add state string helper function

Author: lucasteles

src/Backdash/Options/SyncTestOptions.cs

@@ -78,7 +78,7 @@ public SyncTestOptions<TInput> UseRandomInputProvider()
     /// </summary>
     public SyncTestOptions<TInput> UseJsonStateParser(JsonSerializerOptions? options = null)
     {
-        StateStringParser = new JsonStateStringParser(options);
+        StateStringParser = options is null ? JsonStateStringParser.Singleton : new JsonStateStringParser(options);
         return this;
     }
 

src/Backdash/Session/Backends/LocalSession.cs

@@ -66,7 +66,7 @@ SessionServices<TInput> services
     public Endianness StateSerializationEndianness => endianness.Endianness;
     public Endianness InputSerializationEndianness => options.Protocol.SerializationEndianness;
     public INetcodeRandom Random => random;
-
+    public INetcodeSessionHandler GetHandler() => callbacks;
     public ReadOnlySpan<SynchronizedInput<TInput>> CurrentSynchronizedInputs => syncInputBuffer;
     public ReadOnlySpan<TInput> CurrentInputs => inputBuffer;
 

src/Backdash/Session/Backends/RemoteSession.cs

@@ -203,6 +203,7 @@ void Close()
     public int LocalPort => udp.BindPort;
     public Endianness StateSerializationEndianness => synchronizer.SerializationEndianness;
     public Endianness InputSerializationEndianness => options.Protocol.SerializationEndianness;
+    public INetcodeSessionHandler GetHandler() => callbacks;
     public SessionMode Mode => SessionMode.Remote;
 
     public IReadOnlySet<NetcodePlayer> GetPlayers() => addedPlayers;

src/Backdash/Session/Backends/ReplaySession.cs

@@ -108,7 +108,7 @@ public void Close()
     public int NumberOfPlayers { get; private set; }
 
     public INetcodeRandom Random => random;
-
+    public INetcodeSessionHandler GetHandler() => callbacks;
     public SessionMode Mode => SessionMode.Replay;
     public void DisconnectPlayer(NetcodePlayer player) { }
     public ResultCode AddLocalInput(NetcodePlayer player, in TInput localInput) => ResultCode.Ok;

src/Backdash/Session/Backends/SpectatorSession.cs

@@ -159,6 +159,7 @@ public void Close()
     public bool IsInRollback => false;
     public SavedFrame GetCurrentSavedFrame() => stateStore.Last();
     public INetcodeRandom Random => random;
+    public INetcodeSessionHandler GetHandler() => callbacks;
     public int NumberOfPlayers { get; private set; }
     public int NumberOfSpectators => 0;
     public int LocalPort => udp.BindPort;

src/Backdash/Session/Backends/SyncTestSession.cs

@@ -116,6 +116,7 @@ public async ValueTask DisposeAsync()
     public int NumberOfSpectators => addedSpectators.Count;
     public int LocalPort => 0;
     public INetcodeRandom Random => random;
+    public INetcodeSessionHandler GetHandler() => callbacks;
     public Frame CurrentFrame => synchronizer.CurrentFrame;
     public SessionMode Mode => SessionMode.SyncTest;
     public FrameSpan FramesBehind => synchronizer.FramesBehind;

src/Backdash/Session/INetcodeSession.cs

@@ -79,11 +79,6 @@ public interface INetcodeSessionInfo
     /// </summary>
     SavedFrame GetCurrentSavedFrame();
 
-    /// <summary>
-    ///     Returns the last saved state snapshot.
-    /// </summary>
-    StateSnapshot CurrentStateSnapshot() => GetCurrentSavedFrame().ToSnapshot();
-
     /// <summary>
     ///     Returns the checksum of the current saved state.
     /// </summary>
@@ -105,6 +100,11 @@ public interface INetcodeSession : INetcodeSessionInfo, IDisposable, IAsyncDispo
     /// </summary>
     INetcodeSessionInfo GetInfo() => this;
 
