namespace CheckersSpielBot
{
    public class GameService
    {
        // 0=Empty | 1=Red | 2=Blue | 3=RedKing | 4=BlueKing
        public int[,] Board { get; private set; } = new int[8, 8];

        public int ActivePlayer { get; private set; } = 1;
        public bool IsChainJumpActive { get; private set; } = false;
        public int ChainJumpRow { get; private set; } = -1;
        public int ChainJumpCol { get; private set; } = -1;

        public HashSet<(int, int)> MandatoryCapturePieces { get; private set; } = new();

        private MoveGeneratorService _moveGenerator;

        public GameService()
        {
            _moveGenerator = new MoveGeneratorService(Board);
        }

        // Setup 
        public void InitializeNewGame()
        {
            Board = new int[8, 8];
            ActivePlayer = 1;
            IsChainJumpActive = false;
            ChainJumpRow = -1;
            ChainJumpCol = -1;

            _moveGenerator = new MoveGeneratorService(Board);

            PlaceInitialPieces();
            RefreshMandatoryCaptures();
        }

        private void PlaceInitialPieces()
        {
            for (int row = 0; row < 3; row++)
                for (int col = 0; col < 8; col++)
                    if (BoardHelper.IsPlayableSquare(row, col))
                        Board[row, col] = 2;   // Blue top

            for (int row = 5; row < 8; row++)
                for (int col = 0; col < 8; col++)
                    if (BoardHelper.IsPlayableSquare(row, col))
                        Board[row, col] = 1;   // Red bottom
        }

        //  Move generation  
        public List<Move> GetLegalMoves(int row, int col, bool capturesOnly) =>
            _moveGenerator.GetLegalMoves(row, col, capturesOnly);

        //  Move execution 
        public MoveResult ExecuteMove(int originRow, int originCol, Move move)
        {
            int piece = Board[originRow, originCol];

            Board[move.DestinationRow, move.DestinationCol] = piece;
            Board[originRow, originCol] = 0;

            if (move.IsCapture)
                Board[move.CapturedPieceRow, move.CapturedPieceCol] = 0;

            PromoteToKingIfEligible(move.DestinationRow, move.DestinationCol);

            ResetChainJump();

            // Chain jump
            if (move.IsCapture)
            {
                var furtherJumps = GetLegalMoves(move.DestinationRow, move.DestinationCol,
                                                 capturesOnly: true);
                if (furtherJumps.Count > 0)
                {
                    IsChainJumpActive = true;
                    ChainJumpRow = move.DestinationRow;
                    ChainJumpCol = move.DestinationCol;
                    return MoveResult.ChainJumpRequired;
                }
            }

            // Victory check
            if (EvaluateVictoryCondition(out int victor))
                return MoveResult.Victory(victor);

            // Advance turn
            ActivePlayer = ActivePlayer == 1 ? 2 : 1;
            RefreshMandatoryCaptures();
            return MoveResult.TurnAdvanced;
        }

        private void PromoteToKingIfEligible(int row, int col)
        {
            if (Board[row, col] == 1 && row == 0) Board[row, col] = 3;
            if (Board[row, col] == 2 && row == 7) Board[row, col] = 4;
        }

        private void ResetChainJump()
        {
            IsChainJumpActive = false;
            ChainJumpRow = -1;
            ChainJumpCol = -1;
        }

        //  Mandatory captures 
        public void RefreshMandatoryCaptures()
        {
            MandatoryCapturePieces = new HashSet<(int, int)>();

            for (int r = 0; r < 8; r++)
                for (int c = 0; c < 8; c++)
                {
                    int p = Board[r, c];
                    if (BoardHelper.BelongsToPlayer(p, ActivePlayer) &&
                        GetLegalMoves(r, c, capturesOnly: true).Count > 0)
                        MandatoryCapturePieces.Add((r, c));
                }
        }

        //  Victory 
        private bool EvaluateVictoryCondition(out int victor)
        {
            victor = 0;
            int opponent = ActivePlayer == 1 ? 2 : 1;

            bool opponentHasPieces = false;
            bool opponentCanMove = false;

            for (int r = 0; r < 8; r++)
            {
                for (int c = 0; c < 8; c++)
                {
                    if (!BoardHelper.BelongsToPlayer(Board[r, c], opponent)) continue;
                    opponentHasPieces = true;
                    if (GetLegalMoves(r, c, capturesOnly: false).Count > 0)
                    {
                        opponentCanMove = true;
                        break;
                    }
                }
                if (opponentCanMove) break;
            }

            if (!opponentHasPieces || !opponentCanMove)
            {
                victor = ActivePlayer;
                return true;
            }
            return false;
        }

        public List<Move> GetAllLegalMovesForPlayer(int player)
        {
            var moveGen = new MoveGeneratorService(Board);
            var captures = new List<Move>();
            var normals = new List<Move>();

            for (int r = 0; r < 8; r++)
            {
                for (int c = 0; c < 8; c++)
                {
                    if (!BoardHelper.BelongsToPlayer(Board[r, c], player)) continue;

                    var jumps = moveGen.GetLegalMoves(r, c, capturesOnly: true);
                    if (jumps.Count > 0) { captures.AddRange(jumps); continue; }

                    normals.AddRange(moveGen.GetLegalMoves(r, c, capturesOnly: false));
                }
            }

            return captures.Count > 0 ? captures : normals;
        }

        #region helpers
        public bool BelongsToActivePlayer(int piece) =>
            BoardHelper.BelongsToPlayer(piece, ActivePlayer);
        public (int red, int blue) GetPieceCounts()
        {
            int red = 0, blue = 0;
            for (int r = 0; r < 8; r++)
                for (int c = 0; c < 8; c++)
                {
                    int p = Board[r, c];
                    if (p == 1 || p == 3) red++;
                    else if (p == 2 || p == 4) blue++;
                }
            return (red, blue);
        }
        #endregion
    }
}