// gcc -o taste taste.c
// ./taste

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

typedef struct node_t {
  int value;
  struct node_t *next;
} node;

/*
  We'll have to update the head pointer when the list is empty
  so we get a reference to it, not a copy.
*/
void add_entry(node **head, int new_value) {
  // A reference to the last pointer. Starts out pointing to the head.
  node ***indirect = &head;

  node *new_node = malloc(sizeof(node));
  new_node->value = new_value;
  new_node->next = NULL;

  while(**indirect != NULL) {
    *indirect = &(**indirect)->next;
  }

  // indirect now points to the last pointer in the list whether it was empty or not
  **indirect = new_node;
}

/*
  Returns a pointer to the node that contains the value we're looking for
  or NULL if not found.
*/
node *find_entry(node *head, int value) {
  node *current = head;

  while(current != NULL && current->value != value) {
    current = current->next;
  }

  return current;
}

/*
  The head pointer may need to be modified so we need a double pointer.
  The entry pointer is also passed by reference as we'll free that memory.
*/
void remove_entry(node **head, node **entry) {
  /*
  The indirect pointer point to the pointer that we'll update
  */
  node ***indirect = &head;

  /*
    Walk the list as long as we haven't found the pointer we're looking for
  */
  while((**indirect) != *entry) {
    *indirect = &(**indirect)->next;
  }

  /*
    We remove it.
    indirect, which now points to either null or to the pointer that points to
    the entry we want to delete, is set to whatever comes after that entry.
  */
  **indirect = (*entry)->next;

  free(*entry);
}

void print_list(node *head) {
  node *current = head;

  while(current != NULL) {
    printf("%d ", current->value);
    current = current->next;
  }
  printf("\n");
}

int main(int argc, char const *argv[]) {
  node *head = NULL;

  print_list(head);

  add_entry(&head, 4);
  add_entry(&head, 3);
  add_entry(&head, 10);
  add_entry(&head, 2);
  add_entry(&head, 7);

  print_list(head);

  node *entry = find_entry(head, 2);
  remove_entry(&head, &entry);

  entry = find_entry(head, 4);
  remove_entry(&head, &entry);

  print_list(head);

  return 0;
}