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
from sqlalchemy.orm import relationship
from app.models import Customer


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))

    customer = relationship(
        "Customer",
        primaryjoin="Customer.id == Loan.customer_id",
        foreign_keys=[customer_id],
        back_populates="loans",
    )

    @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)
        except IntegrityError as err:
            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

    def to_dict(self):
        """
        Convert the Loan object to a dictionary format for JSON serialization.
        """
        return {
            'id': self.id,
            'customer_id': self.customer_id,
            'account_id': self.account_id,
            'offer_id': self.offer_id,
            'principal_amount': self.principal_amount,
            'status': self.status,
            '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'<Loan {self.id}>'