#include "stdstuff.h"

#include "IntBag.h"

// note that the constructor and size are not mentioned here as their
// implementations are completely specified in the header file


// adds a value to the bag.  returns true on success (space available)
// and false on failure (bag full)
bool IntBag::add (int value) {

  if (count == MAXVALUES) return false;

  data[count++] = value;
  walkInProgress = false; // scrub any ongoing walk
  return true;

}


// removes one occurance of the specfied value from the bag.  returns
// true on success (value existed) and false on failure (value did not exist)
bool IntBag::remove (int value) {

  int i;

  for (i = 0; i < count; i++) {
    if (data[i] == value) {
      // we've found the data value.
      // overwrite it with the last data value and adjust the count
      // to reflect the fact that there are now one fewer values in
      // the bag.  note that this works even if the value being removed
      // is the last value in the bag.
      data[i] = data[--count];
      walkInProgress = false; // scrub any ongoing walk
      return true;
    }
  }

  return false;

}


// returns the number of times that the specified value occurs in the bag
int IntBag::countOccurrences (int value) const {

  int i, occurrences = 0;

  for (i = 0; i < count; i++) {
    if (data[i] == value) {
      occurrences++;
    }
  }

  return occurrences;

}


bool IntBag::startWalk (int &value) {

  if (count == 0) return false;

  walkInProgress = true; walkPosition = 0;
  value = data[walkPosition];
  return true;

}


bool IntBag::continueWalk (int &value) {

  if (!walkInProgress) {
    throw range_error ("IntBag::continueWalk invalid call");
  }
  if (++walkPosition == count) {
    walkInProgress = false; // we've come to the end of the road
    return false;
  }
  value = data[walkPosition];
  return true;

}


// randomly picks and returns one of the values in the bag.
// throws a range_error exception if the bag is empty.
int IntBag::pickRandom () const {

  int i;

  if (count == 0) {
    throw range_error ("IntBag::pickRandom bag is empty");
  }

  i = (int) ((rand () / (RAND_MAX + 1.0)) * count);
  return data[i];

}