+    /// <summary>
+    ///     Returns session info
+    /// </summary>
+    INetcodeSessionHandler GetHandler();
+
     /// <summary>
     ///     Disconnects a remote player from a game.
     /// </summary>
@@ -234,18 +234,6 @@ public interface INetcodeSession : INetcodeSessionInfo, IDisposable, IAsyncDispo
     /// <returns><see cref="ResultCode.Ok" /> if success.</returns>
     ResultCode AddPlayer(NetcodePlayer player);
 
-    /// <summary>
-    ///     Add a list of <see name="Player" /> into current session.
-    /// </summary>
-    /// <returns>An equivalent <see cref="ResultCode" /> list.</returns>
-    IReadOnlyList<ResultCode> AddPlayers(IReadOnlyList<NetcodePlayer> players)
-    {
-        var result = new ResultCode[players.Count];
-        for (var index = 0; index < players.Count; index++)
-            result[index] = AddPlayer(players[index]);
-        return result;
-    }
-
     /// <summary>
     ///     Find player by unique ID
     /// </summary>

src/Backdash/Session/NetcodeSessionExtensions.cs

@@ -0,0 +1,42 @@
+using Backdash.Serialization;
+using Backdash.Synchronizing.State;
+
+namespace Backdash;
+
+/// <summary>
+/// Extensions for <see cref="INetcodeSession{T}"/>
+/// </summary>
+public static class NetcodeSessionExtensions
+{
+    /// <summary>
+    ///    Returns the current state string representation
+    /// </summary>
+    public static string GetStateString<T>(
+        this INetcodeSession<T> @this,
+        IStateStringParser? parser = null
+    ) where T : unmanaged =>
+        @this.GetStateString(@this.GetCurrentSavedFrame(), parser);
+
+    /// <summary>
+    ///    Returns string representation for given <paramref name="state"/>
+    /// </summary>
+    public static string GetStateString<T>(
+        this INetcodeSession<T> @this,
+        SavedFrame state,
+        IStateStringParser? parser = null
+    ) where T : unmanaged
+    {
+        parser ??= JsonStateStringParser.Singleton;
+        var currentOffset = 0;
+        var currentBytes = state.GameState.WrittenSpan;
+        BinaryBufferReader currentReader = new(currentBytes, ref currentOffset, @this.StateSerializationEndianness);
+        var currentObject = @this.GetHandler().CreateState(state.Frame, ref currentReader);
+        return parser.GetStateString(state.Frame, in currentReader, currentObject);
+    }
+
+    /// <summary>
+    ///     Returns the last saved state snapshot.
+    /// </summary>
+    public static StateSnapshot CurrentStateSnapshot<T>(this INetcodeSession<T> @this) where T : unmanaged =>
+        @this.GetCurrentSavedFrame().ToSnapshot();
+}

src/Backdash/Synchronizing/State/IStateStringParser.cs

@@ -48,6 +48,11 @@ public sealed class JsonStateStringParser(
     IStateStringParser? stateStringFallback = null
 ) : IStateStringParser
 {
+    static readonly Lazy<IStateStringParser> singleton = new(new JsonStateStringParser());
+
+    /// <summary>Singleton instance</summary>
+    public static IStateStringParser Singleton => singleton.Value;
+
     internal Logger? Logger = null;
     readonly JsonSerializerOptions jsonOptions = options ?? CreateDefaultJsonOptions();
     readonly IStateStringParser fallback = stateStringFallback ?? new DefaultStateStringParser();

src/Backdash/Synchronizing/State/StateSnapshot.cs

@@ -16,10 +16,10 @@ public sealed class StateSnapshot(Frame frame, byte[] state)
     public StateSnapshot() : this(Frame.Null, []) { }
 
     /// <summary>Saved frame number</summary>
-    public Frame Frame = frame;
+    public readonly Frame Frame = frame;
 
     /// <summary>Saved game state</summary>
-    public byte[] State = state;
+    public readonly byte[] State = state;
 
     /// <summary>Saved state size</summary>
     public ByteSize Size => ByteSize.FromBytes(State.Length);