Add random number generator

00_Common/dotnet/Games.Common/Randomness/IRandom.cs

@@ -0,0 +1,55 @@
+namespace Games.Common.Randomness;
+
+/// <summary>
+/// Provides access to a random number generator
+/// </summary>
+public interface IRandom
+{
+    /// <summary>
+    /// Gets a random <see cref="float" /> such that 0 <= n < 1.
+    /// </summary>
+    /// <returns>The random number.</returns>
+    float NextFloat();
+
+    /// <summary>
+    /// Gets a random <see cref="float" /> such that 0 <= n < exclusiveMaximum.
+    /// </summary>
+    /// <returns>The random number.</returns>
+    float NextFloat(float exclusiveMaximum);
+
+    /// <summary>
+    /// Gets a random <see cref="float" /> such that inclusiveMinimum <= n < exclusiveMaximum.
+    /// </summary>
+    /// <returns>The random number.</returns>
+    float NextFloat(float inclusiveMinimum, float exclusiveMaximum);
+
+    /// <summary>
+    /// Gets a random <see cref="int" /> such that 0 <= n < exclusiveMaximum.
+    /// </summary>
+    /// <returns>The random number.</returns>
+    int Next(int exclusiveMaximum);
+
+    /// <summary>
+    /// Gets a random <see cref="int" /> such that inclusiveMinimum <= n < exclusiveMaximum.
+    /// </summary>
+    /// <returns>The random number.</returns>
+    int Next(int inclusiveMinimum, int exclusiveMaximum);
+
+    /// <summary>
+    /// Gets the previous random number as a <see cref="float" />.
+    /// </summary>
+    /// <returns>The previous random number.</returns>
+    float PreviousFloat();
+
+    /// <summary>
+    /// Gets the previous random number as an <see cref="int" />.
+    /// </summary>
+    /// <returns>The previous random number.</returns>
+    int Previous();
+
+    /// <summary>
+    /// Reseeds the random number generator.
+    /// </summary>
+    /// <param name="seed">The seed.</param>
+    void Reseed(int seed);
+}

00_Common/dotnet/Games.Common/Randomness/RandomNumberGenerator.cs

@@ -0,0 +1,50 @@
+using System;
+
+namespace Games.Common.Randomness;
+
+public class RandomNumberGenerator : IRandom
+{
+    private Random _random;
+    private float _previous;
+
+    public RandomNumberGenerator()
+    {
+        // The BASIC RNG is seeded based on time with a 1 second resolution
+        _random = new Random((int)(DateTime.UtcNow.Ticks / TimeSpan.TicksPerSecond));
+    }
+
+    public float NextFloat() => NextFloat(1);
+
+    public float NextFloat(float exclusiveMaximum)
+    {
+        if (exclusiveMaximum <= 0)
+        {
+            throw new ArgumentOutOfRangeException(nameof(exclusiveMaximum), "Must be greater than 0.");
+        }
+
+        return NextFloat(0, exclusiveMaximum);
+    }
+
+    public float NextFloat(float inclusiveMinimum, float exclusiveMaximum)
+    {
+        if (exclusiveMaximum <= inclusiveMinimum)
+        {
+            throw new ArgumentOutOfRangeException(nameof(exclusiveMaximum), "Must be greater than inclusiveMinimum.");
+        }
+
+        var range = exclusiveMaximum - inclusiveMinimum;
+        return _previous = ((float)_random.NextDouble()) * range + inclusiveMinimum;
+    }
+
+    public int Next(int exclusiveMaximum) => ToInt(NextFloat(exclusiveMaximum));
+
+    public int Next(int inclusiveMinimum, int exclusiveMaximum) => ToInt(NextFloat(inclusiveMinimum, exclusiveMaximum));
+
+    public float PreviousFloat() => _previous;
+
+    public int Previous() => ToInt(_previous);
+
+    private static int ToInt(float value) => (int)Math.Floor(value);
+
+    public void Reseed(int seed) => _random = new Random(seed);
+}