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#include <array>
#include <cstdint>
#include "board.hpp"
#include "moves.hpp"
static void GeneratePawnMoves(board *b, int from, std::vector<Move> &moves)
{
Piece pawn = b->pieces[from];
if (pawn.type != PAWN)
{
return;
}
Position position = IndexToPosition(from);
int step = (pawn.color ? -1 : 1) * 8;
int next = from + step;
// wrap check
if (position.rank + (pawn.color ? -1 : 1) < 0 || position.rank + (pawn.color ? -1 : 1) >= 8)
{
return;
}
// if piece it want to move to is none and it as legal move
if (b->pieces[next].type == NONE)
{
moves.push_back({position, IndexToPosition(next)}); // adding legal move
// todo find why this code is here and what it does
int startingRank = pawn.color ? 6 : 1;
int twoSteps = from + step * 2;
if (position.rank == startingRank && b->pieces[twoSteps].type == NONE)
{
moves.push_back({position, IndexToPosition(twoSteps)});
}
}
// check
for (int fileOffset : {-1, 1})
{
int targetFile = position.file + fileOffset;
if (targetFile < 0 || targetFile >= 8)
{
continue;
}
int target = (position.rank + (pawn.color ? -1 : 1)) * 8 + targetFile;
if (b->pieces[target].type != NONE &&
b->pieces[target].color != pawn.color)
{
moves.push_back({position, IndexToPosition(target)});
}
}
// the end
}
std::vector<Move> GetLegalMoves(board *b)
{
std::vector<Move> moves;
moves.reserve(50); // almost all position dont have that many moves
constexpr std::array<int, 4> rook_Moves{-1, 1, 8, -8};
constexpr std::array<int, 4> bishop_Moves{-9, 9, -7, 7};
for (int i = 0; i < sizeof(b->pieces) / sizeof(b->pieces[0]); i++)
{
Piece piece = b->pieces[i];
if (piece.type == NONE)
{
continue;
}
if (piece.color != b->turn)
continue;
// add support for knight and king later
if (piece.type == PAWN)
{
GeneratePawnMoves(b, i, moves);
}
if (piece.type == BISHOP)
{
GenerateSlidingMoves(b, i, bishop_Moves, moves);
}
if (piece.type == ROOK)
{
GenerateSlidingMoves(b, i, rook_Moves, moves);
}
if (piece.type == QUEEN)
{
GenerateSlidingMoves(b, i, rook_Moves, moves);
GenerateSlidingMoves(b, i, bishop_Moves, moves);
}
};
return moves;
}
Position IndexToPosition(int i)
{
uint8_t rank = i / 8; // 0-7
uint8_t file = i % 8; // 0-7
return {rank, file};
}
void GenerateSlidingMoves(board *b, int from,
const std::array<int, 4> &directions,
std::vector<Move> &moves)
{
for (int i = 0; i < directions.size(); i++)
{
int direction = directions[i];
int i2 = from;
while (true)
{
i2 += direction;
int oldFile = (i2 - direction) % 8;
int newFile = i2 % 8;
if (direction == 7 || direction == -7 || direction == 9 ||
direction == -9)
{
if (std::abs(newFile - oldFile) != 1)
break;
}
if (i2 >= 64 || i2 < 0)
{
break;
}
if (b->pieces[i2].color == b->turn && b->pieces[i2].type != NONE)
{
break;
}
if ((direction == 1 || direction == -1) &&
(i2 / 8 != (i2 - direction) / 8))
{
break;
}
moves.push_back({IndexToPosition(from), IndexToPosition(i2)});
if (b->pieces[i2].color != b->turn && b->pieces[i2].type != NONE)
{
break;
}
}
};
};
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