#ifndef CHESSY_MOVEGENERATION_H
#define CHESSY_MOVEGENERATION_H

#include "BitBoard.h"
#include <string>
#include <vector>
#include <array>

namespace chessy
{
    // forward declaration
    class ChessGame;

    using Leftright = int;
    const Leftright LEFT = -1;
    const Leftright RIGHT = 1;

    class PositionSet;
    template<Side side>
    class PawnPushGenerator;
    template<Side side>
    class PromotionGenerator;
    template<Side side>
    class PawnDoublePushGenerator;
    template<Side side, Leftright leftright>
    class PawnCaptureGenerator;
    class KnightMoveGenerator;
    class PrimitiveQueenMoveGenerator;
    class PrimitiveRookMoveGenerator;
    class PrimitiveBishopMoveGenerator;
    class KingMoveGenerator;
    template<Side side>
    class CastlingGenerator;

    template<Side side>
    void generatePawnPushes(const ChessGame& cg, std::vector<Move>& moves);
    template<Side side>
    void generatePawnDoublePushes(const ChessGame& cg, std::vector<Move>& moves);
    template<Side side>
    void generatePawnCaptures(const ChessGame& cg, std::vector<Move>& moves);
    template<Side side>
    void generatePawnPromotions(const ChessGame& cg, std::vector<Move>& moves);
    template<Side side>
    void generateKnightMoves(const ChessGame& cg, std::vector<Move>& moves);
    template<Side side>
    void generateQueenMoves(const ChessGame& cg, std::vector<Move>& moves);
    template<Side side>
    void generateRookMoves(const ChessGame& cg, std::vector<Move>& moves);
    template<Side side>
    void generateBishopMoves(const ChessGame& cg, std::vector<Move>& moves);
    template<Side side>
    void generateKingMoves(const ChessGame& cg, std::vector<Move>& moves);
    template<Side side>
    void generateCastling(const ChessGame& cg, std::vector<Move>& moves);
    template<Side side>
    void generateAllMoves(const ChessGame& cg, std::vector<Move>& moves);
}



class chessy::PositionSet
{
    Bitboard bitboard;
public:

    inline PositionSet(Bitboard b) : bitboard{ b } {}

    inline void     setBitboard(Bitboard b) { bitboard = b; }
    inline Bitboard getBitboard(void) const { return bitboard; }

    struct PositionSetIterator
    {
        Bitboard bitboard;

        inline Index operator *(void) const
        {
            return Index{ int8_t(trailingZeroes(bitboard.bits)) };
        }

        inline void operator ++(void)
        {
            bitboard.bits &= bitboard.bits - 1ULL; // remove least significant one bit
        }

        inline bool operator !=(const PositionSetIterator& psi) const
        {
            return bitboard != psi.bitboard;
        }
    };

    inline PositionSetIterator begin(void) const
    {
        return PositionSetIterator{ bitboard };
    }

    inline static PositionSetIterator end(void)
    {
        return PositionSetIterator{ 0 };
    }
};


template<chessy::Side side>
class chessy::PawnPushGenerator
{
    const ChessGame& chessGame;

    struct MoveIterator
    {
        PositionSet::PositionSetIterator pawnPushes;
        inline Move operator *(void) const
        {
            Index pp = *pawnPushes;
            return Move{ int8_t(pp + (side != WHITE_SIDE ? 8 : -8)), pp };
        }

        inline void operator ++(void)
        {
            ++pawnPushes;
        }

        inline bool operator !=(const MoveIterator& psi) const
        {
            return pawnPushes != psi.pawnPushes;
        }
    };
public:
    inline PawnPushGenerator(const ChessGame& cg) : chessGame{ cg } {}

    MoveIterator begin(void) const;
    MoveIterator end(void) const;
};


// TODO: rewrite better
template<chessy::Side side>
class chessy::PromotionGenerator
{
    const ChessGame& chessGame;

    struct MoveIterator
    {
        const ChessGame& chessGame;
        PositionSet::PositionSetIterator pawns;
        PieceType promotionType;
        char direction;

        inline Move operator *(void) const
        {
            Index pp = *pawns;
            return Move{ pp, int8_t(pp + (side == WHITE_SIDE ? 8 : -8) +
                    direction), promotionType };
        }

    private:
        void next(void);
        bool valid(void) const;
    public:

        inline void operator ++(void)
        {
            do {
                next();
            } while(!valid());
        }

