beginning of transition

app/chess_sim/game_board.py

@@ -1,11 +1,13 @@
 from enum import Enum, auto
 from dataclasses import dataclass
 from typing import Iterator, Optional, List, Tuple
-import random
-
+import copy
 FILES = "abcdefgh"
 RANKS = "12345678"
 
+
+
+
 class PieceType(Enum):
     PAWN = auto()
     KNIGHT = auto()
@@ -26,6 +28,19 @@ class Color(Enum):
         else:
             return Color.WHITE
 
+class Outcome(Enum):
+    DRAW = auto()
+    WHITE_WIN = auto()
+    BLACK_WIN = auto()
+    NOT_FINISHED = auto()
+
+    @classmethod
+    def from_color(cls, color: Color) -> "Outcome":
+        if color == Color.WHITE:
+            return Outcome.WHITE_WIN
+        else:
+            return Outcome.BLACK_WIN
+
 
 @dataclass
 class BoardPos:
@@ -99,6 +114,87 @@ class ChessBoard:
     fields: List[List[BoardField]]
     num_moves: int
     move_history: List[Tuple['BoardMove', Optional[Piece]]]
+    initial_board: List[List[BoardField]]
+
+    @property
+    def turn(self) -> "Color":
+        len_mv_history = len(self.move_history)
+        if len_mv_history > 0:
+
+            first_moved_piece_color = self.initial_move_color
+            if len_mv_history % 2 == 0:
+                return first_moved_piece_color
+            else:
+                return first_moved_piece_color.opposite
+        else:
+            return Color.WHITE
+    
+    @property
+    def initial_move_color(self) -> Color:
+        first_move = self.move_history[0]
+        from_pos = first_move[0].m_from
+        # look up what color the piece had that moved first
+        # (odd solution but i think its quite fine)
+        first_moved_field = self.initial_board[from_pos.x][from_pos.y]
+        first_moved_piece_color = Color.WHITE
+        if first_moved_field.piece is not None:
+            first_moved_piece_color = first_moved_field.piece.color
+        return first_moved_piece_color
+
+    def is_checkmate(self) -> bool:
+        cur_turn_color = self.turn
+        return len(self.generate_moves(cur_turn_color)) == 0 and self.is_field_attacked(self.pos_of_king(cur_turn_color), cur_turn_color.opposite)
+    
+    def is_stalemate(self) -> bool:
+        cur_turn_color = self.turn
+        return len(self.generate_moves(cur_turn_color)) == 0 
+    
+    def is_seventyfive_moves(self) -> bool:
+        return len(self.move_history) >= 75
+    
+    def is_fivefold_repetition(self) -> bool:
+        return self.highest_repetiton_amount() >= 5
+
+    def outcome(self) -> Outcome:
+        if self.is_checkmate():
+            return Outcome.from_color(self.turn)
+        if self.is_stalemate() or self.is_seventyfive_moves or self.is_fivefold_repetition:
+            return Outcome.DRAW
+        return Outcome.NOT_FINISHED
+
+    def highest_repetiton_amount(self) -> int:
+        if self.move_history:
+            starting_color = self.initial_move_color
+        else:
+            starting_color = Color.WHITE
+
+        dummy = ChessBoard(
+            copy.deepcopy(self.initial_board),
+            0,
+            [],
+            copy.deepcopy(self.initial_board),
+        )
+
+        color = starting_color
+        states: list[str] = []
+
+        states.append(str(dummy))
+
+        for mv, _ in self.move_history:
+            dummy.make_move(mv, color)
+            color = color.opposite
+            states.append(str(dummy))
+
+        counts: dict[str, int] = {}
+        max_count = 0
+
+        for state in states:
+            counts[state] = counts.get(state, 0) + 1
+            if counts[state] > max_count:
+                max_count = counts[state]
+
+        return max_count
+
 
     def place(self, row: int, col: int, piece_type: PieceType, color: Color):
         self.fields[row][col].piece = Piece(piece_type, color)
@@ -106,8 +202,9 @@ class ChessBoard:
     # initialize default starting position
     @classmethod
     def init_default(cls) -> "ChessBoard":
+        empty_board = [[BoardField() for _ in range(8)] for _ in range(8)]
         brd = cls(
-            [[BoardField() for _ in range(8)] for _ in range(8)], 0, []
+            empty_board, 0, [], empty_board
         )
 
         # place pawns
@@ -135,6 +232,9 @@ class ChessBoard:
         for col, piece_type in enumerate(back_rank):
             brd.place(7, col, piece_type, Color.WHITE)
 
+        #set the inital board for later ref
+        brd.initial_board = brd.fields
+
         return brd
     
     # attempt to make move for color
@@ -317,7 +417,7 @@ class ChessBoard:
                                     color.opposite,
                                 ):  
                                     # check if the last move moved the pawn there from the starting square
-                                    last_move = self.move_history[move_history_len][0]
+                                    last_move = self.move_history[-1][0]  # final move, not past-the-end
 
                                     if last_move.m_from == BoardPos((tr, tc + en_passant_dir)) and last_move.m_to == BoardPos((tr, tc - en_passant_dir)): 
                                         moves.append(BoardMove(pos, BoardPos((tr, tc))))

app/chess_sim/test.py

@@ -65,6 +65,7 @@ def run_random_games(n: int = 20, max_moves: int = 200, verbose: bool = False):
 def test_castling_kingside_both_sides():
     board = ChessBoard.init_default()
 
