#include <stdlib.h>
#include <stdio.h>
#include "linkedlist.h"

void init_node(node* newNode)
{
	newNode->data = 0;
	newNode->next = NULL;
}

node* traverse(node* head, int index)
{
	node* current = head;
	node* previous = NULL;

	int i;
	for(i = 0; i < index && current != NULL; i++)
	{
		previous = current;
		current = current->next;
	}

	if(i == index)
		return previous;

	else
		return NULL;
}

node* insert_node(node* head, int index, int value)
{
	node* newNode = (node*)malloc(sizeof(node));
	init_node(newNode);
	newNode->data = value;

	if(index == 0) // Inserting at the beginning
	{
		if(head == NULL) // Means we have an empty list
		{
			/* For students to do */
			head = newNode;
			newNode->next = NULL;
		}
		else	// Inserting at the beginning, non-empty list
		{
			/* For students to do */
			newNode->next = head;
			head = newNode;
		}
	}
	else	// Inserting at middle or end
	{
		node* previous = traverse(head, index);
		if(previous == NULL) // Index is out of bounds, cannot insert_node
		{
			printf("Index %d is out of bounds.\n", index);
		}
		else // previous is at node before index
		{
			newNode->next = previous->next;
			previous->next = newNode;
		}
	}

	return head;
}


node* delete_node(node* head, int index)
{
	node* tempdlt;
	node* previous = traverse(head, index);

	if(index == 0) // deleting the head node
	{
		if(head == NULL)
		{
			printf("Empty list, nothing to delete.\n");
		}
		else
		{
			tempdlt = head;
			head = head->next;
			free(tempdlt);
		}
	}
	else // delete in the middle or the end
	{
		/* for you to do */
		if(previous == NULL){
			printf("Error 404 not found, Enter correct index\n");
		}
		else{
			tempdlt = previous->next;
			previous->next = previous->next->next;
			free(tempdlt);
		}
	}

	return head;
}

void print_list(node* head)
{
	node* current = head;
	/* for students to do */
	if(head == NULL){
		printf("Current doesn't exist: Error 404 not found\n");
	}
	else{
		while(current != NULL){
			printf("%d \n", current->data);
			current = current->next;
		}
	}
}

node* destroy_list(node* head)
{
	node* previous;
	while(head != NULL)
	{
		previous = head;
		head = head->next;
		free(previous);
	}
	return head;
}

int return_data(node* head, int index)
{
	node* previous = traverse(head, index);
	/* For students to do */
	return previous->next->data; 	// Zero is a place holder.
				// You need to replace it with something else.
}