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

namespace TINK.Services.BluetoothLock.BLE
{
	/// <summary> Manages ILockIt- Locks.</summary>
	public abstract class LockItByScanServiceBase : LockItServiceBase
	{
		/// <summary> Service to manage bluetooth stack. </summary>
		private IBluetoothLE BluetoothService { get; }

		/// <summary> Returns true if location permission is required (Android) but on given. </summary>
		private Func<Task<bool>> IsLocationPermissionMissingDelegate { get; }

		/// <summary> Returns true if location service is required (Android) and off. </summary>
		private Func<bool> IsLocationRequiredAndOffDelegate { get; }

		private Func<IDevice, LockInfoAuthTdo, IAdapter, Task<LockItBase>> AuthenticateDelegate { get; set; }

		public LockItByScanServiceBase(
			ICipher cipher,
			Func<IDevice, LockInfoAuthTdo, IAdapter, Task<LockItBase>> authenticateDelegate,
			IBluetoothLE bluetoothLE,
			Func<Task<bool>> isLocationPermissionMissingDelegate,
			Func<bool> isLocationRequiredAndOffDelegate) : base(cipher)
		{
			BluetoothService = bluetoothLE
					?? throw new ArgumentException($"Can not instantiate {nameof(LockItByScanServiceBase)}- object. No bluetooth service available.");

			IsLocationPermissionMissingDelegate = isLocationPermissionMissingDelegate
					?? throw new ArgumentException($"Can not instantiate {nameof(LockItByScanServiceBase)}- object. No location permission missing delegate available.");

			IsLocationRequiredAndOffDelegate = isLocationRequiredAndOffDelegate
					?? throw new ArgumentException($"Can not instantiate {nameof(LockItByScanServiceBase)}- object. No location .");

			AuthenticateDelegate = authenticateDelegate;
		}

		/// <summary> Connects to lock.</summary>
		/// <remarks> Consists of a bluetooth connect plus invocation of an authentication sequence. </remarks>
		/// <param name="authInfo"> Info required to connect to lock.</param>
		/// <param name="connectTimeout">Timeout for connect operation.</param>
		public async Task<LockInfoTdo> ConnectAsync(LockInfoAuthTdo authInfo, TimeSpan connectTimeout)
		{
			if (DeviceInfo.Platform != DevicePlatform.Unknown && MainThread.IsMainThread == false)
			{
				throw new System.Exception("Can not connect to lock by name. Platform must not be unknown and bluetooth code must be run on main thread.");
			}

			Log.ForContext<LockItByScanServiceBase>().Debug($"Request to connect to device {authInfo.Id}.");

			var lockIt = DeviceList.FirstOrDefault(x => x.Name.GetBluetoothLockId() == authInfo.Id || x.Guid == authInfo.Guid);

			if (lockIt != null && lockIt.GetDeviceState() == DeviceState.Connected)
			{
				// Nothing to do
				Log.ForContext<LockItByScanServiceBase>().Debug($"Nothing to do. Lock is already connected.");
				return await lockIt.GetLockStateAsync();
			}

			if (lockIt != null)
			{
				// Reconnect required
				Log.ForContext<LockItByScanServiceBase>().Debug($"Device {lockIt.Name} has been already connected but needs reconnect.");
				await lockIt.ReconnectAsync(authInfo, connectTimeout);
				return await lockIt.GetLockStateAsync();
			}

			// Device has not yet been discovered.
			Log.ForContext<LockItByScanServiceBase>().Verbose("Starting scan for new devices...");
			var newlyDiscovertedDevice = await ScanForNewDevices(new List<int> { authInfo.Id }, connectTimeout);

			var bleDevice = newlyDiscovertedDevice.FirstOrDefault(x => x.Name.GetBluetoothLockId() == authInfo.Id);

			if (bleDevice == null)
			{
				// Try to check why lock was not found.
				var bluetoothState = await BluetoothService.GetBluetoothState();
				switch (bluetoothState)
				{
					case BluetoothState.On:
						break;

