namespace CheckersSpielBot
{
    public class MoveGeneratorService
    {
        private readonly int[,] _board;

        public MoveGeneratorService(int[,] board)
        {
            _board = board;
        }

        public List<Move> GetLegalMoves(int row, int col, bool capturesOnly)
        {
            var moves = new List<Move>();
            int piece = _board[row, col];
            if (piece == 0) return moves;

            var dirs = ResolveDirections(piece);

            // Captures first
            foreach (var (dr, dc) in dirs)
            {
                int mr = row + dr, mc = col + dc;
                int lr = row + 2 * dr, lc = col + 2 * dc;

                if (!BoardHelper.IsWithinBounds(mr, mc) || !BoardHelper.IsWithinBounds(lr, lc))
                    continue;

                int mid = _board[mr, mc];
                if (mid != 0 && BoardHelper.IsOpponentPiece(piece, mid) && _board[lr, lc] == 0)
                    moves.Add(new Move(lr, lc, mr, mc));
            }

            if (capturesOnly || moves.Count > 0) return moves;

            // Normal moves
            foreach (var (dr, dc) in dirs)
            {
                int lr = row + dr, lc = col + dc;
                if (BoardHelper.IsWithinBounds(lr, lc) && _board[lr, lc] == 0)
                    moves.Add(new Move(lr, lc, -1, -1));
            }

            return moves;
        }

        private static List<(int dr, int dc)> ResolveDirections(int piece)
        {
            bool isKing = BoardHelper.IsKing(piece);
            bool isRedPiece = BoardHelper.IsRedPiece(piece);

            var dirs = new List<(int, int)>();
            if (isRedPiece || isKing) { dirs.Add((-1, -1)); dirs.Add((-1, +1)); }
            if (!isRedPiece || isKing) { dirs.Add((+1, -1)); dirs.Add((+1, +1)); }
            return dirs;
        }
    }
}