using Shogi.Domain.ValueObjects;
using System;
using System.Linq;

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

		[Fact]
		public void MoveAPieceToAnEmptyPosition()
		{
			// Arrange
			var shogi = MockShogiBoard();
			var board = shogi.BoardState;

			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 shogi = MockShogiBoard();
			var board = shogi.BoardState;
			// 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 shogi = MockShogiBoard();
			var board = shogi.BoardState;
			board["D5"].Should().BeNull();

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

			// Assert
			moveResult.Should().NotBeNull();
			moveResult.IsSuccess.Should().BeFalse();
			board["D5"].Should().BeNull();
			board["D6"].Should().BeNull();
			board.Player1Hand.Should().BeEmpty();
			board.Player2Hand.Should().BeEmpty();
		}

		[Fact]
		public void PreventInvalidMoves_MoveToCurrentPosition()
		{
			// Arrange
			var shogi = MockShogiBoard();
			var board = shogi.BoardState;
			var expectedPiece = board["A3"];

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

			// Assert
			using (new AssertionScope())
			{
				moveResult.Should().NotBeNull();
				moveResult.IsSuccess.Should().BeFalse(); board["A3"].Should().Be(expectedPiece);
				board.Player1Hand.Should().BeEmpty();
				board.Player2Hand.Should().BeEmpty();
			}
		}

		[Fact]
		public void PreventInvalidMoves_MoveSet()
		{
			// Arrange
			var shogi = MockShogiBoard();
			var board = shogi.BoardState;
			var expectedPiece = board["D1"];
			expectedPiece!.WhichPiece.Should().Be(WhichPiece.GoldGeneral);

			// Act - Move General illegally
			var moveResult = shogi.Move("D1", "D5", false);

			// Assert
			using (new AssertionScope())
			{
				moveResult.Should().NotBeNull();
				moveResult.IsSuccess.Should().BeFalse(); 
				board["D1"].Should().Be(expectedPiece);
				board["D5"].Should().BeNull();
				board.Player1Hand.Should().BeEmpty();
				board.Player2Hand.Should().BeEmpty();
			}
		}

		[Fact]
		public void PreventInvalidMoves_Ownership()
		{
			// Arrange
			var shogi = MockShogiBoard();
			var board = shogi.BoardState;
			var expectedPiece = board["A7"];
			expectedPiece!.Owner.Should().Be(WhichPlayer.Player2);
			board.WhoseTurn.Should().Be(WhichPlayer.Player1);

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

			// Assert
			using (new AssertionScope())
			{
				moveResult.Should().NotBeNull();
				moveResult.IsSuccess.Should().BeFalse(); board["A7"].Should().Be(expectedPiece);
				board["A6"].Should().BeNull();
			}
		}

		[Fact]
		public void PreventInvalidMoves_MoveThroughAllies()
		{
			// Arrange
			var shogi = MockShogiBoard();
			var board = shogi.BoardState;
			var lance = board["A1"];
			var pawn = board["A3"];
			lance!.Owner.Should().Be(pawn!.Owner);

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

			// Assert
			using (new AssertionScope())
			{
				moveResult.Should().NotBeNull();
				moveResult.IsSuccess.Should().BeFalse(); board["A1"].Should().Be(lance);
				board["A3"].Should().Be(pawn);
				board["A5"].Should().BeNull();
			}
		}

		[Fact]
		public void PreventInvalidMoves_CaptureAlly()
		{
			// Arrange
			var shogi = MockShogiBoard();
			var board = shogi.BoardState;
			var knight = board["B1"];
			var pawn = board["C3"];
			knight!.Owner.Should().Be(pawn!.Owner);

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

			// Arrange
			using (new AssertionScope())
			{
				moveResult.Should().NotBeNull();
				moveResult.IsSuccess.Should().BeFalse(); board["B1"].Should().Be(knight);
				board["C3"].Should().Be(pawn);
				board.Player1Hand.Should().BeEmpty();
				board.Player2Hand.Should().BeEmpty();
			}
		}

		[Fact]
		public void PreventInvalidMoves_Check()
		{
			// Arrange
			var shogi = MockShogiBoard();
			var board = shogi.BoardState;
			// 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);
			var lance = board["I9"];

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

			// Assert
			using (new AssertionScope())
			{
				moveResult.Should().NotBeNull();
				moveResult.IsSuccess.Should().BeFalse(); board.InCheck.Should().Be(WhichPlayer.Player2);
				board["I9"].Should().Be(lance);
				board["I8"].Should().BeNull();
			}
		}

