CommandCenterReplacement.cs

using System;
using System.Linq;
using System.Text;
using UnityEngine;

public static class CommandCenterReplacement
{
	/// <summary>
	/// Returns the test value for this key and user, with different probabilities for each value.
	/// For example, to have a 40-60 split between the first and second value, you'd pass probabilities as
	/// { 0.4, 0.6 }
	/// </summary>
	public static string GetTestValue(string testKey, float[] probabilities, string[] testValues)
	{
		if(probabilities.Length != testValues.Length)
		{
			throw new Exception("Probabilities and test values must be the same length!");
		}

		// get a random value between 0 and sum
		// https://stackoverflow.com/a/1761646/3697679
		var sum = probabilities.Sum();
		var currentValue = GetRandom(testKey).NextDouble() * sum;
		for(var i = 0; i < probabilities.Length; i++)
		{
			if(currentValue < probabilities[i])
			{
				return testValues[i];
			}

			currentValue -= probabilities[i];
		}

		// shouldn't get here anyway
		return testValues[testValues.Length - 1];
	}

	/// <summary>
	/// Returns the test value for this key and user, with an equal probability between each value.
	/// </summary>
	public static string GetTestValue(string testKey, string[] testValues)
	{
		return testValues[GetRandom(testKey).Next(testValues.Length)];
	}

	/// <summary>
	/// Uses the device ID and test key to create a random number generator.
	/// </summary>
	private static System.Random GetRandom(string testKey)
	{
		var bytes = Encoding.ASCII.GetBytes(SystemInfo.deviceUniqueIdentifier + testKey);
		var seedBytes = new byte[] { 0, 0, 0, 0 };
		// xor each group of four bytes together to get a random seed
		for(var i = 0; i < bytes.Length; i++)
		{
			seedBytes[i % 4] ^= bytes[i];
		}

		// convert our bytes to an int
		var seedNum = BitConverter.ToInt32(seedBytes, 0);
		// create random
		return new System.Random(seedNum);
	}
}