/// <summary>
/// Returns an array containing the cumulative sum of frequencies at specified <see cref="Position"/> in specified
/// <see cref="FrequencyMap{T}"/> value collection.
/// </summary>
/// <param name="map"><see cref="FrequencyMap{T}"/> whose cumulative sum of frequencies to get for
/// <paramref name="position"/>.</param>
/// <param name="position"><see cref="Position"/> in <paramref name="map"/>'s value collection to
/// consider.</param>
/// <returns>An array containing the cumulative sum of frequencies at <paramref name="position"/> in
/// <paramref name="map"/>.</returns>
public int[] GetBuckets(FrequencyMap <T> map, Position position)
{
int[] buckets = new int[map.Count];
int sum = 0;
int index = 0;
StateFrequency frequency;
int value;
foreach (var pair in map)
{
frequency = pair.Value;
value = Math.Max(_minFrequency, frequency.GetValue(position));
sum += value;
buckets[index++] = sum;
}
return(buckets);
}
/// <summary>
/// Gets a random <typeparamref name="T"/> key from specified <see cref="FrequencyMap{T}"/> based on all values at
/// specified <see cref="Position"/> in map's frequencies.
/// </summary>
/// <param name="map"><see cref="FrequencyMap{T}"/> used for issuing values.</param>
/// <param name="position"><see cref="Position"/> in <paramref name="map"/>'s frequencies to consider issuing
/// values for.</param>
/// <returns>A random <see cref="T"/> value from <paramref name="map"/>'s keys based on frequencies at
/// <paramref name="position"/> in the map.</returns>
/// <exception cref="NullReferenceException"><paramref name="map"/> is null.</exception>
public T GetValue(FrequencyMap <T> map, Position position)
{
int[] buckets = GetBuckets(map, position);
int length = buckets.Length;
int total = buckets[length - 1];
int value = _random.Next(0, total);
int index = 0;
for (; index < length; index++)
{
if (value < buckets[index])
{
break;
}
}
return(map.Keys.ToList()[index]);
}
