ChessEngine: Add ChessEngine

This engine is pretty bad, but doesn't let itself get checkmated

2 files changed, 83 insertions, 2 deletions

diff --git a/Libraries/LibChess/Chess.cpp b/Libraries/LibChess/Chess.cpp
index 7495acf0fb..6e332e3cc4 100644
--- a/Libraries/LibChess/Chess.cpp
+++ b/Libraries/LibChess/Chess.cpp
@@ -425,8 +425,8 @@ bool Board::apply_illegal_move(const Move& move, Colour colour)
         if (move.to == Square("a8") || move.to == Square("c8")) {
             set_piece(Square("e8"), EmptyPiece);
             set_piece(Square("a8"), EmptyPiece);
-            set_piece(Square("c8"), { Colour::White, Type::King });
-            set_piece(Square("d8"), { Colour::White, Type::Rook });
+            set_piece(Square("c8"), { Colour::Black, Type::King });
+            set_piece(Square("d8"), { Colour::Black, Type::Rook });
             return true;
         } else if (move.to == Square("h8") || move.to == Square("g8")) {
             set_piece(Square("e8"), EmptyPiece);
@@ -463,6 +463,23 @@ bool Board::apply_illegal_move(const Move& move, Colour colour)
     return true;
 }
 
+Move Board::random_move(Colour colour) const
+{
+    if (colour == Colour::None)
+        colour = turn();
+
+    Move move = { { 50, 50 }, { 50, 50 } };
+    int probability = 1;
+    generate_moves([&](Move m) {
+        if (rand() % probability == 0)
+            move = m;
+        ++probability;
+        return IterationDecision::Continue;
+    });
+
+    return move;
+}
+
 Board::Result Board::game_result() const
 {
     bool sufficient_material = false;
@@ -533,6 +550,65 @@ Board::Result Board::game_result() const
     return Result::StaleMate;
 }
 
+Colour Board::game_winner() const
+{
+    if (game_result() == Result::CheckMate)
+        return opposing_colour(turn());
+
+    return Colour::None;
+}
+
+int Board::game_score() const
+{
+    switch (game_winner()) {
+    case Colour::White:
+        return +1;
+    case Colour::Black:
+        return -1;
+    case Colour::None:
+        return 0;
+    }
+    return 0;
+}
+
+bool Board::game_finished() const
+{
+    return game_result() != Result::NotFinished;
+}
+
+int Board::material_imbalance() const
+{
+    int imbalance = 0;
+    Square::for_each([&](Square square) {
+        int value = 0;
+        switch (get_piece(square).type) {
+        case Type::Pawn:
+            value = 1;
+            break;
+        case Type::Knight:
+        case Type::Bishop:
+            value = 3;
+            break;
+        case Type::Rook:
+            value = 5;
+            break;
+        case Type::Queen:
+            value = 9;
+            break;
+        default:
+            break;
+        }
+
+        if (get_piece(square).colour == Colour::White) {
+            imbalance += value;
+        } else {
+            imbalance -= value;
+        }
+        return IterationDecision::Continue;
+    });
+    return imbalance;
+}
+
 bool Board::is_promotion_move(const Move& move, Colour colour) const
 {
     if (colour == Colour::None)
diff --git a/Libraries/LibChess/Chess.h b/Libraries/LibChess/Chess.h
index 2e9c078f78..f0e0b91aab 100644
--- a/Libraries/LibChess/Chess.h
+++ b/Libraries/LibChess/Chess.h
@@ -135,7 +135,12 @@ public:
 
     template<typename Callback>
     void generate_moves(Callback callback, Colour colour = Colour::None) const;
+    Move random_move(Colour colour = Colour::None) const;
     Result game_result() const;
+    Colour game_winner() const;
+    int game_score() const;
+    bool game_finished() const;
+    int material_imbalance() const;
 
     Colour turn() const { return m_turn; }
     const Vector<Move>& moves() const { return m_moves; }