Implement Token Generation Algorithm using snowflakes algorithm

thisisnabi · Sep 10, 2024 · 0317459 · 0317459
1 parent 81b55f7
commit 0317459
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Showing 2 changed files with 60 additions and 2 deletions.
diff --git a/src/Blogger.Infrastructure/GlobalUsings.cs b/src/Blogger.Infrastructure/GlobalUsings.cs
@@ -1,6 +1,8 @@
 // built-int
 global using Microsoft.EntityFrameworkCore;
 global using System.Collections.Immutable;
+global using System.Text;
+
 global using Microsoft.Extensions.Configuration;
 global using Microsoft.Extensions.DependencyInjection;
 

diff --git a/src/Blogger.Infrastructure/Services/LinkGenerator.cs b/src/Blogger.Infrastructure/Services/LinkGenerator.cs
@@ -3,9 +3,65 @@
 namespace Blogger.Infrastructure.Services;
 public class LinkGenerator : ILinkGenerator
 {
+
+    private const string Characters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+    private static readonly object LockObject = new object();
+    private static long _lastTimestamp = -1L;
+    private static long _sequence = 0L;
+    private const long MaxSequence = 4095; // 12-bit sequence
+
+    // implementing snowflakes algorithm to generate short and unique link
     public string Generate()
     {
-        // TODO: implement a generator algorithm
-        return Guid.NewGuid().ToString();
+        lock (LockObject)
+        {
+            long timestamp = GetTimestamp();
+
+            if (timestamp == _lastTimestamp)
+            {
+                _sequence = (_sequence + 1) & MaxSequence;
+                if (_sequence == 0)
+                {
+                    // Wait for the next millisecond if the sequence is full
+                    timestamp = WaitForNextMillis(_lastTimestamp);
+                }
+            }
+            else
+            {
+                _sequence = 0;
+            }
+
+            _lastTimestamp = timestamp;
+
+            string uniqueId = Base62Encode(timestamp) + Base62Encode(_sequence);
+            return uniqueId;
+        }
+    }
+
+    private static long GetTimestamp()
+    {
+        return DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
+    }
+
+    private static long WaitForNextMillis(long lastTimestamp)
+    {
+        long timestamp;
+        do
+        {
+            timestamp = GetTimestamp();
+        } while (timestamp <= lastTimestamp);
+        return timestamp;
+    }
+
+    private static string Base62Encode(long value)
+    {
+        var sb = new StringBuilder();
+        int baseSize = Characters.Length;
+        do
+        {
+            sb.Insert(0, Characters[(int)(value % baseSize)]);
+            value /= baseSize;
+        } while (value > 0);
+        return sb.ToString();
     }
 }