fix: 3 critical chess multiplayer bugs (resign detection, color identity, checkmate sync)

Bug 1: Resign not detected - endGame now skips redundant complete API call
when server already completed the match (resign/draw/abandon via poll).
Bug 2: Players seeing themselves as opponent - verify and correct color
from authoritative server match data on game start.
Bug 3: Checkmate not appearing - send final move to server BEFORE calling
endGame so opponent receives the checkmate FEN position.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

public/js/modules/chess/scenes/game.js

@@ -21,7 +21,8 @@ let board, clock, gameState;
 
 export function mountGame(el, params) {
   const { mode = 'bot', botId = 'amina', timeControl = 'rapid_10_0', matchId, color } = params;
-  const playerColor = color || 'w';
+  // For live games without color, resolve from match data (prevents both players seeing white)
+  let playerColor = color || 'w';
   const tc = parseTimeControl(timeControl);
 
   scene.enterGameMode();
@@ -51,7 +52,7 @@ export function mountGame(el, params) {
         const myId = store.get('auth.userId');
         const isWhite = data.white_player_id === myId;
         const isWin = (data.result === 'white_wins' && isWhite) || (data.result === 'black_wins' && !isWhite);
-        endGame(isWin ? 'win' : data.result === 'draw' ? 'draw' : 'loss', 'resign');
+        endGame(isWin ? 'win' : data.result === 'draw' ? 'draw' : 'loss', 'resign', { serverAlreadyCompleted: true });
         return;
       }
 
@@ -288,7 +289,18 @@ export function mountGame(el, params) {
         handleLivePollData(el, data);
       },
       onGameEnd: (data) => {
-        if (!gameState.gameOver) endGame('loss', 'abandon');
+        // Already handled by handleLivePollData's status===completed check
+        // This is a fallback for edge cases (e.g., abandon detection)
+        if (gameState.gameOver) return;
+        if (data && data.result) {
+          const myId = store.get('auth.userId');
+          const isWhite = data.white_player_id === myId;
+          const isWin = (data.result === 'white_wins' && isWhite) || (data.result === 'black_wins' && !isWhite);
+          const isDraw = data.result === 'draw' || data.result === 'aborted';
+          endGame(isWin ? 'win' : isDraw ? 'draw' : 'loss', data.result.includes('abandon') ? 'abandon' : 'resign', { serverAlreadyCompleted: true });
+        } else {
+          endGame('loss', 'abandon', { serverAlreadyCompleted: true });
+        }
       }
     });
     if (playerColor === 'b') {
@@ -296,16 +308,36 @@ export function mountGame(el, params) {
       clock.start('w');
     }
 
-    // Fetch and render opponent profile bar (photo, name, level)
+    // Fetch match data to verify color and render opponent profile
     let opponentId = params.opponentId;
-    // If no opponentId in params, get it from the match data
-    if (!opponentId && matchId) {
+    if (matchId) {
       net.post('game.php', { action: 'get', match_id: matchId }).then(matchData => {
-        if (matchData && !matchData.error) {
+        if (!matchData || matchData.error) return;
         const myId = store.get('auth.userId');
+
+        // Bug 2 fix: verify and correct player color from authoritative server data
+        const serverColor = matchData.white_player_id === myId ? 'w' : 'b';
+        if (gameState.playerColor !== serverColor) {
+          gameState.playerColor = serverColor;
+          gameState.isPlayerTurn = engine.turn() === serverColor;
+          if (board) {
+            board.flipped = serverColor === 'b';
+            board.canSelect = (piece) => {
+              if (gameState.gameOver || gameState.botThinking) return false;
+              if (!gameState.isPlayerTurn) return false;
+              const pieceColor = piece === piece.toUpperCase() ? 'w' : 'b';
+              return pieceColor === gameState.playerColor;
+            };
+            board.draw();
+          }
+          if (serverColor === 'b' && gameState.moveCount === 0) {
+            clock.start('w');
+          }
+        }
+
+        // Render opponent profile
         const oppId = matchData.white_player_id === myId ? matchData.black_player_id : matchData.white_player_id;
         if (oppId) fetchAndRenderOpponent(el, oppId);
-        }
       }).catch(() => {});
     }
     if (opponentId) {
@@ -442,6 +474,11 @@ function executeMove(el, from, to, promotion) {
   gameState.isPlayerTurn = false;
 
   if (engine.isGameOver()) {
+    // In live mode, send the final move BEFORE ending the game
+    // so the opponent receives the checkmate/stalemate position
+    if (gameState.mode === 'live') {
+      sendLiveMove(el);
+    }
     endGame(engine.getResult(gameState.playerColor), getEndReason());
     return;
   }
@@ -753,7 +790,7 @@ function handleLivePollData(el, data) {
       const isWin = (result === 'white_wins' && gameState.playerColor === 'w') ||
                     (result === 'black_wins' && gameState.playerColor === 'b');
       const isDraw = result === 'draw' || result === 'aborted';
-      endGame(isWin ? 'win' : isDraw ? 'draw' : 'loss', result === 'aborted' ? 'abandon' : 'resign');
+      endGame(isWin ? 'win' : isDraw ? 'draw' : 'loss', result === 'aborted' ? 'abandon' : 'resign', { serverAlreadyCompleted: true });
     }
   }
 }
@@ -848,7 +885,7 @@ function checkDrawOffer(el, rawGameState, myId) {
       action: 'draw',
       match_id: gameState.matchId
     });
-    endGame('draw', 'agreement');
+    endGame('draw', 'agreement', { serverAlreadyCompleted: true });
   });
 
   dialog.querySelector('#draw-reject').addEventListener('click', () => {
@@ -877,7 +914,7 @@ function checkDrawResponse(el, rawGameState, myId) {
   if (!gs) return;
 
   if (gs.draw_accepted) {
-    endGame('draw', 'agreement');
+    endGame('draw', 'agreement', { serverAlreadyCompleted: true });
     return;
   }
 
@@ -910,10 +947,10 @@ function fetchAndRenderOpponent(el, oppId) {
   }).catch(() => {});
 }
 
-function endGame(result, reason) {
+function endGame(result, reason, { serverAlreadyCompleted = false } = {}) {
   if (gameState.gameOver) return;
   mp.cleanup();
-  matchLive.session.destroy(); // Clear recovery so homepage doesn't try to rejoin
+  matchLive.session.destroy();
   gameState.gameOver = true;
   clock.stop();
   board.interactive = false;
@@ -958,6 +995,15 @@ function endGame(result, reason) {
     bus.emit('xp:earned', { amount: xp });
   }
 
+  // If the server already completed this match (opponent resigned/drew/abandoned),
+  // skip redundant complete call — just show the result
+  if (serverAlreadyCompleted) {
+    const fallbackRating = result === 'win' ? 12 : result === 'draw' ? 1 : -8;
+    if (gameState.tournamentId) reportTournamentResult(result);
+    setTimeout(() => navigateToResult(fallbackRating, null, null), 1000);
+    return;
+  }
+
   // Failsafe: always show result within 5s even if network hangs
   const failsafeTimer = setTimeout(() => {
     const fallbackRating = result === 'win' ? 12 : result === 'draw' ? 1 : -8;