made CastleSide a normal enum again to use &

not a pointer

.gitignore

@@ -171,4 +171,4 @@ cython_debug/
 .ruff_cache/
 
 # PyPI configuration file
-.pypirc
+.pypirc

cpp/.gitignore

@@ -0,0 +1,34 @@
+# Prerequisites
+*.d
+
+# Compiled Object files
+*.slo
+*.lo
+*.o
+*.obj
+
+# Precompiled Headers
+*.gch
+*.pch
+
+# Compiled Dynamic libraries
+*.so
+*.dylib
+*.dll
+
+# Fortran module files
+*.mod
+*.smod
+
+# Compiled Static libraries
+*.lai
+*.la
+*.a
+*.lib
+
+# Executables
+*.exe
+*.out
+*.appobj/
+test_bin/
+main

cpp/Makefile

@@ -0,0 +1,56 @@
+# Add .d to Make's recognized suffixes.
+SUFFIXES += .d
+
+#We don't need to clean up when we're making these targets
+NODEPS:=clean tags svn
+#Find all the C++ files in the src/ directory
+SOURCES:=$(shell find src/ -name "*.cpp")
+OBJFILES := $(patsubst src/%.cpp,obj/%.o,$(SOURCES))
+#These are the dependency files, which make will clean up after it creates them
+DEPFILES:=$(patsubst %.cpp,%.d,$(SOURCES))
+
+#Don't create dependencies when we're cleaning, for instance
+ifeq (0, $(words $(findstring $(MAKECMDGOALS), $(NODEPS))))
+	#Chances are, these files don't exist.  GMake will create them and
+	#clean up automatically afterwards
+	-include $(DEPFILES)
+endif
+
+#This is the rule for creating the dependency files
+src/%.d: src/%.cpp
+	$(CXX) $(CXXFLAGS) -MM -MT '$(patsubst src/%.cpp,obj/%.o,$<)' $< -MF $@
+
+#This rule does the compilation
+obj/%.o:
+	@mkdir -p $(dir $@)
+	$(CXX) $(CXXFLAGS) -o $@ -c $<
+
+main: $(OBJFILES)
+	$(CXX) $(LDFLAGS) $(OBJFILES) $(LOADLIBES) $(LDLIBS) -o main
+
+clean:
+	rm -rf obj/* $(DEPFILES) test_bin/
+
+
+# --- Test Support ---
+# Find all test source files in the tests directory
+TESTS := $(shell find tests -name "*.cpp")
+# Define corresponding test executable names, e.g. tests/foo.cpp -> test_bin/foo
+TEST_BIN := $(patsubst tests/%.cpp,test_bin/%,$(TESTS))
+LIBS := $(filter-out obj/main.o,$(OBJFILES))
+
+# Pattern rule: how to build a test executable from a test source file.
+# You can adjust CXXFLAGS or add include directories if needed.
+test_bin/%: tests/%.cpp $(LIBS)
+	@echo $(LIBS)
+	@mkdir -p $(dir $@)
+	$(CXX) $(CXXFLAGS) -o $@ $< $(LIBS)
+
+# The 'test' target builds all tests and then runs each one.
+.PHONY: test
+test: $(TEST_BIN)
+	@echo "Running all tests..."
+	@for t in $(TEST_BIN); do \
+	    echo "---- Running $$t ----"; \
+	    ./$$t || exit 1; \
+	done

