Implement generate and test

Core/Utils/HashUtil.cs

@@ -9,14 +9,40 @@ namespace Core.Utils;
 public class HashUtil
 {
 	private readonly Regex MongoIdRegex = new Regex("^[a-fA-F0-9]{24}$");
+
+	private readonly RandomUtil _randomUtil;
+	
+	public HashUtil(RandomUtil randomUtil)
+	{
+		_randomUtil = randomUtil;
+	}
 	
 	/// <summary>
-	/// Create a 24 character id using the sha256 algorithm + current timestamp
+	/// Create a 24 character MongoId
 	/// </summary>
-	/// <returns>24 character hash</returns>
+	/// <returns>24 character objectId</returns>
 	public string Generate()
 	{
-		throw new NotImplementedException();
+		var objectId = new byte[12];
+		
+		// Time stamp (4 bytes)
+		var timestamp = BitConverter.GetBytes((int)DateTimeOffset.UtcNow.ToUnixTimeSeconds());
+		// Convert to big-endian
+		Array.Reverse(timestamp); 
+		Array.Copy(timestamp, 0, objectId, 0, 4);
+		
+		// Random value (5 bytes)
+		var randomValue = new byte[5];
+		_randomUtil.Random.NextBytes(randomValue);
+		Array.Copy(randomValue, 0, objectId, 4, 5);
+		
+		// Incrementing counter (3 bytes)
+		// 24-bit counter
+		var counter = BitConverter.GetBytes(_randomUtil.GetInt(0, 16777215)); 
+		Array.Reverse(counter);
+		Array.Copy(counter, 0, objectId, 9, 3);
+		
+		return Convert.ToHexStringLower(objectId);
 	}
 	
 	/// <summary>

Core/Utils/RandomUtil.cs

@@ -7,7 +7,7 @@ namespace Core.Utils;
 [Injectable(InjectionType.Singleton)]
 public class RandomUtil
 {
-    private readonly Random _random = new();
+    public readonly Random Random = new();
     
     /// <summary>
     /// The IEEE-754 standard for double-precision floating-point numbers limits the number of digits (including both
@@ -30,7 +30,7 @@ public class RandomUtil
         }
         
         // maxVal is exclusive of the passed value, so add 1
-        return max > min ? _random.Next(min, max + 1) : min;
+        return max > min ? Random.Next(min, max + 1) : min;
     }
 
     /// <summary>
@@ -41,7 +41,7 @@ public class RandomUtil
     /// <returns>A random integer between 1 and max - 1, or 1 if max is less than or equal to 1.</returns>
     public int GetIntEx(int max)
     {
-        return max > 2 ? _random.Next(1, max - 1) : 1;
+        return max > 2 ? Random.Next(1, max - 1) : 1;
     }
 
     /// <summary>
@@ -214,13 +214,13 @@ public class RandomUtil
         // Return a random integer from 0 to low if high is not provided
         if (high is null)
         {
-            return _random.Next(0, low);
+            return Random.Next(0, low);
         }
         
         // Return low directly when low and high are equal
         return low == high
             ? low
-            : _random.Next(low, (int)high);
+            : Random.Next(low, (int)high);
     }
 
     /// <summary>

UnitTests/Tests/Utils/HashUtilTests.cs

@@ -5,7 +5,26 @@ namespace UnitTests.Tests.Utils;
 [TestClass]
 public class HashUtilTests
 {
-	private readonly HashUtil _hashUtil = new();
+	private readonly HashUtil _hashUtil = new(new RandomUtil());
+	
+	[TestMethod]
+	public void GenerateTest()
+	{
+		// Generate 100 MongoId's
+		for (var i = 0; i < 100; i++)
+		{
+			// Invalid mongoId character
+			var result = _hashUtil.Generate();
+		
+			// Invalid mongoId length
+			var test = _hashUtil.IsValidMongoId(result);
+		
+			Assert.AreEqual(
+				true, 
+				test,
+				$"IsValidMongoId() `{result}` is not a valid MongoId.");
+		}
+	}
 	
 	[TestMethod]
 	public void IsValidMongoIdTest()