from datetime import datetime, timezone
from sqlalchemy.orm import relationship
from app.extensions import db
from app.models.account import Account
from sqlalchemy.exc import IntegrityError

class Customer(db.Model):
    __tablename__ = 'customers'

    id = db.Column(db.String(50), primary_key=True) 
    msisdn = db.Column(db.String(20), unique=True, nullable=False)
    country_code = db.Column(db.String(3), nullable=False)
    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))

    accounts = relationship(
        "Account",
        primaryjoin="Customer.id == Account.customer_id",
        foreign_keys="Account.customer_id",
        back_populates="customer",
    )

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

    @classmethod
    def is_valid_customer(cls, customer_id):
        customer = cls.query.filter_by(id=customer_id).first()
        if not customer:
            return False
        return True

    @classmethod
    def create_customer(cls, id, msisdn, country_code, account_id, account_type='savings'):
        if cls.query.filter_by(id=id).first():
            raise ValueError("Customer already exists")
        
        # Create the customer
        customer = cls(id=id, msisdn=msisdn, country_code=country_code)
        try: 
            db.session.add(customer)
            
            # Create an associated account
            account = Account.create_account(
                id=account_id,
                customer_id=id,
                account_type=account_type
            )
            
        except IntegrityError as err:
            raise ValueError(f"Database integrity error: {err}")
        return customer
    
    @classmethod
    def get_customer(cls, customer_id):
        """
        Get customer by  ID.
        """
        customer = cls.query.filter_by(id=customer_id).first()

        if not customer:
            raise ValueError(f"Customer does not exist")        
        return customer

    def __repr__(self):
        return f'<Customer {self.id}>'