		[Fact]
		public void PreventInvalidDrops_MoveSet()
		{
			// Arrange
			var shogi = MockShogiBoard();
			var board = shogi.BoardState;
			// 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 rank.
			board["H9"].Should().BeNull();
			var moveResult = shogi.Move(WhichPiece.Knight, "H9");
			moveResult.Should().NotBeNull();
			moveResult.IsSuccess.Should().BeFalse();
			board["H9"].Should().BeNull();
			board.Player1Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Knight);

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

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

			// Act | Assert - Illegally place Pawn from the hand.
			board["H9"].Should().BeNull();
			moveResult = shogi.Move(WhichPiece.Pawn, "H9");
			moveResult.Should().NotBeNull();
			moveResult.IsSuccess.Should().BeFalse();
			board["H9"].Should().BeNull();
			board.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 shogi = MockShogiBoard();
			// P1 Pawn
			shogi.Move("C3", "C4", false).IsSuccess.Should().BeTrue();
			// P2 Pawn
			shogi.Move("G7", "G6", false).IsSuccess.Should().BeTrue();
			// P1 Pawn, arbitrary move.
			shogi.Move("A3", "A4", false).IsSuccess.Should().BeTrue();
			// P2 Bishop takes P1 Bishop
			shogi.Move("H8", "B2", false).IsSuccess.Should().BeTrue();
			// P1 Silver takes P2 Bishop
			shogi.Move("C1", "B2", false).IsSuccess.Should().BeTrue();
			// P2 Pawn, arbtrary move
			shogi.Move("A7", "A6", false).IsSuccess.Should().BeTrue();
			// P1 drop Bishop, place P2 in check
			shogi.Move(WhichPiece.Bishop, "G7").IsSuccess.Should().BeTrue();
			shogi.BoardState.InCheck.Should().Be(WhichPlayer.Player2);
			shogi.BoardState.Player2Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Bishop);
			shogi.BoardState["E5"].Should().BeNull();

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

			// Assert
			using var scope = new AssertionScope();
			moveResult.Should().NotBeNull();
			moveResult.IsSuccess.Should().BeFalse();
			shogi.BoardState["E5"].Should().BeNull();
			shogi.BoardState.InCheck.Should().Be(WhichPlayer.Player2);
			shogi.BoardState.Player2Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Bishop);
		}

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

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

			// Assert
			using var scope = new AssertionScope();
			moveResult.Should().NotBeNull();
			moveResult.IsSuccess.Should().BeFalse();
			shogi.BoardState.Player1Hand.Should().ContainSingle(_ => _.WhichPiece == WhichPiece.Bishop);
			shogi.BoardState["I9"].Should().NotBeNull();
			shogi.BoardState["I9"]!.WhichPiece.Should().Be(WhichPiece.Lance);
			shogi.BoardState["I9"]!.Owner.Should().Be(WhichPlayer.Player2);
		}

		[Fact]
		public void Check()
		{
			// Arrange
			var shogi = MockShogiBoard();
			var board = shogi.BoardState;
			// P1 Pawn
			shogi.Move("C3", "C4", false);
			// P2 Pawn
			shogi.Move("G7", "G6", false);

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

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

		[Fact]
		public void Promote()
		{
			// Arrange
			var shogi = MockShogiBoard();
			var board = shogi.BoardState;
			// P1 Pawn
			shogi.Move("C3", "C4", false);
			// P2 Pawn
			shogi.Move("G7", "G6", false);

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

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

		[Fact]
		public void Capture()
		{
			// Arrange
			var shogi = MockShogiBoard();
			var board = shogi.BoardState;
			var p1Bishop = board["B2"];
			p1Bishop!.WhichPiece.Should().Be(WhichPiece.Bishop);
			shogi.Move("C3", "C4", false);
			shogi.Move("G7", "G6", false);

			// Act - P1 Bishop captures P2 Bishop
			shogi.Move("B2", "H8", false);

			// Assert
			board["B2"].Should().BeNull();
			board["H8"].Should().Be(p1Bishop);

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

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

			console.WriteLine(shogi.ToStringStateAsAscii());


			// Act - P1 Pawn wins by checkmate.
			shogi.Move("E7", "E8", false);

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

		private static ShogiBoard MockShogiBoard() => new(BoardState.StandardStarting);
	}
}