#undef NDEBUG
#include "dbg.h"
#include <stdio.h>
#include <assert.h>

/*
 * naive copy that assumes all inputs are always valid
 * taken from K&R C and cleaned up a bit;
 */
void copy(char to[], char from[])
{
  int i = 0;

  // while loop will not end if from isn't '\0' terminated
  while((to[i] = from[i]) != '\0') {
    ++i;
  }
}

/*
 * A safer version that checks for many common errors using the
 * length of each string to control the loops and termination.
 */
int safercopy(int from_len, char *from, int to_len, char *to)
{
  assert(from != NULL && to != NULL && "from and to can't be NULL");
  int i = 0;
  int max = from_len > to_len - 1 ? to_len - 1 : from_len;

  // to_len must have at least 1 byte
  if(from_len < 0 || to_len <= 0) return -1;

  for(i = 0; i < max; i++) {
    to[i] = from[i];
  }

  to[to_len - 1] = '\0';

  return i;
}


int main(int argc, char *argv[])
{
  // careful to understand why we can get these sizes
  char from[] = "0123456789";
  int from_len = sizeof(from);

  // notice that it's 7 chars + \0
  char to[] = "0123456";
  int to_len = sizeof(to);

  debug("Copying '%s':%d to '%s':%d", from, from_len, to, to_len);

  int rc = safercopy(from_len, from, to_len, to);
  check(rc > 0, "Failed to safercopy.");
  check(to[to_len - 1] == '\0', "String not terminated.");

  debug("Result is '%s':%d", to, to_len);

  // now try to break it
  rc = safercopy(from_len * -1, from, to_len, to);
  check(rc == -1, "safercopy should fail #1");
  check(to[to_len - 1] == '\0', "String not terminated.");

  rc = safercopy(from_len, from, 0, to);
  check(rc == -1, "safercopy should fail #2");
  check(to[to_len - 1] == '\0', "String not terminated.");

  return 0;

error:
  return 1;
}