Shifts.hpp

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/*
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#pragma once
 
#include <libchess/board/Bitboard.hpp>
#include <libchess/board/Masks.hpp>
#include <libchess/pieces/Colors.hpp>

namespace chess::board::shifts {
 
using pieces::Color;


[[nodiscard, gnu::const]] constexpr auto north(Bitboard board) noexcept -> Bitboard;

[[nodiscard, gnu::const]] constexpr auto south(Bitboard board) noexcept -> Bitboard;

[[nodiscard, gnu::const]] constexpr auto east(Bitboard board) noexcept -> Bitboard;

[[nodiscard, gnu::const]] constexpr auto west(Bitboard board) noexcept -> Bitboard;

[[nodiscard, gnu::const]] constexpr auto northeast(Bitboard board) noexcept -> Bitboard;

[[nodiscard, gnu::const]] constexpr auto northwest(Bitboard board) noexcept -> Bitboard;

[[nodiscard, gnu::const]] constexpr auto southeast(Bitboard board) noexcept -> Bitboard;

[[nodiscard, gnu::const]] constexpr auto southwest(Bitboard board) noexcept -> Bitboard;

template <Color Side>
[[nodiscard, gnu::const]] constexpr auto pawn_forward(Bitboard board) noexcept -> Bitboard;

template <Color Side>
[[nodiscard, gnu::const]] constexpr auto pawn_backward(Bitboard board) noexcept -> Bitboard;

template <Color Side>
[[nodiscard, gnu::const]] constexpr auto pawn_capture_east(Bitboard board) noexcept -> Bitboard;

template <Color Side>
[[nodiscard, gnu::const]] constexpr auto pawn_capture_west(Bitboard board) noexcept -> Bitboard;

template <Color Side>
[[nodiscard, gnu::const]] constexpr auto pawn_inv_capture_east(Bitboard board) noexcept -> Bitboard;

template <Color Side>
[[nodiscard, gnu::const]] constexpr auto pawn_inv_capture_west(Bitboard board) noexcept -> Bitboard;

 
/*
                         ___                           ,--,
      ,---,            ,--.'|_                ,--,   ,--.'|
    ,---.'|            |  | :,'             ,--.'|   |  | :
    |   | :            :  : ' :             |  |,    :  : '    .--.--.
    |   | |   ,---.  .;__,'  /    ,--.--.   `--'_    |  ' |   /  /    '
  ,--.__| |  /     \ |  |   |    /       \  ,' ,'|   '  | |  |  :  /`./
 /   ,'   | /    /  |:__,'| :   .--.  .-. | '  | |   |  | :  |  :  ;_
.   '  /  |.    ' / |  '  : |__  \__\/: . . |  | :   '  : |__ \  \    `.
'   ; |:  |'   ;   /|  |  | '.'| ," .--.; | '  : |__ |  | '.'| `----.   \
|   | '/  ''   |  / |  ;  :    ;/  /  ,.  | |  | '.'|;  :    ;/  /`--'  /__  ___  ___
|   :    :||   :    |  |  ,   /;  :   .'   \;  :    ;|  ,   /'--'.     /  .\/  .\/  .\
 \   \  /   \   \  /    ---`-' |  ,     .-./|  ,   /  ---`-'   `--'---'\  ; \  ; \  ; |
  `----'     `----'             `--`---'     ---`-'                     `--" `--" `--"
 
 */
 
constexpr auto north(const Bitboard board) noexcept -> Bitboard
{
    return board << 8uz;
}
 
constexpr auto south(const Bitboard board) noexcept -> Bitboard
{
    return board >> 8uz;
}
 
constexpr auto east(const Bitboard board) noexcept -> Bitboard
{
    constexpr auto notHFile = masks::files::H.inverse();
 
    return (board & notHFile) << 1uz;
}
 
constexpr auto west(const Bitboard board) noexcept -> Bitboard
{
    constexpr auto notAFile = masks::files::A.inverse();
 
    return (board & notAFile) >> 1uz;
}
 
constexpr auto northeast(const Bitboard board) noexcept -> Bitboard
{
    constexpr auto notHFile = masks::files::H.inverse();
 
    return (board & notHFile) << 9uz;
}
 
constexpr auto northwest(const Bitboard board) noexcept -> Bitboard
{
    constexpr auto notAFile = masks::files::A.inverse();
 
    return (board & notAFile) << 7uz;
}
 
constexpr auto southeast(const Bitboard board) noexcept -> Bitboard
{
    constexpr auto notHFile = masks::files::H.inverse();
 
    return (board & notHFile) >> 7uz;
}
 
constexpr auto southwest(const Bitboard board) noexcept -> Bitboard
{
    constexpr auto notAFile = masks::files::A.inverse();
 
    return (board & notAFile) >> 9uz;
}
 
template <Color Side>
constexpr auto pawn_forward(const Bitboard board) noexcept -> Bitboard
{
    if constexpr (Side == Color::White)
        return north(board);
    else
        return south(board);
}
 
template <Color Side>
constexpr auto pawn_backward(const Bitboard board) noexcept -> Bitboard
{
    if constexpr (Side == Color::White)
        return south(board);
    else
        return north(board);
}
 
template <Color Side>
constexpr auto pawn_capture_east(const Bitboard board) noexcept -> Bitboard
{
    if constexpr (Side == Color::White)
        return northeast(board);
    else
        return southeast(board);
}
 
template <Color Side>
constexpr auto pawn_inv_capture_east(const Bitboard board) noexcept -> Bitboard
{
    if constexpr (Side == Color::White)
        return southwest(board);
    else
        return northwest(board);
}
 
template <Color Side>
constexpr auto pawn_capture_west(const Bitboard board) noexcept -> Bitboard
{
    if constexpr (Side == Color::White)
        return northwest(board);
    else
        return southwest(board);
}
 
template <Color Side>
constexpr auto pawn_inv_capture_west(const Bitboard board) noexcept -> Bitboard
{
    if constexpr (Side == Color::White)
        return southeast(board);
    else
        return northeast(board);
}
 
} // namespace chess::board::shifts