using System;
using System.Collections.Generic;

/// <summary>
/// Shuffle bag based off http://gamedev.tutsplus.com/tutorials/implementation/shuffle-bags-making-random-feel-more-random/
/// </summary>
public class ShuffleBag<T>
{
	private Random random = new Random();
	private List<T> data;
	private T currentItem;
	private int currentPosition = -1;
 
	private int Capacity { get { return data.Capacity; } }

	public int Size { get { return data.Count; } }
 
	public ShuffleBag(int initCapacity)
	{
		data = new List<T>(initCapacity);
	}

	public void Add(T item, int amount = 1)
	{
		for (int i = 0; i < amount; i++)
		{
			data.Add(item);
		}
 
		currentPosition = Size - 1;
	}

	public T Next()
	{
		if (currentPosition < 1)
		{
			currentPosition = Size - 1;
			currentItem = data[0];
 
			return currentItem;
		}
 
		var pos = random.Next(currentPosition);
 
		currentItem = data[pos];
		data[pos] = data[currentPosition];
		data[currentPosition] = currentItem;
		currentPosition--;
 
		return currentItem;
	}

}