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#include <array>
#include <cassert>
#include <cstdint>
#include <sys/types.h>
#include <vector>
#include "board.hpp"
#include "moves.hpp"
void GenerateKnightMoves(Board *b, int from, std::vector<Move> &moves) {
Piece knight = b->pieces[from];
if (knight.type != KNIGHT) {
assert(false && "Calling generate knight moves on non knight");
return;
}
// Knight moves: https://www.chessprogramming.org/Knight_Pattern
constexpr std::array<int, 8> knight_moves{-10, 6, 15, 17, 10, -6, -15, -17};
for (int offset : knight_moves) {
int next = from + offset;
if (next >= 64 || next < 0) {
continue;
}
const int fileDelta = std::abs((next % 8) - (from % 8));
if (fileDelta != 1 && fileDelta != 2) {
continue;
};
if (b->pieces[next].type != NONE) {
if (b->pieces[next].color == b->turn) {
continue;
};
}
moves.push_back({IndexToPosition(from), IndexToPosition(next)});
}
};
void GeneratePawnMoves(Board *b, int from, std::vector<Move> &moves) {
Piece pawn = b->pieces[from];
if (pawn.type != PAWN) {
assert(false && "Calling generate pawn moves on non 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> GetPseudoLegalMoves(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 (uint 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 == KNIGHT) {
GenerateKnightMoves(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);
}
if (piece.type == KING) {
GenerateKingMoves(b, i, moves);
};
};
return moves;
}
std::vector<Move> GetLegalMoves(Board *b) {
std::vector<Move> moves = GetPseudoLegalMoves(b);
std::vector<Move> legalMove;
for (Move move : moves) {
bool isLegal = true;
Board testBoard = *b;
PlayMove(move, &testBoard);
testBoard.turn = !testBoard.turn;
auto opponentResponse = GetPseudoLegalMoves(&testBoard);
for (Move move : opponentResponse) {
if (testBoard.pieces[PositionToIndex(move.To)].type == KING) {
isLegal = false;
}
}
if (isLegal) {
legalMove.push_back(move);
};
}
if (legalMove.size() == 0) {
bool isCheck = false;
Board testBoard = *b;
testBoard.turn = !testBoard.turn;
auto opponentResponse = GetPseudoLegalMoves(&testBoard);
for (Move move : opponentResponse) {
if (testBoard.pieces[PositionToIndex(move.To)].type == KING) {
isCheck = true;
}
}
if (isCheck) {
if (b->turn) {
b->state = BLACK_WON;
} else {
b->state = WHITE_WON;
};
} else {
b->state = STALEMATE;
}
}
return legalMove;
}
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 (uint 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;
}
}
};
};
void GenerateKingMoves(Board *b, int from, std::vector<Move> &moves) {
if (b->pieces[from].type != KING) {
assert(false && "calling generate king moves on non king");
return;
}
if (b->pieces[from].color != b->turn) {
assert(false && "calling generate king moves on king of opposite color");
return;
}
constexpr std::array<int, 8> king_moves{-1, 1, 8, -8, -9, 9, -7, 7};
for (int offset : king_moves) {
int next = from + offset;
if (next >= 64 || next < 0) {
continue;
}
if (std::abs((next % 8) - (from % 8)) > 1) {
continue;
};
if (b->pieces[next].type != NONE) {
if (b->pieces[next].color == b->turn) {
continue;
};
}
moves.push_back({IndexToPosition(from), IndexToPosition(next)});
}
}
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