feat: 新增 AI 记账服务

internal/service/ai_bookkeeping_service.go

@@ -259,6 +259,7 @@ type ConfirmationCard struct {
 	Date       string  `json:"date"`
 	Note       string  `json:"note,omitempty"`
 	IsComplete bool    `json:"is_complete"`
+	Warning    string  `json:"warning,omitempty"` // Budget overrun warning
 }
 
 // AIChatResponse represents the response from AI chat
@@ -1456,45 +1457,72 @@ func (s *AIBookkeepingService) ConfirmTransaction(ctx context.Context, sessionID
 		txType = models.TransactionTypeIncome
 	}
 
-	// Create transaction
-	tx := &models.Transaction{
-		UserID:          userID,
-		Amount:          *params.Amount,
-		Type:            txType,
-		CategoryID:      *params.CategoryID,
-		AccountID:       *params.AccountID,
-		TransactionDate: txDate,
-		Note:            params.Note,
-		Currency:        "CNY",
-	}
+	var transaction *models.Transaction
 
-	// Save transaction
-	if err := s.transactionRepo.Create(tx); err != nil {
-		return nil, fmt.Errorf("failed to create transaction: %w", err)
-	}
+	// Execute within a database transaction to ensure atomicity
+	err := s.db.Transaction(func(tx *gorm.DB) error {
+		txAccountRepo := repository.NewAccountRepository(tx)
+		txTransactionRepo := repository.NewTransactionRepository(tx)
+
+		// Get account first to check balance
+		account, err := txAccountRepo.GetByID(userID, *params.AccountID)
+		if err != nil {
+			return fmt.Errorf("failed to find account: %w", err)
+		}
+
+		// Calculate new balance
+		newBalance := account.Balance
+		if txType == models.TransactionTypeExpense {
+			newBalance -= *params.Amount
+		} else {
+			newBalance += *params.Amount
+		}
+
+		// Critical Check: Prevent negative balance for non-credit accounts
+		if !account.IsCredit && newBalance < 0 {
+			return fmt.Errorf("insufficient balance: account '%s' does not support negative balance (current: %.2f, try: %.2f)",
+				account.Name, account.Balance, *params.Amount)
+		}
+
+		// Create transaction model
+		transaction = &models.Transaction{
+			UserID:          userID,
+			Amount:          *params.Amount,
+			Type:            txType,
+			CategoryID:      *params.CategoryID,
+			AccountID:       *params.AccountID,
+			TransactionDate: txDate,
+			Note:            params.Note,
+			Currency:        models.Currency(account.Currency), // Use account currency
+		}
+		if transaction.Currency == "" {
+			transaction.Currency = "CNY"
+		}
+
+		// Save transaction
+		if err := txTransactionRepo.Create(transaction); err != nil {
+			return fmt.Errorf("failed to create transaction: %w", err)
+		}
+
+		// Update account balance
+		account.Balance = newBalance
+		if err := txAccountRepo.Update(account); err != nil {
+			return fmt.Errorf("failed to update account balance: %w", err)
+		}
+
+		return nil
+	})
 
-	// Update account balance
-	account, err := s.accountRepo.GetByID(userID, *params.AccountID)
 	if err != nil {
-		return nil, fmt.Errorf("failed to find account: %w", err)
+		return nil, err
 	}
 
-	if txType == models.TransactionTypeExpense {
-		account.Balance -= *params.Amount
-	} else {
-		account.Balance += *params.Amount
-	}
-
-	if err := s.accountRepo.Update(account); err != nil {
-		return nil, fmt.Errorf("failed to update account balance: %w", err)
-	}
-
-	// Clean up session
+	// Clean up session only on success
 	s.sessionMutex.Lock()
 	delete(s.sessions, sessionID)
 	s.sessionMutex.Unlock()
 
-	return tx, nil
+	return transaction, nil
 }
 
 // GetSession returns session by ID