in context of getting locking state.");
			try
			{
				deviceState = Device?.State.GetDeviceState()
					?? throw new System.Exception("Can not get bluetooth device state. State must not be null.");
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Can not get battery percentage. Retrieving bluetooth state failed. {Exception}", exception);
				throw new System.Exception(string.Format("Can not get battery percentage. Getting bluetooth state failed. {0}", exception.Message), exception);
			}

			switch (deviceState)
			{
				case DeviceState.Disconnected:
					throw new BluetoothDisconnectedException();

				case DeviceState.Connected:
					break;

				default:
					// Can not get state if device is not connected.
					Log.ForContext<LockItBase>().Error($"Getting battery percentage failed. Unexpected battery percentage {deviceState} detected.");
					throw new System.Exception(string.Format("Can not get battery percentage. Unexpected bluetooth state {0} detected.", deviceState));
			}

			Log.ForContext<LockItBase>().Debug($"Connection state is {deviceState}.");

			var batteryCharacteristic = await GetBatteryCharacteristicAsync();
			if (batteryCharacteristic == null)
			{
				Log.ForContext<LockItBase>().Error($"Can not get battery percentage. State characteristic is not available.");
				throw new CoundntGetCharacteristicException("Can not get battery percentage. State characteristic must not be null.");
			}

			byte[] percentage;
			var cts = new CancellationTokenSource();
			cts.CancelAfter(READ_TIMEOUT_MS);
			try
			{
				percentage = await batteryCharacteristic.ReadAsync(cts.Token);
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Retrieving charging level (ReadAsync-call) failed. {BatteryCharacteristic}{Exception}", ToSerilogString(batteryCharacteristic), exception);
				throw new System.Exception(string.Format("Can not get battery percentage. Reading data failed. {0}", exception.Message), exception);
			}
			finally
			{
				cts.Dispose();
			}

			if (percentage == null || percentage.Length <= 0)
			{
				Log.ForContext<LockItBase>().Debug("Retrieving charging level (ReadAsync-call) failed. Data read is null or empty.{BatteryCharacteristic}", ToSerilogString(batteryCharacteristic));
				throw new System.Exception("Can not get battery percentage. No data read.");
			}

			Log.ForContext<LockItBase>().Debug("Retrieving charging level (ReadAsync-call) succeeded.{Level}{BatteryCharacteristic}{Reading}", percentage[0], ToSerilogString(batteryCharacteristic), percentage);

			return percentage[0];
		}

		/// <summary> Gets version info about the lock. </summary>
		/// <remarks> 
		/// Lock state is first byte of of value read from state characteristic ("0000baaa-1212-efde-1523-785fef13d123").
		/// Values are as follows
		/// Byte number 0: firmware version,
		/// Byte number 1: lock version (2 – classic, 3 – plus, 4 – GPS)
		/// Byte number 2: hardware version,
		/// </remarks>
		/// <returns> .</returns>
		public async Task<VersionInfoTdo> GetVersionInfoAsync()
		{
			if (DeviceInfo.Platform != DevicePlatform.Unknown && MainThread.IsMainThread == false)
			{
				throw new System.Exception("Can not get versions info. Platform must not be unknown and bluetooth code must be run on main thread.");
			}

			DeviceState? deviceState;
			Log.ForContext<LockItBase>().Debug("Request to get connection state in context of getting versions info.");
			try
			{
				deviceState = Device?.State.GetDeviceState()
					?? throw new System.Exception("Can not get bluetooth device state. State must not be null.");
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Can not get versions info. Retrieving bluetooth state failed. {Exception}", exception);
				throw new System.Exception(string.Format("Can not get versions info. Getting bluetooth state failed. {0}", exception.Message), exception);
			}

			switch (deviceState)
			{
				case DeviceState.Disconnected:
					throw new BluetoothDisconnectedException();

				case DeviceState.Connected:
					break;

				default:
					// Can not get state if device is not connected.
					Log.ForContext<LockItBase>().Error($"Getting versions info failed. Unexpected versions info {deviceState} detected.");
					throw new System.Exception(string.Format("Can not get versions info. Unexpected bluetooth state {0} detected.", deviceState));
			}