        inline bool operator !=(const MoveIterator& psi) const
        {
            return pawns != psi.pawns;
        }
    };

public:
    inline PromotionGenerator(const ChessGame& cg) : chessGame{ cg } {}
    MoveIterator begin(void) const;
    MoveIterator end(void) const;
};


template<chessy::Side side>
class chessy::PawnDoublePushGenerator
{
    const ChessGame& chessGame;

    struct MoveIterator
    {
        PositionSet::PositionSetIterator pawnPushes;
        inline Move operator *(void) const
        {
            Index pp = *pawnPushes;
            return Move{ int8_t(pp + (side != WHITE_SIDE ? 16 : -16)), pp };
        }

        inline void operator ++(void)
        {
            ++pawnPushes;
        }

        inline bool operator !=(const MoveIterator& psi) const
        {
            return pawnPushes != psi.pawnPushes;
        }
    };
public:
    inline PawnDoublePushGenerator(const ChessGame& cg) : chessGame{ cg } {}

    MoveIterator begin(void) const;
    MoveIterator end(void) const;
};


template<chessy::Side side, chessy::Leftright leftright>
class chessy::PawnCaptureGenerator
{
    const ChessGame& chessGame;

    struct MoveIterator
    {
        PositionSet::PositionSetIterator pawnPushes;
        inline Move operator *(void) const
        {
            Index pp = *pawnPushes;
            return Move{
                int8_t(pp + (side != WHITE_SIDE ? 8 : -8) - leftright), pp
            };
        }

        inline void operator ++(void)
        {
            ++pawnPushes;
        }

        inline bool operator !=(const MoveIterator& psi) const
        {
            return pawnPushes != psi.pawnPushes;
        }
    };
public:
    inline PawnCaptureGenerator(const ChessGame& cg) : chessGame{ cg } {}

    MoveIterator begin(void) const;
    MoveIterator end(void) const;
};


/*!
 * extends \link PositionSet \endlink so that all possible destinations for
 * a knight can be iterated over.
 */
class chessy::KnightMoveGenerator :
    public PositionSet
{
    static const std::array<Bitboard, 64> moveSets;

public:
    inline KnightMoveGenerator(Index knight, Bitboard occupied) :
        PositionSet{ moveSets[knight] & ~occupied } {}

private:
    static Bitboard generateFromIndex(Index i);
    static std::array<Bitboard, 64> generateKnightMoves(void);
};


/*!
 * uses a primitive algorithm to calculate all possible move destinations
 * for a queen.
 */
class chessy::PrimitiveQueenMoveGenerator :
    public PositionSet
{
protected:
    inline PrimitiveQueenMoveGenerator(Index i, Bitboard enemies, Bitboard friendly,
        bool straight, bool diagonal) :
        PositionSet{ generateAttackSet(i, enemies, friendly, straight, diagonal) } {}
public:
    inline PrimitiveQueenMoveGenerator(Index i, Bitboard enemies,
        Bitboard friendly) :
        PrimitiveQueenMoveGenerator{ i, enemies, friendly, true, true } {}
private:
    Bitboard generateAttackSet(Index i, Bitboard enemies, Bitboard friendly,
        bool straight, bool diagonal);
};


class chessy::PrimitiveBishopMoveGenerator :
    public PrimitiveQueenMoveGenerator
{
public:
    inline PrimitiveBishopMoveGenerator(Index i, Bitboard enemies,
        Bitboard friendly) :
        // bishop moves are actually just diagonal queen moves
        PrimitiveQueenMoveGenerator{ i, enemies, friendly, false, true } {}
};


class chessy::PrimitiveRookMoveGenerator :
    public PrimitiveQueenMoveGenerator
{
public:
    inline PrimitiveRookMoveGenerator(Index i, Bitboard enemies,
        Bitboard friendly) :
        // rook moves are actually just straight queen moves
        PrimitiveQueenMoveGenerator{ i, enemies, friendly, true, false } {}
};


class chessy::KingMoveGenerator :
    public PositionSet
{
public:
    inline KingMoveGenerator(Bitboard king, Bitboard friendly) :
        PositionSet{ generateKingMoves(king) & ~friendly } {}
private:
    Bitboard generateKingMoves(Bitboard king);
};


template<chessy::Side side>
class chessy::CastlingGenerator :
    public PositionSet
{
public:
    CastlingGenerator(const ChessGame& game);
};


#endif // CHESSY_MOVEGENERATION_H