/**************************************
 * stringlist.c
 * author: Erin Nichols
 * date: 02.22.00
 * version: 0.1
 * utilities for a doubly linked list
 *************************************/
#include <stdio.h>

struct node {        /* our behind the scenes node struct */
	char *contents;    /* contents of the node */
	struct node *next; /* pointer to the next node */
	struct node *prev; /* pointer to the previous node */
}; /* struct node */
 	
struct list {           /* wrapper struct (for extra fun) */
	struct node *current; /* pointer to our current node */
	struct node *front;   /* pointer to the front of the list */
	struct node *back;    /* pointer to the back of the list */
	int len;              /* the length of our list */
}; /* struct list */


/* get, set, and basic functions */

void setContents(struct node c, char *s) {
	c.contents = s; /* set contents of node c to s */
} /* void setContents(struct node *, char *) */

void setNext(struct node *c, struct node *n) {
	(*c).next = n;
} /* void setNext(struct node *, struct node *) */

void setPrev(struct node *c, struct node *p) {
	(*c).prev = p;
} /* void setPrev(struct node *, struct node *) */

char *getContents(struct node c) {
	return c.contents;
} /* char *getContents(struct node *) */

struct node *getNext(struct node c) {
	return c.next;
} /* struct node *getNext(struct node *) */

struct node *getPrev(struct node c) {
	printf("getPrev starting...\n");
	return c.prev;
} /* struct node *getPrev(struct node *) */

struct node *makeNode(char *c, struct node *p, struct node *n) {
	/* create a temporary node in which to store parameters */
	struct node *tmp;
	(*tmp).contents = c;
	(*tmp).prev = p;
	(*tmp).next = n;
	return tmp;
} /* struct node makeNode(char *, struct node *, struct node *) */

void advance(struct list ls) {
	/* point current to the next element */
	ls.current = getNext(*ls.current);
} /* void advance(struct list) */

/* now to put the fun back in FUNction! */

void addToEnd(struct list ls, char *toAdd) {
	/* if the list is empty */
	if ((getPrev(*ls.back) == NULL) && (getNext(*ls.front) == NULL)) {
		/* create a node and make it the front, current, and back */
		ls.front = makeNode(toAdd, NULL, NULL);
		ls.current = ls.front;
		ls.back = ls.front;
		/* set len to 1 */
		ls.len = 1;
	} /* if */
	else { /* the list is nonempty */
		/* point current to the back */
		ls.current = ls.back;
		/* point next to a new node */
		setNext(ls.current, makeNode(toAdd, ls.back, NULL));
		/* advance to the new node */
		advance(ls);
		/* increment len */
		ls.len++;
	} /* else */
} /* void addToEnd(struct list, char *) */

void addToFront(struct list ls, char *toAdd) {
	/* check whether list is empty */
	if ((getPrev(*ls.back) == NULL) && (getNext(*ls.front) == NULL)) {
		/* set front, current, and back to new node */
		ls.front = makeNode(toAdd, NULL, NULL);
		ls.current = ls.front;
		ls.back = ls.front;
		ls.len = 1;
	} /* if */
	else { /* the list is nonempty */
		/* make the front element's previous element be a new node */
		setPrev(ls.front, makeNode(toAdd, NULL, ls.front));
		/* set front to the new node */
		ls.front = (struct node *)getPrev(*ls.front);
		/* set current to the front */
		ls.current = ls.front;
		/* increment len */
		ls.len++;
	} /* else */
} /* void addToFront(struct list, char *) */

int atEnd(struct list ls) {
	/* if the current element is the back of the list */
	if (getNext(*ls.current) == NULL)
		return 0;
	else return 1;
} /* int atEnd(struct list) */

void printList(struct list ls) {
	/* go to the front */
	ls.current = ls.front;
	printf("( ");
	/* while we're not at the end */
	while (!atEnd(ls)) {
		/* print the current element */
		printf("%s,", getContents(*ls.current));
		/* advance */
		advance(ls);
	} /* while */
	printf(")\n");
} /* void printList(struct list) */

/* quicksort the list.  to be implemented. */
struct list sortList(struct list ls) {
	return ls;
} /* struct list sortList(struct list) */

/* delete the current element.  awaiting testing. */
void del(struct node *c) {
	setNext(getPrev(*c), getNext(*c));
	setPrev(getNext(*c), getPrev(*c));
	free(getNext(*c));
	free(getNext(*c));
} /* del(struct node *) */