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

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> m_oDateTimeNowProvider;

        /// <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.
            m_oDateTimeNowProvider = () => 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="p_oDateTimeNowProvider">
        /// 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>
        /// <param name="p_oRemainingTime">Time span which holds duration how long bike still will be reserved.</param>
        public StateRequestedInfo(
            Func<DateTime> p_oDateTimeNowProvider, 
            DateTime p_oFrom, 
            string p_strMailAddress,
            string p_strCode) : base(InUseStateEnum.Reserved)
        {
            m_oDateTimeNowProvider = p_oDateTimeNowProvider ?? (() => DateTime.Now);
            From = p_oFrom;
            MailAddress = p_strMailAddress;
            Code = p_strCode;
        }

        /// <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 = m_oDateTimeNowProvider().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; }
    }
}