#include "list_ops.h"

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

// Appends entries to a list and returns the new list
list_t *append_list(list_t *list1, list_t *list2) {
    size_t length1 = list1->length;
    size_t length2 = list2->length;
    size_t new_length = length1 + length2;
    list_t *new_list = malloc(sizeof(list_t) + new_length * sizeof(list_element_t));
    if (new_list) {
        new_list->length = new_length;
        for (size_t i = 0; i < length1; i++) {
            new_list->elements[i] = list1->elements[i];
        }
        for (size_t i = 0; i < length2; i++) {
            new_list->elements[length1 + i] = list2->elements[i];
        }
    }
    return new_list;
}

// Filters list returning only values that satisfy the filter function
list_t *filter_list(list_t *list, bool (*filter)(list_element_t)) {
    size_t length = list->length;
    size_t new_length = 0;
    // Count the number of elements that satisfy the filter
    for (size_t i = 0; i < length; i++) {
        if (filter(list->elements[i])) {
            new_length++;
        }
    }
    // Create a new list with filtered elements
    list_t *new_list = malloc(sizeof(list_t) + new_length * sizeof(list_element_t));
    if (new_list) {
        new_list->length = new_length;
        size_t j = 0;
        for (size_t i = 0; i < length; i++) {
            if (filter(list->elements[i])) {
                new_list->elements[j++] = list->elements[i];
            }
        }
    }
    return new_list;
}

// Returns the length of the list
size_t length_list(list_t *list) {
    return list->length;
}

// Returns a list of elements whose values equal the list value transformed by the mapping function
list_t *map_list(list_t *list, list_element_t (*map)(list_element_t)) {
    size_t length = list->length;
    list_t *new_list = malloc(sizeof(list_t) + length * sizeof(list_element_t));
    if (new_list) {
        new_list->length = length;
        for (size_t i = 0; i < length; i++) {
            new_list->elements[i] = map(list->elements[i]);
        }
    }
    return new_list;
}

// Folds (reduces) the given list from the left with a function
list_element_t foldl_list(list_t *list, list_element_t initial,
                          list_element_t (*foldl)(list_element_t, list_element_t)) {
    size_t length = list->length;
    list_element_t result = initial;
    for (size_t i = 0; i < length; i++) {
        result = foldl(result, list->elements[i]);
    }
    return result;
}

// Folds (reduces) the given list from the right with a function
list_element_t foldr_list(list_t *list, list_element_t initial,
                          list_element_t (*foldr)(list_element_t, list_element_t)) {
    size_t length = list->length;
    list_element_t result = initial;
    for (size_t i = length; i > 0; i--) {
        result = foldr(list->elements[i - 1], result);
    }
    return result;
}

// Reverse the elements of the list
list_t *reverse_list(list_t *list) {
    size_t length = list->length;
    list_t *new_list = malloc(sizeof(list_t) + length * sizeof(list_element_t));
    if (new_list) {
        new_list->length = length;
        for (size_t i = 0; i < length; i++) {
            new_list->elements[i] = list->elements[length - i - 1];
        }
    }
    return new_list;
}

// Destroy the entire list
void delete_list(list_t *list) {
    free(list);
}