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

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, 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="LoanRepaymentSchedule.loan_id == Loan.id",
    #     foreign_keys=[loan_id],
    #     back_populates="loan_repayment_schedules",
    # )

    @classmethod
    def get_all_repayment_schedules(cls, loan_id=None, product_id=None, transaction_id=None, paid=None,
                                   due_before=None, due_after=None, installment_number=None,
                                   page=1, limit=20):
        """
        Get all loan repayment schedules with optional filtering

        Args:
            loan_id (int, optional): Filter by loan ID
            product_id (str, optional): Filter by product ID
            transaction_id (str, optional): Filter by transaction ID
            paid (bool, optional): Filter by paid status
            due_before (datetime, optional): Filter schedules due before this date
            due_after (datetime, optional): Filter schedules due after this date
            installment_number (int, optional): Filter by installment number
            page (int, optional): Page number for pagination
            limit (int, optional): Number of items per page

        Returns:
            tuple: (list of LoanRepaymentSchedule objects, total count)
        """
        query = cls.query

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

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

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

        if paid is not None:
            query = query.filter(cls.paid == paid)

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

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

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

        # Order by due_date and installment_number
        query = query.order_by(cls.due_date.asc(), cls.installment_number.asc())

        # Get total count before pagination
        total_count = query.count()

        # Apply pagination
        offset = (page - 1) * limit
        query = query.limit(limit).offset(offset)

        return query.all(), total_count

    def to_dict(self):
        return {
            'id': self.id,
            'loan_id': self.loan_id,
            'product_id': self.product_id,
            'transaction_id': self.transaction_id,
            'installment_number': self.installment_number,
            'due_date': self.due_date.isoformat() if self.due_date else None,
            'installment_amount': self.installment_amount,
            'total_repayment_amount': self.total_repayment_amount,
            'paid': self.paid,
            'paid_at': self.paid_at.isoformat() if self.paid_at 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'<LoanRepaymentSchedule Loan:{self.loan_id} Installment:{self.installment_number}>'