A C# Shuffler

generator.cs

/*
Copyright 2019 Tariq Ali

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

using System;
using System.Collections.Generic;

public static class Generator
{
  static Random _random = new Random();

  //https://www.dotnetperls.com/fisher-yates-shuffle
  public static List<T> Shuffle<T>(List<T> list)
  {
      int n = list.Count;
      for (int i = 0; i < n; i++)
      {
          int r = i + _random.Next(n - i);
          T t = list[r];
          list[r] = list[i];
          list[i] = t;
      }
      return list;
  }
  
  public static T Random<T>(List<T> list)
  {
    var index = _random.Next(list.Count);
    return list[index];
  }
  
  public static Func<T> GenerateRule<T>(List<T> inputList)
  {
    return () => Random(inputList);
  }

  public static Func<T> GenerateUniqueRule<T>(List<T> inputList)
  {
    IEnumerable<T> shuffledList = Shuffle(inputList);

    var enumerator = shuffledList.GetEnumerator();

    Func<T> func = () =>
        {
            if (enumerator.MoveNext())
            {
              //do nothing
            }
            else
            {
              enumerator.Reset();
              enumerator.MoveNext();
            }
            return enumerator.Current;
        };
    return func;
  }
}