#include <stdbool.h>
#include <stdint.h>
#include "list.h"
#include "pool.h"

/**
 * Remove a node from a list.
 *
 * Remove a @ref ListNode from a @ref List. There are no checks to ensure that the
 * passed `node` is actually part of the passed `list`. Handle with care.
 * This is used with the @ref ListItr specifically. 
 *
 * @param list pointer to a @ref List
 * @param node pointer to a @ref ListNode 
 */
static void _list_remove_node(List *list, ListNode *node);

/**
 * Get the next @ref ListNode in a @ref ListItr
 *
 * Note: Use of this function outside of testing is strongly discouraged. Unless
 * you really want to access the @ref ListNode itself, it's preferred to just use
 * @ref list_itr_next .
 *
 * @param itr pointer to the @ref ListItr
 *
 * @return A pointer to the @ref ListNode in the itr, otherwise return NULL.
 */
static ListNode* _list_itr_node_next(ListItr* itr);


List list_create(void)
{
    List list = { .head = NULL, .tail = NULL, .len = 0 };
    return list;
}

void list_clear(List* list)
{
    if(list_is_empty(list)) return;

    ListItr itr = list_itr_create(list);
    ListNode* ln;

    while((ln = _list_itr_node_next(&itr)))
    {
        POOL_FREE(ListNode, ln);
    }

    list->head = NULL;
    list->tail = NULL;
    list->len = 0;
}

bool list_is_empty(const List* list)
{
    return list->len == 0;
}

void list_push_front(List *list, void* data)
{
    ListNode *node = POOL_GET(ListNode);

    node->data = data;
    node->prev = NULL;
    node->next = list->head;

    if (list_is_empty(list))
    {
        list->tail = node;
    }
    else
    {
        list->head->prev = node;
    }

    list->head = node;

    list->len++;
}

void list_push_back(List *list, void* data)
{
    ListNode* node = POOL_GET(ListNode);
    node->data = data;
    node->prev = list->tail;
    node->next = NULL;

    if (list_is_empty(list))
    {
        list->head = node;
    }
    else
    {
        list->tail->next = node;
    }

    list->tail = node;

    list->len++;
}

static void _list_remove_node(List *list, ListNode *node)
{
    if(node->prev && !node->next) // end of list
    {
        node->prev->next = NULL;
        list->tail = node->prev;
    }
    else if(node->prev && node->next) // somewhere in between
    {
        node->prev->next = node->next;
        node->next->prev = node->prev;
    }
    else if(node->next && !node->prev) // beginning of list
    {
        node->next->prev = NULL;
        list->head = node->next;
    }
    else if(!node->prev && !node->next) // only element in list
    {
        list->head = NULL;
        list->tail = NULL;
    }

    POOL_FREE(ListNode, node);

    list->len--;
}

int list_get_len(const List* list)
{
    return list->len;
}

void* list_get_at_idx(List* list, int n)
{
    if(n >= list_get_len(list) || n < 0) return NULL;

    int curr_idx = 0;
    ListItr itr = list_itr_create(list);
    void* data = NULL;

    while((data = list_itr_next(&itr)))
    {
        if (n == curr_idx++) return data;
    }

    return NULL;
}

bool list_remove_at_idx(List* list, int n)
{
    if(n >= list_get_len(list) || n < 0) return false;

    int len = 0;
    ListItr itr = list_itr_create(list);
    ListNode* ln;

    while((ln = _list_itr_node_next(&itr)))
    {
        if(n == len++)
        {
            _list_remove_node(list, ln);
            return true;
        }
    }
    return false;
}

ListItr list_itr_create(List* list)
{
    ListItr itr =
    {
        .list = list,
        .next_node = !list_is_empty(list) ? list->head : NULL,
        .current_node = NULL,
    };

    return itr;
}

void* list_itr_next(ListItr* itr)
{
    ListNode* ln = _list_itr_node_next(itr);
    return ln ? ln->data : NULL;
}

static ListNode* _list_itr_node_next(ListItr* itr)
{
    if(!itr->next_node) return NULL;

    itr->current_node = itr->next_node;

    ListNode* ln = itr->next_node;

    if(ln->next)
    {
        itr->next_node = ln->next;
        return ln;
    }

    itr->next_node = NULL;
    return ln;
}

void list_itr_remove_current_node(ListItr* itr)
{
    if(!itr || !itr->current_node) return;
    ListNode* tmp_prev = itr->current_node->prev;
    _list_remove_node(itr->list, itr->current_node);
    itr->current_node = tmp_prev;
}