cpp/src/board.cpp

@@ -0,0 +1,131 @@
+#include "board.hpp"
+
+#include "coords.hpp"
+#include "pieces/piece.hpp"
+
+#include <algorithm>
+#include <cctype>
+#include <map>
+#include <stdexcept>
+
+Board Board::setup_fen_position(std::string fen) {
+    Board board;
+    std::map<char, Piece> c2p{
+        {'k', Piece::King},
+        {'p', Piece::Pawn},
+        {'n', Piece::Knigt},
+        {'b', Piece::Bishop},
+        {'r', Piece::Rook},
+        {'q', Piece::Queen},
+    };
+
+    std::string fen_board = fen.substr(0, fen.find(' '));
+    int rank = 7, file = 0;
+    for (char symbol : fen_board) {
+        if (symbol == '/') {
+            file = 0;
+            rank--;
+            continue;
+        }
+
+        if (std::isdigit(symbol))
+            file += symbol - '0';
+        else {
+            Colour colour =
+                std::isupper(symbol) ? Colour::White : Colour::Black;
+
+            Piece piece = c2p[std::tolower(symbol)];
+            board.squares[rank * 8 + file] = colour | piece;
+            file++;
+        }
+    }
+    return board;
+}
+
+std::string Board::to_fen() const {
+    std::map<int, char> p2c{
+        {Piece::King, 'k'},
+        {Piece::Pawn, 'p'},
+        {Piece::Knigt, 'n'},
+        {Piece::Bishop, 'b'},
+        {Piece::Rook, 'r'},
+        {Piece::Queen, 'q'},
+    };
+
+    std::string ret;
+    for (int rank = 7; rank >= 0; rank--) {
+        int empty_cell_counter = 0;
+        for (int file = 0; file < 8; file++) {
+            if (this->squares[rank * 8 + file] == Piece::None) {
+                empty_cell_counter++;
+                continue;
+            }
+
+            int full_piece = this->squares[rank * 8 + file];
+            char piece = p2c[full_piece & 0b111];
+            int8_t colour = colour_at({file, rank});
+
+            if (empty_cell_counter > 0) {
+                ret += std::to_string(empty_cell_counter);
+                empty_cell_counter = 0;
+            }
+            ret += colour == Colour::White ? std::toupper(piece) : piece;
+        }
+        if (empty_cell_counter > 0)
+            ret += std::to_string(empty_cell_counter);
+        if (rank > 0)
+            ret += "/";
+    }
+    return ret;
+}
+
+Board Board::make_move(Move move) const {
+    int8_t dest_piece = this->squares[move.target_square];
+
+    Board ret;
+    std::copy(
+        std::begin(this->squares),
+        std::end(this->squares),
+        std::begin(ret.squares)
+    );
+    ret.white_to_play = !this->white_to_play;
+
+    // -- Actually make the move
+    ret.squares[move.source_square] = Piece::None;
+    ret.squares[move.target_square] = this->squares[move.source_square];
+
+    // -- Handle en passant target being eaten
+    if (move.en_passant)
+        ret.squares[move.target_square - 8] = Piece::None;
+    return ret;
+}
+
+int8_t Board::get_king_of(int8_t colour) const {
+    for (int i = 0; i < 64; i++)
+        if (this->squares[i] == (colour | Piece::King))
+            return i;
+    throw std::domain_error(
+        "Apparently there no kings of the such color in this board"
+    );
+}
+
+std::vector<int8_t> to_target_square(std::vector<Move> moves) {
+    std::vector<int8_t> ret;
+    for (Move move : moves)
+        ret.push_back(move.target_square);
+    return ret;
+}
+
+bool Board::is_check_for(int8_t colour) const {
+    int8_t king_idx = this->get_king_of(colour);
+    for (int i = 0; i < 64; i++) {
+        if (this->squares[i] == Piece::None)
+            continue;
+        std::vector<Move> moves =
+            legal_moves(this->squares[i], *this, Coords::from_index(i), true);
+        std::vector<int8_t> targets = to_target_square(moves);
+        if (std::find(targets.begin(), targets.end(), i) != targets.end())
+            return true;
+    }
+    return false;
+}

cpp/src/board.hpp

@@ -0,0 +1,32 @@
+#pragma once
+
+#include "coords.hpp"
+#include "move.hpp"
+#include "pieces/piece.hpp"
+
+#include <string>
+
+struct Board {
+  private:
+    int8_t get_king_of(int8_t colour) const;
+
+  public:
+    int8_t squares[64] = {Piece::None};
+    bool white_to_play;
+    CastleSide w_castle_rights;
+    CastleSide b_castle_rights;
+
+    static Board setup_fen_position(std::string fen);
+
+    Board make_move(Move) const;
+    std::string to_fen() const;
+    bool is_check_for(int8_t) const;
+
+    int8_t colour_at(int8_t idx) const {
+        return squares[idx] & 0b11000;
+    }
+
+    int8_t colour_at(Coords xy) const {
+        return colour_at(xy.to_index());
+    }
+};