			Log.ForContext<LockItBase>().Debug($"Connection state is {deviceState}.");

			var firmwareVersionCharacteristic = await GetVersionsCharacteristicAsync();
			if (firmwareVersionCharacteristic == null)
			{
				Log.ForContext<LockItBase>().Error($"Can not get versions info. versions info characteristic is not available.");
				throw new CoundntGetCharacteristicException("Can not get versions info. versions info characteristic must not be null.");
			}

			byte[] version;
			var cts = new CancellationTokenSource();
			cts.CancelAfter(READ_TIMEOUT_MS);
			try
			{
				version = await firmwareVersionCharacteristic.ReadAsync(cts.Token);
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Retrieving versions info (ReadAsync-call) failed inside delegate.{StateCharacteristic}{Exception}", ToSerilogString(firmwareVersionCharacteristic), exception);
				throw;
			}
			finally
			{
				cts.Dispose();
			}

			if (version == null || version.Length <= 0)
			{
				Log.ForContext<LockItBase>().Debug("Retrieving versions info (ReadAsync-call) failed. Data read is null or empty.{StateCharacteristic}", ToSerilogString(firmwareVersionCharacteristic));
				throw new System.Exception("Can not get versions info. No data read");
			}

			VersionInfo = new VersionInfoTdo.Builder
			{
				FirmwareVersion = version[0],
				LockVersion = version[1],
				HardwareVersion = version[2]
			}.Build();

			Log.ForContext<LockItBase>().Debug("Retrieving versions info (ReadAsync-call) succeeded. {@LockInfoTdo}{StateCharacteristic}{Reading}",
				VersionInfo,
				ToSerilogString(firmwareVersionCharacteristic),
				version);

			return VersionInfo;
		}

		public VersionInfoTdo VersionInfo { get; private set; }

		/// <summary> Opens lock. </summary>
		/// <returns> Locking state.</returns>
		public abstract Task<LockitLockingState?> OpenAsync();

		/// <summary> Close the lock.</summary>
		/// <returns>Locking state.</returns>
		public abstract Task<LockitLockingState?> CloseAsync();

		/// <summary> Opens/ closes lock.</summary>
		/// <param name="counter"></param>
		/// <param name="open"></param>
		/// <returns>True if opening/ closing command could be written successfully.</returns>
		protected async Task<bool> OpenCloseLockAsync(bool open)
		{
			DeviceState deviceState;
			Log.ForContext<LockItBase>().Debug(open
				? "Request to get connection state in context of opening lock."
				: "Request to get connection state in context of closing lock.");
			try
			{
				deviceState = Device?.State.GetDeviceState()
					?? throw new System.Exception(open
						? "Can not open lock. Getting bluetooth device state failed. State must not be null."
						: "Can not close lock. Getting bluetooth device state failed. State must not be null.");
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error(open
						? "Retrieving bluetooth state failed when opening lock failed. {Exception}"
						: "Retrieving bluetooth state failed when closing lock failed. {Exception}",
					exception);
				throw new System.Exception(open
							? $"Can not open lock. Getting bluetooth failed. {exception.Message}"
							: $"Can not close lock. Getting bluetooth failed. {exception.Message}",
						exception);
			}

			switch (deviceState)
			{
				case DeviceState.Disconnected:
					throw new BluetoothDisconnectedException();

				case DeviceState.Connected:
					break;

				default:
					// Can not open lock if bluetooth state is not connected.
					Log.ForContext<LockItBase>().Debug(open
						? $"Can not open lock. Unexpected connection state detected {deviceState}."
						: $"Can not close lock. Unexpected connection state detected {deviceState}.");
					return false;
			}

			Log.ForContext<LockItBase>().Debug(open
				? $"Connection state before opening lock is {deviceState}."
				: $"Connection state before closing lock is {deviceState}.");

			var activateLockCharacteristic = await GetActivateLockCharacteristicAsync();
			if (activateLockCharacteristic == null)
			{
				Log.ForContext<LockItBase>().Debug(open
					? "Can not open lock. Getting lock control service failed."
					: "Can not close lock. Getting lock control service failed.");
				return false;
			}

			byte[] state = bitShift(
				new byte[] { 0, 0, open ? (byte)1 : (byte)2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
				++ActivateLockWriteCounter);

