using System;

namespace TINK.Model.State
{
	using System.ComponentModel;
	using System.Runtime.Serialization;

	/// <summary>
	/// Manges the state of a bike.
	/// </summary>
	[DataContract]
	public class StateInfoMutable : INotifyPropertyChanged, IStateInfoMutable
	{
		/// <summary>
		/// Provider for current date time to calculate remaining time on demand for state of type reserved.
		/// </summary>
		private readonly Func<DateTime> _DateTimeNowProvider;

		// Holds the current disposable state value
		private StateInfo _StateInfo;

		/// <summary>
		/// Backs up remaining time of child object.
		/// </summary>
		private TimeSpan? _RemainingTime = null;

		/// <summary> Notifies clients about state changes. </summary>
		public event PropertyChangedEventHandler PropertyChanged;

		/// <summary>
		/// Constructs a state object from source.
		/// </summary>
		/// <param name="state">State info to load from.</param>
		public StateInfoMutable(
			Func<DateTime> dateTimeNowProvider = null,
			IStateInfo state = null)
		{
			// Back up date time provider to be able to pass this to requested- object if state changes to requested.
			_DateTimeNowProvider = dateTimeNowProvider != null
				? dateTimeNowProvider
				: () => DateTime.Now;

			_StateInfo = Create(state, dateTimeNowProvider);
		}

		/// <summary>
		/// Loads state from immutable source.
		/// </summary>
		/// <param name="state">State to load from.</param>
		public void Load(IStateInfo state)
		{
			if (state == null)
			{
				throw new ArgumentException("Can not load state info, object must not be null.");
			}

			// Back up last state value and remaining time value
			// to be able to check whether an event has to be fired or not.
			var l_oLastState = Value;
			var l_oLastRemainingTime = _RemainingTime;

			// Create new state info object from source.
			_StateInfo = Create(state, _DateTimeNowProvider);

			// Update remaining time value.
			_StateInfo.GetIsStillReserved(out _RemainingTime);

			if (l_oLastState == _StateInfo.Value
				&& l_oLastRemainingTime == _RemainingTime)
			{
				return;
			}

			// State has changed, notify clients.
			PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(State)));
		}

		/// <summary>
		/// Creates a state info object.
		/// </summary>
		/// <param name="state">State to load from.</param>
		private static StateInfo Create(
			IStateInfo state,
			Func<DateTime> dateTimeNowProvider)
		{
			switch (state != null ? state.Value : InUseStateEnum.Disposable)
			{
				case InUseStateEnum.Disposable:
				case InUseStateEnum.FeedbackPending:
					return new StateInfo(state != null ? state.Value == InUseStateEnum.FeedbackPending : false);

				case InUseStateEnum.Reserved:
					// Todo: Handle p_oFrom == null here.
					// Todo: Handle p_oDuration == null here.
					return new StateInfo(
						dateTimeNowProvider,
						state.From.Value,
						state.MailAddress,
						state.Code);


				case InUseStateEnum.Booked:
					// Todo: Handle p_oFrom == null here.
					// Todo: Clearify question: What to do if code changes form one value to another? This should never happen.
					// Todo: Clearify question: What to do if from time changes form one value to another? This should never happen.
					return new StateInfo(
						state.From.Value,
						state.MailAddress,
						state.Code);

				default:
					// Todo: New state Busy has to be defined.
					throw new Exception(string.Format("Can not create new state info object. Unknown state {0} detected.", state.Value));
			}
		}

		/// <summary>
		/// Gets the state value of object.
		/// </summary>
		public InUseStateEnum Value
			=> _StateInfo.Value;

		/// <summary>
		/// Member for serialization purposes.
		/// </summary>
		[DataMember]
		private BaseState StateInfoObject
		{
			get { return _StateInfo.StateInfoObject; }
			set
			{
				var l_oStateOccupied = value as StateOccupiedInfo;
				if (l_oStateOccupied != null)
				{
					_StateInfo = new StateInfo(l_oStateOccupied.From, l_oStateOccupied.MailAddress, l_oStateOccupied.Code);
					return;
				}

				var l_oStateRequested = value as StateRequestedInfo;
				if (l_oStateRequested != null)
				{
					_StateInfo = new StateInfo(_DateTimeNowProvider, l_oStateRequested.From, l_oStateRequested.MailAddress, l_oStateRequested.Code);
					return;
				}