cpp/src/castle_side.hpp

@@ -0,0 +1,7 @@
+#include <cstdint>
+
+enum CastleSide : int8_t {
+    NeitherSide = 0,
+    KingSide = 1,
+    QueenSide = 2,
+};

cpp/src/coords.hpp

@@ -0,0 +1,19 @@
+#pragma once
+
+#include <cstdint>
+
+struct Coords {
+    int x, y;
+
+    int8_t to_index() const {
+        return this->y * 8 + this->x;
+    }
+
+    static Coords from_index(int idx) {
+        return {idx % 8, idx / 8};
+    }
+
+    bool is_within_bounds() const {
+        return this->to_index() < 64;
+    }
+};

cpp/src/main.cpp

@@ -0,0 +1,10 @@
+#include "board.hpp"
+
+#include <iostream>
+
+int main(int argc, char* argv[]) {
+    std::string pos =
+        "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
+    Board b = Board::setup_fen_position(pos);
+    return 0;
+}

cpp/src/move.hpp

@@ -0,0 +1,15 @@
+#pragma once
+
+#include "castle_side.hpp"
+
+#include <cstdint>
+
+struct Move {
+    int8_t source_square;
+    int8_t target_square;
+
+    bool is_capturing = false;
+    CastleSide castle_side = CastleSide::NeitherSide;
+    bool en_passant = false;
+    int8_t promoting_to = 0;
+};

cpp/src/pieces/bishop.cpp

@@ -0,0 +1,23 @@
+#include "../board.hpp"
+#include "../coords.hpp"
+#include "../move.hpp"
+#include "piece.hpp"
+
+#include <vector>
+
+std::vector<Move> bishop_moves(const Board& b, const Coords xy) {
+    std::vector<Move> ret;
+    auto ne = look_direction(b, xy, 1, 1);
+    ret.insert(ret.end(), ne.begin(), ne.end());
+
+    auto se = look_direction(b, xy, 1, -1);
+    ret.insert(ret.end(), se.begin(), se.end());
+
+    auto sw = look_direction(b, xy, -1, -1);
+    ret.insert(ret.end(), sw.begin(), sw.end());
+
+    auto nw = look_direction(b, xy, -1, 1);
+    ret.insert(ret.end(), nw.begin(), nw.end());
+
+    return ret;
+}

