using System;
using System.Runtime.Serialization;
using Newtonsoft.Json;

namespace TINK.Model.State
{
	/// <summary>
	/// Manages state reserved.
	/// </summary>
	[DataContract]
	public sealed class StateRequestedInfo : BaseState, IBaseState, INotAvailableState
	{
		// Maximum time while reserving request is kept.
		public static readonly TimeSpan MaximumReserveTime = new TimeSpan(0, 15, 0); // 15 mins

		// Reference to date time provider.
		private Func<DateTime> _DateTimeNowProvider;

		/// <summary>
		/// Prevents an invalid instance to be created.
		/// Used by serializer only.
		/// </summary>
		private StateRequestedInfo() : base(InUseStateEnum.Reserved)
		{
			// Is called in context of JSON deserialization.
			_DateTimeNowProvider = () => DateTime.Now;
		}

		/// <summary>
		/// Reservation performed with other device/ before start of app. 
		/// Date time info when bike was reserved has been received from webserver.
		/// </summary>
		/// <param name="p_oRemainingTime">Time span which holds duration how long bike still will be reserved.</param>
		[JsonConstructor]
		private StateRequestedInfo(
			InUseStateEnum Value,
			DateTime From,
			string MailAddress,
			string Code) : this(() => DateTime.Now, From, MailAddress, Code)
		{
		}

		/// <summary>
		/// Reservation performed with other device/ before start of app. 
		/// Date time info when bike was reserved has been received from webserver.
		/// </summary>
		/// <param name="dateTimeNowProvider">
		/// Used to  to provide current date time information for potential calls of <seealso cref="GetIsStillReserved"/>.
		/// Not used to calculate remaining time because this duration whould always be shorter as the one received from webserver.
		/// </param>
		public StateRequestedInfo(
			Func<DateTime> dateTimeNowProvider,
			DateTime from,
			string mailAddress,
			string code) : base(InUseStateEnum.Reserved)
		{
			_DateTimeNowProvider = dateTimeNowProvider ?? (() => DateTime.Now);
			From = from;
			MailAddress = mailAddress;
			Code = code;
		}

		/// <summary>
		/// Tries update 
		/// </summary>
		/// <returns>True if reservation span has not exeeded and state remains reserved, false otherwise.</returns>
		/// <todo>Implement logging of time stamps.</todo>
		public bool GetIsStillReserved(out TimeSpan? p_oRemainingTime)
		{
			var l_oTimeReserved = _DateTimeNowProvider().Subtract(From);
			if (l_oTimeReserved > MaximumReserveTime)

			{
				// Reservation has elapsed. To not update remaining time.                
				p_oRemainingTime = null;
				return false;
			}

			p_oRemainingTime = MaximumReserveTime - l_oTimeReserved;
			return true;
		}

		/// <summary>
		/// State reserved. 
		/// Setter exists only for serialization purposes.
		/// </summary>
		public override InUseStateEnum Value
		{
			get
			{
				return InUseStateEnum.Reserved;
			}
		}

		/// <summary>
		/// Date time when bike was reserved.
		/// </summary>
		[DataMember]
		public DateTime From { get; }

		/// <summary>
		/// Mail address of user who reserved the bike.
		/// </summary>
		[DataMember]
		public string MailAddress { get; }

		/// <summary>
		/// Booking code.
		/// </summary>
		[DataMember]
		public string Code { get; }
	}
}