#include <stdio.h>
#include <stdlib.h>
#include "list_ops.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;
}



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

size_t length_list(list_t *lst) {
    return (lst == NULL) ? 0 : lst->length;
}

list_t *append_list(list_t *first, list_t *second) {
    size_t a = first ? first->length : 0;
    size_t b = second ? second->length : 0;

    size_t total = a + b;
    list_t *joined = malloc(sizeof(list_t) + total * sizeof(list_element_t));
    if (!joined) { 
        return NULL;
    }
    joined->length = total;

    for (size_t i = 0; i < a; i++) {
        joined->elements[i] = first->elements[i];
    }

    for (size_t j = 0; j < b; j++) {
        joined->elements[a + j] = second->elements[j];
    }

    return joined;
}

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

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

    return new;
}

list_t *map_list(list_t *lst, list_element_t (*func)(list_element_t)) {
    if (lst == NULL || func == NULL) return NULL;

    size_t n = lst->length;
    list_t *mapped = malloc(sizeof(list_t) + n * sizeof(list_element_t));
    if (mapped == NULL) {
        return NULL;
    }
    mapped->length = n;

    for (size_t i = 0; i < n; ++i) {
        list_element_t val = lst->elements[i];
        mapped->elements[i] = func(val);
    }

    return mapped;
}

list_element_t foldl_list(list_t *lst, list_element_t init,
    list_element_t (*folder)(list_element_t, list_element_t)) {
list_element_t acc = init;

    if (lst && folder) {
        for (size_t i = 0; i < lst->length; ++i) {
            acc = folder(acc, lst->elements[i]);
    }
}

return acc;
}



list_element_t foldr_list(list_t *lst, list_element_t init,
    list_element_t (*folder)(list_element_t, list_element_t)) {
list_element_t acc = init;

    if (lst && folder) {
        for (size_t i = lst->length; i > 0; --i) {
            acc = folder(lst->elements[i - 1], acc);
    }
}

return acc;
}




list_t *reverse_list(list_t *lst) {
    if (!lst) return NULL;

    size_t n = lst->length;
    list_t *reversed = malloc(sizeof(list_t) + n * sizeof(list_element_t));
    if (!reversed) { 
        return NULL;
    }
    reversed->length = n;

    for (size_t i = 0; i < n; ++i) {
        reversed->elements[i] = lst->elements[n - i - 1];
    }

    return reversed;
}