#include <iostream>
#include "double_list.h"

using namespace std;

DoubleList::DoubleList()
{
    first = nullptr;
    last = nullptr;
    size = 0;
}

DoubleList::DoubleList(const DoubleList &l2)
{
    if (l2.first == nullptr)
    {
        first = nullptr;
        last = nullptr;
        size = 0;
    }
    else
    {
        size = 0;
        list_node *p = l2.first;
        while (p != nullptr)
        {
            add_last_node(p->info);
            p = p->next;
        }
    }
}

DoubleList::~DoubleList()
{
    while (!empty())
    delete_first_node();
}

void DoubleList::add_first_node(int x)
{
    if (empty())
    {
        first = new list_node;
        last = first;
        first->info = x;
        first->prev = nullptr;
        first->next = nullptr;
        size++;
    }
    else
    {
        list_node *p = new list_node;
        first->prev = p;
        p->next = first;
        p->info = x;
        p->prev = nullptr;
        first = p;
        size++;
    }
}

void DoubleList::add_last_node(int x)
{
    if (empty())
    {
        first = new list_node;
        last = first;
        first->info = x;
        first->prev = nullptr;
        first->next = nullptr;
        size++;
    }
    else
    {
        list_node *p = new list_node;
        p->prev = last;
        p->info = x;
        p->next = nullptr;
        last->next = p;
        last = p;
        size++;
    }
}

void DoubleList::print_list()
{
    list_node *p = first;
    while (p != nullptr)
    {
        cout << p->info << " ";
        p = p->next;
    }
    cout << endl;
}

int DoubleList::list_size()
{
    return size;
}

bool DoubleList::empty()
{
    return (size == 0);
}

DoubleList unite_lists(const DoubleList &l1, const DoubleList &l2)
{
    if (!l1.first && !l2.first)
    {
        DoubleList l;
        return l;
    }
    if (!l1.first)
    {
        DoubleList l(l2);
        return l;
    }
    if (!l2.first)
    {
        DoubleList l(l1);
        return l;
    }
    DoubleList copy1(l1);
    DoubleList copy2(l2);
    copy1.last->next = copy2.first;
    copy2.first->prev = copy1.last;
    copy1.last = copy2.last;
    copy1.size += copy2.size;
    DoubleList l(copy1);
    copy2.first = nullptr;
    copy2.last = nullptr;
    copy2.size = 0;
    return l;
}

void DoubleList::delete_first_node()
{
    if (first == last)
    {
        delete first;
        size--;
    }
    else
    {
        first = first->next;
        delete first->prev;
        first->prev = nullptr;
        size--;
    }
}

void DoubleList::delete_last_node()
{
    if (last == first)
    {
        delete last;
        size--;
    }
    else
    {
        last = last->prev;
        delete last->next;
        last->next = nullptr;
        size--;
    }
}

bool DoubleList::element_exists(int x)
{
    list_node *p = first;
    while (p != nullptr)
    {
        if (p->info == x)
            return true;
        p = p->next;
    }
    return false;
}