from datetime import date, timedelta

from sqlalchemy.exc import SQLAlchemyError
from sqlalchemy.orm import Session

from backend.app.repositories.config_repository import ConfigRepository
from backend.app.repositories.reminder_repository import ReminderRepository


class ArrearsService:
    def __init__(self) -> None:
        self.config_repository = ConfigRepository()
        self.reminder_repository = ReminderRepository()

    def sync_order_arrears(self, session: Session, order) -> None:
        trigger_mode = self._get_config_value(session, "arrears_generate_mode", "delivered")
        if not self._should_generate(trigger_mode, order.order_status):
            return

        existed = self.reminder_repository.get_arrears_by_order_id(session, order.id)
        if existed is not None:
            return

        settlement_days = 0
        customer = None
        if order.customer_id:
            customer = self.reminder_repository.get_customer(session, order.customer_id)
            settlement_days = int(customer.settlement_days or 0) if customer else 0

        settlement_start_date = date.today()
        due_date = settlement_start_date + timedelta(days=max(settlement_days, 0))
        arrears_amount = float(order.sale_price_total or 0)
        if arrears_amount <= 0:
            return

        self.reminder_repository.create_arrears(
            session,
            {
                "customer_id": order.customer_id or 0,
                "order_id": order.id,
                "arrears_amount": arrears_amount,
                "settlement_start_date": settlement_start_date,
                "due_date": due_date,
                "status": "pending",
            },
        )

    def _get_config_value(self, session: Session, config_key: str, default: str) -> str:
        config = self.config_repository.get_by_key(session, config_key)
        return config.config_value if config is not None and config.config_value else default

    def _should_generate(self, trigger_mode: str, order_status: str) -> bool:
        if trigger_mode == "shipped":
            return order_status in {"shipped", "delivered", "completed", "settled"}
        return order_status in {"delivered", "completed", "settled"}


arrears_service = ArrearsService()