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

#define MAX_NAME_SIZE 30
#define INITIAL_STRUCT_SIZE 3

/* declaration of a stucture */
typedef struct {
   int age;
   float weight;
   char name[MAX_NAME_SIZE];
} Persons;

/* fonction that adds a new person */
void addPerson(Persons *ptr, int *counter) {
  int incrementer = 0; /* Moves to next position in memory to prevent data overwriting */

  /* while there is enought of memory in ptr, we user `incrementer = (*counter)`, in other cases we call fonction to expand memory */

  if (ptr == NULL)
    expandStruct(&ptr, &counter);  /* calling fonction to realloc memory and affecting result to `incrementer` variable */

  printf("Counter : %d\n", *counter);

   /* adding data to structure */
    printf("Enter age, weight and name of the person respectively:\n");
    scanf("%d%*c", &(ptr+*counter)->age);
    scanf("%f%*c", &(ptr+*counter)->weight);
    scanf("%s%*c", &(ptr+*counter)->name);
    (*counter)++; /* incrementing coutner after each new data */
    //printf("Counter = %d\n", *counter);
    //printf("Incrementer = %d\n", incrementer);
}

/* dipplaying data */
void displayPerson(Persons *ptr, int *counter)   {
  int i = 0;
  int j = 0;

  j = (*counter);
  i = 0;

  if (j == 0) {
   printf("Currently there is no records\n");
   return;
  }

  printf("Displaying Infromation:\n");

  do {
      printf("%d\t%.2f\t%s\n", (ptr+i)->age, (ptr+i)->weight, (ptr+i)->name);
      i++;
    } while (i < j);
}

/* expanding memory if needed */
void expandStruct(Persons **ptr, int **counter)
{
    (*counter)++;
    *ptr = realloc(*ptr, sizeof(Persons));

    if(*ptr == NULL)
    {
        printf("Cannot allocate more memory\n");
        exit(EXIT_FAILURE);
    }
}

int main(int argc, char * argv[])
{
   Persons *ptr = NULL;
   int counter = 0;
   int input = 0;

   /* initial memory allocating */
   ptr = (Persons*) malloc(INITIAL_STRUCT_SIZE * sizeof(Persons));

   if (ptr == NULL) {
     printf("Allocation memory fail\n");
     exit(EXIT_FAILURE);
   }

   do {
     printf("1. Add Person\n");
     printf("2. Display Persons\n");
     scanf("%d%*c", &input);

     switch (input) {
       case 1:
          addPerson(ptr, &counter);
          break;
       case 2:
          displayPerson(ptr, &counter);
          break;
       case -1:
          break;
      default:
          printf("Wrong input\n");
          break;
     }
   } while (input != -1);

   return 0;
}