#region Copyright & License Information
/*
 * Copyright 2007-2015 The OpenRA Developers (see AUTHORS)
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation. For more information,
 * see COPYING.
 */
#endregion

using System;
using System.Collections.Generic;
using System.Linq;
using OpenRA.Activities;
using OpenRA.Mods.Common.Activities;
using OpenRA.Mods.Common.Orders;
using OpenRA.Primitives;
using OpenRA.Traits;

namespace OpenRA.Mods.Common.Traits
{
	public class AircraftInfo : ITraitInfo, IFacingInfo, IOccupySpaceInfo, ICruiseAltitudeInfo, UsesInit<LocationInit>, UsesInit<FacingInit>
	{
		public readonly WRange CruiseAltitude = new WRange(1280);
		public readonly WRange IdealSeparation = new WRange(1706);
		[Desc("Whether the aircraft can be repulsed.")]
		public readonly bool Repulsable = true;
		[Desc("The speed at which the aircraft is repulsed from other aircraft. Specify -1 for normal movement speed.")]
		public readonly int RepulsionSpeed = -1;

		[ActorReference]
		public readonly string[] RepairBuildings = { "fix" };
		[ActorReference]
		public readonly string[] RearmBuildings = { "hpad", "afld" };
		public readonly int InitialFacing = 0;
		public readonly int ROT = 255;
		public readonly int Speed = 1;
		public readonly string[] LandableTerrainTypes = { };

		[Desc("Can the actor be ordered to move in to shroud?")]
		public readonly bool MoveIntoShroud = true;

		public virtual object Create(ActorInitializer init) { return new Aircraft(init, this); }
		public int GetInitialFacing() { return InitialFacing; }
		public WRange GetCruiseAltitude() { return CruiseAltitude; }
	}

	public class Aircraft : IFacing, IPositionable, ISync, INotifyKilled, IIssueOrder, IOrderVoice, INotifyAddedToWorld, INotifyRemovedFromWorld
	{
		static readonly Pair<CPos, SubCell>[] NoCells = { };

		readonly AircraftInfo info;
		readonly Actor self;

		[Sync] public int Facing { get; set; }
		[Sync] public WPos CenterPosition { get; private set; }
		public CPos TopLeft { get { return self.World.Map.CellContaining(CenterPosition); } }
		public IDisposable Reservation;
		public int ROT { get { return info.ROT; } }

		public Aircraft(ActorInitializer init, AircraftInfo info)
		{
			this.info = info;
			this.self = init.Self;

			if (init.Contains<LocationInit>())
				SetPosition(self, init.Get<LocationInit, CPos>());

			if (init.Contains<CenterPositionInit>())
				SetPosition(self, init.Get<CenterPositionInit, WPos>());

			Facing = init.Contains<FacingInit>() ? init.Get<FacingInit, int>() : info.InitialFacing;
		}

		public void Repulse()
		{
			var repulsionForce = GetRepulsionForce();

			var repulsionFacing = Util.GetFacing(repulsionForce, -1);
			if (repulsionFacing == -1)
				return;

			var speed = info.RepulsionSpeed != -1 ? info.RepulsionSpeed : MovementSpeed;
			SetPosition(self, CenterPosition + FlyStep(speed, repulsionFacing));
		}

		public virtual WVec GetRepulsionForce()
		{
			if (!info.Repulsable)
				return WVec.Zero;

			// Repulsion only applies when we're flying!
			var altitude = CenterPosition.Z;
			if (altitude != info.CruiseAltitude.Range)
				return WVec.Zero;

			return self.World.FindActorsInCircle(self.CenterPosition, info.IdealSeparation)
				.Where(a => !a.IsDead && a.HasTrait<Aircraft>() && a.Info.Traits.Get<AircraftInfo>().CruiseAltitude == info.CruiseAltitude)
				.Select(GetRepulsionForce)
				.Aggregate(WVec.Zero, (a, b) => a + b);
		}

		public WVec GetRepulsionForce(Actor other)
		{
			if (self == other || other.CenterPosition.Z < self.CenterPosition.Z)
				return WVec.Zero;

			var d = self.CenterPosition - other.CenterPosition;
			var distSq = d.HorizontalLengthSquared;
			if (distSq > info.IdealSeparation.Range * info.IdealSeparation.Range)
				return WVec.Zero;

			if (distSq < 1)
			{
				var yaw = self.World.SharedRandom.Next(0, 1023);
				var rot = new WRot(WAngle.Zero, WAngle.Zero, new WAngle(yaw));
				return new WVec(1024, 0, 0).Rotate(rot);
			}

			return (d * 1024 * 8) / (int)distSq;
		}

		public Actor GetActorBelow()
		{
			if (self.CenterPosition.Z != 0)
				return null; // not on the ground.

			return self.World.ActorMap.GetUnitsAt(self.Location)
				.FirstOrDefault(a => a.HasTrait<Reservable>());
		}

		protected void ReserveSpawnBuilding()
		{
			/* HACK: not spawning in the air, so try to assoc. with our afld. */
			var afld = GetActorBelow();
			if (afld == null)
				return;

			var res = afld.TraitOrDefault<Reservable>();

			if (res != null)
			{
				UnReserve();
				Reservation = res.Reserve(afld, self, this);
			}
		}

		public void UnReserve()
		{
			if (Reservation != null)
			{
				Reservation.Dispose();
				Reservation = null;
			}
		}

		public void Killed(Actor self, AttackInfo e)
		{
			UnReserve();
		}

		public void SetPosition(Actor self, WPos pos)
		{
			CenterPosition = pos;

			if (self.IsInWorld)
			{
				self.World.ScreenMap.Update(self);
				self.World.ActorMap.UpdatePosition(self, this);
			}
		}

