#include <stdlib.h>
#include "single_list.h"

void single_node_init( single_node_t *const node, int v, single_node_t *n );

void single_node_init( single_node_t *const node, int v, single_node_t *n ) {
	node->value = v;
	node->next = n;
}

// Set the head and tail to NULL and the size is 0.
void single_list_init( single_list_t *const list ) {
	list->head = NULL;
	list->tail = NULL;
	list->size = 0;
}

void single_list_destroy( single_list_t *const list ) {

	// Remove all remaining nodes in the linked list
	//  - note that this is not recursive
	while ( list->size != 0 ) {
		single_list_pop_front( list );
	}
}

int single_list_front( single_list_t *const list ) {

	// If the list is empty, return 0
	if ( list->size == 0 ) {
		return 0;
	}

	return list->head->value;
}

int single_list_back( single_list_t *const list ) {

	// If the list is empty, return 0
	if ( list->size == 0 ) {
		return 0;
	}

	return list->tail->value;
}

void single_list_push_front( single_list_t *const list, int n ) {

	// Create a new node that stores 'n' and points to the node
	// currently stored in 'head'.  Assign the address of
	// this new node to 'head'.

	single_node_t *new_head = (single_node_t *) malloc( sizeof( single_node_t ) );
	single_node_init( new_head, n, list->head );
	list->head = new_head;

	// If the list was empty prior to this function being called,
	// we need to have 'tail' point to the same node as 'head'.

	if ( list->size == 0 ) {
		list->tail = list->head;
	}

	// Increment the number of nodes stored in this linked list
	++( list->size );
}

void single_list_pop_front( single_list_t *const list ) {
	single_node_t *tmp;

	// If it is empty, do nothing

	if ( list->size == 0 ) {
		return;
	}

	// Temporarily store the address of the node currently at the head of
	// the linked list, set 'head' to be the address of the node
	// pointed to by the current head of the linked list, and then
	// free the temporary node.

	tmp = list->head;
	list->head = list->head->next;
	free( tmp );

	// Decrement the number of nodes stored in this linked list
	--( list->size );

	// If the list is now empty, set the tail pointer to null, as well

	if ( list->size == 0 ) {
		list->tail = NULL;
	}
}