GoakeFlax/Source/Game/GameMode/NetworkManager_Demo.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.IO.Compression;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using FlaxEngine;
using FlaxEngine.Networking;
using Console = Game.Console;
using Object = FlaxEngine.Object;

namespace Game;

public static unsafe partial class NetworkManager
{
    public const byte DemoVer = 2;
    private struct DemoNetworkEventHeader
    {
        public NetworkEventType EventType;
        public uint SenderId;
        public uint MessageId;
        public uint Length;
    }

    private static List<NetworkEvent> buffer;
    private static IEnumerator<NetworkEvent> bufferEnumerable;
    private static GZipStream demoStream; // record
    private static FileStream demoFileStream;

    public static bool IsRecording => demoStream != null;
    private static long flushedFrames = 0;

    public static bool IsDemoPlaying => bufferEnumerable != null;

    public static bool PlayDemo(string demoName)
    {
        {
            Cleanup();
            //clientWorldStateManager = new WorldStateManager(isServer: true);
            World.InitServer();
        }

        if (!ReadDemo(demoName))
        {
            Console.Print("Failed to read demo.");
            return false;
        }
        
        /*if (client == null)
        {
            Console.Print("Failed to create NetworkPeer.");
            return false;
        }
        if (!client.Connect())
        {
            Console.Print("Failed to connect to the server.");
            return false;
        }*/

        Scripting.FixedUpdate += OnDemoUpdate;
        //if (!listenServer)
        {
            Scripting.Exit += Cleanup;
            //Level.ActorSpawned += OnClientActorSpawned;
        }
        return true;
    }

    public static void RecordDemo(string demoPath)
    {
        if (IsRecording)
            StopRecording();

        buffer = new List<NetworkEvent>();
        var demoFolder = Directory.GetParent(demoPath);
        if (!demoFolder.Exists)
            Directory.CreateDirectory(demoFolder.FullName);

        demoFileStream = File.Open(demoPath, FileMode.Create, FileAccess.Write);
        demoStream = new GZipStream(demoFileStream, CompressionMode.Compress);
        demoStream.WriteByte(DemoVer);
    }

    private static void RecordMessage(ref NetworkEvent networkEvent)
    {
        if (!IsRecording)
            return;

        NetworkEvent recordedEvent = networkEvent;
        recordedEvent.Message.Buffer = (byte*)NativeMemory.Alloc(recordedEvent.Message.Length);
        recordedEvent.Sender.ConnectionId = networkEvent.Sender.ConnectionId;

        NativeMemory.Copy(networkEvent.Message.Buffer, recordedEvent.Message.Buffer, recordedEvent.Message.Length);
        buffer.Add(recordedEvent);
    }

    public static void FlushDemo()
    {
        if (!IsRecording)
            return;

        Stopwatch sw = Stopwatch.StartNew();

        Span<byte> bytes = stackalloc byte[Unsafe.SizeOf<DemoNetworkEventHeader>()];
        foreach (ref NetworkEvent networkEvent in CollectionsMarshal.AsSpan(buffer))
        {
            DemoNetworkEventHeader header = new DemoNetworkEventHeader()
            {
                EventType = networkEvent.EventType,
                SenderId = networkEvent.Sender.ConnectionId,
                Length = networkEvent.Message.Length,
                MessageId = networkEvent.Message.MessageId,
            };
            MemoryMarshal.Write(bytes, header);
            demoStream.Write(bytes);

            Span<byte> messageBytes = new Span<byte>(networkEvent.Message.Buffer, (int)networkEvent.Message.Length);
            demoStream.Write(messageBytes);
            
            // TODO: free networkEvent buffer
        }

        sw.Stop();
        
        flushedFrames += buffer.Count;
        buffer.Clear();

        FlaxEngine.Debug.Write(LogType.Info, $"Wrote demo in {sw.Elapsed.TotalMilliseconds}ms, frames: {flushedFrames}");
    }

    public static void StopRecording()
    {
        if (!IsRecording)
            return;

        FlushDemo();
        demoStream.Close();
        demoStream = null;
        demoFileStream.Close();
        demoFileStream = null;
    }

    private static unsafe bool ReadDemo(string demoPath)
    {
        if (!File.Exists(demoPath))
            return false;

        buffer = new List<NetworkEvent>();

