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 sqlalchemy import and_, or_, not_
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)
    initial_loan_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))
    product_id = db.Column(db.String(20))
    current_loan_amount = db.Column(db.Float)
    default_penalty_fee = db.Column(db.Float)
    continuous_fee = db.Column(db.Float)
    due_date = db.Column(db.DateTime)

    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, initial_loan_amount, status='pending',
                    product_id=None, current_loan_amount=None, default_penalty_fee=None,
                    continuous_fee=None, due_date=None):

        # 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,
            initial_loan_amount=initial_loan_amount,
            status=status,
            product_id=product_id,
            current_loan_amount=current_loan_amount or initial_loan_amount,
            default_penalty_fee=default_penalty_fee,
            continuous_fee=continuous_fee,
            due_date=due_date
        )

        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

    @classmethod
    def get_all_loans(cls, customer_id=None, account_id=None, status=None, offer_id=None,
                      product_id=None, start_date=None, end_date=None, due_before=None, due_after=None):
        """
        Get all loans with optional filtering

        Args:
            customer_id (str, optional): Filter by customer ID
            account_id (str, optional): Filter by account ID
            status (str, optional): Filter by loan status
            offer_id (str, optional): Filter by offer ID
            product_id (str, optional): Filter by product ID
            start_date (datetime, optional): Filter by start date (created_at)
            end_date (datetime, optional): Filter by end date (created_at)
            due_before (datetime, optional): Filter loans due before this date
            due_after (datetime, optional): Filter loans due after this date

        Returns:
            list: List of Loan objects
        """
        query = cls.query

        # Apply filters if provided
        if customer_id:
            query = query.filter(cls.customer_id == customer_id)

        if account_id:
            query = query.filter(cls.account_id == account_id)

        if status:
            query = query.filter(cls.status == status)

        if offer_id:
            query = query.filter(cls.offer_id == offer_id)

        if product_id:
            query = query.filter(cls.product_id == product_id)

        if start_date:
            query = query.filter(cls.created_at >= start_date)

        if end_date:
            query = query.filter(cls.created_at <= end_date)

        if due_before:
            query = query.filter(cls.due_date <= due_before)

        if due_after:
            query = query.filter(cls.due_date >= due_after)

        # Order by created_at descending (newest first)
        query = query.order_by(cls.created_at.desc())

        return query.all()

    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,
            'initial_loan_amount': self.initial_loan_amount,
            'current_loan_amount': self.current_loan_amount,
            'status': self.status,
            'product_id': self.product_id,
            'default_penalty_fee': self.default_penalty_fee,
            'continuous_fee': self.continuous_fee,
            'due_date': self.due_date.isoformat() if self.due_date 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'<Loan {self.id}>'