using System;
using System.Drawing;
using System.Diagnostics;
using freetrain.world.rail;
using freetrain.world.road;

namespace freetrain.world
{
	public delegate void TrafficVoxelHandler( TrafficVoxel v );

	/// <summary>
	/// 線路や道路などによって占有されているブロック
	/// </summary>
	/// TrafficOccupantには線路・道路・および車（電車もしくは自動車）が入れる
	[Serializable]
	public sealed class TrafficVoxel : AbstractVoxelImpl, Entity
	{
		private Car _car;

		private RailRoad _railRoad;

		private Road _road;

		private Accessory _accessory;
		public override bool transparent { get { return true; } }

		/// <summary>
		/// Fired when a car enters/leaves this traffic voxel
		/// </summary>
		public event TrafficVoxelHandler onCarChanged;

		/// <summary>
		/// Fired when a railroad is placed or removed.
		/// </summary>
		public static event TrafficVoxelHandler onRailRoadChanged;



		private TrafficVoxel( Location loc ) : base(loc) {}


		public interface Accessory {
			void drawBefore( DrawContext display, Point pt );
			void drawAfter( DrawContext display, Point pt );
			/// <summary>
			/// Called right after the accessory is removed.
			/// </summary>
			void onRemoved();
		}



		/// <summary>
		/// Car that occupies this voxel, if any, or null.
		/// </summary>
		public Car car {
			get {
				return _car;
			}
			set {
				_car = value;
				onModified();
				if(onCarChanged!=null)	onCarChanged(this);
			}
		}


		/// <summary>
		/// Railroad that occupies this voxel, or null otherwise.
		/// </summary>
		public RailRoad railRoad {
			get {
				return _railRoad;
			}
			set {
				Debug.Assert(car==null);
				_railRoad = value;
				onModified();
				if(onRailRoadChanged!=null)	onRailRoadChanged(this);
			}
		}

		/// <summary>
		/// Road that occupies this voxel, or null otherwise.
		/// </summary>
		public Road road {
			get {
				return _road;
			}
			set {
				Debug.Assert(car==null);
				_road = value;
				onModified();
			}
		}

		public Accessory accessory {
			get {
				return _accessory;
			}
			set {
				if( value==null && _accessory!=null )	_accessory.onRemoved();
				_accessory = value;
				onModified();
			}
		}
		
		/// <summary>
		/// Returns true if a car is already in this voxel.
		/// </summary>
		public bool isOccupied { get { return car!=null; }}



		public override object queryInterface( Type aspect ) {
			object o;

			if( railRoad!=null
			&&  (o=railRoad.queryInterface(aspect))!=null )		return o;

			// TODO: add queryInterface for trains and roads.

			return null;
		}
		
		public override bool onClick() {
			if( car!=null && car.onClick() )	return true;
			if( _railRoad!=null && _railRoad.onClick() )	return true;
			return false;
		}


		private void onModified() {
			if( _accessory==null && _railRoad==null && _road==null )
				remove();

			// update surrounding voxels if necessary
			if( _railRoad!=null )
				_railRoad.invalidateVoxel();
			if( _road!=null )
				_road.invalidateVoxel();

			// create/remove crossing.
			bool b = shouldHaveCrossing();
			if( b && _accessory==null ) {
				accessory = new RRCrossing(this);
				return;
			}
			if( !b && _accessory is RRCrossing ) {
				accessory = null;
				return;
			}
		}

		/// <summary>
		/// Check if this voxel should have a rail road crossing.
		/// </summary>
		/// <returns></returns>
		private bool shouldHaveCrossing() {
			if( _railRoad==null || _road==null )	return false;

			RailPattern rp = _railRoad.getPattern();
			Direction rdir1 = _railRoad.dir1;
			if( rp.numberOfRails!=2 || !rp.hasRail(rdir1.opposite) )
				return false;	// the rail must be going straight.
			if( !rdir1.isSharp )
				return false;	// rail must be paralell to X-axis or Y-axis.

			if( !_road.hasRoad(rdir1.left90) || !_road.hasRoad(rdir1.right90) )
				return false;	// road must be orthogonal to rail road

			return true;
		}


		public override Entity entity { get { return this; } }
		
		#region Entity implementation
		public bool isSilentlyReclaimable { get { return false; } }
		public bool isOwned { get { return true; } }

		// TODO: what's the value?
		public int entityValue { get { return 0; } }
		
		public void remove() {
			if(isOccupied) {
				if(car is Train.TrainCar)
					((Train.TrainCar)car).parent.remove();
				else
					car.remove();
			}
			BridgePierVoxel.teardownBridgeSupport(location,this);
			if( onEntityRemoved!=null )
				onEntityRemoved(this,null);
			World.world.remove(this);
		}

		public event EventHandler onEntityRemoved;
		#endregion



		public override void draw( DrawContext display, Point pt, int heightCutDiff ) {
			if(_road!=null)			_road.drawBefore(display,pt);
			if(_accessory!=null)	_accessory.drawBefore(display,pt);
			if(_railRoad!=null)		_railRoad.drawBefore(display,pt);
			if(_car!=null)			_car.draw(display,pt);
			if(_railRoad!=null)		_railRoad.drawAfter(display,pt);
			if(_accessory!=null)	_accessory.drawAfter(display,pt);
		}

		/// <summary>
		/// Gets the existing TrafficVoxel in the specified location,
		/// or create new TrafficVoxel if the location is unoccupied.
		/// </summary>
		/// <returns>null if the specified location is already occupied</returns>
		public static TrafficVoxel getOrCreate( Location loc ) {
			Voxel v = World.world[loc];
			if(v!=null)		return v as TrafficVoxel;

			return new TrafficVoxel(loc);
		}
		public static TrafficVoxel getOrCreate( int x, int y, int z ) {
			return getOrCreate( new Location(x,y,z) );
		}

		/// <summary>
		/// Gets a TrafficVoxel in the specified location, if any.
		/// Otherwise null.
		/// </summary>
		public static TrafficVoxel get( Location loc ) {
			return World.world[loc] as TrafficVoxel;
		}

		public static TrafficVoxel get( int x, int y, int z ) {
			return get( new Location(x,y,z) );
		}
	}
}
