#include "list_ops.h"
#include <stdlib.h>
#include <stdbool.h>

list_t *new_list(size_t length, list_element_t elements[]) {
    size_t size = sizeof(list_t) + length * sizeof(list_element_t);

    list_t *newList = (list_t *)malloc(size);

    if (newList == NULL) {
        return NULL;
    }

    newList->length = length;

    for (size_t i = 0; i < length; ++i) {
        newList->elements[i] = elements[i];
    }

    return newList;
}

list_t *append_list(list_t *list1, list_t *list2) {
    if (list1 == NULL) {
        return (list2 != NULL) ? new_list(list2->length, list2->elements) : NULL;
    }

    if (list2 == NULL) {
        return new_list(list1->length, list1->elements);
    }

    size_t totalSize = sizeof(list_t) + (list1->length + list2->length) * sizeof(list_element_t);

    list_t *newList = (list_t *)malloc(totalSize);

    if (!newList) {
        return NULL;
    }

    newList->length = list1->length + list2->length;

    for (size_t i = 0; i < list1->length; ++i) {
        newList->elements[i] = list1->elements[i];
    }

    for (size_t i = 0; i < list2->length; ++i) {
        newList->elements[list1->length + i] = list2->elements[i];
    }

    return newList;
}

list_t *filter_list(list_t *list, bool (*filter)(list_element_t)) {
    if (list == NULL || filter == NULL) {
        return NULL;
    }

    size_t count = 0;
    for (size_t i = 0; i < list->length; ++i) {
        if (filter(list->elements[i])) {
            count++;
        }
    }

    if (count == 0) {
        return new_list(0, NULL);
    }

    size_t totalSize = sizeof(list_t) + count * sizeof(list_element_t);
    list_t *filtered_list = (list_t *)malloc(totalSize);

    if (!filtered_list) {
        return NULL;
    }

    filtered_list->length = count;

    size_t filteredIndex = 0;
    for (size_t i = 0; i < list->length; ++i) {
        if (filter(list->elements[i])) {
            filtered_list->elements[filteredIndex] = list->elements[i];
            filteredIndex++;
        }
    }

    return filtered_list;
}

size_t length_list(list_t *list) {
    if (list == NULL) {
        return 0;
    }

    return list->length;
}

list_t *map_list(list_t *list, list_element_t (*map)(list_element_t)) {
    if (list == NULL || map == NULL) {
        return NULL;
    }

    list_t *mapped_list = new_list(list->length, NULL);

    if (mapped_list == NULL) {
        return NULL;
    }

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

    return mapped_list;
}


list_element_t foldl_list(list_t *list, list_element_t initial,
                          list_element_t (*foldl)(list_element_t,
                                                  list_element_t)) {
    if (list == NULL || foldl == NULL) {
        return initial;
    }

    list_element_t accumulator = initial;

    for (size_t i = 0; i < list->length; ++i) {
        accumulator = foldl(accumulator, list->elements[i]);
    }

    return accumulator;
}

list_t *reverse_list(list_t *list) {
    if (!list) {
        return NULL;
    }

    list_t *reversed_list = new_list(list->length, NULL);

    if (!reversed_list) {
        return NULL;
    }

    for (size_t i = list->length; i > 0; --i) {
        reversed_list->elements[list->length - i] = list->elements[i - 1];
    }

    return reversed_list;
}

void delete_list(list_t *list) {
    if (list != NULL) {
        free(list);
    }
}