myLinkedList_doubly

class Node():
    def __init__(self, value, next_node=None, prev_node=None):
        self.value = value
        self.next_node = next_node
        self.prev_node = prev_node


class LinkedList():
    def __init__(self, value_first_item):
        self.head = Node(value_first_item)
        self.length = 1
        self.tail = self.head
    
        
    def get_head(self):
        return self.head.value
    
        
    def get_tail(self):
        return self.tail.value
        
    
    def append(self, value):
        new_node = Node(value, next_node=None, prev_node=self.tail)
        self.tail.next_node = new_node
        self.tail = new_node
        self.length+=1
    
    
    def prepend(self, value):
        new_node = Node(value, next_node=self.head)
        self.head.prev_node = new_node
        self.head = new_node
        self.length+=1
    
    
    def traverse_to_index(self, index):
        if index > self.length-1:
            return None
            raise IndexError("index out of boundaries")
        
        curr_node = self.head
        curr_index = 0
        if index == 0:
            return curr_node
        while curr_node.next_node != None:
            curr_node = curr_node.next_node
            curr_index+=1
            if curr_index == index:
                return curr_node
        
        
    def traverse_to_index_backwards(self, index):
        if index > self.length-1:
            return None
            raise IndexError("index out of boundaries")
        
        curr_node = self.tail
        curr_index = self.length-1
        while curr_node.prev_node != None:
            if curr_index == index:
                break
            curr_node = curr_node.prev_node
            curr_index-=1
        return curr_node
        
    
    def traverse(self, index):
        if index > (self.length/2):
            return self.traverse_to_index_backwards(index)
        else:
            return self.traverse_to_index(index)
    
    
    def get(self, index):
        """ get the value of a specific index in the linked list."""
        
        if index < 0:
            return None
            raise IndexError("No negative indexes")
        elif index > self.length-1:
            return None
            raise IndexError("index out of boundaries")
        elif index == self.length:
            return self.get_tail()
        elif index == 0:
            return self.get_head()
       
        return self.traverse(index).value


    def insert(self, value, index):
        """ Insert a new node in the middle of the list"""
        
        if index < 0:
            raise IndexError("No negative indexes")
        elif index > self.length-1:
            raise IndexError("index out of boundaries")
        
        new_node = Node(value)
        curr_node = self.traverse(index)
        
        new_node.next_node = curr_node
        new_node.prev_node = curr_node.prev_node
        
        prev_node = new_node.prev_node
        prev_node.next_node = new_node
        
        curr_node.prev_node = new_node
        
        self.length+=1
    
    
    def printLinkedList(self):
        
        curr_node = self.head
        curr_index = 0
        print(f"{curr_index}: {curr_node.value}")
        while curr_node.next_node != None:
            curr_node = curr_node.next_node
            curr_index+=1
            print(f"{curr_index}: {curr_node.value}")
        
        
        
print("Hello World!")
myLinkedList = LinkedList(5)
myLinkedList.append(10)
myLinkedList.append(15)
assert(myLinkedList.get_head() == 5)
assert(myLinkedList.get_tail() == 15)

assert(myLinkedList.traverse_to_index(2).value == 15)

myLinkedList.append(20)

assert(myLinkedList.traverse_to_index(3).value == 20)
assert(myLinkedList.traverse_to_index(4) == None)
assert(myLinkedList.traverse_to_index(0).value == 5)

assert(myLinkedList.traverse_to_index_backwards(3).value == 20)
assert(myLinkedList.traverse_to_index_backwards(4) == None)

assert(myLinkedList.get(index=0) == 5)
assert(myLinkedList.get(index=1) == 10)
assert(myLinkedList.get(index=2) == 15)
assert(myLinkedList.get(index=3) == 20)
assert(myLinkedList.get(index=4) == None)

myLinkedList.prepend(2)

assert(myLinkedList.get(index=0) == 2)
assert(myLinkedList.get(index=1)== 5)
assert(myLinkedList.get(index=2) == 10)
assert(myLinkedList.get(index=3) == 15)
assert(myLinkedList.get(index=4) == 20)
assert(myLinkedList.get(index=5) == None)

myLinkedList.insert(value=7,index=2)

assert(myLinkedList.get(index=0) == 2)
assert(myLinkedList.get(index=1)== 5)
assert(myLinkedList.get(index=2)== 7)
assert(myLinkedList.get(index=3) == 10)
assert(myLinkedList.get(index=4) == 15)
assert(myLinkedList.get(index=5) == 20)
assert(myLinkedList.get(index=6) == None)

# assert(myLinkedList.get_head() == 2)
# assert(myLinkedList.get(0) == 2)
# assert(myLinkedList.get(2)==7)
# myLinkedList.printLinkedList()


print("Good-bye Cruel World")