import abc
import logging
from datetime import datetime

from lib_b2b.change import ChangeRecord, ChangeDataProvider
from lib_b2b.errors import VersionConflictError
from lib_b2b.order import Order
from lib_b2b.order_change import OrderChangeRequest, SimpleOrderPredicate
from lib_b2b.order_status import OrderStatus
from lib_b2b.order_totals import OrderTotals
from lib_b2b.policy import Policy

logger = logging.getLogger(__name__)


class OrderTotalChangeDataProvider(ChangeDataProvider, metaclass=abc.ABCMeta):
    @property
    @abc.abstractmethod
    def new_totals(self) -> OrderTotals:
        raise NotImplementedError


class OrderTotalChangeRequest(OrderChangeRequest):
    # TODO: - Move these policies to be data driven
    _policy = Policy(
        name='total_change_policy',
        subject=Policy.SUBJECT_ALL,
        predicates=[
            SimpleOrderPredicate(
                lambda o: o.status < OrderStatus.SHIPPED,
                'Totals can only be updated prior to shipping.')
        ]
    )

    def __init__(self, on_behalf_of: str, change_data_provider: OrderTotalChangeDataProvider):
        super().__init__(on_behalf_of, OrderTotalChangeRequest._policy)
        self.change_data_provider = change_data_provider

    def will_change(self, order: Order) -> bool:
        return self.change_data_provider.new_totals != order.totals

    def apply(self, order: Order):
        try:
            self.changeable_object = order
            if super().permitted(order):
                if self.will_change(order):
                    before_totals = order.totals.as_dict()
                    order.set_totals(self.change_data_provider.new_totals,
                                     version=self.change_data_provider.version())
                    after_totals = self.change_data_provider.new_totals.as_dict()
                    order.record(
                        ChangeRecord(before=before_totals, after=after_totals, description="Totals were updated",
                                     when=datetime.now().astimezone(UTC), who=self.on_behalf_of)
                        )
        except ValueError as ve:
            raise VersionConflictError(str(ve))