From 2c31de83b7a615c00467ea7a8db96e96078c5b5c Mon Sep 17 00:00:00 2001
From: Arthur Bols <arthur@bols.dev>
Date: Thu, 22 Dec 2022 23:35:07 +0100
Subject: [PATCH] [MoveGenerator] Implement generateKnightMoves

---
 BitBoard.cpp      | 15 +++++++++++++++
 BitBoard.hpp      |  1 +
 Board.cpp         |  3 ++-
 MoveGenerator.cpp |  7 +++++++
 MoveGenerator.hpp |  1 +
 5 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/BitBoard.cpp b/BitBoard.cpp
index 486f87e..9d28a3e 100644
--- a/BitBoard.cpp
+++ b/BitBoard.cpp
@@ -102,6 +102,21 @@ BitBoard BitBoard::queenAttacks(BitBoard queens, BitBoard empty) {
     return rookAttacks(queens, empty) | bishopAttacks(queens, empty);
 }
 
+BitBoard BitBoard::knightAttacks(BitBoard knights) {
+    BitBoard east, west, result;
+
+    east = knights.east();
+    west = knights.west();
+    result = (east | west) << 16;
+    result |= (east | west) >> 16;
+    east = east.east();
+    west = west.west();
+    result |= (east | west) << 8;
+    result |= (east | west) >> 8;
+
+    return result;
+}
+
 BitBoard BitBoard::pawnNorthAttacks(BitBoard pawns, BitBoard targets) {
     return (pawns.northEast() | pawns.northWest()) & targets;
 }
diff --git a/BitBoard.hpp b/BitBoard.hpp
index d6e69a5..7c574d4 100644
--- a/BitBoard.hpp
+++ b/BitBoard.hpp
@@ -111,6 +111,7 @@ public:
     static BitBoard queenAttacks(BitBoard queens, BitBoard empty);
     static BitBoard kingAttacks(BitBoard kings);
     static BitBoard castlingMoves(BitBoard kings, BitBoard rooks, BitBoard empty);
+    static BitBoard knightAttacks(BitBoard knights);
 
     static BitBoard pawnNorthAttacks(BitBoard pawns, BitBoard targets);
     static BitBoard pawnSouthAttacks(BitBoard pawns, BitBoard targets);
diff --git a/Board.cpp b/Board.cpp
index 9d5427e..a3edaff 100644
--- a/Board.cpp
+++ b/Board.cpp
@@ -160,7 +160,8 @@ void Board::pseudoLegalMovesFrom(const Square &from, Board::MoveVec &moves) cons
     switch (p.type()) {
     case PieceType::Pawn: MoveGenerator::generatePawnMoves(bs, from, moves);
         return;
-    case PieceType::Knight: break;
+    case PieceType::Knight: MoveGenerator::generateKnightMoves(bs, from, moves);
+        return;
     case PieceType::Bishop: MoveGenerator::generateBishopMoves(bs, from, moves);
         return;
     case PieceType::Rook: MoveGenerator::generateRookMoves(bs, from, moves);
diff --git a/MoveGenerator.cpp b/MoveGenerator.cpp
index 609537d..41853d3 100644
--- a/MoveGenerator.cpp
+++ b/MoveGenerator.cpp
@@ -113,6 +113,13 @@ void MoveGenerator::generateQueenMoves(const BoardState &bs, const Square &from,
     generateMoves(from, movesBB, moves);
 }
 
+void MoveGenerator::generateKnightMoves(const BoardState &bs, const Square &from, MoveVec &moves) {
+
+    auto fromBB = BitBoard::fromIndex(from.index());
+    auto movesBB = BitBoard::knightAttacks(fromBB) & ~(*bs.pieceBBs)[Board::toIndex(bs.turn)];
+    generateMoves(from, movesBB, moves);
+}
+
 //BitBoard MoveGenerator::generateAttackedSquares(const BoardState &bs, BitBoard target, PieceColor opColor) const {
 //    auto opponentBB = (*bs.pieceBBs)[Board::toIndex(opColor)];
 //
diff --git a/MoveGenerator.hpp b/MoveGenerator.hpp
index 310be79..5a98170 100644
--- a/MoveGenerator.hpp
+++ b/MoveGenerator.hpp
@@ -22,6 +22,7 @@ public:
     static void generateKingMoves(const BoardState &bs, const Square &from, MoveVec &moves);
     static void generateRookMoves(const BoardState &bs, const Square &from, MoveVec &moves);
     static void generateQueenMoves(const BoardState &bs, const Square &from, MoveVec &moves);
+    static void generateKnightMoves(const BoardState &bs, const Square &from, MoveVec &moves);
 
 private:
     static void generatePawnMoves(const BoardState &bs, const Square &from, BitBoard targets, MoveVec &moves);