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.loan_charge import LoanCharge


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)
    transaction_id = db.Column(db.String(50), nullable=True)
    account_id = db.Column(db.String(50), nullable=False)
    offer_id = db.Column(db.String(20), nullable=False)
    product_id = db.Column(db.String(20), nullable=True)
    collection_type = db.Column(db.String(20), nullable=True) 
    current_loan_amount = db.Column(db.Float, nullable=True)  
    initial_loan_amount = db.Column(db.Float, nullable=False) 
    default_penalty_fee = db.Column(db.Float, default=0)  
    continuous_fee = db.Column(db.Float, default=0)
    status = db.Column(db.String(20), default='pending')
    due_date = db.Column(db.DateTime, nullable=True) 
    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",
    )

    loan_charges = relationship(
        "LoanCharge",
        primaryjoin="Loan.id == LoanCharge.loan_id",
        foreign_keys="LoanCharge.loan_id",
        back_populates="loan",
    )

    @classmethod
    def create_loan(cls, customer_id, account_id, offer_id, product_id, initial_loan_amount, collection_type, transaction_id, status='pending'):

        # Check if customer exists
        customer = Customer.is_valid_customer(customer_id)
        if not customer:
            raise ValueError("Customer does not exist")

        now = datetime.now(timezone.utc)

        # Create and save the loan
        loan = cls(
            customer_id = customer_id,
            account_id = account_id,
            offer_id = offer_id,
            product_id = product_id,
            collection_type = collection_type,
            transaction_id = transaction_id,
            initial_loan_amount = initial_loan_amount,
            current_loan_amount = initial_loan_amount,
            due_date=now, 
            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 {
            'debtId': self.id,
            'initialLoanAmount': self.initial_loan_amount,
            'currentLoanAmount': self.current_loan_amount,
            'defaultPenaltyFee': self.default_penalty_fee,
            'continuousFee': self.continuous_fee,
            'collectionType': self.collection_type,
            'status': self.status,
            'dueDate': self.due_date.isoformat() if self.due_date else None,
            'loanDate': self.created_at.isoformat() if self.created_at else None,
        }
    
    def __repr__(self):
        return f'<Loan {self.id}>'