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

list_t *new_list(size_t length, list_element_t elements[]) {
    list_t *list = malloc(sizeof(list_t) + length * sizeof(list_element_t));
    if (!list) {
        return NULL;
    }

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

list_t *append_list(list_t *list1, list_t *list2) {
    if (!list1 || !list2) return NULL;

    size_t total_length = list1->length + list2->length;
    list_t *result = malloc(sizeof(list_t) + total_length * sizeof(list_element_t));
    if (!result) return NULL;

    result->length = total_length;

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

    return result;
}

list_t *concatenate_lists(list_t **lists, size_t count) {
    if (!list) {
        return NULL;
    }

    size_t total_length = 0;
    for (size_t i = 0; i < count; ++i) {
        if (lists[i])
            total_length += lists[i]->length;
    }

    list_t *result = malloc(sizeof(list_t) + total_length * sizeof(list_element_t));
    if (!result) {
        return NULL;
    }

    result->length = total_length;
    size_t pos = 0;

    for (size_t i = 0; i < count; ++i) {
        if (!lists[i]) continue;
        for (size_t j = 0; j < lists[i]->length; ++j) {
            result->elements[pos++] = lists[i]->elements[j];
        }
    }

    return result;
}

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

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

    list_t *result = malloc(sizeof(list_t) + count * sizeof(list_element_t));
    if (!result) {
        return NULL;
    }

    result->length = count;
    size_t j = 0;
    for (size_t i = 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 ? list->length : 0;
}

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

    list_t *result = malloc(sizeof(list_t) + list->length * sizeof(list_element_t));
    if (!result) {
        return NULL;
    }

    result->length = list->length;
    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)) {
    if (!list || !foldl) return initial;

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

    return acc;
}

list_element_t foldr_list(list_t *list, list_element_t initial, list_element_t (*foldr)(list_element_t, list_element_t)) {
    if (!list || !foldr) return initial;

    list_element_t acc = initial;
    for (size_t i = list->length; i > 0; --i) {
        acc = foldr(list->elements[i - 1], acc);
    }

    return acc;
}

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

    list_t *result = malloc(sizeof(list_t) + list->length * sizeof(list_element_t));
    if (!result) {
        return NULL;
    }

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

    return result;
}

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