from datetime import datetime, timezone
from app.extensions import db
from app.models.customer import Customer
from app.models.account import Account
from sqlalchemy.exc import IntegrityError


class Loan(db.Model):
    __tablename__ = 'loans'

    id = db.Column(
        db.Integer,
        primary_key=True,
        autoincrement=True,
    )
    customer_id = db.Column(db.String(50), nullable=False)
    account_id = db.Column(db.String(50), nullable=False)
    offer_id = db.Column(db.String(20), nullable=False)
    principal_amount = db.Column(db.Float, nullable=False)
    status = db.Column(db.String(20), default='pending')
    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))


    @classmethod
    def create_loan(cls, customer_id, account_id, offer_id, principal_amount, status='pending'):

        # Check if customer exists
        is_valid = Customer.is_valid_customer(customer_id)
        if not is_valid:
            raise ValueError("Customer does not exist")
        
        # # Check for active loans
        # has_active_loans = cls.has_active_loans(customer_id)
        # if has_active_loans:
        #     raise ValueError("Customer has active loans")


        # Create and save the loan
        loan = cls(
            customer_id=customer_id,
            account_id=account_id,
            offer_id=offer_id,
            principal_amount=principal_amount,
            status=status
        )

        try:
            db.session.add(loan)
            db.session.commit()
        except IntegrityError as err:
            db.session.rollback()
            raise ValueError(f"Database integrity error: {err}")
        return loan


    @classmethod
    def has_active_loans(cls, customer_id):
        active_loans = cls.query.filter_by(
            customer_id=customer_id,
            status='active'
        ).count()

        if active_loans > 0:
            return False
        return True
    

    @classmethod
    def get_customer_loan(cls, loan_id, customer_id):
        """
        Get customer's active loans.
        """
        loan = cls.query.filter_by(id = loan_id, customer_id = customer_id).first()
        if not loan:
            raise ValueError(f"Loan with ID {loan_id} does not exist or does not belong to customer {customer_id}.")        
        return loan
    
    @classmethod
    def update_status(cls, loan_id, status):
        """
        Update the status of the loan with the given loan_id.
        """
        # Retrieve loan 
        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
        
        # Update loan status and the updated_at timestamp
        loan.status = status
        
        db.session.commit()
    
    def __repr__(self):
        return f'<Loan {self.id}>'