""" Node and LinkedList classes """


class LinkedListNode:
    """
    Node to be used in linked list

    === Attributes ===
    @param LinkedListNode next_: successor to this LinkedListNode
    @param object value: data this LinkedListNode represents
    """

    def __init__(self, value, next_=None):
        """
        Create LinkedListNode self with data value and successor next_.

        @param LinkedListNode self: this LinkedListNode
        @param object value: data of this linked list node
        @param LinkedListNode|None next_: successor to this LinkedListNode.
        @rtype: None
        """

    def __str__(self):
        """
        Return a user-friendly representation of this LinkedListNode.

        @param LinkedListNode self: this LinkedListNode
        @rtype: str

        >>> n = LinkedListNode(5, LinkedListNode(7))
        >>> print(n)
        5 -> 7 ->|
        """

    def __eq__(self, other):
        """
        Return whether LinkedListNode self is equivalent to other.

        @param LinkedListNode self: this LinkedListNode
        @param LinkedListNode|object other: object to compare to self.
        @rtype: bool

        >>> LinkedListNode(5).__eq__(5)
        False
        >>> n1 = LinkedListNode(5, LinkedListNode(7))
        >>> n2 = LinkedListNode(5, LinkedListNode(7, None))
        >>> n1.__eq__(n2)
        True
        """


class LinkedList:
    """
    Collection of LinkedListNodes

    === Attributes ==
    @param: LinkedListNode front: first node of this LinkedList
    @param LinkedListNode back: last node of this LinkedList
    @param int size: number of nodes in this LinkedList
                        a non-negative integer
    """

    def __init__(self):
        """
        Create an empty linked list.

        @param LinkedList self: this LinkedList
        @rtype: None
        """

    def __str__(self):
        """
        Return a human-friendly string representation of
        LinkedList self.

        @param LinkedList self: this LinkedList

        >>> lnk = LinkedList()
        >>> lnk.prepend(5)
        >>> print(lnk)
        5 ->|
        """

    def __eq__(self, other):
        """
        Return whether LinkedList self is equivalent to
        other.

        @param LinkedList self: this LinkedList
        @param LinkedList|object other: object to compare to self
        @rtype: bool

        >>> LinkedList().__eq__(None)
        False
        >>> lnk = LinkedList()
        >>> lnk.prepend(5)
        >>> lnk2 = LinkedList()
        >>> lnk2.prepend(5)
        >>> lnk.__eq__(lnk2)
        True
        """

    def append(self, value):
        """
        Insert a new LinkedListNode with value after self.back.

        @param LinkedList self: this LinkedList.
        @param object value: value of new LinkedListNode
        @rtype: None

        >>> lnk = LinkedList()
        >>> lnk.append(5)
        >>> lnk.size
        1
        >>> print(lnk.front)
        5 ->|
        >>> lnk.append(6)
        >>> lnk.size
        2
        >>> print(lnk.front)
        5 -> 6 ->|
        """

    def prepend(self, value):
        """
        Insert value before LinkedList self.front.

        @param LinkedList self: this LinkedList
        @param object value: value for new LinkedList.front
        @rtype: None

        >>> lnk = LinkedList()
        >>> lnk.prepend(0)
        >>> lnk.prepend(1)
        >>> lnk.prepend(2)
        >>> str(lnk.front)
        '2 -> 1 -> 0 ->|'
        >>> lnk.size
        3
        """

    def delete_front(self):
        """
        Delete LinkedListNode self.front from self.

        Assume self.front is not None

        @param LinkedList self: this LinkedList
        @rtype: None

        >>> lnk = LinkedList()
        >>> lnk.prepend(0)
        >>> lnk.prepend(1)
        >>> lnk.prepend(2)
        >>> lnk.delete_front()
        >>> str(lnk.front)
        '1 -> 0 ->|'
        >>> lnk.size
        2
        >>> lnk.delete_front()
        >>> lnk.delete_front()
        >>> str(lnk.front)
        'None'
        """

    def __getitem__(self, index):
        """
        Return the value at LinkedList self's position index.

        @param LinkedList self: this LinkedList
        @param int index: position to retrieve value from
        @rtype: object

        >>> lnk = LinkedList()
        >>> lnk.prepend(1)
        >>> lnk.prepend(0)
        >>> lnk.__getitem__(1)
        1
        >>> lnk[-1]
        1
        """

    def __contains__(self, value):
        """
        Return whether LinkedList self contains value.

        @param LinkedList self: this LinkedList.
        @param object value: value to search for in self
        @rtype: bool

        >>> lnk = LinkedList()
        >>> lnk.prepend(0)
        >>> lnk.prepend(1)
        >>> lnk.prepend(2)
        >>> lnk.__contains__(1)
        True
        >>> 1 in lnk
        True
        >>> lnk.__contains__(3)
        False
        """


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