#region References
using System;

using Server.Network;
#endregion

namespace Server.Targeting
{
	public abstract class Target
	{
		private static int m_NextTargetID;

		private static bool m_TargetIDValidation = true;

		public static bool TargetIDValidation { get => m_TargetIDValidation; set => m_TargetIDValidation = value; }

		private readonly int m_TargetID;
		private int m_Range;
		private bool m_CheckLOS;
		private bool m_AllowNonlocal;
		private DateTime m_TimeoutTime;

		public DateTime TimeoutTime => m_TimeoutTime;

		protected Target(int range, bool allowGround, TargetFlags flags)
		{
			m_TargetID = ++m_NextTargetID;
			m_Range = range;
			AllowGround = allowGround;
			Flags = flags;

			m_CheckLOS = true;
		}

		public static void Cancel(Mobile m)
		{
			var ns = m.NetState;

			if (ns != null)
			{
				ns.Send(CancelTarget.Instance);
			}

			var targ = m.Target;

			if (targ != null)
			{
				targ.OnTargetCancel(m, TargetCancelType.Canceled);
			}
		}

		private Timer m_TimeoutTimer;

		public void BeginTimeout(Mobile from, TimeSpan delay)
		{
			m_TimeoutTime = DateTime.UtcNow + delay;

			if (m_TimeoutTimer != null)
			{
				m_TimeoutTimer.Stop();
			}

			m_TimeoutTimer = new TimeoutTimer(this, from, delay);
			m_TimeoutTimer.Start();
		}

		public void CancelTimeout()
		{
			if (m_TimeoutTimer != null)
			{
				m_TimeoutTimer.Stop();
			}

			m_TimeoutTimer = null;
		}

		public void Timeout(Mobile from)
		{
			CancelTimeout();
			from.ClearTarget();

			Cancel(from);

			OnTargetCancel(from, TargetCancelType.Timeout);
			OnTargetFinish(from);
		}

		private class TimeoutTimer : Timer
		{
			private readonly Target m_Target;
			private readonly Mobile m_Mobile;

			private static readonly TimeSpan ThirtySeconds = TimeSpan.FromSeconds(30.0);
			private static readonly TimeSpan TenSeconds = TimeSpan.FromSeconds(10.0);
			private static readonly TimeSpan OneSecond = TimeSpan.FromSeconds(1.0);

			public TimeoutTimer(Target target, Mobile m, TimeSpan delay)
				: base(delay)
			{
				m_Target = target;
				m_Mobile = m;

				if (delay >= ThirtySeconds)
				{
					Priority = TimerPriority.FiveSeconds;
				}
				else if (delay >= TenSeconds)
				{
					Priority = TimerPriority.OneSecond;
				}
				else if (delay >= OneSecond)
				{
					Priority = TimerPriority.TwoFiftyMS;
				}
				else
				{
					Priority = TimerPriority.TwentyFiveMS;
				}
			}

			protected override void OnTick()
			{
				if (m_Mobile.Target == m_Target)
				{
					m_Target.Timeout(m_Mobile);
				}
			}
		}

		public bool CheckLOS { get => m_CheckLOS; set => m_CheckLOS = value; }

		public bool DisallowMultis { get; set; }

		public bool AllowNonlocal { get => m_AllowNonlocal; set => m_AllowNonlocal = value; }

		public int TargetID => m_TargetID;

		public virtual Packet GetPacketFor(NetState ns)
		{
			return new TargetReq(this);
		}

		public void Cancel(Mobile from, TargetCancelType type)
		{
			CancelTimeout();
			from.ClearTarget();

			OnTargetCancel(from, type);
			OnTargetFinish(from);
		}

		public void Invoke(Mobile from, object targeted)
		{
			var enhancedClient = from.NetState != null && from.NetState.IsEnhancedClient;

			CancelTimeout();
			from.ClearTarget();

			if (from.Deleted)
			{
				OnTargetCancel(from, TargetCancelType.Canceled);
				OnTargetFinish(from);
				return;
			}

