Add snowflake generator

Directory.Packages.props

@@ -4,6 +4,7 @@
     </PropertyGroup>
     <ItemGroup>
         <PackageVersion Include="dotenv.net" Version="3.2.0" />
+        <PackageVersion Include="IdGen" Version="3.0.7" />
         <PackageVersion Include="JsonSubTypes" Version="2.0.1" />
         <PackageVersion Include="Microsoft.EntityFrameworkCore" Version="8.0.16" />
         <PackageVersion Include="Microsoft.Extensions.Configuration.Binder" Version="8.0.0" />

src/Tribufu.Database/FlakeGenerator.cs

@@ -0,0 +1,45 @@
+// Copyright (c) Tribufu. All Rights Reserved.
+// SPDX-License-Identifier: UNLICENSED
+
+using IdGen;
+using System;
+
+namespace Tribufu.Database
+{
+    public static class FlakeGenerator
+    {
+        public static readonly DateTime EPOCH = new(2016, 1, 1, 0, 0, 0, DateTimeKind.Utc);
+
+        private static readonly IdStructure _structure = new(41, 10, 12);
+
+        private static readonly IdGeneratorOptions _options = new(_structure, new DefaultTimeSource(EPOCH));
+
+        private static readonly IdGenerator _generator = new(0, _options);
+
+        public static ulong New()
+        {
+            //Console.WriteLine("Max. generators       : {0}", _structure.MaxGenerators);
+            //Console.WriteLine("Id's/ms per generator : {0}", _structure.MaxSequenceIds);
+            //Console.WriteLine("Id's/ms total         : {0}", _structure.MaxGenerators * _structure.MaxSequenceIds);
+            //Console.WriteLine("Wraparound interval   : {0}", _structure.WraparoundInterval(_generator.Options.TimeSource));
+            //Console.WriteLine("Wraparound date       : {0}", _structure.WraparoundDate(_generator.Options.TimeSource.Epoch, _generator.Options.TimeSource).ToString("O"));
+
+            return (ulong)_generator.CreateId();
+        }
+
+        public static ulong FromTimestamp(DateTime timestamp, ushort sequence = 0)
+        {
+            var diff = (long)(timestamp - EPOCH).TotalMilliseconds;
+            if (diff < 0 || diff > (1L << 41) - 1)
+            {
+                throw new ArgumentOutOfRangeException(nameof(timestamp), "Timestamp out of range for flake.");
+            }
+
+            ulong timestampPart = (ulong)diff << 22;        // 41 bits << (10+12)
+            ulong generatorPart = 0ul << 12;                // Always 0
+            ulong sequencePart = (ulong)(sequence & 0xFFF); // 12 bits
+
+            return timestampPart | generatorPart | sequencePart;
+        }
+    }
+}

src/Tribufu.Database/Tribufu.Database.csproj

@@ -16,6 +16,7 @@
         <None Include="README.md" Pack="true" PackagePath="\" />
     </ItemGroup>
     <ItemGroup>
+        <PackageReference Include="IdGen" />
         <PackageReference Include="Microsoft.EntityFrameworkCore" />
     </ItemGroup>
     <ItemGroup>