Added structured logging across services and repositories. Updated SQL queries to use parameterized placeholders for better readability and security. Enhanced error handling for external service communication.

backend/src/api/services/transactions.go

@@ -3,10 +3,12 @@ package services
 import (
 	"FamilyHub/src/domain"
 	"FamilyHub/src/repositories"
+	"FamilyHub/src/utils"
 	"context"
 	"database/sql"
 	"errors"
 	"fmt"
+	"log"
 	"strings"
 )
 
@@ -38,7 +40,10 @@ var (
 )
 
 func (s *transactionService) Create(ctx context.Context, req domain.CreateTransactionRequest) (*domain.Transaction, error) {
+	log.Printf("transaction create request: payload=%s", utils.ToLogJSON(req))
+
 	if strings.TrimSpace(req.Type) == "" || strings.TrimSpace(req.Category) == "" {
+		log.Printf("transaction create failed: err=%v payload=%s", ErrInvalidTransaction, utils.ToLogJSON(req))
 		return nil, ErrInvalidTransaction
 	}
 
@@ -55,8 +60,10 @@ func (s *transactionService) Create(ctx context.Context, req domain.CreateTransa
 
 	if err := s.repo.Create(ctx, transaction); err != nil {
 		if errors.Is(err, repositories.ErrReceiptNotFound) {
+			log.Printf("transaction create failed: err=%v payload=%s", ErrReceiptNotFound, utils.ToLogJSON(req))
 			return nil, ErrReceiptNotFound
 		}
+		log.Printf("transaction create failed: err=%v payload=%s", err, utils.ToLogJSON(req))
 		return nil, err
 	}
 
@@ -72,6 +79,7 @@ func (s *transactionService) Create(ctx context.Context, req domain.CreateTransa
 		})
 	}
 
+	log.Printf("transaction create response: payload=%s", utils.ToLogJSON(transaction))
 	return transaction, nil
 }