        Stopwatch sw = Stopwatch.StartNew();

        using FileStream fileStream = File.OpenRead(demoPath);
        using GZipStream stream = new GZipStream(fileStream, CompressionMode.Decompress);

        int ver = stream.ReadByte();
        if (ver != DemoVer)
        {
            Console.Print($"Demo version mismatch, expected {DemoVer}, got {ver}");
            stream.Close();
            return false;
        }

        int headerSize = Unsafe.SizeOf<DemoNetworkEventHeader>();
        Span<byte> headerBuffer = stackalloc byte[headerSize];
        while (true)
        {
            {
                int bytesLeftInBuffer = headerSize;
                do
                {
                    int readBytes = stream.Read(headerBuffer.Slice(headerSize - bytesLeftInBuffer, bytesLeftInBuffer));
                    if (readBytes == 0)
                        break;
                    bytesLeftInBuffer -= readBytes;
                } while (bytesLeftInBuffer > 0);

                if (bytesLeftInBuffer > 0)
                    break; // EOF;
            }

            DemoNetworkEventHeader header = MemoryMarshal.Read<DemoNetworkEventHeader>(headerBuffer);

            //buffer.Add(new NetworkEvent());
            //ref NetworkEvent networkEvent = ref buffer[buffer.Length]; // collectionmarshal
            NetworkEvent networkEvent = new NetworkEvent();
            networkEvent.EventType = header.EventType;
            networkEvent.Message.Position = 0;
            networkEvent.Message.MessageId = header.MessageId;
            networkEvent.Message.Length = networkEvent.Message.BufferSize = header.Length;
            networkEvent.Sender.ConnectionId = header.SenderId;

            if (header.Length > 0)
            {
                networkEvent.Message.Buffer = (byte*)NativeMemory.Alloc(header.Length);

                Span<byte> messageBufferSpan = new Span<byte>(networkEvent.Message.Buffer, (int)networkEvent.Message.BufferSize);
                {
                    int bytesLeftInBuffer = (int)header.Length;
                    do
                    {
                        int readBytes = stream.Read(messageBufferSpan.Slice((int)header.Length - bytesLeftInBuffer, bytesLeftInBuffer));
                        if (readBytes == 0)
                            break;
                        bytesLeftInBuffer -= readBytes;
                    } while (bytesLeftInBuffer > 0);

                    if (bytesLeftInBuffer > 0)
                        break; // EOF;
                }
            }
            buffer.Add(networkEvent);
        }

        sw.Stop();

        bufferEnumerable = buffer.GetEnumerator();

        Console.Print($"Demo parse time {sw.Elapsed.TotalMilliseconds}ms, frames: {buffer.Count} ");

        DemoEndFrame(); // advances to first frame
        return true;
    }

    private static void DemoEndFrame()
    {
        // TODO: check if the current state frame matches the current frame number before advancing

        /*asdf++;
        if (asdf < 8)
            return;*/

        if (bufferEnumerable == null || !bufferEnumerable.MoveNext())
        {
            if (buffer.Any())
            {
                bufferEnumerable.Dispose();
                bufferEnumerable = null;
                buffer.Clear();
                Console.Print("Demo ended");
            }

            return;
        }

        //var actorState = currentState.actor;
        //currentState.input = bufferEnumerable.Current;
        //frame++;
        //currentState.actor = actorState;
    }

    private static void OnDemoUpdate()
    {
        if (!IsDemoPlaying)
            return;

        using Utilities.ScopeProfiler _ = Utilities.ProfileScope("NetworkManager_OnDemoUpdate");

        NetworkEvent demoEvent = bufferEnumerable.Current; // ref?

        // TODO: change/randomize Sender.ConnectionId?
        try
        {
            //IsLocalClient = server != null;
            //IsClient = true;
            OnClientReadMessage(ref demoEvent);
        }
        finally
        {
            //IsLocalClient = false;
            //IsClient = false;
            //TODO: recycle event?
        }
        
        DemoEndFrame();
    }
}