//queuelib.c stack library body file
//PAC: jleblanc: 2.16.06

#include "queuelib.h"

boolean qempty(const queuetype q)
{  
	return ((boolean) (q.top == NULL));
	// we could also test the count field, but we are emphasizing pointers
} 

boolean qfull (const queuetype q)
{  
	return FALSE; 
	//we should check available memory first, but we'll keep it simple for now
}

void qmany(int *answer, queuetype *q)
{
	*answer=q->count;
}

void qinit ( queuetype *q )
{  
	q -> count = 0;
  	q -> top   = NULL;
	q->rear = NULL;
}

//ADD to rear of the list
void qadd(char item, queuetype *q )
{
	qnode *p;
 	 if (! qfull(*q))
  	{
  		p = malloc(sizeof(qnode));   //  request the space, put address in p 
  		p -> info = item;           //  transfer the item into p's info     
  		p->next=NULL;	//set new node's pointer to NULL since at the end
		if(q->rear != NULL)
		{
			q->rear->next=p;    //set the current rear node's next to the new node (only if current rear exsists)
		}
		else
		{
			q->top=p;  // if rear is NULL then there are no nodes, so top must be set to the new node
		}
		q->rear=p; 	//set the queue's rear to the new rear
  		q -> count ++;            //  increment the 'count' field         
  	}

}

//REMOVE from the front of the list
void qremove( char *item, queuetype *q )
{
 	qnode *p;
 	if (! qempty(*q))
 	{
		*item=q->top->info;   //get the item info of first node
		p=q->top;	//p points to first node
		q->top=p->next;  //top points to the next node
		free(p);   //delete the node
		q->count--;  //decrement the count field
		if(q->top==NULL)
		{
			q->rear=NULL; //if top points to NULL then there are no nodes so rear points to NULL also
		}
	}
}

//Below here is the implimentation to Add to the Front, and Remove from the Rear.
//As the code shows it requires a bit more work.
//This code can be substituted for the 2 functions above with no difference to the user.
/*
void qadd ( char item, queuetype *q )
{  
	node *p;
 	 if (! full(*q))
  	{
  		p = malloc(sizeof(node));   //  request the space, put address in p 
  		p -> info = item;           //  transfer the item into p's info     
  		p -> next = q -> top;     //  set p's next to the old top         
 		q -> top = p;             //  set new top of stack to point to p  
  		q -> count ++;            //  increment the 'count' field         
  	}
	if(q->count==1)
	{
		q->rear=q->top;
	}
}

void qremove( char *item, queuetype *q )
{
 	node *p;
 	if (! empty(*q))
 	{
 		*item = q -> rear -> info;  // transfer the info from rear of queue 
		
		//Figure out how to do this more cleanly
		
		p     = q -> top;          //  set temporary pointer p to top      
		if(q->count == 1)
		{
			q->top=NULL;
			q->rear=NULL;
			q->count--;
			free(p);
		}
		else
		{
			for(int x=1; x<((q->count)-1); x++)
			{
				p=p->next;
			}
 			free(p->next); //kills the last one
			p->next=NULL;
			q->rear=p;
 			q -> count--;              //  decrement the count field of stack  
		}
 	}
}
*/