feat(client): add rendezvous traversal coordinators (#12)

2026-07-16 08:39:05 +02:00
parent 6d076c281a
commit b4b6072fe1
28 changed files with 2949 additions and 57 deletions
@@ -0,0 +1,83 @@
+using System.Text;
+using FinalFactory.Rendezvous.Contracts;
+
+namespace FinalFactory.Rendezvous.Client;
+
+public sealed class DirectConnectionRequest
+{
+    public JoinAttemptId AttemptId { get; set; }
+    public string ConnectionTicket { get; set; } = string.Empty;
+
+    public override string ToString() =>
+        $"[DirectConnectionRequest {AttemptId}; ticket redacted]";
+}
+
+public static class DirectConnectionRequestCodec
+{
+    public const int EncodedLength = 63;
+
+    private const int MagicLength = 4;
+    private const int AttemptIdLength = 16;
+    private const int TicketLength = ContractLimits.DerivedCredentialCharacters;
+    private static readonly byte[] Magic = [(byte)'R', (byte)'V', (byte)'D', (byte)'1'];
+
+    public static bool IsRendezvousRequest(ReadOnlySpan<byte> encoded) =>
+        encoded.Length >= MagicLength && encoded[..MagicLength].SequenceEqual(Magic);
+
+    public static byte[] Encode(JoinAttemptId attemptId, string connectionTicket)
+    {
+        if (attemptId.Value == Guid.Empty
+            || connectionTicket is null
+            || connectionTicket.Length != TicketLength
+            || !ContractValidation.IsConnectionTicketValid(connectionTicket))
+        {
+            throw new ArgumentException("The direct connection request fields are invalid.");
+        }
+
+        byte[] encoded = new byte[EncodedLength];
+        Magic.CopyTo(encoded, 0);
+        if (!attemptId.Value.TryWriteBytes(encoded.AsSpan(MagicLength, AttemptIdLength)))
+        {
+            throw new InvalidOperationException("The join attempt identifier could not be encoded.");
+        }
+
+        Encoding.ASCII.GetBytes(
+            connectionTicket,
+            0,
+            connectionTicket.Length,
+            encoded,
+            MagicLength + AttemptIdLength);
+        return encoded;
+    }
+
+    public static bool TryDecode(
+        ReadOnlySpan<byte> encoded,
+        out DirectConnectionRequest? request)
+    {
+        request = null;
+        if (encoded.Length != EncodedLength
+            || !encoded[..MagicLength].SequenceEqual(Magic))
+        {
+            return false;
+        }
+
+        Guid attemptId = new(encoded.Slice(MagicLength, AttemptIdLength));
+        if (attemptId == Guid.Empty)
+        {
+            return false;
+        }
+
+        string ticket = Encoding.ASCII.GetString(encoded[(MagicLength + AttemptIdLength)..]);
+        if (!ContractValidation.IsConnectionTicketValid(ticket))
+        {
+            return false;
+        }
+
+        request = new DirectConnectionRequest
+        {
+            AttemptId = new JoinAttemptId(attemptId),
+            ConnectionTicket = ticket,
+        };
+        return true;
+    }
+}