from datetime import datetime, timezone, timedelta
from app.extensions import db
from sqlalchemy.orm import relationship


class LoanCharge(db.Model):
    __tablename__ = 'loan_charges'

    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    loan_id = db.Column(db.Integer, nullable=False)
    transaction_id = db.Column(db.String(50), nullable=True)
    code = db.Column(db.String(50), nullable=False) 
    amount = db.Column(db.Float, default=0.0)
    percent = db.Column(db.Float, default=0.0)
    description = db.Column(db.Text, nullable=True)
    due = db.Column(db.Integer, nullable=False)
    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))

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

    @classmethod
    def create_charges_for_loan(cls, loan_id, transaction_id, charges, referenced_amount = 0.0):
        """
        Create loan charges for a given loan.

        Args:
            loan_id (int): ID of the loan to associate charges with.
            charges (list): A list of dictionaries with keys: 
            code (str), amount (float), percent (float), description (str), due (int)
        """
        if not charges or not isinstance(charges, list):
            raise ValueError("Charges must be a non-empty list of dictionaries")
        
        if loan_id is None:
            raise ValueError("loan_id cannot be None")

        loan_charges = []
        now = datetime.now(timezone.utc)

        for charge in charges:
            due_days = getattr(charge, "due", 0)
            amount = getattr(charge, "amount", 0.0)
            percent = getattr(charge, "percent", 0.0)

            if amount == 0.0:
                amount = (percent / 100.0) * referenced_amount

            charge_obj = cls(
                loan_id = loan_id,
                transaction_id = transaction_id,
                code = getattr(charge, "code"),
                amount = round(amount, 2),
                percent = percent,
                description = getattr(charge, "description", ""),
                due = due_days,
                due_date = now + timedelta(days=due_days)
            )

            db.session.add(charge_obj)
            loan_charges.append(charge_obj)

        return loan_charges

    

    def to_dict(self):
        return {
            'id': self.id,
            'loanId': self.loan_id,
            'transactionId': self.transaction_id,
            'code': self.code,
            'amount': self.amount,
            'percent': self.percent,
            'description': self.description,
            'due': self.due,
        }

    def __repr__(self):
        return f"<LoanCharge {self.id} - Loan {self.loan_id} - {self.code}>"