ServerEventsClient.Receiver.cs

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.Runtime.Serialization;
using ServiceStack.Configuration;
using ServiceStack.Logging;
using ServiceStack.Text;

namespace ServiceStack;

public delegate void ServerEventCallback(ServerEventsClient source, ServerEventMessage args);

public class ServerEventReceiver : IReceiver
{
    public static ILog Log = LogManager.GetLogger(typeof(ServerEventReceiver));

    public ServerEventsClient Client { get; set; }
    public ServerEventMessage Request { get; set; }

    public virtual void NoSuchMethod(string selector, object message)
    {
        if (Log.IsDebugEnabled)
            Log.Debug($"NoSuchMethod defined for {selector}");
    }
}

public class NewInstanceResolver : IResolver
{
    public T TryResolve<T>()
    {
        return typeof(T).CreateInstance<T>();
    }
}

public class SingletonInstanceResolver : IResolver
{
    readonly ConcurrentDictionary<Type, object> Cache = new();

    public T TryResolve<T>()
    {
        return (T) Cache.GetOrAdd(typeof (T), type => type.CreateInstance<T>());
    }
}

public partial class ServerEventsClient
{
    public IResolver Resolver { get; set; }

    public ConcurrentDictionary<string, ServerEventCallback> Handlers { get; }
    public ConcurrentDictionary<string, ServerEventCallback> NamedReceivers { get; }
    public List<Type> ReceiverTypes { get; } 
    public bool StrictMode { get; set; }

    public ServerEventsClient RegisterReceiver<T>()
        where T : IReceiver
    {
        return RegisterNamedReceiver<T>("cmd");
    }

    public ServerEventsClient RegisterNamedReceiver<T>(string receiverName)
        where T : IReceiver
    {
        ReceiverExec<T>.Reset();

        lock (NamedReceivers)
        {
            NamedReceivers[receiverName] = CreateReceiverHandler<T>;

            ReceiverTypes.Add(typeof(T));
        }

        return this;
    }

    private void CreateReceiverHandler<T>(ServerEventsClient client, ServerEventMessage msg)
    {
        if (!(Resolver.TryResolve<T>() is IReceiver receiver))
            throw new ArgumentNullException("receiver", "Resolver returned null receiver");

        if (receiver is ServerEventReceiver injectRecevier)
        {
            injectRecevier.Client = client;
            injectRecevier.Request = msg;
        }

        var target = msg.Target.Replace("-", ""); //css bg-image

        ReceiverExec<T>.RequestTypeExecMap.TryGetValue(target, out var receiverCtx);
        if (StrictMode && receiverCtx != null && !receiverCtx.Method.EqualsIgnoreCase(target))
            receiverCtx = null;

        if (receiverCtx == null)
            ReceiverExec<T>.MethodNameExecMap.TryGetValue(target, out receiverCtx);

        if (receiverCtx == null)
        {
            receiver.NoSuchMethod(msg.Target, msg);
            return;
        }

        object requestDto;
        try
        {
            requestDto = string.IsNullOrEmpty(msg.Json)
                ? receiverCtx.RequestType.CreateInstance()
                : JsonSerializer.DeserializeFromString(msg.Json, receiverCtx.RequestType);
        }
        catch (Exception ex)
        {
            throw new SerializationException($"Could not deserialize into '{typeof(T).Name}' from '{msg.Json}'", ex);
        }


        receiverCtx.Exec(receiver, requestDto);
    }
}

internal delegate object ActionInvokerFn(object intance, object request);
internal delegate object ActionNoArgInvokerFn(object intance);
internal delegate void VoidActionInvokerFn(object intance, object request);
internal delegate void VoidActionNoArgInvokerFn(object intance);

internal class ReceiverExecContext
{
    public const string AnyAction = "ANY";
    public string Id { get; set; }
    public Type RequestType { get; set; }
    public Type ServiceType { get; set; }
    public string Method { get; set; }
    public ActionInvokerFn Exec { get; set; }

    public static string Key(string method)
    {
        return method.ToUpper();
    }

    public static string Key(string method, string requestDtoName)
    {
        return method.ToUpper() + " " + requestDtoName;
    }

