"""Lecture 29 (Food Delivery System)
"""
import datetime
from typing import Optional


from entities import Courier, Customer, Order, Vendor


class FoodDeliverySystem:
    """A system that maintains all entities (vendors, customers, couriers, and orders).

    Representation Invariants:
        - all(vendor == self._vendors[vendor].name for vendor in self._vendors)
        - all(customer == self._customers[customer].name for customer in self._customers)
        - all(courier == self._couriers[courier].name for courier in self._couriers)
    """
    # Private Instance Attributes:
    #   - _vendors: a mapping from vendor name to Vendor object.
    #       This represents all the vendors in the system.
    #   - _customers: a mapping from customer name to Customer object.
    #       This represents all the customers in the system.
    #   - _couriers: a mapping from courier name to Courier object.
    #       This represents all the couriers in the system.
    #   - _orders: a list of all orders (both open and completed orders).

    _vendors: dict[str, Vendor]
    _customers: dict[str, Customer]
    _couriers: dict[str, Courier]
    _orders: list[Order]

    def __init__(self) -> None:
        self._vendors = {}
        self._customers = {}
        self._couriers = {}
        self._orders = []

    def add_vendor(self, vendor: Vendor) -> bool:
        if vendor.name in self._vendors:  # Vendor with the same name already exists
            return False
        else:    # Vendor doesn't already exist
            self._vendors[vendor.name] = vendor

            return True
    def add_customer(self, customer: Customer) -> bool:
        if customer.name in self._customers:
            return False
        else:
            self._customers[customer.name] = customer
            return True
    def add_courier(self, courier: Courier) -> bool:
        if courier.name in self._couriers:
            return False
        else:
            self._couriers[courier.name] = courier
            return True

    def place_order(self, order: Order) -> bool:
        courier = self._assign_courier(order)

        if courier is None:
            return False
        else:
            self._orders.append(order)
            return True

    def _assign_courier(self, order: Order) -> Optional[Courier]:
        for name in self._couriers:
            courier = self._couriers[name]
            if courier.current_order is None:
                order.courier = courier
                courier.current_order = order

                return courier

        return None

    def complete_order(self, order: Order, timestamp: datetime.datetime) -> None:
        """
        Preconditions:
            - order in self._orders
            - order.end_time is None
            - order.start_time < timestamp
        """
        order.courier.current_order = None
        order.end_time = timestamp

    ###########################################################################
    # Additional methods used for events
    ###########################################################################
    def get_vendors(self) -> list[Vendor]:
        """Return a list of all vendors registered with this system."""
        return list(self._vendors.values())

    def get_customers(self) -> list[Customer]:
        """Return a list of all customers registered with this system."""
        return list(self._customers.values())

    ###########################################################################
    # Additional methods used for example runners
    ###########################################################################
    def get_customer(self, name: str) -> Customer:
        """Return the customer with the given name.

        Preconditions:
        - a customer with the given name exists
        """
        return self._customers[name]

    def get_vendor(self, name: str) -> Vendor:
        """Return the food vendor with the given name.

        Preconditions:
        - a vendor with the given name exists
        """
        return self._vendors[name]

    def get_courier(self, name: str) -> Courier:
        """Return the courier with the given name.

        Preconditions:
        - a courier with the given name exists
        """
        return self._couriers[name]


if __name__ == '__main__':
    import doctest
    doctest.testmod(verbose=True)