+    # rewrite with  boardmove from string
     seq = [
         (BoardMove(BoardPos((7, 6)), BoardPos((5, 5))), Color.WHITE),
         (BoardMove(BoardPos((0, 1)), BoardPos((2, 2))), Color.BLACK),
@@ -139,6 +140,32 @@ def main():
     test_castling_kingside_both_sides()
     run_random_games(verbose=False)
 
+    board = ChessBoard.init_default()
+    # helper to create boardmove from two-square string
+    def bm(s):
+        return BoardMove(
+            ChessBoard.algebraic_to_pos(s[0:2]),
+            ChessBoard.algebraic_to_pos(s[2:4])
+        )
+
+    # perform four cycles of the knight shuffle
+    # Nf3-Nf6-Ng1-Ng8 and returns to the starting position.
+    seq = []
+    for _ in range(4):
+        seq.extend([
+            (bm("g1f3"), Color.WHITE),
+            (bm("g8f6"), Color.BLACK),
+            (bm("f3g1"), Color.WHITE),
+            (bm("f6g8"), Color.BLACK),
+        ])
+    for move, color in seq:
+        ok = board.make_move(move, color)
+        assert ok, "repetition test move failed"
+
+    rep = board.highest_repetiton_amount()
+    assert rep >= 5, f"expected at least 5 repetitions, got {rep}"
+    assert board.is_fivefold_repetition(), "board should report fivefold repetition"
+
     print(f"all tests passed")
 
 

app/sockets/socket.py

@@ -5,7 +5,8 @@ from dataclasses import dataclass, field
 from threading import Lock
 from typing import Optional
 
-import chess #todo: replace with own chess logic implementation to remove dependency
+import chess
+from chess_sim.game_board import ChessBoard, Color, Outcome
 from flask_login import current_user
 from flask import request
 from flask_socketio import emit, join_room, leave_room
@@ -23,7 +24,7 @@ class GameRoom:
     p2_sid: Optional[str] = None
     p2_name: Optional[str] = None
     ready: dict[str, bool] = field(default_factory=dict)
-    board: chess.Board = field(default_factory=chess.Board)
+    board: ChessBoard = ChessBoard.init_default()
     color_by_sid: dict[str, str] = field(default_factory=dict)
     initial_ms: int = 600000
     increment_ms: int = 0
@@ -81,14 +82,14 @@ def _sid_for_color(room: GameRoom, color: str) -> Optional[str]:
 
 
 def _turn_sid(room: GameRoom) -> Optional[str]:
-    return _sid_for_color(room, "w" if room.board.turn == chess.WHITE else "b")
+    return _sid_for_color(room, "w" if room.board.turn == Color.WHITE else "b")
 
 
 def _clock_payload(room: GameRoom) -> dict:
     return {
         "white_time_left_ms": max(0, room.white_ms),
         "black_time_left_ms": max(0, room.black_ms),
-        "turn": "w" if room.board.turn == chess.WHITE else "b",
+        "turn": "w" if room.board.turn == Color.WHITE else "b",
     }
 
 
@@ -101,7 +102,7 @@ def _apply_elapsed(room: GameRoom) -> Optional[str]:
     if elapsed_ms <= 0:
         return None
 
-    active_color = "w" if room.board.turn == chess.WHITE else "b"
+    active_color = "w" if room.board.turn == Color.WHITE else "b"
     if active_color == "w":
         room.white_ms = max(0, room.white_ms - elapsed_ms)
     else:
@@ -125,13 +126,14 @@ def _cleanup_room(code: str) -> None:
         code_by_sid.pop(room.p2_sid, None)
 
 
-def _game_over_reason(board: chess.Board) -> str:
+def _game_over_reason(board: ChessBoard) -> str:
     if board.is_checkmate():
         return "checkmate"
     if board.is_stalemate():
         return "stalemate"
-    if board.is_insufficient_material():
-        return "insufficient material"
+    # todo introduce game over reason insufficient material 
+    # if board.is_insufficient_material():
+    #     return "insufficient material"
     if board.is_seventyfive_moves():
         return "75-move rule"
     if board.is_fivefold_repetition():
@@ -143,10 +145,11 @@ def _emit_game_over(room: GameRoom, reason: str) -> None:
     room.completed = True
     room.game_active = False
 
-    outcome = room.board.outcome(claim_draw=True)
+    outcome = room.board.outcome()
     p1_result = "draw"
     p2_result = "draw"
 
+
     if outcome and outcome.winner is not None:
         winner_color = "w" if outcome.winner == chess.WHITE else "b"
         if room.color_by_sid.get(room.p1_sid) == winner_color:
@@ -181,7 +184,7 @@ def _start_game_if_ready(room: GameRoom) -> None:
     if not room.ready.get(room.p1_sid) or not room.ready.get(room.p2_sid):
         return
 
-    room.board = chess.Board()
+    room.board = ChessBoard.init_default()
     if room.p1_pref == "w":
         p1_color = "w"
     elif room.p1_pref == "b":
@@ -202,14 +205,14 @@ def _start_game_if_ready(room: GameRoom) -> None:
     p1_payload = {
         "play_as": p1_color,
         "time_left_ms": room.white_ms if p1_color == "w" else room.black_ms,
-        "fen": room.board.fen(),
+        "fen": room.board.to_fen(),
         "opponent": room.p2_name,
         **_clock_payload(room),
     }
     p2_payload = {
         "play_as": p2_color,
         "time_left_ms": room.white_ms if p2_color == "w" else room.black_ms,
-        "fen": room.board.fen(),
+        "fen": room.board.to_fen(),
         "opponent": room.p1_name,
         **_clock_payload(room),
     }