namespace Shogi.Domain
{
	/// <summary>
	/// Facilitates Shogi board state transitions, cognisant of Shogi rules.
	/// The board is always from Player1's perspective.
	/// [0,0] is the lower-left position, [8,8] is the higher-right position
	/// </summary>
	public sealed class Shogi
	{
		private readonly ShogiBoardState board;
		private readonly StandardRules rules;
		public string Error { get; private set; }

		public Shogi(ShogiBoardState board)
		{
			this.board = board;
			rules = new StandardRules(this.board);
		}

		//public Shogi(IList<Move> moves) : this(new ShogiBoardState())
		//{
		//	for (var i = 0; i < moves.Count; i++)
		//	{
		//		if (!Move(moves[i]))
		//		{
		//			throw new InvalidOperationException($"Unable to construct ShogiBoard with the given move at index {i}.");
		//		}
		//	}
		//}


		public MoveResult CanMove(string from, string to, bool isPromotion)
		{
			var simulator = new StandardRules(new ShogiBoardState(board));
			return simulator.Move(from, to, isPromotion);
		}

		public MoveResult CanMove(WhichPiece pieceInHand, string to)
		{
			var simulator = new StandardRules(new ShogiBoardState(board));
			return simulator.Move(pieceInHand, to);
		}

		public void Move(string from, string to, bool isPromotion)
		{
			var fromVector = ShogiBoardState.FromBoardNotation(from);
			var toVector = ShogiBoardState.FromBoardNotation(to);
			var moveResult = rules.Move(from, to, isPromotion);
			if (!moveResult.Success)
			{
				throw new InvalidOperationException(moveResult.Reason);
			}

			var otherPlayer = board.WhoseTurn == WhichPlayer.Player1 ? WhichPlayer.Player2 : WhichPlayer.Player1;
			if (rules.EvaluateCheckAfterMove(fromVector, toVector, otherPlayer))
			{
				board.InCheck = otherPlayer;
				board.IsCheckmate = rules.EvaluateCheckmate();
			}
			else
			{
				board.InCheck = null;
			}
			board.WhoseTurn = otherPlayer;
		}

		///// <summary>
		///// Attempts a given move. Returns false if the move is illegal.
		///// </summary>
		//private bool TryMove(Move move)
		//{
		//	// Try making the move in a "throw away" board.
		//	var simulator = new StandardRules(new ShogiBoardState(this.board));

		//	var simulatedMoveResults = move.PieceFromHand.HasValue
		//		? simulator.PlaceFromHand(move)
		//		: simulator.PlaceFromBoard(move);
		//	if (!simulatedMoveResults)
		//	{
		//		// Surface the error description.
		//		Error = simulationBoard.Error;
		//		return false;
		//	}
		//	// If already in check, assert the move that resulted in check no longer results in check.
		//	if (InCheck == WhoseTurn)
		//	{
		//			// Sneakily using this.WhoseTurn instead of validationBoard.WhoseTurn;
		//		if (simulationBoard.EvaluateCheckAfterMove(MoveHistory[^1], WhoseTurn))
		//		{
		//			return false;
		//		}
		//	}

		//	// The move is valid and legal; update board state.
		//	if (move.PieceFromHand.HasValue) PlaceFromHand(move);
		//	else PlaceFromBoard(move);
		//	return true;
		//}
	}
}