cpp/src/pieces/king.cpp

@@ -0,0 +1,76 @@
+#include "../board.hpp"
+#include "../coords.hpp"
+#include "piece.hpp"
+
+static bool is_clear_king_side(const Board& b, const Coords xy) {
+    for (int dx = 1; dx < 3; dx++) {
+        Coords c{xy.x + dx, xy.y};
+        if (b.squares[c.to_index()] != Piece::None)
+            return false;
+
+        std::optional<Move> move = move_for_position(b, xy, c);
+        Board board_after_move = b.make_move(move.value());
+        if (board_after_move.is_check_for(b.colour_at(xy)))
+            return false;
+    }
+    return true;
+}
+
+static bool is_clear_queen_side(const Board& b, const Coords xy) {
+    for (int dx = 1; dx < 4; dx++) {
+        Coords c{xy.x - dx, xy.y};
+        if (b.squares[c.to_index()] != Piece::None)
+            return false;
+
+        std::optional<Move> move = move_for_position(b, xy, c);
+        Board board_after_move = b.make_move(move.value());
+        if (dx < 3 && board_after_move.is_check_for(b.colour_at(xy)))
+            return false;
+    }
+    return true;
+}
+
+std::vector<Move> king_moves(const Board& b, const Coords xy) {
+    std::vector<Move> ret;
+
+    // -- Regular moves
+    for (int dx = -1; dx <= 1; dx++) {
+        for (int dy = -1; dy <= 1; dy++) {
+            if (dx == 0 && dy == 0) // skip staying in the same position
+                continue;
+            Coords c{xy.x + dx, xy.y + dy};
+            std::optional<Move> move = move_for_position(b, xy, c);
+            if (move.has_value())
+                ret.push_back(move.value());
+        }
+    }
+
+    if (b.is_check_for(b.colour_at(xy)))
+        return ret;
+
+    // -- Castles
+    CastleSide castling_rights = b.colour_at(xy) == Colour::White
+                                   ? b.w_castle_rights
+                                   : b.b_castle_rights;
+
+    if (castling_rights == CastleSide::NeitherSide)
+        return ret;
+
+    if (castling_rights & CastleSide::KingSide && is_clear_king_side(b, xy)) {
+        ret.push_back(Move{
+            xy.to_index(),
+            Coords{6, xy.y}.to_index(),
+            .castle_side = CastleSide::KingSide
+        });
+    }
+
+    if (castling_rights & CastleSide::QueenSide && is_clear_queen_side(b, xy)) {
+        ret.push_back(Move{
+            xy.to_index(),
+            Coords{2, xy.y}.to_index(),
+            .castle_side = CastleSide::QueenSide
+        });
+    }
+
+    return ret;
+}

cpp/src/pieces/knight.cpp

@@ -0,0 +1,28 @@
+#include "../board.hpp"
+#include "../coords.hpp"
+#include "../move.hpp"
+#include "piece.hpp"
+
+#include <vector>
+
+std::vector<Move> knight_moves(const Board& b, const Coords xy) {
+    std::vector<Move> ret;
+    std::vector<std::pair<int, int>> moves = {
+        {+2, +1},
+        {+1, +2}, // north east
+        {+2, -1},
+        {+1, -2}, // south east
+        {-2, -1},
+        {-1, -2}, // south west
+        {-2, +1},
+        {-1, +2} // north west
+    };
+
+    for (const auto& [dx, dy] : moves) {
+        std::optional<Move> move =
+            move_for_position(b, xy, Coords{xy.x + dx, xy.y + dy});
+        if (move.has_value())
+            ret.push_back(move.value());
+    }
+    return ret;
+}

cpp/src/pieces/pawn.cpp

@@ -0,0 +1,51 @@
+#include "../board.hpp"
+#include "../coords.hpp"
+#include "../move.hpp"
+#include "piece.hpp"
+
+std::vector<Move> pawn_moves(const Board& b, const Coords xy) {
+    std::vector<Move> ret{};
+    int8_t my_colour = b.colour_at(xy);
+
+    // -- Capture to the left
+    if (xy.x > 0) {
+        int dy = my_colour == Colour::White ? 1 : -1;
+        Coords left{xy.x - 1, xy.y + dy};
+        int8_t capturable_piece = b.squares[left.to_index()];
+        if (capturable_piece != 0) {
+            if (my_colour != b.colour_at(left))
+                ret.push_back(Move{xy.to_index(), left.to_index()});
+        }
+    }
+
+    // -- Capture to the right
+    if (xy.x < 7) {
+        int dy = my_colour == Colour::White ? 1 : -1;
+        Coords right{xy.x + 1, xy.y + dy};
+        int8_t capturable_piece = b.squares[right.to_index()];
+        if (capturable_piece != 0) {
+            if (my_colour != b.colour_at(right))
+                ret.push_back(Move{xy.to_index(), right.to_index()});
+        }
+    }
+
+    // -- Promotion
+    bool is_on_starting_rank =
+        my_colour == Colour::White ? xy.y == 1 : xy.y == 6;
+    int max_dy = is_on_starting_rank ? 3 : 2;
+    for (int dy = 1; dy < max_dy; dy++) {
+        int actual_dy = my_colour == Colour::White ? dy : -dy;
+        Coords new_xy{xy.x, xy.y + actual_dy};
+        if (b.squares[new_xy.to_index()] != Piece::None)
+            break;
+        if (new_xy.y == 7 || new_xy.y == 0)
+            for (auto piece : {Queen, Knigt, Bishop, Rook})
+                ret.push_back(Move{
+                    xy.to_index(),
+                    new_xy.to_index(),
+                    .promoting_to = piece
+                });
+    }
+
+    return ret;
+}

