using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using OpenRa.Game.Graphics;

namespace OpenRa.Game.GameRules
{
	static class Footprint
	{
		public static IEnumerable<int2> Tiles( UnitInfo unitInfo, int2 position )
		{
			var buildingInfo = unitInfo as UnitInfo.BuildingInfo;
			var dim = buildingInfo.Dimensions;

			var footprint = buildingInfo.Footprint.ToCharArray().Where( x => !char.IsWhiteSpace( x ) );
			if( buildingInfo.Bib )
			{
				dim.Y += 1;
				footprint = footprint.Concat( new char[ dim.X ] );
			}
			foreach( var tile in TilesWhere( unitInfo.Name, dim, footprint.ToArray(), a => a != '_' ) )
				yield return tile + position - AdjustForBuildingSize( buildingInfo );
		}

		public static IEnumerable<int2> UnpathableTiles( UnitInfo unitInfo, int2 position )
		{
			var buildingInfo = unitInfo as UnitInfo.BuildingInfo;

			var footprint = buildingInfo.Footprint.ToCharArray().Where( x => !char.IsWhiteSpace( x ) ).ToArray();
			foreach( var tile in TilesWhere( unitInfo.Name, buildingInfo.Dimensions, footprint, a => a == 'x' ) )
				yield return tile + position;
		}

		static IEnumerable<int2> TilesWhere( string name, int2 dim, char[] footprint, Func<char, bool> cond )
		{
			if( footprint.Length != dim.X * dim.Y )
				throw new InvalidOperationException( "Invalid footprint for " + name );
			int index = 0;
			for( int y = 0 ; y < dim.Y ; y++ )
			{
				for( int x = 0 ; x < dim.X ; x++ )
				{
					if( cond( footprint[ index ] ) )
						yield return new int2( x, y );
					++index;
				}
			}
		}

		public static int2 AdjustForBuildingSize( string name )
		{
			return AdjustForBuildingSize( Rules.UnitInfo[ name ] as UnitInfo.BuildingInfo );
		}

		public static int2 AdjustForBuildingSize( UnitInfo.BuildingInfo unitInfo )
		{
			var dim = unitInfo.Dimensions;
			return new int2( dim.X / 2, ( dim.Y + 1 ) / 2 );
		}
	}
}