			Point3D loc;
			Map map;

			if (targeted is LandTarget)
			{
				loc = ((LandTarget)targeted).Location;
				map = from.Map;

				if (enhancedClient && loc.X == 0 && loc.Y == 0 && !from.InRange(loc, 10))
				{
					OnTargetCancel(from, TargetCancelType.Canceled);
					OnTargetFinish(from);
					return;
				}
			}
			else if (targeted is StaticTarget)
			{
				loc = ((StaticTarget)targeted).Location;
				map = from.Map;
			}
			else if (targeted is Mobile)
			{
				if (((Mobile)targeted).Deleted)
				{
					OnTargetDeleted(from, targeted);
					OnTargetFinish(from);
					return;
				}
				else if (!((Mobile)targeted).CanTarget)
				{
					OnTargetUntargetable(from, targeted);
					OnTargetFinish(from);
					return;
				}

				loc = ((Mobile)targeted).Location;
				map = ((Mobile)targeted).Map;
			}
			else if (targeted is Item)
			{
				var item = (Item)targeted;

				if (item.Deleted)
				{
					OnTargetDeleted(from, targeted);
					OnTargetFinish(from);
					return;
				}
				else if (!item.CanTarget)
				{
					OnTargetUntargetable(from, targeted);
					OnTargetFinish(from);
					return;
				}

				var root = item.RootParent;

				if (!m_AllowNonlocal && root is Mobile && root != from && from.AccessLevel == AccessLevel.Player)
				{
					OnNonlocalTarget(from, targeted);
					OnTargetFinish(from);
					return;
				}

				loc = item.GetWorldLocation();
				map = item.Map;
			}
			else
			{
				OnTargetCancel(from, TargetCancelType.Canceled);
				OnTargetFinish(from);
				return;
			}

			if (map == null || map != from.Map || (m_Range != -1 && !from.InRange(loc, m_Range)))
			{
				OnTargetOutOfRange(from, targeted);
			}
			else
			{
				if (!from.CanSee(targeted))
				{
					OnCantSeeTarget(from, targeted);
				}
				else if (m_CheckLOS && !from.InLOS(targeted))
				{
					OnTargetOutOfLOS(from, targeted);
				}
				else if (targeted is Item && ((Item)targeted).InSecureTrade)
				{
					OnTargetInSecureTrade(from, targeted);
				}
				else if (targeted is Item && !((Item)targeted).IsAccessibleTo(from))
				{
					OnTargetNotAccessible(from, targeted);
				}
				else if (targeted is Item && !((Item)targeted).CheckTarget(from, this, targeted))
				{
					OnTargetUntargetable(from, targeted);
				}
				else if (targeted is Mobile && !((Mobile)targeted).CheckTarget(from, this, targeted))
				{
					OnTargetUntargetable(from, targeted);
				}
				else if (from.Region.OnTarget(from, this, targeted))
				{
					OnTarget(from, targeted);
				}
			}

			OnTargetFinish(from);
		}

		protected virtual void OnTarget(Mobile from, object targeted)
		{ }

		protected virtual void OnTargetNotAccessible(Mobile from, object targeted)
		{
			from.SendLocalizedMessage(500447); // That is not accessible.
		}

		protected virtual void OnTargetInSecureTrade(Mobile from, object targeted)
		{
			from.SendLocalizedMessage(500447); // That is not accessible.
		}

		protected virtual void OnNonlocalTarget(Mobile from, object targeted)
		{
			from.SendLocalizedMessage(500447); // That is not accessible.
		}

		protected virtual void OnCantSeeTarget(Mobile from, object targeted)
		{
			from.SendLocalizedMessage(500237); // Target can not be seen.
		}

		protected virtual void OnTargetOutOfLOS(Mobile from, object targeted)
		{
			from.SendLocalizedMessage(500237); // Target can not be seen.
		}

		protected virtual void OnTargetOutOfRange(Mobile from, object targeted)
		{
			from.SendLocalizedMessage(500446); // That is too far away.
		}

		protected virtual void OnTargetDeleted(Mobile from, object targeted)
		{ }

		protected virtual void OnTargetUntargetable(Mobile from, object targeted)
		{
			from.SendLocalizedMessage(500447); // That is not accessible.
		}

		protected virtual void OnTargetCancel(Mobile from, TargetCancelType cancelType)
		{ }

		protected virtual void OnTargetFinish(Mobile from)
		{ }

		public int Range { get => m_Range; set => m_Range = value; }

		public bool AllowGround { get; set; }

		public TargetFlags Flags { get; set; }
	}
}