from datetime import datetime, timezone
from app.extensions import db
from app.utils.logger import logger
from sqlalchemy.exc import SQLAlchemyError
# from dateutil.relativedelta import relativedelta

class LoanRepaymentSchedule(db.Model):
    __tablename__ = 'loan_repayment_schedules'

    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    loan_id = db.Column(db.Integer, nullable=False)
    transaction_id = db.Column(db.String(50), nullable=True)
    product_id = db.Column(db.String(20), nullable=True)
    installment_number = db.Column(db.Integer, nullable=False)
    due_date = db.Column(db.DateTime, nullable=False)
    installment_amount= db.Column(db.Float, default=0.0)
    total_repayment_amount = db.Column(db.Float, default=0.0)
    paid = db.Column(db.Boolean, default=False)
    paid_at = db.Column(db.DateTime, nullable=True)
    due_process_date = db.Column(db.DateTime, nullable=True)
    due_process_count = db.Column(db.Integer, default=0)
    created_at = db.Column(db.DateTime, default=datetime.now(timezone.utc))
    updated_at = db.Column(db.DateTime, default=datetime.now(timezone.utc), onupdate=datetime.now(timezone.utc))



    def to_dict(self):
        return {
            'id': self.id,
            'loan_id': self.loan_id,
            'product_id': self.product_id,
            'transaction_id': self.transaction_id,
            'installment_number': self.installment_number,
            'due_date': self.due_date.isoformat() if self.due_date else None,
            'installment_amount': self.installment_amount,
            'total_repayment_amount': self.total_repayment_amount,
            'paid': self.paid,
            'due_process_date': self.due_process_date.isoformat() if self.due_process_date else None,
            'due_process_count': self.due_process_count,
            'paid_at': self.paid_at.isoformat() if self.paid_at else None,
            'created_at': self.created_at.isoformat() if self.created_at else None,
            'updated_at': self.updated_at.isoformat() if self.updated_at else None
        }

    def __repr__(self):
        return f'<LoanRepaymentSchedule Loan:{self.loan_id} Installment:{self.installment_number}>'
    
    @classmethod
    def get_repayment_schedule_by_loan_id(cls, loan_id):
        """
        Get repayment schedule by loan ID
        """
        try:
            return cls.query.filter_by(loan_id=loan_id).all()
        except Exception as e:
            logger.error(f"Error fetching repayment schedule for loan_id={loan_id}: {e}")
            return []

    
    @classmethod
    def get_repayment_schedule_by_transaction_id(cls, transaction_id):
        """
        Get repayment schedule by transaction ID
        """
        return cls.query.filter_by(transaction_id=transaction_id).all()
    
    @classmethod
    def update_repayment_schedule_status(cls, schedule_id, paid=False):
        """
        Update repayment schedule status.
        Args:
            schedule_id (int): ID of the repayment schedule.
            paid (bool): Whether the repayment is marked as paid or not.
        Returns:
            schedule (RepaymentSchedule | None): The updated schedule object, or None if not found.
        """
        try:
            # Fetch the repayment schedule by ID
            schedule = cls.query.get(schedule_id)

            if schedule:
                # Update payment status
                schedule.paid = paid
                schedule.paid_at = datetime.now(timezone.utc) if paid else None
                if schedule.due_process_count is None:
                    schedule.due_process_count = 0
                schedule.due_process_count += 1
                schedule.due_process_date = datetime.now(timezone.utc)

                # Commit changes to the database
                db.session.commit()

            return schedule

        except SQLAlchemyError as e:
            # Rollback changes if something goes wrong at the DB level
            db.session.rollback()
            logger.error(f"Database error updating repayment schedule {schedule_id}: {e}")
            return None

        except Exception as e:
            # Catch any other unexpected error
            logger.error(f"Unexpected error updating repayment schedule {schedule_id}: {e}")
            return None