#include <cassert>
#include <cstdlib>
#include "node1.h"
#include "sequence3.h"

using namespace std;

namespace main_savitch_5

{
    sequence::sequence()
    {
	head_ptr = NULL;
	tail_ptr = NULL;
	cursor = NULL;
	precursor= NULL;
	many_nodes = 0;
	
    }

    sequence::sequence(const sequence& source)
    {
	list_copy(source.head_ptr, head_ptr, tail_ptr);

	if(source.precursor == NULL)
	{
	    if(source.cursor == NULL)
	    {
		cursor = NULL;
		precursor = NULL;
	    }
	    else
	    {
		cursor = head_ptr;
		precursor = NULL;
	    }
	}
	else
	{
	    node* tmp_ptr = head_ptr;
	    node* source_ptr = source.head_ptr;

	    while(source_ptr != source.precursor)
	    {
		source_ptr = source_ptr -> link();
		tmp_ptr = tmp_ptr -> link();
	    }
	}
    }

    sequence::~sequence()
    {
	list_clear(head_ptr);
    }

    void sequence::start()
    {
	if(head_ptr==NULL)
	{
	    cursor=NULL;

	    precursor=NULL;
	}

	else
	{
	    precursor = NULL;



	    cursor=head_ptr;
	}
    }

    void sequence::advance()
    {
	assert(is_item());

	precursor=cursor;

	cursor = cursor->link();
    }

    void sequence::insert(const value_type& entry)
    {
	if (is_item( ))
	{
	    if(precursor==NULL || cursor==NULL)
	    {

		list_head_insert(head_ptr, entry);

		cursor=head_ptr;

		precursor=NULL;

	    }
	    else
	    {
		list_insert(precursor, entry);

		cursor= precursor->link();
	    }
	}
	else
	{
	    list_head_insert(head_ptr, entry);
	    
	    cursor = head_ptr;

	    precursor=NULL;
	}

	many_nodes++;
    }

    void sequence::attach(const value_type& entry)
    {
	if (is_item( ))
	{
	    precursor = cursor;

	    list_insert(cursor, entry);

	    cursor=cursor->link();
	}
	else
	{
	    if(head_ptr==NULL)
	    {
		list_head_insert(head_ptr, entry);

		cursor = head_ptr;

		precursor=NULL;

	    }
	    else
	    {
		precursor=list_locate(head_ptr,list_length(head_ptr));

		list_insert(precursor,entry);

		cursor=precursor;
	    }

	}

	many_nodes++;
    }

    void sequence::remove_current()
    {

	assert(is_item());

	if(cursor == head_ptr)
	{
	    if(many_nodes == 1)
	    {
		list_head_remove(head_ptr);
		precursor = NULL;
		cursor = NULL;
		head_ptr = NULL;
	    }
	    else
	    {
		node* tmp = head_ptr;
		head_ptr = head_ptr->link();
		delete (tmp);
		cursor = head_ptr;
		precursor = NULL;
	    }
	}
	else
	{
	    cursor = cursor -> link();
	    list_remove(precursor);
	}

	 
	--many_nodes;
    }

    void sequence::operator =(const sequence& source)
    {
	if(this == &source)
	{
	    return;
	}
	else
	{
	    list_copy(source.head_ptr, head_ptr, tail_ptr);

	    if(source.precursor == NULL)
	    {
		if(source.cursor == NULL)
		{
		    cursor = NULL;
		    precursor = NULL;
		}
		else
		{
		    cursor = head_ptr;
		    precursor = NULL;
		}
	    }
	    else
	    {
		node *tmp_ptr = head_ptr;
		node *source_ptr = source.head_ptr;

		while(source_ptr != source.precursor)
		{
		    source_ptr = source_ptr -> link();

		    tmp_ptr = tmp_ptr -> link();
		}

		cursor = tmp_ptr -> link();
		precursor = tmp_ptr;
	    }
	}

	many_nodes = source.many_nodes;
	
    }
    
    sequence::value_type sequence::current() const
    {
	assert(is_item());

	return cursor->data();
    }

}