added penal charge to schedule

app/models/loan_charge.py

@@ -1,6 +1,6 @@
 from datetime import datetime, timezone, timedelta
 from os.path import devnull
-
+from sqlalchemy.exc import IntegrityError
 from app.extensions import db
 from sqlalchemy.orm import relationship
 
@@ -43,7 +43,85 @@ class LoanCharge(db.Model):
             'description': self.description,
             'due': self.due
         }
+    #get last penal
+    @classmethod
+    def get_last_penal_no(cls, loan_id):
+        """
+        Returns the last penal number created for a loan.
+        Example:
+            PENAL1 -> returns 1
+            PENAL3 -> returns 3
+        If none exists, returns 0.
+        """
+        last_penal = (
+            cls.query
+            .filter(cls.loan_id == loan_id)
+            .filter(cls.code.like("PENAL%"))
+            .order_by(cls.id.desc())
+            .first()
+        )
 
+        if not last_penal:
+            return 0
+
+        try:
+            return int(last_penal.code.replace("PENAL", ""))
+        except ValueError:
+            return 0
+    @classmethod
+    def get_penal_charges_by_loan_id(cls, loan_id):
+        """
+        Returns all penal charges for a specific loan.
+        """
+        return cls.query.filter(
+            cls.loan_id == loan_id,
+            cls.code.like("PENAL%")
+        ).all()
+    
+    
     @classmethod
     def get_loan_charge_by_debt_id(cls, debt_id):
-        return cls.query.filter_by(loan_id=debt_id)
+        return cls.query.filter_by(loan_id=debt_id)
+    
+    #create penal charge
+    @classmethod
+    def create_penal_charges_for_loan(cls, loan_id, transaction_id, percent, penal_no, schedule_number, penal_amount=0.0):
+        """
+        Create a penal charge for a given loan and schedule.
+        """
+
+        if loan_id is None:
+            raise ValueError("loan_id cannot be None")
+
+        code = f"PENAL{penal_no:02d}-SCHEDULE{schedule_number:02d}"
+
+        # Check if this penal charge already exists
+        existing = cls.query.filter_by(
+            loan_id=loan_id,
+            code=code
+        ).first()
+
+        if existing:
+            return existing
+
+        now = datetime.now(timezone.utc)
+
+        penal_charge = cls(
+            loan_id=loan_id,
+            transaction_id=transaction_id,
+            code=code,
+            amount=penal_amount,
+            percent=percent,
+            description=f"Penal Charge {penal_no} for loan {loan_id} schedule {schedule_number}",
+            due=True,
+            due_date=now
+        )
+
+        try:
+            db.session.add(penal_charge)
+            db.session.commit()
+        except IntegrityError as err:
+            db.session.rollback()
+            raise ValueError(f"Database integrity error: {err}")
+
+        return penal_charge