cpp/src/pieces/piece.cpp

@@ -0,0 +1,72 @@
+#include "piece.hpp"
+
+#include "../board.hpp"
+#include "../coords.hpp"
+
+std::vector<Move>
+keep_only_blocking(const std::vector<Move> candidates, const Board& board) {
+    if (candidates.size() == 0)
+        return {};
+
+    int8_t my_colour = board.colour_at(candidates[0].source_square);
+    std::vector<Move> ret;
+    for (Move move : candidates) {
+        Board board_after_move = board.make_move(move);
+        if (!board_after_move.is_check_for(my_colour))
+            ret.push_back(move);
+    }
+    return ret;
+}
+
+std::vector<Move> legal_moves(
+    int8_t p, const Board& b, const Coords xy, bool looking_for_check = false
+) {
+    std::vector<Move> ret;
+    switch (p) {
+    case Piece::Pawn:
+        ret = pawn_moves(b, xy);
+    case Piece::Bishop:
+        break;
+    default:
+        break;
+    }
+
+    if (!looking_for_check)
+        return keep_only_blocking(ret, b);
+
+    return {};
+}
+
+std::optional<Move>
+move_for_position(const Board& board, const Coords source, const Coords dest) {
+    if (dest.is_within_bounds())
+        return {};
+
+    int8_t piece = board.squares[dest.to_index()];
+    if (piece == Piece::None)
+        return Move{source.to_index(), dest.to_index()};
+
+    int8_t source_colour = board.colour_at(source);
+    int8_t dest_colour = board.colour_at(dest);
+    if (source_colour != dest_colour)
+        return Move{source.to_index(), dest.to_index(), true};
+    return {};
+}
+
+std::vector<Move>
+look_direction(const Board& board, const Coords xy, int mult_dx, int mult_dy) {
+    std::vector<Move> ret;
+    for (int d = 0; d < 8; d++) {
+        int dx = mult_dx * d;
+        int dy = mult_dy * d;
+
+        std::optional<Move> move =
+            move_for_position(board, xy, Coords{xy.x + dx, xy.y + dy});
+        if (move.has_value()) {
+            ret.push_back(move.value());
+            if (move.value().is_capturing)
+                break;
+        }
+    }
+    return ret;
+}

cpp/src/pieces/piece.hpp

@@ -0,0 +1,37 @@
+#pragma once
+
+#include "../move.hpp"
+
+#include <cstdint>
+#include <optional>
+#include <vector>
+
+enum Piece : int8_t {
+    None = 0,
+    King = 1,
+    Pawn = 2,
+    Knigt = 3,
+    Bishop = 4,
+    Rook = 5,
+    Queen = 6,
+};
+
+enum Colour : int8_t {
+    White = 8,
+    Black = 16,
+};
+
+class Board;
+struct Coords;
+
+std::vector<Move> legal_moves(int8_t, const Board&, const Coords, bool);
+std::vector<Move> keep_only_blocking(const std::vector<Move>, const Board&);
+std::optional<Move> move_for_position(const Board&, const Coords, const Coords);
+std::vector<Move> look_direction(const Board&, const Coords, int, int);
+
+std::vector<Move> pawn_moves(const Board&, const Coords);
+std::vector<Move> rook_moves(const Board&, const Coords);
+std::vector<Move> knight_moves(const Board&, const Coords);
+std::vector<Move> bishop_moves(const Board&, const Coords);
+std::vector<Move> queen_moves(const Board&, const Coords);
+std::vector<Move> king_moves(const Board&, const Coords);