				_StateInfo = new StateInfo();

			}
		}
		/// Transforms object to string.
		/// </summary>
		/// <returns></returns>
		public new string ToString()
		{
			return _StateInfo.ToString();
		}

		/// <summary>
		/// Checks and updates state if required.
		/// </summary>
		/// <returns>Value indicating wheter state has changed</returns>
		public void UpdateOnTimeElapsed()
		{
			switch (_StateInfo.Value)
			{
				// State is disposable or booked. No need to update "OnTimeElapsed"
				case InUseStateEnum.Disposable:
				case InUseStateEnum.Booked:
					return;
			}

			// Check if maximum reserved time has elapsed.
			if (!_StateInfo.GetIsStillReserved(out _RemainingTime))
			{
				// Time has elapsed, switch state to disposable and notfiy client
				_StateInfo = new StateInfo();
				PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(State)));
				return;
			}

			PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(RemainingTime)));
		}

		/// <summary> Updates state from webserver. </summary>
		/// <param name="state">State of the bike.</param>
		/// <param name="from">Date time when bike was reserved/ booked.</param>
		/// <param name="mailAddress">Mailaddress of the one which reserved/ booked.</param>
		/// <param name="code">Booking code if bike is booked or reserved.</param>
		/// <param name="supressNotifyPropertyChanged">Controls whether notify property changed events are fired or not.</param>
		public void Load(
			InUseStateEnum state,
			DateTime? from = null,
			string mailAddress = null,
			string code = null,
			Bikes.BikeInfoNS.BC.NotifyPropertyChangedLevel notifyLevel = Bikes.BikeInfoNS.BC.NotifyPropertyChangedLevel.All)
		{
			var lastState = _StateInfo.Value;

			switch (state)
			{
				case InUseStateEnum.Disposable:
					_StateInfo = new StateInfo();

					// Set value to null. Otherwise potentially obsolete value will be taken remaining time.
					_RemainingTime = null;
					break;

				case InUseStateEnum.Reserved:
					// Todo: Handle p_oFrom == null here.
					// Todo: Handle p_oDuration == null here.
					_StateInfo = new StateInfo(
						_DateTimeNowProvider,
						from.Value,
						mailAddress,
						code);

					// Set value to null. Otherwise potentially obsolete value will be taken remaining time.
					_RemainingTime = null;
					break;

				case InUseStateEnum.Booked:
					// Todo: Handle p_oFrom == null here.
					// Todo: Clearify question: What to do if code changes form one value to another? This should never happen.
					// Todo: Clearify question: What to do if from time changes form one value to another? This should never happen.
					_StateInfo = new StateInfo(
						from.Value,
						mailAddress,
						code);

					// Set value to null. Otherwise potentially obsolete value will be taken remaining time.
					_RemainingTime = null;
					break;

				default:
					// Todo: New state Busy has to be defined.
					break;
			}

			if (lastState != _StateInfo.Value
				&& notifyLevel == Bikes.BikeInfoNS.BC.NotifyPropertyChangedLevel.All)
			{
				// State has changed, notify clients.
				PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(State)));
			}
		}

		/// <summary>
		/// If bike is reserved time raimaining while bike stays reserved, null otherwise.
		/// </summary>
		public TimeSpan? RemainingTime
		{
			get
			{
				switch (_StateInfo.Value)
				{
					// State is either available or occupied.
					case InUseStateEnum.Disposable:
					case InUseStateEnum.Booked:
						return null;
				}

				if (_RemainingTime.HasValue == false)
				{
					// Value was not yet querried.
					// Do query before returning object.
					_StateInfo.GetIsStillReserved(out _RemainingTime);
				}

				return _RemainingTime;
			}
		}

		public DateTime? From
		{
			get
			{
				return _StateInfo.From;
			}
		}

		public string MailAddress
		{
			get
			{
				return _StateInfo.MailAddress;
			}
		}

		public string Code
		{
			get
			{
				return _StateInfo.Code;
			}
		}
	}
}