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

#include "person3.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];
  }
  result[length] = 0;

  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));
  return result;
}


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


struct person copy_person(struct person p1)
{
  struct person result = p1;
  result.name = copy_string(p1.name);

  return result;
}


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

// foo changes the contents of p1.name. Note that foo
// does not change the VALUE of p1.name, which still
// points to the same memory location.
void foo(struct person p1)
{
  p1.name[0] = 'X';
}


// foo2 does NOT change the value or contents of p1.name
// (it is an incorrect version of foo3)
void foo2(struct person p1)
{
  p1.name = copy_string("Mary");
}


// foo3 changes the value or p1->name
// (it is an corrected version of foo2)
void foo3(struct person * p1)
{
  free(p1->name);
  p1->name = copy_string("Mary");
}


int main(void)
{
  struct person p1 = input_person();
  print_person("p1", p1);

  foo(p1);
  print_person("\np1, after foo", p1);

  foo2(p1);
  print_person("\np1, after foo2", p1);

  foo3(&p1);
  print_person("\np1, after foo3", p1);

  free(p1.name);
}