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

typedef struct myString_t {
  int  length;
  char *str;
} * MyString; // Note that type MyString is a pointer type

// takes a null terminated array of char as the argument
MyString MyString_create(const char * cstring) {
  MyString result = malloc(sizeof(*result));
  if ( result == NULL ) return NULL;
  if (cstring == NULL ) {
    result->length = 0;
    result->str = NULL;
    return result;
  }
  result->length = strlen(cstring);
  result->str = malloc(result->length);
  if ( result->str == NULL ) {
    free(result);
    return NULL;
  }
  memcpy(result->str, cstring, result->length); // don't copy '\0'
  return result;
}

// deep copy - takes another MyString as the argument
// beware "MyString_copy(str, str);"
bool MyString_copy(MyString dest, const MyString src) {
  if ( src == NULL || dest == NULL ) return false;
  // if malloc() fails here, we want dest to be unchanged
  char *strcopy = malloc(sizeof(char) * src->length);
  if ( strcopy == NULL ) return false;
  if ( dest->str != NULL ) free(dest->str);
  memcpy(strcopy, src->str, src->length);
  dest->str = strcopy;
  dest->length = src->length;
  return true;
}

void MyString_print(MyString s) {
  if ( s == NULL ) return;
  printf("(%d) ", s->length); 
  for ( int i = 0; i < s->length; i++ ) {
    putchar(s->str[i]);
  }
  putchar('\n');
}

int main(int argc, char *argv[]) {

  MyString myString = MyString_create("mystring");
  MyString_print(myString);

  MyString yourString = MyString_create("yourstring");
  MyString_print(yourString);

  if ( !MyString_copy(myString, yourString) ) exit(1);
  MyString_print(myString);

  // what does valgrind say about the exeution of this code?

  return EXIT_SUCCESS;
}