					case BluetoothState.Off:
						Log.ForContext<LockItByScanServiceBase>().Debug("Lock probable not found because bluetooth is off.");
						throw new ConnectBluetoothNotOnException();

					default:
						Log.ForContext<LockItByScanServiceBase>().Debug("Lock probable not found because unexpected bluetooth state {state} detected.", bluetoothState);
						throw new ConnectBluetoothNotOnException(bluetoothState);
				}

				if (await IsLocationPermissionMissingDelegate())
				{
					Log.ForContext<LockItByScanServiceBase>().Debug("Lock probable not found because missing location permission.");
					throw new ConnectLocationPermissionMissingException();
				}
				if (IsLocationRequiredAndOffDelegate())
				{
					Log.ForContext<LockItByScanServiceBase>().Debug("Lock probable not found because location is off.");
					throw new ConnectLocationOffException();
				}

				Log.ForContext<LockItByScanServiceBase>().Debug("Can not connect because device was not discovered. List of discovered devices {deviceList}.", String.Join(";", newlyDiscovertedDevice?.Select(x => x?.Id)));
				throw new OutOfReachException();
			}

			var adapter = CrossBluetoothLE.Current.Adapter;
			var cts = new CancellationTokenSource(connectTimeout);

			// Connect to device and authenticate.
			Log.ForContext<LockItByScanServiceBase>().Debug($"Device sucessfully discovered. Request connect to device {bleDevice?.Name}. Connect state is {bleDevice?.State}.");
			try
			{
				await adapter.ConnectToDeviceAsync(
					bleDevice,
					new ConnectParameters(forceBleTransport: true /* Force BLE transport */),
					cts.Token);
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItByScanServiceBase>().Error("Can not connect to device by name. {Exception}", exception);
				if (exception is TaskCanceledException)
				{
					// A timeout occurred.
					throw new System.Exception($"Can not connect to lock by name.\r\nTimeout is {connectTimeout.TotalMilliseconds} [ms].\r\n{exception.Message}", exception);
				}

				Log.ForContext<LockItByScanServiceBase>().Error("Bluetooth connect to known device request failed. {Exception}", exception);
				throw new System.Exception($"Can not connect to lock by name. {exception.Message}", exception);
			}

			lockIt = await AuthenticateDelegate(bleDevice, authInfo, CrossBluetoothLE.Current.Adapter);
			if (lockIt == null)
			{
				await adapter.DisconnectDeviceAsync(bleDevice);
				return await Task.FromResult<LockInfoTdo>(null);
			}

			DeviceList.Add(lockIt);

			return await lockIt.GetLockStateAsync();
		}

		/// <summary> Checks for locks which have not yet been discoverted and connects them. </summary>
		/// <remarks> Consists of a bluetooth connect plus invocation of an authentication sequence for each lock to be connected. </remarks>
		/// <param name="locksInfo">Locks to reconnect.</param>
		/// <param name="connectTimeout">Timeout for connect operation of a single lock.</param>
		protected override async Task<IEnumerable<ILockService>> CheckConnectMissing(IEnumerable<LockInfoAuthTdo> locksInfo, TimeSpan connectTimeout)
		{
			// Get list of target locks without invalid entries.
			var validLocksInfo = locksInfo
				.Where(x => x.IsIdValid)
				.Where(x => x.K_seed.Length > 0 && x.K_u.Length > 0)
				.ToList();

			// Get Locks to scan for
			var locksInfoToScanFor = validLocksInfo.Where(x => !DeviceList.Any(y => y.Name.GetBluetoothLockId() == x.Id)).ToList();

			// Check if bluetooth scan is required
			if (locksInfoToScanFor.Count <= 0)
			{
				// No Scan required.
				return new List<LockItBase>();
			}

			// Do bluetooth scan
			var scanTargets = locksInfoToScanFor.Select(x => x.Id).ToList();
			var newlyDiscovertedDevicesList = await ScanForNewDevices(scanTargets, TimeSpan.FromSeconds(connectTimeout.TotalSeconds * scanTargets.Count));

			var locksList = new List<LockItBase>();

