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linked-list.py

from typing import Generic, TypeVar


T = TypeVar("T")


class Node(Generic[T]):
    def __init__(self, value: T, head: "Node | None" = None, next_node: "Node | None" = None):
        self.head = self if head is None else head
        self.next = next_node
        self.value = value

        if head is None and next_node is not None:
            self._set_head_node(self)

    def append(self, value: T) -> "Node[T]":
        tail = self._get_tail_node()
        tail.next = Node[T](value, self.head)
        return tail.next

    def _get_tail_node(self) -> "Node[T]":
        node = self
        while node.next is not None:
            node = node.next

        return node

    def insert(self, value: T) -> "Node[T]":
        self.next = Node[T](value, self.head, self.next)
        return self.next

    def delete(self) -> "Node[T] | None":
        if self.head is self:
            self._set_head_node(self.next)

        else:
            self._remove_node()

        return self.next

    def _remove_node(self):
        previous = self._get_previous_node()
        previous.next = self.next
        return self.next

    def _set_head_node(self, new_head: "Node[T]"):
        node = self.next
        while node is not None:
            node.head = new_head
            node = node.next

    def _get_previous_node(self) -> "Node[T] | None":
        if self.head is self:
            return None

        node = self.head
        while node is not None and node.next is not self:
            node = node.next

        return node

    def __repr__(self):
        return f"<Node{':HEAD' if self.head is self else ''}{'' if self.next else ':TAIL'} {self.value!r}>{self.next if self.next else ''}"