		// Changes position, but not altitude
		public void SetPosition(Actor self, CPos cell, SubCell subCell = SubCell.Any)
		{
			SetPosition(self, self.World.Map.CenterOfCell(cell) + new WVec(0, 0, CenterPosition.Z));
		}

		public void SetVisualPosition(Actor self, WPos pos) { SetPosition(self, pos); }

		public void AddedToWorld(Actor self)
		{
			self.World.ActorMap.AddInfluence(self, this);
			self.World.ActorMap.AddPosition(self, this);
			self.World.ScreenMap.Add(self);
		}

		public void RemovedFromWorld(Actor self)
		{
			self.World.ActorMap.RemoveInfluence(self, this);
			self.World.ActorMap.RemovePosition(self, this);
			self.World.ScreenMap.Remove(self);
		}

		public bool AircraftCanEnter(Actor a)
		{
			if (self.AppearsHostileTo(a))
				return false;

			return info.RearmBuildings.Contains(a.Info.Name)
				|| info.RepairBuildings.Contains(a.Info.Name);
		}

		public bool IsLeavingCell(CPos location, SubCell subCell = SubCell.Any) { return false; } // TODO: Handle landing
		public SubCell GetValidSubCell(SubCell preferred) { return SubCell.Invalid; }
		public SubCell GetAvailableSubCell(CPos a, SubCell preferredSubCell = SubCell.Any, Actor ignoreActor = null, bool checkTransientActors = true)
		{
			// Does not use any subcell
			return SubCell.Invalid;
		}

		public bool CanEnterCell(CPos cell, Actor ignoreActor = null, bool checkTransientActors = true) { return true; }

		public bool CanEnterTargetNow(Actor self, Target target)
		{
			if (target.Positions.Any(p => self.World.ActorMap.GetUnitsAt(self.World.Map.CellContaining(p)).Any(a => a != self && a != target.Actor)))
				return false;
			var res = target.Actor.TraitOrDefault<Reservable>();
			if (res == null)
				return true;
			UnReserve();
			Reservation = res.Reserve(target.Actor, self, this);
			return true;
		}

		public int MovementSpeed
		{
			get
			{
				var modifiers = self.TraitsImplementing<ISpeedModifier>()
					.Select(m => m.GetSpeedModifier());
				return Util.ApplyPercentageModifiers(info.Speed, modifiers);
			}
		}

		public IEnumerable<Pair<CPos, SubCell>> OccupiedCells() { return NoCells; }

		public WVec FlyStep(int facing)
		{
			return FlyStep(MovementSpeed, facing);
		}

		public WVec FlyStep(int speed, int facing)
		{
			var dir = new WVec(0, -1024, 0).Rotate(WRot.FromFacing(facing));
			return speed * dir / 1024;
		}

		public bool CanLand(CPos cell)
		{
			if (!self.World.Map.Contains(cell))
				return false;

			if (self.World.ActorMap.AnyUnitsAt(cell))
				return false;

			var type = self.World.Map.GetTerrainInfo(cell).Type;
			return info.LandableTerrainTypes.Contains(type);
		}

		public virtual IEnumerable<Activity> GetResupplyActivities(Actor a)
		{
			var name = a.Info.Name;
			if (info.RearmBuildings.Contains(name))
				yield return new Rearm(self);
			if (info.RepairBuildings.Contains(name))
				yield return new Repair(a);
		}

		public IEnumerable<IOrderTargeter> Orders
		{
			get
			{
				yield return new EnterAlliedActorTargeter<Building>("Enter", 5,
					target => AircraftCanEnter(target), target => !Reservable.IsReserved(target));

				yield return new AircraftMoveOrderTargeter(info);
			}
		}

		public Order IssueOrder(Actor self, IOrderTargeter order, Target target, bool queued)
		{
			if (order.OrderID == "Enter")
				return new Order(order.OrderID, self, queued) { TargetActor = target.Actor };

			if (order.OrderID == "Move")
				return new Order(order.OrderID, self, queued) { TargetLocation = self.World.Map.CellContaining(target.CenterPosition) };

			return null;
		}

		public string VoicePhraseForOrder(Actor self, Order order)
		{
			switch (order.OrderString)
			{
				case "Move":
				case "Enter":
				case "ReturnToBase":
				case "Stop":
					return "Move";
				default: return null;
			}
		}
	}

	class AircraftMoveOrderTargeter : IOrderTargeter
	{
		public string OrderID { get { return "Move"; } }
		public int OrderPriority { get { return 4; } }
		public bool OverrideSelection { get { return false; } }

		readonly AircraftInfo info;

		public AircraftMoveOrderTargeter(AircraftInfo info) { this.info = info; }

		public bool CanTarget(Actor self, Target target, List<Actor> othersAtTarget, TargetModifiers modifiers, ref string cursor)
		{
			if (target.Type != TargetType.Terrain)
				return false;

			var location = self.World.Map.CellContaining(target.CenterPosition);
			var explored = self.Owner.Shroud.IsExplored(location);
			cursor = self.World.Map.Contains(location) ?
				(self.World.Map.GetTerrainInfo(location).CustomCursor ?? "move") :
				"move-blocked";

			IsQueued = modifiers.HasModifier(TargetModifiers.ForceQueue);

			if (!explored && !info.MoveIntoShroud)
				cursor = "move-blocked";

			return true;
		}

		public bool IsQueued { get; protected set; }
	}
}