			// Connect to newly discovered devices.
			foreach (var lockInfo in locksInfoToScanFor)
			{
				var device = newlyDiscovertedDevicesList.FirstOrDefault(x => x.Name.GetBluetoothLockId() == lockInfo.Id);
				if (device == null)
				{
					// No device found for given lock.
					continue;
				}

				Log.ForContext<LockItByScanServiceBase>().Debug($"Request connect to device {device?.Name}. Connect state is {device?.State}.");

				var cts = new CancellationTokenSource(connectTimeout);

				try
				{
					// Connect to device and authenticate.
					await CrossBluetoothLE.Current.Adapter.ConnectToDeviceAsync(
						device,
						new ConnectParameters(forceBleTransport: true), // Force BLE transport 
						cts.Token);
				}
				catch (System.Exception exception)
				{
					Log.ForContext<LockItByScanServiceBase>().Error("Can not connect to lock. {Exception}", exception);
					continue;
				}

				LockItBase lockIt = null;
				try
				{
					lockIt = await AuthenticateDelegate(device, lockInfo, CrossBluetoothLE.Current.Adapter);
				}
				catch (System.Exception exception)
				{
					// Member is called for background update of missing devices. 
					// Do not display any error messages.
					Log.ForContext<LockItByScanServiceBase>().Error($"Authentication failed. {exception.Message}");
					continue;
				}
				if (lockIt == null)
				{
					// connectiong to device succeded.
					continue;
				}

				Log.ForContext<LockItByScanServiceBase>().Debug($"Auth succeeded for device {device}.");
				locksList.Add(lockIt);
			}

			return locksList;
		}

		/// <summary> Scans for a given set of devices.</summary>
		/// <param name="targetLocks">Locks to scan for.</param>
		/// <returns></returns>
		private static async Task<IEnumerable<IDevice>> ScanForNewDevices(
			IEnumerable<int> targetLocks,
			TimeSpan connectTimeout)
		{
			var adapter = CrossBluetoothLE.Current.Adapter;

			var newlyDiscovertedDevicesList = new List<IDevice>();

			var cts = new CancellationTokenSource(connectTimeout);

			// Not all devices already connected.
			// Start scanning
			adapter.DeviceDiscovered += (s, a) =>
			{
				var name = a.Device.Name;
				if (string.IsNullOrEmpty(name))
				{
					// Lock without name detected.
					Log.ForContext<LockItByScanServiceBase>().Debug($"Ble decvice without name discovered. RSSI={a.Device.Rssi}, GUID={a.Device.Id}, State={a.Device.State}.");
					return;
				}

				if (targetLocks.Where(x => x != TextToLockItTypeHelper.INVALIDLOCKID).Contains(name.GetBluetoothLockId()))
				{
					Log.ForContext<LockItByScanServiceBase>().Debug($"New LOCKIT device {name} discovered.  RSSI={a.Device.Rssi}, GUID={a.Device.Id}, State={a.Device.State}.");

					newlyDiscovertedDevicesList.Add(a.Device);

					if (newlyDiscovertedDevicesList.Count() >= targetLocks.Count())
					{
						cts.Cancel();
					}

					return;
				}

				Log.ForContext<LockItByScanServiceBase>().Verbose($"Device of unknown advertisement name {name} discovered.  RSSI={a.Device.Rssi}, GUID={a.Device.Id}, State={a.Device.State}.");
			};

			try
			{
				await adapter.StartScanningForDevicesAsync(cancellationToken: cts.Token);
			}
			catch (System.Exception exception)
			{
				Log.ForContext<LockItByScanServiceBase>().Error("Bluetooth scan failed. {Exception}", exception);
				throw;
			}
			finally
			{
				try
				{
					await adapter.StopScanningForDevicesAsync();
				}
				catch (System.Exception exception)
				{
					Log.ForContext<LockItByScanServiceBase>().Error("Stop scanning failed. {Excpetion}", exception);
					throw;
				}
			}

			return newlyDiscovertedDevicesList;
		}
	}
}