#include "list.h"

@implementation LinkedList

-init
{
	head = tail = nil;
	objectCount = 0;
	return self;
}

-free
{
	[self emptyList];
	return [super free];
}

-(id)objectAtIndex:(int)i
{
	id tmp = head;
	int k=0;
	while(tmp && (k<i)) {
		tmp = [tmp getNext];
	}
	if(tmp)
		return [tmp getData];
	else
		return nil;
}

-(id)insertObject:(id)obj atIndex:(int)i
{
	id tmp;
	if([self isEmpty]) {
		head = obj;
		tail = obj;
		objectCount++;
		return obj;
	}
	
	tmp = [self getObjectAtIndex:i];
	if(!tmp) {
		return nil;
	}
	if([tmp isDoublyAttached]) {
		[[tmp getPrevious] setNext:obj];
		[obj setPrevious:[tmp getPrevious]];
		[obj setNext:tmp];
		[tmp setPrevious:obj];
		tmp = nil;
		return obj;
	}
	if([tmp isFrontlyAttached]) {
		[tmp setNext:obj];
		[obj setPrevious:tmp];
		return obj;
	}
	if([tmp isRearlyAttached]) {
		[tmp setPrevious:obj];
		[obj setNext:tmp];
		return obj;
	}
}

-removeObjectAtIndex:(int)i
{
	id tmp;
	tmp = [self getObjectAtIndex:i];
	if(!tmp) 
		return nil;
	if([tmp isDoublyAttached]) {
		[[tmp getPrevious] setNext:[tmp getNext]];
		[[tmp getNext] setPrevious:[tmp getPrevious]];
		[tmp setNext:nil];
		[tmp setPrevious:nil];
	}
	if([tmp isFrontlyAttached]) {
		[[tmp getPrevious] setNext:nil];
		[tmp setPrevious:nil];
	}
	if([tmp isRearlyAttached]) {
		[[tmp getNext] setPrevious:nil];
		[tmp setNext:nil];
	}
	[tmp free];
	return self;
}

-(BOOL)isEmpty
{
	if(head || tail)
		return NO;
	else
		return YES;
}

-emptyList
{
	id tmp = head;
	int i=0;
	
}

@end