from datetime import datetime, timezone
from app.extensions import db
from sqlalchemy.orm import relationship
from dateutil.relativedelta import relativedelta
from sqlalchemy.sql import func

class LoanRepaymentSchedule(db.Model):
    __tablename__ = 'loan_repayment_schedules'

    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)
    product_id = db.Column(db.String(20), nullable=True)
    installment_number = db.Column(db.Integer, nullable=False)
    due_date = db.Column(db.DateTime, nullable=False)
    installment_amount= db.Column(db.Float, default=0.0)
    total_repayment_amount = db.Column(db.Float, default=0.0)
    paid = db.Column(db.Boolean, default=False)
    paid_at = db.Column(db.DateTime, nullable=True)

    created_at = db.Column(db.DateTime(timezone=True), server_default=func.now())
    updated_at = db.Column(db.DateTime(timezone=True), server_default=func.now(), onupdate=func.now())
    loan = relationship(
        "Loan",
        primaryjoin="LoanRepaymentSchedule.loan_id == Loan.id",
        foreign_keys=[loan_id],
        back_populates="loan_repayment_schedules",
    )


    @classmethod
    def add_repayment_schedule(cls, loan, num_schedules, transaction_id):
        """
        Add repayment schedules for a given loan.
        """
        now = datetime.now(timezone.utc)
        schedules = []

        for i in range(num_schedules):
            due_date = now + relativedelta(months=i + 1)
            schedule = LoanRepaymentSchedule(
                loan_id=loan.id,
                installment_number=i + 1,
                due_date=due_date,
                total_repayment_amount = round(loan.repayment_amount, 2),
                installment_amount=round(loan.installment_amount, 2),
                product_id = loan.product_id,
                transaction_id = transaction_id,
                created_at=datetime.now(timezone.utc),
                updated_at=datetime.now(timezone.utc)
            )
            
            db.session.add(schedule)
            schedules.append(schedule)

        return schedules

    def to_dict(self):
        return {
            'id': self.id,
            'loanId': self.loan_id,
            'installmentNumber': self.installment_number,
            'dueDate': self.due_date.isoformat(),
            'principalAmount': self.principal_amount,
            'interestAmount': self.interest_amount,
            'totalInstallment': self.total_installment,
            'paid': self.paid,
            'paidAt': self.paid_at.isoformat() if self.paid_at else None
        }

    def __repr__(self):
        return f'<LoanRepaymentSchedule Loan:{self.loan_id} Installment:{self.installment_number}>'