#include "list_ops.h"

#ifndef LIST_OPS_H
#define LIST_OPS_H

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

typedef int list_element_t;

typedef struct {
   size_t length;
   list_element_t elements[];
} list_t;

// constructs a new list
list_t *new_list(size_t length, list_element_t elements[]);

// append entries to a list and return the new list
list_t *append_list(list_t *list1, list_t *list2);

// filter list returning only values that satisfy the filter function
list_t *filter_list(list_t *list, bool (*filter)(list_element_t));

// returns the length of the list
size_t length_list(list_t *list);

// return 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));

// 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));

// 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));

// reverse the elements of the list
list_t *reverse_list(list_t *list);

// destroy the entire list
// list will be a dangling pointer after calling this method on it
void delete_list(list_t *list);

#endif

#include "list_ops.h"


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

list_t *new_list(size_t length, list_element_t elements[]) {

    // Calculate the memory size
    size_t size = sizeof(list_t) + length * sizeof(list_element_t);

    // Allocate memory
    list_t *list = malloc(size);

    if (list == NULL) {
        return NULL; // Check if allocation failed
    }

    // Set the length of the list
    list->length = length;

    // Copy the input elements to the list
    for (size_t i = 0; i < length; i++) {
        list->elements[i] = elements[i];
    }

    return list;
}

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

list_t *append_list(list_t *list1, list_t *list2) {
    size_t new_length = list1->length + list2->length;
    list_element_t new_elements[new_length];

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

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

    return new_list(new_length, new_elements);
}

list_t *reverse_list(list_t *list) {
    list_element_t reversed_elements[list->length];

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

    return new_list(list->length, reversed_elements);
}

list_t *map_list(list_t *list, list_element_t (*map)(list_element_t)) {
    list_element_t mapped_elements[list->length];

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

    return new_list(list->length, mapped_elements);
}

list_t *filter_list(list_t *list, bool (*filter)(list_element_t)) {
    list_element_t filtered_elements[list->length];
    size_t count = 0;

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

    return new_list(count, filtered_elements);
}

list_element_t foldr_list(list_t *list, list_element_t initial, list_element_t (*foldr)(list_element_t, list_element_t)) {

    list_element_t result = initial;  // Start with initial value

    // Traverse the list from last to first
    for (size_t i = 0; i < list->length; ++i) {
        result = foldr(list->elements[list->length - 1 - i], result);
    }

    return result;
}

list_element_t foldl_list(list_t *list, list_element_t initial, list_element_t (*foldl)(list_element_t, list_element_t)) {

    list_element_t result = initial;  // Start with initial value

    // Traverse the list from first to last
    for (size_t i = 0; i < list->length; ++i) {
        result = foldl(result, list->elements[i]);
    }

    return result;
}