			byte[] stateEnctryped;
			try
			{
				stateEnctryped = Cipher.Encrypt(CopriKey, state);
			}
			catch (System.Exception exception)
			{
				ActivateLockWriteCounter--;
				Log.ForContext<LockItBase>().Error(open
						? "Encypting command to open lock failed. {Exception}"
						: "Encypting command to close lock failed. {Exception}",
					exception);
				throw new System.Exception(open
						? $"Can not open lock. Encrypting command to lock/ unlock failed. {exception.Message}"
						: $"Can not close lock. Encrypting command to lock/ unlock failed. {exception.Message}",
					exception);
			}

			bool success;
			try
			{
				success = await activateLockCharacteristic.WriteAsync(stateEnctryped);
			}
			catch (System.Exception exception)
			{
				ActivateLockWriteCounter--;
				Log.ForContext<LockItBase>().Error(open
						? "Writing data to open lock failed.{ActivateLockCharacteristic}{CommandWritten}{Exception}"
						: "Writing data to close lock failed.{ActivateLockCharacteristic}{CommandWritten}{Exception}",
					ToSerilogString(activateLockCharacteristic),
					ToSerilogString(stateEnctryped),
					exception);
				throw new System.Exception(open
					? $"Can not open lock. Writing command failed. {exception.Message}"
					: $"Can not close lock. Writing command failed. {exception.Message}",
					exception);
			}

			Log.ForContext<LockItBase>().Debug(open
					? "Command to open lock written successfully.{ActivateLockCharacteristic}{CommandWritten}"
					: "Command to close lock written successfully.{ActivateLockCharacteristic}{CommandWritten}",
				ToSerilogString(activateLockCharacteristic),
				ToSerilogString(stateEnctryped));

			return success;
		}

		/// <summary> Gets a value indicating whether alarm is on or off.</summary>
		public async Task<bool> GetIsAlarmOffAsync()
		{
			if (DeviceInfo.Platform != DevicePlatform.Unknown && MainThread.IsMainThread == false)
			{
				throw new System.Exception("Can not turn alarm off. Platform must not be unknown and bluetooth code must be run on main thread.");
			}

			var alarmCharacteristic = await GetAlarmCharacteristicAsync();
			if (alarmCharacteristic == null)
			{
				Log.ForContext<LockItBase>().Debug("Getting alarm characteristic failed.");
				throw new System.Exception($"Can not get alarm whether alarm is on or off. Getting alarm characteristic returned null.");
			}

			byte[] alarmSettings;
			var cts = new CancellationTokenSource();
			cts.CancelAfter(READ_TIMEOUT_MS);
			try
			{
				alarmSettings = await alarmCharacteristic.ReadAsync(cts.Token);
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Retrieving alarm settings (ReadAsync-call) failed.{AlarmCharacteristic}{Exception}", ToSerilogString(alarmCharacteristic), exception);
				throw new System.Exception($"Can not get whether alarm is off or on {exception.Message}.");
			}
			finally
			{
				cts.Dispose();
			}

			if (alarmSettings == null || alarmSettings.Length < 1)
			{
				Log.ForContext<LockItBase>().Error("Retrieving alarm settings (ReadAsync-call) failed.{AlarmCharacteristic}{Reading}", ToSerilogString(alarmCharacteristic));
				throw new System.Exception("Can not get whether alarm is off or on. Reading failed.");
			}

			var isAlarmOff = alarmSettings[0] == 0;
			Log.ForContext<LockItBase>().Debug("Retrieving alarm settings (ReadAsync-call) succeeded.{IsArlarmOff}{AlarmCharacteristic}{Reading}", isAlarmOff, ToSerilogString(alarmCharacteristic), alarmSettings);
			return isAlarmOff;
		}

		/// <summary> Sets alarm on or off.</summary>
		public async Task SetIsAlarmOffAsync(bool isActivated)
		{
			if (DeviceInfo.Platform != DevicePlatform.Unknown && MainThread.IsMainThread == false)
			{
				throw new System.Exception("Can not turn alarm off. Platform must not be unknown and bluetooth code must be run on main thread.");
			}

