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

struct node {
  int data;
  struct node* next;
};

int DeleteNth(struct node** headRef, int index){
  struct node* current = *headRef; struct node* next; struct node* nextnext;
  int i;
  for(i=1; i<index-1; i++){
    assert(current != NULL);
    current = current->next;
  }
  next = current->next;
  nextnext = next->next;
  if (nextnext == NULL){
    current->next = NULL;
    assert(next!=NULL);
    free(next);
    return 0;
  }
  current->next = nextnext;
  assert(next!=NULL);
  free(next);
  return 0;

}


int Pop(struct node** headRef){
  struct node* current = *headRef;
  struct node* next;
  if(current != NULL){
    int value = current->data;
    next = current->next;
    free(current);
    *headRef = next;
    return value;
  }
  printf("You can't pop anymore!");
  return 0;

}

void PrintList(struct node* head){
  struct node* current = head;
  int count = 0;
  printf("The following values are in the list:\n");
  while (current != NULL){
    count++;
    printf("%d. %d\n", count ,current->data);
    current = current->next;
  }
}
void Push(struct node** headRef, int data){
  struct node* newNode = malloc(sizeof(struct node));
  newNode->data = data;

  newNode->next = *headRef;
  *headRef = newNode;

}
void insertNth(struct node** headRef, int index, int data ){
  if(index==0) Push(headRef,data);
  else{
    struct node* current = *headRef;
    int i;
    for (i=1;i<index-1; i++){
      assert(current != NULL);
      current = current->next;
    }
    assert(current!=NULL);
    Push(&(current->next),data);
  }
}
void deleteList(struct node** headRef){
  struct node* current = *headRef;
  struct node* next;

  while (current != NULL){
    next = current->next;
    free(current);
    current = next;
  }
  *headRef = NULL;

}

void UserInput(struct node** headRef){
  int ans;
  int index;
    printf("What do you want to do?\n (1) Add value, (2) Add value to certain index, (3) Delete first value\n (4) Delete specific index (5) Delete list: ");
    scanf(" %d",&ans);
    switch (ans) {
      case 1:
        printf("What value?: ");
        scanf(" %d",&ans);
        insertNth(&*headRef,0, ans);
        break;
      case 2:
        printf("What value?: ");
        scanf(" %d",&ans);
        printf("What index?: ");
        scanf(" %d",&index);
        insertNth(&*headRef, index, ans);
        break;
      case 3:
        Pop(&*headRef);
        break;
      case 4:
        printf("What index?: ");
        scanf(" %d",&index);
        if (index == 1) Pop(&*headRef);
        else{
          DeleteNth(&*headRef, index);}
          break;
      case 5:
        deleteList(&*headRef);
        break;
    }
  }

void main(){
  struct node* head = malloc(sizeof(struct node));
  Pop(&head);
  while(1){
    int a; int b;
    UserInput(&head);
    PrintList(head);
  }
}