""" A Queue using a Linked List like structure """
from typing import Any, Optional


class Node:
 def __init__(self, data: Any, next: Optional["Node"] = None):
 self.data: Any = data
 self.next: Optional["Node"] = next


class LinkedQueue:
 """
 Linked List Queue implementing put (to end of queue),
 get (from front of queue) and is_empty

 >>> queue = LinkedQueue()
 >>> queue.is_empty()
 True
 >>> queue.put(5)
 >>> queue.put(9)
 >>> queue.put('python')
 >>> queue.is_empty();
 False
 >>> queue.get()
 5
 >>> queue.put('algorithms')
 >>> queue.get()
 9
 >>> queue.get()
 'python'
 >>> queue.get()
 'algorithms'
 >>> queue.is_empty()
 True
 >>> queue.get()
 Traceback (most recent call last):
 ...
 IndexError: get from empty queue
 """

 def __init__(self) -> None:
 self.front: Optional[Node] = None
 self.rear: Optional[Node] = None

 def is_empty(self) -> bool:
 """ returns boolean describing if queue is empty """
 return self.front is None

 def put(self, item: Any) -> None:
 """ append item to rear of queue """
 node: Node = Node(item)
 if self.is_empty():
 # the queue contains just the single element
 self.front = node
 self.rear = node
 else:
 # not empty, so we add it to the rear of the queue
 assert isinstance(self.rear, Node)
 self.rear.next = node
 self.rear = node

 def get(self) -> Any:
 """ returns and removes item at front of queue """
 if self.is_empty():
 raise IndexError("get from empty queue")
 else:
 # "remove" element by having front point to the next one
 assert isinstance(self.front, Node)
 node: Node = self.front
 self.front = node.next
 if self.front is None:
 self.rear = None

 return node.data