			ICharacteristic alarmCharacteristic = await GetAlarmCharacteristicAsync();
			if (alarmCharacteristic == null)
			{
				Log.ForContext<LockItBase>().Debug("Getting alarm characteristic failed.");
				throw new System.Exception($"Can not set alarm {isActivated}. Getting alarm characteristic returned null.");
			}

			bool success;
			var command = new byte[] { isActivated ? (byte)1 : (byte)0 };
			try
			{
				success = await alarmCharacteristic.WriteAsync(command);
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Writing alarm settings failed.{AlarmCharacteristic}{CommandWritten}{Exception}", ToSerilogString(alarmCharacteristic), command[0], exception);
				throw new System.Exception($"Can not set alarm settings. {exception.Message}", exception);
			}

			if (!success)
			{
				Log.ForContext<LockItBase>().Error("Writing alarm settings failed.{AlarmCharacteristic}{CommandWritten}", ToSerilogString(alarmCharacteristic), command[0]);
				throw new System.Exception($"Can not set alarm settings. Writing  settings did not succeed.");
			}

			Log.ForContext<LockItBase>().Debug("Alarm settings written successfully.{AlarmCharacteristic}{CommandWritten}.", ToSerilogString(alarmCharacteristic), command[0]);
		}

		public async Task<bool> SetSoundAsync(SoundSettings settings)
		{
			if (DeviceInfo.Platform != DevicePlatform.Unknown && MainThread.IsMainThread == false)
			{
				throw new System.Exception("Can not set sound settings. Platform must not be unknown and bluetooth code must be run on main thread.");
			}

			ICharacteristic soundCharacteristic = await GetSoundCharacteristicAsync();
			if (soundCharacteristic == null)
			{
				Log.ForContext<LockItBase>().Debug("Getting sound characteristic failed.");
				return false;
			}

			bool success;
			byte command = (byte)settings;
			try
			{
				success = await soundCharacteristic.WriteAsync(new byte[] { command });
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Writing sound settings failed.{SoundCharacteristic}{CommandWritten}{Exception}", ToSerilogString(soundCharacteristic), command, exception);
				throw new System.Exception($"Can not set sound settings. {exception.Message}", exception);
			}

			Log.ForContext<LockItBase>().Debug(success
					? "Writing sound settings failed.{SoundCharacteristic}{CommandWritten}"
					: "Sound settings written successfully.{SoundCharacteristic}{CommandWritten}",
				ToSerilogString(soundCharacteristic), command);

			return success;
		}

		public async Task<bool> SetAlarmSettingsAsync(AlarmSettings settings)
		{
			if (DeviceInfo.Platform != DevicePlatform.Unknown && MainThread.IsMainThread == false)
			{
				throw new System.Exception("Can not set alarm settings. Platform must not be unknown and bluetooth code must be run on main thread.");
			}

			ICharacteristic alarmSettingsCharacteristic = await GetAlarmSettingsCharacteristicAsync();
			if (alarmSettingsCharacteristic == null)
			{
				Log.ForContext<LockItBase>().Debug("Getting alarm settings characteristic failed.");
				return false;
			}

			bool success;
			byte command = (byte)settings;
			try
			{
				success = await alarmSettingsCharacteristic.WriteAsync(new byte[] { command });
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItBase>().Error("Writing alarm settings failed.{SoundCharacteristic}{CommandWritten}{Exception}", ToSerilogString(alarmSettingsCharacteristic), command, exception);
				throw new System.Exception($"Can not set alarm settings. {exception.Message}", exception);
			}

			Log.ForContext<LockItBase>().Debug(success
					? "Writing alarm settings failed.{SoundCharacteristic}{CommandWritten}"
					: "Alarm settings written successfully.{SoundCharacteristic}{CommandWritten}",
				ToSerilogString(alarmSettingsCharacteristic), command);

			return success;
		}

		private static byte[] bitShift(byte[] data, int counter)
		{
			int mask = 0x000000FF;
			data[0] = (byte)(counter & mask);
			data[1] = (byte)(counter >> 8);

			return data;
		}


		/// <summary> Disconnect from bluetooth lock. </summary>
		public async Task Disconnect() => await Adapter.DisconnectDeviceAsync(Device);

		/// <summary>
		/// Don' t use .Destructure.ByTransforming<ICharacteristic>(...) because this would introduce a dependency to Plugin.BLE in main project.
		/// </summary> 
		/// <param name="charcteristic"></param>
		/// <returns></returns>
		private static string ToSerilogString(ICharacteristic charcteristic)
			=> charcteristic.Id.ToString();

		private static string ToSerilogString(byte[] byteArray)
			=> "***"; // For debuging purposes it might be reqired to return string.Join(",", byteArray); Do not log any confidental value in production context.
	}
}