cpp/src/pieces/queen.cpp

@@ -0,0 +1,35 @@
+#include "../board.hpp"
+#include "../coords.hpp"
+#include "../move.hpp"
+#include "piece.hpp"
+
+#include <vector>
+
+std::vector<Move> rook_moves(const Board& b, const Coords xy) {
+    std::vector<Move> ret;
+    auto e = look_direction(b, xy, 1, 0);
+    ret.insert(ret.end(), e.begin(), e.end());
+
+    auto s = look_direction(b, xy, 0, -1);
+    ret.insert(ret.end(), s.begin(), s.end());
+
+    auto w = look_direction(b, xy, -1, 0);
+    ret.insert(ret.end(), w.begin(), w.end());
+
+    auto n = look_direction(b, xy, 0, 1);
+    ret.insert(ret.end(), n.begin(), n.end());
+
+    auto ne = look_direction(b, xy, 1, 1);
+    ret.insert(ret.end(), ne.begin(), ne.end());
+
+    auto se = look_direction(b, xy, 1, -1);
+    ret.insert(ret.end(), se.begin(), se.end());
+
+    auto sw = look_direction(b, xy, -1, -1);
+    ret.insert(ret.end(), sw.begin(), sw.end());
+
+    auto nw = look_direction(b, xy, -1, 1);
+    ret.insert(ret.end(), nw.begin(), nw.end());
+
+    return ret;
+}

cpp/src/pieces/rook.cpp

@@ -0,0 +1,23 @@
+#include "../board.hpp"
+#include "../coords.hpp"
+#include "../move.hpp"
+#include "piece.hpp"
+
+#include <vector>
+
+std::vector<Move> rook_moves(const Board& b, const Coords xy) {
+    std::vector<Move> ret;
+    auto e = look_direction(b, xy, 1, 0);
+    ret.insert(ret.end(), e.begin(), e.end());
+
+    auto s = look_direction(b, xy, 0, -1);
+    ret.insert(ret.end(), s.begin(), s.end());
+
+    auto w = look_direction(b, xy, -1, 0);
+    ret.insert(ret.end(), w.begin(), w.end());
+
+    auto n = look_direction(b, xy, 0, 1);
+    ret.insert(ret.end(), n.begin(), n.end());
+
+    return ret;
+}

cpp/tests/fen.cpp

@@ -0,0 +1,22 @@
+#include "../src/board.hpp"
+#include "lib.hpp"
+
+int main() {
+    std::string pos = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR";
+    ASSERT_EQUALS(pos, Board::setup_fen_position(pos)->to_fen());
+
+    pos = "r1bk3r/p2pBpNp/n4n2/1p1NP2P/6P1/3P4/P1P1K3/q5b1";
+    ASSERT_EQUALS(pos, Board::setup_fen_position(pos)->to_fen());
+
+    pos = "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR";
+    ASSERT_EQUALS(pos, Board::setup_fen_position(pos)->to_fen());
+
+    pos = "4k2r/6r1/8/8/8/8/3R4/R3K3";
+    ASSERT_EQUALS(pos, Board::setup_fen_position(pos)->to_fen());
+
+    pos = "8/8/8/4p1K1/2k1P3/8/8/8";
+    ASSERT_EQUALS(pos, Board::setup_fen_position(pos)->to_fen());
+
+    pos = "8/5k2/3p4/1p1Pp2p/pP2Pp1P/P4P1K/8/8";
+    ASSERT_EQUALS(pos, Board::setup_fen_position(pos)->to_fen());
+}

cpp/tests/lib.hpp

@@ -0,0 +1,12 @@
+#pragma once
+
+#include <iostream>
+
+#define ASSERT_EQUALS(expected, actual)                                        \
+    {                                                                          \
+        if (expected != actual)                                                \
+            std::cout << "Expected: " << std::endl                             \
+                      << '\t' << expected << std::endl                         \
+                      << "Got: " << std::endl                                  \
+                      << '\t' << actual << std::endl;                          \
+    }