[CHANGE] WIP YouTubeClient & HTML parsing

Manager.YouTube/Util/AuthenticationUtilities.cs

@@ -0,0 +1,37 @@
+using System.Globalization;
+using System.Net.Http.Headers;
+using System.Security.Cryptography;
+using System.Text;
+
+namespace Manager.YouTube.Util;
+
+public static class AuthenticationUtilities
+{
+    private const string HeaderScheme = "SAPISIDHASH";
+    
+    // Dave Thomas @ https://stackoverflow.com/a/32065323/9948300
+    public static AuthenticationHeaderValue? GetSapisidHashHeader(string sapisid, string origin)
+    {
+        if (string.IsNullOrWhiteSpace(sapisid) || string.IsNullOrWhiteSpace(origin))
+            return null;
+        var time = GetTime();
+        var sha1 = HashString($"{time} {sapisid} {origin}");
+        var completeHash = $"{time}_{sha1}";
+        return new AuthenticationHeaderValue(HeaderScheme, completeHash);
+    }
+    
+    private static string HashString(string stringData)
+    {
+        var dataBytes = Encoding.ASCII.GetBytes(stringData);
+        var hashData = SHA1.HashData(dataBytes);
+        return hashData.Aggregate(string.Empty, (current, item) => current + item.ToString("x2"));
+    }
+    
+    private static string GetTime()
+    {
+        var st = new DateTime(1970, 1, 1);
+        var t = DateTime.Now.ToUniversalTime() - st;
+        var time = (t.TotalMilliseconds + 0.5).ToString(CultureInfo.InvariantCulture);
+        return time[..10];
+    }
+}