using FluentAssertions;
using FluentAssertions.Execution;
using System;
using System.Linq;
using Xunit;
using Xunit.Abstractions;

namespace Shogi.Domain.UnitTests
{
	public class ShogiShould
	{
		private readonly ITestOutputHelper output;
		public ShogiShould(ITestOutputHelper output)
		{
			this.output = output;
		}

		[Fact]
		public void MoveAPieceToAnEmptyPosition()
		{
			// Arrange
			var board = new ShogiBoardState();
			var shogi = new Shogi(board);
			board["A4"].Should().BeNull();
			var expectedPiece = board["A3"];
			expectedPiece.Should().NotBeNull();

			// Act
			shogi.Move("A3", "A4", false);

			// Assert
			board["A3"].Should().BeNull();
			board["A4"].Should().Be(expectedPiece);
		}

		[Fact]
		public void AllowValidMoves_AfterCheck()
		{
			// Arrange
			var board = new ShogiBoardState();
			var shogi = new Shogi(board);
			// P1 Pawn
			shogi.Move("C3", "C4", false);
			// P2 Pawn
			shogi.Move("G7", "G6", false);
			// P1 Bishop puts P2 in check
			shogi.Move("B2", "G7", false);
			board.InCheck.Should().Be(WhichPlayer.Player2);

			// Act - P2 is able to un-check theirself.
			/// P2 King moves out of check
			shogi.Move("E9", "E8", false);

			// Assert
			using (new AssertionScope())
			{
				board.InCheck.Should().BeNull();
			}
		}

		[Fact]
		public void PreventInvalidMoves_MoveFromEmptyPosition()
		{
			// Arrange
			var board = new ShogiBoardState();
			var shogi = new Shogi(board);
			board["D5"].Should().BeNull();

			// Act
			var act = () => shogi.Move("D5", "D6", false);

			// Assert
			act.Should().Throw<InvalidOperationException>();
			board["D5"].Should().BeNull();
			board["D6"].Should().BeNull();
		}

		[Fact]
		public void PreventInvalidMoves_MoveToCurrentPosition()
		{
			// Arrange
			var board = new ShogiBoardState();
			var shogi = new Shogi(board);

			// Act - P1 "moves" pawn to the position it already exists at.
			var act = () => shogi.Move("A3", "A3", false);

			// Assert
			act.Should().Throw<InvalidOperationException>();
			board["A3"].Should().NotBeNull();
			board["A3"]!.WhichPiece.Should().Be(WhichPiece.Pawn);
			board.Player1Hand.Should().BeEmpty();
			board.Player2Hand.Should().BeEmpty();
		}

		[Fact]
		public void PreventInvalidMoves_MoveSet()
		{
			// Arrange
			var board = new ShogiBoardState();
			var shogi = new Shogi(board);

			// Act - Move Lance illegally
			var act = () => shogi.Move("A1", "D5", false);

			// Assert
			act.Should().Throw<InvalidOperationException>();
			board["A1"].Should().NotBeNull();
			board["A1"]!.WhichPiece.Should().Be(WhichPiece.Lance);
			board["A5"].Should().BeNull();
			board.Player1Hand.Should().BeEmpty();
			board.Player2Hand.Should().BeEmpty();
		}

		[Fact]
		public void PreventInvalidMoves_Ownership()
		{
			// Arrange
			var board = new ShogiBoardState();
			var shogi = new Shogi(board);
			board.WhoseTurn.Should().Be(WhichPlayer.Player1);
			board["A7"].Should().NotBeNull();
			board["A7"]!.Owner.Should().Be(WhichPlayer.Player2);

			// Act - Move Player2 Pawn when it is Player1 turn.
			var act = () => shogi.Move("A7", "A6", false);

			// Assert
			act.Should().Throw<InvalidOperationException>();
			board["A7"].Should().NotBeNull();
			board["A7"]!.WhichPiece.Should().Be(WhichPiece.Pawn);
			board["A6"].Should().BeNull();
		}

