Generate ID from Key

Author: tiksn

src/API.Web/DependencyInjection/ServiceCollectionExtensions.cs

@@ -1,4 +1,6 @@
-using IdGen;
+using System.IO.Hashing;
+using System.Text;
+using IdGen;
 using IdGen.DependencyInjection;
 
 namespace Fossa.API.Web.DependencyInjection;
@@ -13,12 +15,12 @@ public static IServiceCollection AddIdGen(
     var epoch = new DateTimeOffset(initialReleaseDate.ToDateTime(TimeOnly.MinValue, DateTimeKind.Utc));
     var idGeneratorOptions = new IdGeneratorOptions(timeSource: new DefaultTimeSource(epoch));
 
-    var generatorId = GetGeneratorId(configuration);
+    var generatorId = GetGeneratorId(configuration, idGeneratorOptions.IdStructure.MaxGenerators);
 
     return services.AddIdGen(generatorId, () => idGeneratorOptions);
   }
 
-  private static int GetGeneratorId(IConfiguration configuration)
+  private static int GetGeneratorId(IConfiguration configuration, int maxGenerators)
   {
     var generatorIdConfiguration = configuration.GetValue<int?>("GeneratorId");
 
@@ -27,6 +29,29 @@ private static int GetGeneratorId(IConfiguration configuration)
       return generatorIdConfiguration.Value;
     }
 
-    throw new InvalidOperationException("GeneratorId Configuration is missing");
+    var generatorKeyConfiguration = configuration.GetValue<string?>("GeneratorKey");
+    if (!string.IsNullOrWhiteSpace(generatorKeyConfiguration))
+    {
+      if (uint.TryParse(generatorKeyConfiguration, out uint uintKey))
+      {
+        return (int)(uintKey % maxGenerators);
+      }
+      else if (ulong.TryParse(generatorKeyConfiguration, out ulong ulongKey))
+      {
+        return (int)(ulongKey % (ulong)maxGenerators);
+      }
+      else if (Guid.TryParse(generatorKeyConfiguration, out Guid guidKey))
+      {
+        byte[] bytes = guidKey.ToByteArray();
+        return (int)(XxHash32.HashToUInt32(bytes) % maxGenerators);
+      }
+      else
+      {
+        byte[] bytes = Encoding.UTF8.GetBytes(generatorKeyConfiguration);
+        return (int)(XxHash32.HashToUInt32(bytes) % maxGenerators);
+      }
+    }
+
+    throw new InvalidOperationException("GeneratorId and or GeneratorKey Configuration is missing");
   }
 }