#include "list_ops.h"
#include <string.h>

static list_t *allocate_list(size_t length) {
    list_t *list = malloc(sizeof(list_t) + sizeof(list_element_t) * length);
    if (list) list->length = length;
    return list;
}

list_t *new_list(size_t length, list_element_t elements[]) {
    list_t *list = allocate_list(length);
    if (!list) return NULL;
    if (length && elements)
        memcpy(list->elements, elements, sizeof(list_element_t) * length);
    return list;
}

void delete_list(list_t *list) {
    free(list);
}

list_t *append_list(list_t *list1, list_t *list2) {
    list_t *result = allocate_list(list1->length + list2->length);
    if (!result) return NULL;

    memcpy(result->elements, list1->elements, sizeof(list_element_t) * list1->length);
    memcpy(result->elements + list1->length, list2->elements, sizeof(list_element_t) * list2->length);

    return result;
}

list_t *filter_list(list_t *list, bool (*filter)(list_element_t)) {
    size_t count = 0;
    for (size_t i = 0; i < list->length; i++)
        if (filter(list->elements[i])) count++;

    list_t *result = allocate_list(count);
    if (!result) return NULL;

    for (size_t i = 0, j = 0; i < list->length; i++)
        if (filter(list->elements[i]))
            result->elements[j++] = list->elements[i];

    return result;
}

size_t length_list(list_t *list) {
    return list->length;
}

list_t *map_list(list_t *list, list_element_t (*map)(list_element_t)) {
    list_t *result = allocate_list(list->length);
    if (!result) return NULL;

    for (size_t i = 0; i < list->length; i++)
        result->elements[i] = map(list->elements[i]);

    return result;
}

list_element_t foldl_list(list_t *list, list_element_t initial,
                          list_element_t (*foldl)(list_element_t, list_element_t)) {
    for (size_t i = 0; i < list->length; i++)
        initial = foldl(initial, list->elements[i]);
    return initial;
}

list_element_t foldr_list(list_t *list, list_element_t initial,
                          list_element_t (*foldr)(list_element_t, list_element_t)) {
    for (size_t i = list->length; i-- > 0;)
        initial = foldr(list->elements[i], initial);
    return initial;
}

list_t *reverse_list(list_t *list) {
    list_t *result = allocate_list(list->length);
    if (!result) return NULL;

    for (size_t i = 0; i < list->length; i++)
        result->elements[i] = list->elements[list->length - 1 - i];

    return result;
}