worked on balance

app/models/loan.py

@@ -240,19 +240,66 @@ class Loan(db.Model):
         return customer_loans, total_amount
 
 
+    
     @classmethod
     def update_status(cls, loan_id, status):
         """
-        Update the status of the loan with the given loan_id.
+        Update the status of the loan record with the given loan_id.
         """
-        # Retrieve loan
-        loan = cls.query.get(loan_id)
+        try:
+            # Retrieve loan record
+            loan = cls.query.get(loan_id)
+            
+            if not loan:
+                raise ValueError(f"Loan with ID {loan_id} does not exist.")
+            
+            if loan.status == status:
+                return loan.to_dict()  # Still return the current state if no change
+            
+            # Update status and timestamp
+            loan.status = status
+            loan.updated_at = datetime.now(timezone.utc)
+            db.session.commit()
 
-        if not loan:
-            raise ValueError(f"Loan with ID {loan_id} does not exist.")
+            logger.info("Loan status updated and committed.")
+            return loan.to_dict()
 
-        if loan.status == status:
-            return
+        except Exception as e:
+            db.session.rollback()
+            logger.error(f"Error updating loan status: {e}")
+            raise Exception(f"Error updating loan status: {str(e)}")
+    
+  
+    @classmethod
+    def update_loan_balance(cls, loan_id, amount_collected):
+        """
+        Update the balance of a loan after successful repayment.
+        """
+        try:
+            # Fetch the loan record
+            loan = cls.query.get(loan_id)
 
-        # Update loan status and the updated_at timestamp
-        loan.status = status
+            if not loan:
+                raise ValueError(f"Loan with ID {loan_id} does not exist.")
+
+            # Ensure valid repayment amount
+            if amount_collected <= 0:
+                raise ValueError("Repayment amount must be greater than zero.")
+            if loan.balance is None:
+                raise ValueError("There is no balance for this loan")
+
+            if amount_collected > loan.balance:
+                raise ValueError("Repayment amount exceeds current loan balance.")
+
+            # Deduct the amount from the current balance
+            loan.balance -= amount_collected
+            loan.updated_at = datetime.now(timezone.utc)
+            db.session.commit()
+
+            logger.info(f"Loan balance updated for loan ID {loan_id}. New balance: {loan.balance}")
+            return loan.to_dict()
+
+        except Exception as e:
+            db.session.rollback()
+            logger.error(f"Error updating loan balance: {e}")
+            raise Exception(f"Error updating loan balance: {str(e)}")