		[Fact]
		public void PreventInvalidMoves_MoveThroughAllies()
		{
			// Arrange
			var board = new ShogiBoardState();
			var shogi = new Shogi(board);

			// Act - Move P1 Lance through P1 Pawn.
			var act = () => shogi.Move("A1", "A5", false);

			// Assert
			act.Should().Throw<InvalidOperationException>();
			board["A1"].Should().NotBeNull();
			board["A1"]!.WhichPiece.Should().Be(WhichPiece.Lance);
			board["A3"].Should().NotBeNull();
			board["A3"]!.WhichPiece.Should().Be(WhichPiece.Pawn);
			board["A5"].Should().BeNull();
		}

		[Fact]
		public void PreventInvalidMoves_CaptureAlly()
		{
			// Arrange
			var board = new ShogiBoardState();
			var shogi = new Shogi(board);

			// Act - P1 Knight tries to capture P1 Pawn.
			var act = () => shogi.Move("B1", "C3", false);

			// Arrange
			act.Should().Throw<InvalidOperationException>();
			board["B1"].Should().NotBeNull();
			board["B1"]!.WhichPiece.Should().Be(WhichPiece.Knight);
			board["C3"].Should().NotBeNull();
			board["C3"]!.WhichPiece.Should().Be(WhichPiece.Pawn);
			board.Player1Hand.Should().BeEmpty();
			board.Player2Hand.Should().BeEmpty();
		}

		[Fact]
		public void PreventInvalidMoves_Check()
		{
			// Arrange
			var board = new ShogiBoardState();
			var shogi = new Shogi(board);
			// P1 Pawn
			shogi.Move("C3", "C4", false);
			// P2 Pawn
			shogi.Move("G7", "G6", false);
			// P1 Bishop puts P2 in check
			shogi.Move("B2", "G7", false);
			board.InCheck.Should().Be(WhichPlayer.Player2);

			// Act - P2 moves Lance while in check.
			var act = () => shogi.Move("I9", "I8", false);

			// Assert
			act.Should().Throw<InvalidOperationException>();
			board.InCheck.Should().Be(WhichPlayer.Player2);
			board["I9"].Should().NotBeNull();
			board["I9"]!.WhichPiece.Should().Be(WhichPiece.Lance);
			board["I8"].Should().BeNull();
		}

		[Fact]
		public void PreventInvalidDrops_MoveSet()
		{
			// Arrange
			var board = new ShogiBoardState();
			var shogi = new Shogi(board);


			// P1 Pawn
			shogi.Move("C3", "C4", false);
			// P2 Pawn
			shogi.Move("I7", "I6", false);
			// P1 Bishop takes P2 Pawn.
			shogi.Move("B2", "G7", false);
			// P2 Gold, block check from P1 Bishop.
			shogi.Move("F9", "F8", false);
			// P1 Bishop takes P2 Bishop, promotes so it can capture P2 Knight and P2 Lance
			shogi.Move("G7", "H8", true);
			// P2 Pawn again
			shogi.Move("I6", "I5", false);
			// P1 Bishop takes P2 Knight
			shogi.Move("H8", "H9", false);
			// P2 Pawn again
			shogi.Move("I5", "I4", false);
			// P1 Bishop takes P2 Lance
			shogi.Move("H9", "I9", false);
			// P2 Pawn captures P1 Pawn
			shogi.Move("I4", "I3", false);

			board.Player1Hand.Count.Should().Be(4);
			board.Player1Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Knight);
			board.Player1Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Lance);
			board.Player1Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Pawn);
			board.Player1Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Bishop);
			board.WhoseTurn.Should().Be(WhichPlayer.Player1);

			// Act | Assert - Illegally placing Knight from the hand in farthest row.
			board["H9"].Should().BeNull();
			shogi.Move()
			var dropSuccess = shogi.Move(new Move(WhichPiece.Knight, "H9"));
			dropSuccess.Should().BeFalse();
			shogi.Board["H9"].Should().BeNull();
			shogi.Player1Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Knight);

