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

// Declare/define a struct type called 'struct _Node' -OR- 'Node' (two names).
typedef struct _Node {
    int value;
    struct _Node* next;
} Node;

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

void append(int value, Node** a_head, Node** a_tail) {
    // Create new (one and only) node.
    Node* new_tail = malloc(sizeof *new_tail);
    *new_tail = (Node) { .value = value, .next = NULL };

    // List is currently empty, so create new list of size 1.
    if(*a_head == NULL) {
        // Set the list to that node (list of size 1).
        *a_head = new_tail;
    }
    else {
        // List is not empty, so add a new node to the end.
        //
        // Add new node to end of existing list.
        (*a_tail) -> next = new_tail;  // attach new tail after old tail
    }
    *a_tail = new_tail;  // in any case, new_tail becomes the tail, obviously
}

void free_list(Node** a_head, Node** a_tail) {
    while(*a_head != NULL) {  // while list not empty
        // Detach head
        Node* old_head = *a_head;
        *a_head = (*a_head) -> next;  // head becomes 2nd node
        
        // Free your mind (head)
        free(old_head);
    }
    assert(*a_head == NULL);
    *a_tail = NULL;
}

int main(int argc, char* argv[]) {
    // Linked list of size 0
    Node* head = NULL;
    Node* tail = NULL;

    append(5, &head, &tail);  // now size == 1
    append(6, &head, &tail);  // now size == 2
    append(7, &head, &tail);  // now size == 3

    print_list(head);

    free_list(&head);
    assert(head == NULL);
    
    return EXIT_SUCCESS;
}
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