using System;
using System.Diagnostics;
using System.Drawing;
using System.Runtime.Serialization;
using freetrain.framework;
using freetrain.DirectXWrapper;

namespace freetrain.world
{
	/// <summary>
	/// 方向（８方向。速度を伴わない）
	/// </summary>
	[Serializable]
	public sealed class Direction : ISerializable
	{
		/// <summary>
		/// 方向ベクトルからオブジェクトを得る
		/// </summary>
		public static Direction get( int x, int y ) {
			for( int i=0; i<directions.Length; i++ )
				if( directions[i].offsetX==x && directions[i].offsetY==y )
					return directions[i];
			
			Debug.Assert(false);
			return null;
		}

		/// <summary>
		/// インデックスからオブジェクトを得る
		/// </summary>
		public static Direction get( int idx ) {
			return directions[idx];
		}

		public static Direction NORTH		{ get { return get(0); } }
		public static Direction NORTHEAST	{ get { return get(1); } }
		public static Direction EAST		{ get { return get(2); } }
		public static Direction SOUTHEAST	{ get { return get(3); } }
		public static Direction SOUTH		{ get { return get(4); } }
		public static Direction SOUTHWEST	{ get { return get(5); } }
		public static Direction WEST		{ get { return get(6); } }
		public static Direction NORTHWEST	{ get { return get(7); } }
		

		/// <summary>
		/// オフセット
		/// </summary>
		public readonly int offsetX,offsetY;

		/// <summary>
		/// 表示用の名称
		/// </summary>
		public readonly string displayName;

		/// <summary>
		/// Returns true if the direction is one of N,E,S, or W.
		/// </summary>
		public bool isSharp { get { return (index%2)==0; } }

		/// <summary>
		/// Returns true if the direction is EAST or WEST
		/// </summary>
		public bool isParallelToX { get { return (index%4)==2; } }

		/// <summary>
		/// Returns true if the direction is NORTH or SOUTH
		/// </summary>
		public bool isParallelToY { get { return (index%4)==0; } }

		/// <summary>
		/// [0,8)のインデックス。
		/// </summary>
		public readonly int index;

		/// <summary>
		/// 反時計回りに４５度回転したDirectionを得る
		/// </summary>
		public Direction left { get { return directions[(index+7)%8]; } }
		public Direction left90 { get { return directions[(index+6)%8]; } }

		/// <summary>
		/// 時計回りに４５度回転したDirectionを得る
		/// </summary>
		public Direction right { get { return directions[(index+1)%8]; } }
		public Direction right90 { get { return directions[(index+2)%8]; } }

		/// <summary>Gets the opposite direction.</summary>
		public Direction opposite { get { return directions[(index+4)%8]; } }

		/// <summary>
		/// ２つのDirectionの交差角を４５度の倍数で得る。
		/// 戻り値は[0,4]。1なら４５度で交差。
		/// </summary>
		public static int angle( Direction a, Direction b ) {
			int d = a.index - b.index;
			if(d<0)	d = -d;
			if(d>4) d = 8-d;
			Debug.Assert( 0<=d && d<=4 );
			return d;
		}

		/// <summary>
		/// Cast operators
		/// </summary>
		public static implicit operator Distance ( Direction d ) {
			return new Distance( d.offsetX, d.offsetY, 0 );
		}


		private static readonly Surface arrowImage = ResourceUtil.loadTimeIndependentSystemSurface("Arrows.bmp");
		private static readonly Surface darkArrowImage = ResourceUtil.loadTimeIndependentSystemSurface("Arrows.dark.bmp");

		/// <summary> Draws an arrow on the given surface. </summary>
		public void drawArrow( Surface display, Point pt, bool isDark ) {
			if( isDark )	drawDarkArrow(display,pt);
			else			drawArrow(display,pt);
		}

		/// <summary> Draws an arrow on the given surface. </summary>
		public void drawArrow( Surface display, Point pt ) {
			display.blt( pt, arrowImage, new Point(32*index,0), new Size(32,16) );
		}

		/// <summary> Draws a dark arrow on the given surface. </summary>
		public void drawDarkArrow( Surface display, Point pt ) {
			display.blt( pt, darkArrowImage, new Point(32*index,0), new Size(32,16) );
		}



		// singleton.
		private Direction( int x, int y, string name, int idx ) {
			this.offsetX = x;
			this.offsetY = y;
			this.index = idx;
			this.displayName = name;
		}

		/// <summary>
		/// 存在する全てのオブジェクト。北から時計回り
		/// </summary>
		public static readonly Direction[] directions = {
			new Direction( 0,-1,"北"  ,0),
			new Direction( 1,-1,"北東",1),
			new Direction( 1, 0,  "東",2),
			new Direction( 1, 1,"南東",3),
			new Direction( 0, 1,"南"  ,4),
			new Direction(-1, 1,"南西",5),
			new Direction(-1, 0,  "西",6),
			new Direction(-1,-1,"北西",7) };



		public void GetObjectData( SerializationInfo info, StreamingContext context) {
			info.SetType(typeof(ReferenceImpl));
			info.AddValue("index",index);
		}
		
		[Serializable]
		internal sealed class ReferenceImpl : IObjectReference {
			private int index=0;
			public object GetRealObject(StreamingContext context) {
				return Direction.get(index);
			}
		}
	}
}