			// Act | Assert - Illegally placing Knight from the hand in second farthest row.
			shogi.Board["H8"].Should().BeNull();
			dropSuccess = shogi.Move(new Move(WhichPiece.Knight, "H8"));
			dropSuccess.Should().BeFalse();
			shogi.Board["H8"].Should().BeNull();
			shogi.Player1Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Knight);

			// Act | Assert - Illegally place Lance from the hand.
			shogi.Board["H9"].Should().BeNull();
			dropSuccess = shogi.Move(new Move(WhichPiece.Knight, "H9"));
			dropSuccess.Should().BeFalse();
			shogi.Board["H9"].Should().BeNull();
			shogi.Player1Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Lance);

			// Act | Assert - Illegally place Pawn from the hand.
			shogi.Board["H9"].Should().BeNull();
			dropSuccess = shogi.Move(new Move(WhichPiece.Pawn, "H9"));
			dropSuccess.Should().BeFalse();
			shogi.Board["H9"].Should().BeNull();
			shogi.Player1Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Pawn);

			// Act | Assert - Illegally place Pawn from the hand in a row which already has an unpromoted Pawn.
			// TODO
		}

		//[Fact]
		//public void PreventInvalidDrop_Check()
		//{
		//	// Arrange
		//	var moves = new[]
		//	{
		//        // P1 Pawn
		//        new Move("C3", "C4"),
		//        // P2 Pawn
		//        new Move("G7", "G6"),
		//        // P1 Pawn, arbitrary move.
		//        new Move("A3", "A4"),
		//        // P2 Bishop takes P1 Bishop
		//        new Move("H8", "B2"),
		//        // P1 Silver takes P2 Bishop
		//        new Move("C1", "B2"),
		//        // P2 Pawn, arbtrary move
		//        new Move("A7", "A6"),
		//        // P1 drop Bishop, place P2 in check
		//        new Move(WhichPiece.Bishop, "G7")
		//	};
		//	var shogi = new Shogi(moves);
		//	shogi.InCheck.Should().Be(WhichPlayer.Player2);
		//	shogi.Player2Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Bishop);
		//	shogi.Board["E5"].Should().BeNull();

		//	// Act - P2 places a Bishop while in check.
		//	var dropSuccess = shogi.Move(new Move(WhichPiece.Bishop, "E5"));

		//	// Assert
		//	dropSuccess.Should().BeFalse();
		//	shogi.Board["E5"].Should().BeNull();
		//	shogi.InCheck.Should().Be(WhichPlayer.Player2);
		//	shogi.Player2Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Bishop);
		//}

		//[Fact]
		//public void PreventInvalidDrop_Capture()
		//{
		//	// Arrange
		//	var moves = new[]
		//	{
		//      // P1 Pawn
		//      new Move("C3", "C4"),
		//      // P2 Pawn
		//      new Move("G7", "G6"),
		//      // P1 Bishop capture P2 Bishop
		//      new Move("B2", "H8"),
		//      // P2 Pawn
		//      new Move("G6", "G5")
		//	};
		//	var shogi = new Shogi(moves);
		//	using (new AssertionScope())
		//	{
		//		shogi.Player1Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Bishop);
		//		shogi.Board["I9"].Should().NotBeNull();
		//		shogi.Board["I9"].WhichPiece.Should().Be(WhichPiece.Lance);
		//		shogi.Board["I9"].Owner.Should().Be(WhichPlayer.Player2);
		//	}

		//	// Act - P1 tries to place a piece where an opponent's piece resides.
		//	var dropSuccess = shogi.Move(new Move(WhichPiece.Bishop, "I9"));

		//	// Assert
		//	using (new AssertionScope())
		//	{
		//		dropSuccess.Should().BeFalse();
		//		shogi.Player1Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Bishop);
		//		shogi.Board["I9"].Should().NotBeNull();
		//		shogi.Board["I9"].WhichPiece.Should().Be(WhichPiece.Lance);
		//		shogi.Board["I9"].Owner.Should().Be(WhichPlayer.Player2);
		//	}
		//}

