/*
   linkList_2.c Tim Hoffman 15-123
   create, initiailize, print and free a simple Linked Listed of dynamic structs
	differs from linkedList_1 in that we pass head's addy into insertAtFront function

*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct Node
{
  int data;
  struct Node *next;
} Node; /* Node is now a data type */


void insertAtFront( Node ** head, int data );
void freeList( Node * head );
void printList( Node * head );
void fatal( char * msg );

int main( int argc, char *argv[])
{
	Node *head =  NULL;
	int maxLen;
	int i;

	if (argc < 2) fatal("must enter an int >= 0 on cmd line\n");
	maxLen = atoi( argv[1]);
	if (maxLen < 0) fatal("must enter an int >=  0 on cmd line\n");

	for (i=0 ; i < maxLen ; ++i )
	{
		insertAtFront( &head, i );
	}

	/* print the list */

	printList( head );

	/* free the list */

	freeList( head );
	head =  NULL;

	return 0;
}

/*
	mallocs a new Node and links it into  front of List

	node the code in here is taken from the main in linkedList_1
	except in this function there is a star before variable head
	everywhere because head in here is the address of main's head
*/
void insertAtFront( Node ** head, int data )
{
	Node * new = malloc( sizeof(Node) );
	if (!new) fatal("malloc of  Node failed");
	new->data=data;
	new->next = *head;
	*head = new;
}

/* ----------------------------------------------------------------------------- */

/* use recursion to free string and struct on the way back up the list.
   Going forward would be cutting our bridge off in front of us
*/
void freeList( Node * head )
{
	while (head)removeAtFront(&head);
	/* caller should put a NULL in the head pointer now that list is gone */
}

/* Notice we use our incoming head pointer as an iterator
   We are not corrupting the real head in main - this is just a copy!
*/
void printList( Node * head )
{
	printf("\nHEAD: ");

	while ( head )
	{
		printf(" %d ", head->data );

		head = head->next;
	}
	printf("\n");
}

void fatal( char * msg )
{
	printf("\nFatal Error: %s\n\n", msg );
	exit(0);
}