/*********************************************

This code illustrates what goes wrong when we
do a shallow copy instead of a deep copy.

See the (wrong) implementation of function
copy_person, and the output of the program.

*********************************************/


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

#include "person_wrong.h"


int string_length(char * my_string)
{
  int counter = 0;
  while(1)
  {
    if (my_string[counter] != 0)
    {
      counter++;
    }
    else
    {
      break;
    }
  }

  return counter;
}


char * copy_string(char * input)
{
  int length = string_length(input);
  char * result = (char *) malloc(sizeof(char) * (length + 1));

  int i;
  for (i = 0; i <= length; i++)
  {
    result[i] = input[i];
  }

  return result;
}


struct date input_date()
{
  struct date result;
  printf("please enter month day year:\n");

  scanf("%d %d %d", &(result.month), &(result.day), &(result.year));
  return result;
}


void print_date(char * name, struct date d1)
{
  printf("%s = %d/%d/%d\n", name, d1.month, d1.day, d1.year);
}


struct date copy_date(struct date input)
{
  struct date result = input;
  return result;
}


struct person input_person()
{
  struct person result;
  printf("please enter name:\n");
  char * input = (char *) malloc(sizeof(char) * 1000);
  scanf("%s", input);
  result.name = copy_string(input);
  free(input);

  printf("please enter age:\n");
  scanf("%d", &(result.age));

  printf("please enter date of birth:\n");
  result.dob = input_date();
  return result;
}


void print_person(char * name, struct person p1)
{
  printf("%s name: %s\n", name, p1.name);
  printf("age = %d\n", p1.age);
  print_date("date of birth = ", p1.dob);
}


// Note: This is the WRONG way to copy a person. Since
// name is a pointer, we need to make a DEEP copy,
// but this function only makes a SHALLOW copy.
struct person copy_person(struct person p1)
{
  struct person result = p1;

  return result;
}


void change_age(struct person p1)
{
  printf("please enter new age:\n");
  scanf("%d", &(p1.age));
}


int main(void)
{
  struct person p1 = input_person();
  struct person p2 = copy_person(p1);

  // change the first letter of the name of p1 to 'C'
  p1.name[0] = 'C';

  // change the age of p1 to 40
  p1.age = 40;

  print_person("p1", p1);
  print_person("p2", p2);
  // note, in the printout, that p2.age is not changed,
  // but p2.name has been changed, because it is equal
  // to p1.name.

  free(p1.name);

  // note that, since p2.name = p1.name, we should NOT free p2.name
}