#include <stdio.h>
#include <stdlib.h>

#include "dlist.h"

int dlist_get(const struct dlist *list, size_t index)
{
    if (index >= list->size)
        return -1;

    struct dlist_item *i;
    for (i = list->head; index; index--, i = i->next)
    {
        continue;
    }

    return i->data;
}

int dlist_insert_at(struct dlist *list, int element, size_t index)
{
    if (index > list->size || element < 0)
        return 0;
    else if (index == list->size)
        dlist_push_back(list, element);
    else if (index == 0)
        dlist_push_front(list, element);
    else
    {
        struct dlist_item *new = malloc(sizeof(struct dlist_item));
        if (new == NULL)
            return 0;
        new->data = element;

        struct dlist_item *i;
        for (i = list->head; index - 1; index--, i = i->next)
            continue;
        new->next = i->next;
        i->next->prev = new;
        i->next = new;
        new->prev = i;
        list->size++;
    }
    return 1;
}

int dlist_find(const struct dlist *list, int element)
{
    int index = 0;
    struct dlist_item *i;
    for (i = list->head; i && i->data != element; index++, i = i->next)
        continue;
    if (!i)
        return -1;
    return index;
}

int dlist_remove_at(struct dlist *list, size_t index)
{
    if (index >= list->size)
        return -1;
    int res;
    struct dlist_item *item;
    if (list->size == 1)
    {
        item = list->head;
        res = list->head->data;
        list->head = NULL;
        list->tail = NULL;
    }
    else if (index == 0)
    {
        item = list->head;
        res = item->data;
        item->next->prev = NULL;
        list->head = item->next;
    }
    else if (index == list->size - 1)
    {
        item = list->tail;
        res = item->data;
        item->prev->next = NULL;
        list->tail = item->prev;
    }
    else
    {
        for (item = list->head; index; index--, item = item->next)
            continue;

        res = item->data;
        item->prev->next = item->next;
        item->next->prev = item->prev;
    }

    free(item);
    list->size--;
    return res;
}

void dlist_clear(struct dlist *list)
{
    if (list->size == 0)
        return;
    for (struct dlist_item *i = list->head; i;)
    {
        struct dlist_item *tmp = i->next;
        free(i);
        i = tmp;
    }
    list->size = 0;
    list->head = NULL;
    list->tail = NULL;
}