Patterns.hpp

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

namespace chess::moves::patterns {
 
using board::Bitboard;
using pieces::Color;


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

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

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

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

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

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

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

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

 
/*
                         ___                           ,--,
      ,---,            ,--.'|_                ,--,   ,--.'|
    ,---.'|            |  | :,'             ,--.'|   |  | :
    |   | :            :  : ' :             |  |,    :  : '    .--.--.
    |   | |   ,---.  .;__,'  /    ,--.--.   `--'_    |  ' |   /  /    '
  ,--.__| |  /     \ |  |   |    /       \  ,' ,'|   '  | |  |  :  /`./
 /   ,'   | /    /  |:__,'| :   .--.  .-. | '  | |   |  | :  |  :  ;_
.   '  /  |.    ' / |  '  : |__  \__\/: . . |  | :   '  : |__ \  \    `.
'   ; |:  |'   ;   /|  |  | '.'| ," .--.; | '  : |__ |  | '.'| `----.   \
|   | '/  ''   |  / |  ;  :    ;/  /  ,.  | |  | '.'|;  :    ;/  /`--'  /__  ___  ___
|   :    :||   :    |  |  ,   /;  :   .'   \;  :    ;|  ,   /'--'.     /  .\/  .\/  .\
 \   \  /   \   \  /    ---`-' |  ,     .-./|  ,   /  ---`-'   `--'---'\  ; \  ; \  ; |
  `----'     `----'             `--`---'     ---`-'                     `--" `--" `--"
 
 */
 
template <Color Side>
constexpr auto pawn_pushes(const Bitboard starting) noexcept
    -> Bitboard
{
    return board::shifts::pawn_forward<Side>(starting);
}
 
template <Color Side>
constexpr auto pawn_double_pushes(const Bitboard starting) noexcept
    -> Bitboard
{
    namespace rank_masks = board::masks::ranks;
 
    if constexpr (Side == Color::White) {
        return (starting << 16uz) // north 2 ranks
             & rank_masks::FOUR;
    } else {
        return (starting >> 16uz) // south 2 ranks
             & rank_masks::FIVE;
    }
}
 
template <Color Side>
constexpr auto pawn_attacks(const Bitboard starting) noexcept
    -> Bitboard
{
    namespace shifts = board::shifts;
 
    return shifts::pawn_capture_east<Side>(starting) | shifts::pawn_capture_west<Side>(starting);
}
 
constexpr auto knight(const Bitboard starting) noexcept
    -> Bitboard
{
    namespace file_masks = board::masks::files;
 
    constexpr auto notAFile  = file_masks::A.inverse();
    constexpr auto notHFile  = file_masks::H.inverse();
    constexpr auto notABFile = (file_masks::A | file_masks::B).inverse();
    constexpr auto notGHFile = (file_masks::G | file_masks::H).inverse();
 
    Bitboard moves;
 
    moves |= (starting & notHFile) << 17uz;  // noNoEa
    moves |= (starting & notGHFile) << 10uz; // noEaEa
    moves |= (starting & notGHFile) >> 6uz;  // soEaEa
    moves |= (starting & notHFile) >> 15uz;  // soSoEa
    moves |= (starting & notAFile) << 15uz;  // noNoWe
    moves |= (starting & notABFile) << 6uz;  // noWeWe
    moves |= (starting & notABFile) >> 10uz; // soWeWe
    moves |= (starting & notAFile) >> 17uz;  // soSoWe
 
    return moves;
}
 
constexpr auto bishop(const Bitboard starting) noexcept
    -> Bitboard
{
    const auto diags     = board::fills::diagonal(starting);
    const auto antiDiags = board::fills::antidiagonal(starting);
 
    return (diags | antiDiags) & starting.inverse();
}
 
constexpr auto rook(const Bitboard starting) noexcept
    -> Bitboard
{
    const auto ranks = board::fills::rank(starting);
    const auto files = board::fills::file(starting);
 
    return (ranks | files) & starting.inverse();
}
 
constexpr auto queen(const Bitboard starting) noexcept
    -> Bitboard
{
    const auto ranks     = board::fills::rank(starting);
    const auto files     = board::fills::file(starting);
    const auto diags     = board::fills::diagonal(starting);
    const auto antiDiags = board::fills::antidiagonal(starting);
 
    return (ranks | files | diags | antiDiags) & starting.inverse();
}
 
constexpr auto king(Bitboard starting) noexcept
    -> Bitboard
{
    namespace shifts = board::shifts;
 
    auto moves = shifts::east(starting) | shifts::west(starting);
 
    starting |= moves;
 
    moves |= shifts::north(starting) | shifts::south(starting);
 
    return moves;
}
 
} // namespace chess::moves::patterns