feat: add stand and get game features to blackjack game

backend/requests/blackjack.http

@@ -10,3 +10,11 @@ Content-Type: application/json
 POST http://localhost:8080/blackjack/54/hit
 Authorization: Bearer {{token}}
 
+###
+POST http://localhost:8080/blackjack/202/stand
+Authorization: Bearer {{token}}
+
+###
+GET http://localhost:8080/blackjack/202
+Authorization: Bearer {{token}}
+

backend/src/main/java/de/szut/casino/blackjack/BlackJackGameController.java

@@ -26,6 +26,23 @@ public class BlackJackGameController {
         this.userService = userService;
     }
 
+    @GetMapping("/blackjack/{id}")
+    public ResponseEntity<Object> getGame(@PathVariable Long id, @RequestHeader("Authorization") String token) {
+        Optional<UserEntity> optionalUser = userService.getCurrentUser(token);
+
+        if (optionalUser.isEmpty()) {
+            return ResponseEntity.notFound().build();
+        }
+
+        UserEntity user = optionalUser.get();
+        BlackJackGameEntity game = blackJackService.getBlackJackGame(id);
+        if (game == null || !Objects.equals(game.getUserId(), user.getId())) {
+            return ResponseEntity.notFound().build();
+        }
+
+        return ResponseEntity.ok(game);
+    }
+
     @PostMapping("/blackjack/{id}/hit")
     public ResponseEntity<Object> hit(@PathVariable Long id, @RequestHeader("Authorization") String token) {
         Optional<UserEntity> optionalUser = userService.getCurrentUser(token);
@@ -40,13 +57,24 @@ public class BlackJackGameController {
             return ResponseEntity.notFound().build();
         }
 
-        if (game.getState() != BlackJackState.IN_PROGRESS) {
-            Map<String, String> errorResponse = new HashMap<>();
-            errorResponse.put("error", "Invalid state");
-            return ResponseEntity.badRequest().body(errorResponse);
+        return ResponseEntity.ok(blackJackService.hit(game));
+    }
+
+    @PostMapping("/blackjack/{id}/stand")
+    public ResponseEntity<Object> stand(@PathVariable Long id, @RequestHeader("Authorization") String token) {
+        Optional<UserEntity> optionalUser = userService.getCurrentUser(token);
+
+        if (optionalUser.isEmpty()) {
+            return ResponseEntity.notFound().build();
         }
 
-        return ResponseEntity.ok(blackJackService.hit(game, user));
+        UserEntity user = optionalUser.get();
+        BlackJackGameEntity game = blackJackService.getBlackJackGame(id);
+        if (game == null || !Objects.equals(game.getUserId(), user.getId())) {
+            return ResponseEntity.notFound().build();
+        }
+
+        return ResponseEntity.ok(blackJackService.stand(game));
     }
 
     @PostMapping("/blackjack/start")

backend/src/main/java/de/szut/casino/blackjack/BlackJackGameEntity.java

@@ -24,12 +24,15 @@ public class BlackJackGameEntity {
     @GeneratedValue
     private Long id;
 
+    @Version
+    @JsonIgnore
+    private Long version;
+
     @ManyToOne
     @JoinColumn(name = "user_id", nullable = false)
     @JsonIgnore
     private UserEntity user;
 
-    // Expose UserID to JSON output
     public Long getUserId() {
         return user != null ? user.getId() : null;
     }

backend/src/main/java/de/szut/casino/blackjack/BlackJackService.java

@@ -3,6 +3,7 @@ package de.szut.casino.blackjack;
 import de.szut.casino.user.UserEntity;
 import de.szut.casino.user.UserRepository;
 import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
 
 import java.math.BigDecimal;
 import java.util.List;
@@ -26,6 +27,7 @@ public class BlackJackService {
         return optionalBlackJackGame.orElse(null);
     }
 
+    @Transactional
     public BlackJackGameEntity createBlackJackGame(UserEntity user, BigDecimal betAmount) {
         BlackJackGameEntity game = new BlackJackGameEntity();
         game.setUser(user);
@@ -46,21 +48,79 @@ public class BlackJackService {
         game.setState(state);
 
         userRepository.save(user);
-        blackJackGameRepository.save(game);
-
-        return game;
+        return blackJackGameRepository.save(game);
     }
 
-    public BlackJackGameEntity hit(BlackJackGameEntity game, UserEntity user) {
+    @Transactional
+    public BlackJackGameEntity hit(BlackJackGameEntity game) {
+        game = blackJackGameRepository.findById(game.getId()).orElse(game);
+        
+        if (game.getState() != BlackJackState.IN_PROGRESS) {
+            return game;
+        }
+        
         CardEntity drawnCard = drawCardFromDeck(game);
         drawnCard.setCardType(CardType.PLAYER);
         game.getPlayerCards().add(drawnCard);
 
-        game.setState(handleState(game, user));
+        game.setState(handleState(game, game.getUser()));
+
+        if (game.getState() == BlackJackState.PLAYER_WON) {
+            updateUserBalance(game, true);
+        } else if (game.getState() == BlackJackState.PLAYER_LOST) {
+            updateUserBalance(game, false);
+        }
 
         return blackJackGameRepository.save(game);
     }
 
+    @Transactional
+    public BlackJackGameEntity stand(BlackJackGameEntity game) {
+        game = blackJackGameRepository.findById(game.getId()).orElse(game);
+        
+        if (game.getState() != BlackJackState.IN_PROGRESS) {
+            return game;
+        }
+        
+        while (calculateHandValue(game.getDealerCards()) < 17) {
+            CardEntity dealerCard = drawCardFromDeck(game);
+            dealerCard.setCardType(CardType.DEALER);
+            game.getDealerCards().add(dealerCard);
+        }
+
+        int playerValue = calculateHandValue(game.getPlayerCards());
+        int dealerValue = calculateHandValue(game.getDealerCards());
+
+        if (dealerValue > 21 || playerValue > dealerValue) {
+            game.setState(BlackJackState.PLAYER_WON);
+            updateUserBalance(game, true);
+        } else {
+            game.setState(BlackJackState.DRAW);
+            updateUserBalance(game, false);
+        }
+
+        return blackJackGameRepository.save(game);
+    }
+
+    @Transactional
+    private void updateUserBalance(BlackJackGameEntity game, boolean isWin) {
+        UserEntity user = game.getUser();
+        user = userRepository.findById(user.getId()).orElse(user);
+        BigDecimal balance = user.getBalance();
+        
+        BigDecimal betAmount = game.getBet();
+        
+        if (isWin) {
+            balance = balance.add(betAmount.multiply(BigDecimal.valueOf(2)));
+        } 
+        else if (game.getState() == BlackJackState.DRAW) {
+            balance = balance.add(betAmount);
+        }
+        
+        user.setBalance(balance);
+        userRepository.save(user);
+    }
+
     private void initializeDeck(BlackJackGameEntity game) {
         for (Suit suit : Suit.values()) {
             for (Rank rank : Rank.values()) {

backend/src/main/java/de/szut/casino/blackjack/BlackJackState.java

@@ -4,5 +4,5 @@ public enum BlackJackState {
     IN_PROGRESS,
     PLAYER_BLACKJACK,
     PLAYER_LOST,
-    STANDOFF,
+    DRAW,
 }

backend/src/main/java/de/szut/casino/blackjack/CardEntity.java

@@ -19,6 +19,10 @@ public class CardEntity {
     @JsonIgnore
     private Long id;
 
+    @Version
+    @JsonIgnore
+    private Long version;
+
     @ManyToOne
     @JoinColumn(name = "game_id", nullable = false)
     @JsonBackReference