using System;
using System.Collections.Generic;
using System.Text;

namespace OpenRa.Game
{
	//Unit Missions:
	//{
	//in rules.ini:
	//	Sleep - no-op
	//	Harmless - no-op, and also not considered a threat
	//	Sticky
	//	Attack
	//	Move
	//	QMove
	//	Retreat
	//	Guard
	//	Enter
	//	Capture
	//	Harvest
	//	Area Guard
	//	[Return] - unused
	//	Stop
	//	[Ambush] - unused
	//	Hunt
	//	Unload
	//	Sabotage
	//	Construction
	//	Selling
	//	Repair
	//	Rescue
	//	Missile
	//
	//not in original RA:
	//	Deploy (Mcv -> Fact) [should this be construction/unload?]
	//}

	[Flags]
	enum SupportedMissions
	{
		Stop = 0,
		Harvest = 1,
		Deploy = 2,
	}

	delegate void UnitMission( int t );
	static class UnitMissions
	{
		public static UnitMission Sleep()
		{
			return t => { };
		}

		public static UnitMission Move( Unit unit, int2 destination )
		{
			return t =>
			{
				Game game = unit.game;

				if( unit.nextOrder != null )
					destination = unit.toCell;

				if( Turn( unit, unit.GetFacing( unit.toCell - unit.fromCell ) ) )
					return;

				unit.moveFraction += t * unit.unitInfo.Speed;
				if( unit.moveFraction < unit.moveFractionTotal )
					return;

				unit.moveFraction = 0;
				unit.moveFractionTotal = 0;
				unit.fromCell = unit.toCell;

				if( unit.toCell == destination )
				{
					unit.currentOrder = null;
					return;
				}

				List<int2> res = game.pathFinder.FindUnitPath( unit.toCell, PathFinder.DefaultEstimator( destination ) );
				if( res.Count != 0 )
				{
					unit.toCell = res[ res.Count - 1 ];

					int2 dir = unit.toCell - unit.fromCell;
					unit.moveFractionTotal = ( dir.X != 0 && dir.Y != 0 ) ? 2500 : 2000;
				}
				else
					destination = unit.toCell;
			};
		}

		public static UnitMission Deploy( Unit unit )
		{
			return t =>
			{
				Game game = unit.game;

				if( Turn( unit, 12 ) )
					return;

				game.world.AddFrameEndTask( _ =>
				{
					game.world.Remove( unit );
					game.world.Add( new ConstructionYard( unit.fromCell - new int2( 1, 1 ), unit.owner, game ) );
				} );
				unit.currentOrder = null;
			};
		}


		public static UnitMission Harvest( Unit unit )
		{
			UnitMission order = null;
			order = t =>
			{
				// TODO: check that there's actually some ore in this cell :)

				// face in one of the 8 directions
				if( Turn( unit, ( unit.facing + 1 ) & ~3 ) )
					return;

				unit.currentOrder = _ => { };
				if( unit.nextOrder == null )
					unit.nextOrder = order;

				string sequenceName = string.Format( "harvest{0}", unit.facing / 4 );
				unit.animation.PlayThen( sequenceName, () =>
				{
					unit.currentOrder = null;
					unit.animation.PlayFetchIndex("idle", () => unit.facing);
				} );
			};
			return order;
		}

		static bool Turn( Unit unit, int desiredFacing )
		{
			if( unit.facing == desiredFacing )
				return false;

			int df = ( desiredFacing - unit.facing + 32 ) % 32;
			unit.facing = ( unit.facing + ( df > 16 ? 31 : 1 ) ) % 32;
			return true;
		}
	}
}