galaxy brain 2: bit of restructure (Bootstrap)

Dalamud.Bootstrap/SqexArg/ArgumentDecoder.cs

@@ -0,0 +1,47 @@
+using System;
+
+namespace Dalamud.Bootstrap.SqexArg
+{
+    internal static class ArgumentDecoder
+    {
+        public static void Decode(ReadOnlySpan<char> argument, uint key)
+        {
+            // 1. strip //**sqex003 and **//
+            // 2. extract checksum
+            // 3. deduce upper nibble key
+            // 4. 
+
+            // //**c**//
+            if (argument.Length <= 9)
+            {
+                throw new ArgumentException(nameof(argument));
+            }
+
+            if (!argument.StartsWith("//**") || !argument.EndsWith("**//"))
+            {
+                throw new ArgumentException(nameof(argument));
+            }
+
+            var payload = argument[4..^5];
+            var checksum = argument[^5];
+
+            // undo url safe
+            //payload.re
+
+            
+            
+            // stuff
+            
+        }
+
+        private static void DecodeUrlSafeBase64(ReadOnlySpan<char> content)
+        {
+            var buffer = new byte[(content.Length / 3) * 4];
+            if (!Convert.TryFromBase64Chars(payload, buffer, out var _))
+            {
+                // TODO
+            }
+        }
+
+    }
+}