    public static string AnyKey(string requestDtoName)
    {
        return AnyAction + " " + requestDtoName;
    }
}

internal class ReceiverExec<T>
{
    internal static Dictionary<string, ReceiverExecContext> RequestTypeExecMap;
    internal static Dictionary<string, ReceiverExecContext> MethodNameExecMap;

    public static void Reset()
    {
        RequestTypeExecMap = new Dictionary<string, ReceiverExecContext>(StringComparer.OrdinalIgnoreCase);
        MethodNameExecMap = new Dictionary<string, ReceiverExecContext>(StringComparer.OrdinalIgnoreCase);

        var methods = typeof(T).GetMethods().Where(x => x.IsPublic && !x.IsStatic);
        foreach (var mi in methods)
        {
            var actionName = mi.Name;
            var args = mi.GetParameters();
            if (args.Length > 1) 
                continue;
            if (mi.Name.StartsWith("get_"))
                continue;
            if (mi.DeclaringType == typeof(object))
                continue;
            if (mi.Name == "Equals")
                continue;

            if (actionName.StartsWith("set_"))
                actionName = actionName.Substring("set_".Length);

            if (args.Length == 0)
            {
                var voidExecCtx = new ReceiverExecContext
                {
                    Id = ReceiverExecContext.Key(actionName),
                    ServiceType = typeof(T),
                    RequestType = null,
                    Method = mi.Name
                };
                MethodNameExecMap[actionName] = voidExecCtx;
                voidExecCtx.Exec = CreateExecFn(mi);
                continue;
            }

            var requestType = args[0].ParameterType;
            var execCtx = new ReceiverExecContext
            {
                Id = ReceiverExecContext.Key(actionName, requestType.GetOperationName()),
                ServiceType = typeof(T),
                RequestType = requestType,
                Method = mi.Name
            };

            try
            {
                execCtx.Exec = CreateExecFn(requestType, mi);
            }
            catch
            {
                //Potential problems with MONO, using reflection for fallback
                execCtx.Exec = (receiver, request) =>
                    mi.Invoke(receiver, new[] { request });
            }

            RequestTypeExecMap[requestType.Name] = execCtx;
            MethodNameExecMap[actionName] = execCtx;
        }
    }

    private static ActionInvokerFn CreateExecFn(Type requestType, MethodInfo mi)
    {
        var receiverType = typeof(T);

        var receiverParam = Expression.Parameter(typeof(object), "receiverObj");
        var receiverStrong = Expression.Convert(receiverParam, receiverType);

        var requestDtoParam = Expression.Parameter(typeof(object), "requestDto");
        var requestDtoStrong = Expression.Convert(requestDtoParam, requestType);

        Expression callExecute = Expression.Call(
            receiverStrong, mi, requestDtoStrong);

        if (mi.ReturnType != typeof(void))
        {
            var executeFunc = Expression.Lambda<ActionInvokerFn>
                (callExecute, receiverParam, requestDtoParam).Compile();

            return executeFunc;
        }
        else
        {
            var executeFunc = Expression.Lambda<VoidActionInvokerFn>
                (callExecute, receiverParam, requestDtoParam).Compile();

            return (service, request) =>
            {
                executeFunc(service, request);
                return null;
            };
        }
    }

    private static ActionInvokerFn CreateExecFn(MethodInfo mi)
    {
        var receiverType = typeof(T);

        var receiverParam = Expression.Parameter(typeof(object), "receiverObj");
        var receiverStrong = Expression.Convert(receiverParam, receiverType);

        Expression callExecute = Expression.Call(receiverStrong, mi);

        if (mi.ReturnType != typeof(void))
        {
            var executeFunc = Expression.Lambda<ActionNoArgInvokerFn>
                (callExecute, receiverParam).Compile();

            return (service, request) => executeFunc(service);
        }
        else
        {
            var executeFunc = Expression.Lambda<VoidActionNoArgInvokerFn>
                (callExecute, receiverParam).Compile();

            return (service, request) =>
            {
                executeFunc(service);
                return null;
            };
        }
    }
}