#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#pragma pack(1) // OPTIONAL: Makes the Valgrind messages more predictable

typedef struct _Node {
    int           value;
    struct _Node* next;
} Node;

void print_linked_list_of_ints(Node* head) {
    for(Node* curr = head; curr != NULL; curr = curr -> next) {
        printf("curr -> value == %d\n", curr -> value);
    }
}

void append(int value, Node** a_head, Node** a_tail) {
    // If head is NULL, tail must be, too.
    assert( (*a_tail == NULL) == (*a_head == NULL) );  // OK for class demo

    // Create new list node
    Node* new_node = malloc(sizeof(*new_node));  // »add an object to HEAP
    *new_node = (Node) { .value = value, .next = NULL };

    // Connect the new node into the existing list
    if(*a_tail == NULL) {  // If list is empty…
        *a_head = new_node;
    }
    else {
        (*a_tail) -> next = new_node;
    }
    *a_tail = new_node;
}

void destroy_list(Node** a_head, Node** a_tail) {
    // Free head repeatedly until list is empty
    while(*a_head != NULL) {
        Node* victim = *a_head;
        *a_head = (*a_head) -> next;
        free(victim);  // You would think that freeing the victim would
    }                  // let it get away.  This victim will not escape.

    // Set head and tail to NULL to avoid accidentally accessing freed memory.
    *a_head = NULL;
    *a_tail = NULL;
}

int main(int argc, char* argv[]) {
    // Create empty list
    Node* head = NULL;
    Node* tail = NULL;

    // Append six nodes with numbers 10 to 15
    append(10, &head, &tail);
    append(11, &head, &tail);
    append(12, &head, &tail);
    append(13, &head, &tail);
    append(14, &head, &tail);
    append(15, &head, &tail);

    print_linked_list_of_ints(head);

    destroy_list(&head, &tail);  

    return EXIT_SUCCESS;
}
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