		//[Fact]
		//public void Check()
		//{
		//	// Arrange
		//	var moves = new[]
		//	{
		//      // P1 Pawn
		//      new Move("C3", "C4"),
		//      // P2 Pawn
		//      new Move("G7", "G6"),
		//	};
		//	var shogi = new Shogi(moves);

		//	// Act - P1 Bishop, check
		//	shogi.Move(new Move("B2", "G7"));

		//	// Assert
		//	shogi.InCheck.Should().Be(WhichPlayer.Player2);
		//}

		//[Fact]
		//public void Promote()
		//{
		//	// Arrange
		//	var moves = new[]
		//	{
		//      // P1 Pawn
		//      new Move("C3", "C4" ),
		//      // P2 Pawn
		//      new Move("G7", "G6" )
		//	};
		//	var shogi = new Shogi(moves);

		//	// Act - P1 moves across promote threshold.
		//	var moveSuccess = shogi.Move(new Move("B2", "G7", true));

		//	// Assert
		//	using (new AssertionScope())
		//	{
		//		moveSuccess.Should().BeTrue();
		//		shogi.Board["B2"].Should().BeNull();
		//		shogi.Board["G7"].Should().NotBeNull();
		//		shogi.Board["G7"].WhichPiece.Should().Be(WhichPiece.Bishop);
		//		shogi.Board["G7"].Owner.Should().Be(WhichPlayer.Player1);
		//		shogi.Board["G7"].IsPromoted.Should().BeTrue();
		//	}
		//}

		//[Fact]
		//public void CheckMate()
		//{
		//	// Arrange
		//	var moves = new[]
		//	{
		//        // P1 Rook
		//        new Move("H2", "E2"),
		//        // P2 Gold
		//        new Move("F9", "G8"),
		//        // P1 Pawn
		//        new Move("E3", "E4"),
		//        // P2 other Gold
		//        new Move("D9", "C8"),
		//        // P1 same Pawn
		//        new Move("E4", "E5"),
		//        // P2 Pawn
		//        new Move("E7", "E6"),
		//        // P1 Pawn takes P2 Pawn
		//        new Move("E5", "E6"),
		//        // P2 King
		//        new Move("E9", "E8"),
		//        // P1 Pawn promotes, threatens P2 King
		//        new Move("E6", "E7", true),
		//        // P2 King retreat
		//        new Move("E8", "E9"),
		//		};
		//	var shogi = new Shogi(moves);
		//	output.WriteLine(shogi.PrintStateAsAscii());

		//	// Act - P1 Pawn wins by checkmate.
		//	var moveSuccess = shogi.Move(new Move("E7", "E8"));
		//	output.WriteLine(shogi.PrintStateAsAscii());

		//	// Assert - checkmate
		//	moveSuccess.Should().BeTrue();
		//	shogi.IsCheckmate.Should().BeTrue();
		//	shogi.InCheck.Should().Be(WhichPlayer.Player2);
		//}

		//[Fact]
		//public void Capture()
		//{
		//	// Arrange
		//	var moves = new[]
		//	{
		//			new Move("C3", "C4"),
		//			new Move("G7", "G6")
		//		};
		//	var shogi = new Shogi(moves);

		//	// Act - P1 Bishop captures P2 Bishop
		//	var moveSuccess = shogi.Move(new Move("B2", "H8"));

		//	// Assert
		//	moveSuccess.Should().BeTrue();
		//	shogi.Board["B2"].Should().BeNull();
		//	shogi.Board["H8"].WhichPiece.Should().Be(WhichPiece.Bishop);
		//	shogi.Board["H8"].Owner.Should().Be(WhichPlayer.Player1);
		//	shogi.Board.Values
		//		.Where(p => p != null)
		//		.Should().ContainSingle(piece => piece.WhichPiece == WhichPiece.Bishop);

		//	shogi.Player1Hand
		//		.Should()
		//		.ContainSingle(p => p.WhichPiece == WhichPiece.Bishop && p.Owner == WhichPlayer.Player1);
		//}
	}
}