"""This module defines a simple doubly-linked list implementation.

"""

class LinkedList:
    """A doubly-linked list.

    """

    def __init__(self):
        self.head = None
        self.tail = None
        self.size = 0

    def append(self, value):
        n = Node(value)

        if self.tail is None:
            self.head = n
            self.tail = n
        else:
            self.tail.next = n
            n.prev = self.tail
            self.tail = n

        self.size += 1

    def pop(self, i):
        """Remove and return the ith element of the list

        """

        if i >= len(self):
            raise IndexError('Pop index out of range')

        z = self.head
        while i > 0:
            z = z.next
            i -= 1

        if z.prev is not None:
            z.prev.next = z.next

        if z.next is not None:
            z.next.prev = z.prev

        return z.value

    def __len__(self):
        return self.size

    def __iter__(self):
        if self.head is None:
            return

        z = self.head
        while True:
            yield z.value

            if z.next is not None:
                z = z.next
            else:
                break

    def __str__(self):
        return '[' + ', '.join(map(str, self)) + ']'

        
class Node:
    """A node in the linked list

    """

    def __init__(self, value):
        self.value = value
        self.prev = None
        self.next = None


if __name__ == '__main__':
    li = LinkedList()

    for x in [5, 4, 3, 2, 1]:
        li.append(x)

    print(li)

    li.pop(2)

    print(li)

    print(len(li))

    for x in li:
        print(x)