esiur-dotnet/Esiur/Proxy/ResourceProxy.cs

using Esiur.Data;
using Esiur.Resource;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Reflection.Emit;
using System.Text;

namespace Esiur.Proxy;
public static class ResourceProxy
{
    static Dictionary<Type, Type> cache = new Dictionary<Type, Type>();

#if NETSTANDARD
    static MethodInfo modifyMethod = typeof(Instance).GetTypeInfo().GetMethod("Modified");
    static MethodInfo instanceGet = typeof(IResource).GetTypeInfo().GetProperty("Instance").GetGetMethod();
#else
        static MethodInfo modifyMethod = typeof(Instance).GetMethod("Modified");
        static MethodInfo instanceGet = typeof(IResource).GetProperty("Instance").GetGetMethod();
#endif


    public static Type GetBaseType(object resource)
    {
        return GetBaseType(resource.GetType());
    }

    public static Type GetBaseType(Type type)
    {
        if (type == null)
            throw new NullReferenceException("Type can't be null.");

        if (type.Assembly.IsDynamic)
            return type.GetTypeInfo().BaseType;
        else
            return type;

        //            if (type.FullName.Contains("Esiur.Proxy.T"))
        //#if NETSTANDARD
        //                return type.GetTypeInfo().BaseType;
        //#else
        //            return type.BaseType;
        //#endif
        //            else
        //                return type;
    }

    public static Type GetProxy(Type type)
    {

        if (cache.ContainsKey(type))
            return cache[type];

        // check if the type was made with code generation
        if (type.GetCustomAttribute<ResourceAttribute>(false) != null)
        {
            cache.Add(type, type);
            return type;
        }

        if (!Codec.ImplementsInterface(type, typeof(IResource)))
        {
            cache.Add(type, type);
            return type;
        }

#if NETSTANDARD
        var typeInfo = type.GetTypeInfo();

        if (typeInfo.IsSealed || typeInfo.IsAbstract)
            throw new Exception("Sealed/Abastract classes can't be proxied.");

        var props = from p in typeInfo.GetProperties(BindingFlags.Instance | BindingFlags.Public)
                    where p.CanWrite && p.SetMethod.IsVirtual && !p.SetMethod.IsFinal &&
                    p.GetCustomAttribute<ExportAttribute>(false) != null
                    select p;

#else
            if (type.IsSealed)
                throw new Exception("Sealed class can't be proxied.");

            var props = from p in type.GetProperties()
                where p.CanWrite && p.GetSetMethod().IsVirtual && 
                p.GetCustomAttributes(typeof(ExportAttribute), false).Count() > 0
                select p;

#endif
        var assemblyName = new AssemblyName("Esiur.Proxy.T." + type.Assembly.GetName().Name);// type.Namespace);
        assemblyName.Version = type.Assembly.GetName().Version;
        assemblyName.CultureInfo = type.Assembly.GetName().CultureInfo;
        //assemblyName.SetPublicKeyToken(null);

        var assemblyBuilder = AssemblyBuilder.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.Run);
        var moduleBuilder = assemblyBuilder.DefineDynamicModule(assemblyName.Name);
        var typeName = "Esiur.Proxy.T." + type.FullName;// Assembly.CreateQualifiedName(assemblyName.FullName, "Esiur.Proxy.T." + type.FullName);

        var typeBuilder = moduleBuilder.DefineType(typeName,
            TypeAttributes.Public | TypeAttributes.Class, type);

        foreach (PropertyInfo propertyInfo in props)
            CreateProperty(propertyInfo, typeBuilder, type);



#if NETSTANDARD
        var t = typeBuilder.CreateTypeInfo().AsType();
        cache.Add(type, t);
        return t;
#else
            
            var t = typeBuilder.CreateType();
            cache.Add(type, t);
            return t;
#endif
    }

    public static Type GetProxy<T>()
        where T : IResource
    {
        return GetProxy(typeof(T));
    }



    //private static void C
    private static void CreateProperty(PropertyInfo pi, TypeBuilder typeBuilder, Type resourceType)
    {
        var propertyBuilder = typeBuilder.DefineProperty(pi.Name, PropertyAttributes.None, pi.PropertyType, null);

        // Create set method
        MethodBuilder builder = typeBuilder.DefineMethod("set_" + pi.Name,
            MethodAttributes.Public | MethodAttributes.Virtual, null, new Type[] { pi.PropertyType });
        builder.DefineParameter(1, ParameterAttributes.None, "value");
        ILGenerator g = builder.GetILGenerator();

        var getInstance = resourceType.GetTypeInfo().GetProperty("Instance").GetGetMethod();


        //g.Emit(OpCodes.Ldarg_0);
        //g.Emit(OpCodes.Ldarg_1);
        //g.Emit(OpCodes.Call, pi.GetSetMethod());
        //g.Emit(OpCodes.Nop);

        //g.Emit(OpCodes.Ldarg_0);
        //g.Emit(OpCodes.Call, getInstance);
        //g.Emit(OpCodes.Ldstr, pi.Name);
        //g.Emit(OpCodes.Call, modifyMethod);
        //g.Emit(OpCodes.Nop);

        //g.Emit(OpCodes.Ret);

        Label exitMethod = g.DefineLabel();
        Label callModified = g.DefineLabel();

        g.Emit(OpCodes.Nop);

        g.Emit(OpCodes.Ldarg_0);
        g.Emit(OpCodes.Ldarg_1);
        g.Emit(OpCodes.Call, pi.GetSetMethod());
        g.Emit(OpCodes.Nop);

        g.Emit(OpCodes.Ldarg_0);
        g.Emit(OpCodes.Call, getInstance);
        g.Emit(OpCodes.Dup);

        g.Emit(OpCodes.Brtrue_S, callModified);

        g.Emit(OpCodes.Pop);
        g.Emit(OpCodes.Br_S, exitMethod);

        g.MarkLabel(callModified);

        g.Emit(OpCodes.Ldstr, pi.Name);
        g.Emit(OpCodes.Call, modifyMethod);
        g.Emit(OpCodes.Nop);

        g.MarkLabel(exitMethod);
        g.Emit(OpCodes.Ret);
        propertyBuilder.SetSetMethod(builder);


        builder = typeBuilder.DefineMethod("get_" + pi.Name, MethodAttributes.Public | MethodAttributes.Virtual, pi.PropertyType, null);
        g = builder.GetILGenerator();
        g.Emit(OpCodes.Ldarg_0);
        g.Emit(OpCodes.Call, pi.GetGetMethod());
        g.Emit(OpCodes.Ret);

        propertyBuilder.SetGetMethod(builder);

        // g.Emit(OpCodes.Ldarg_0);
        // g.Emit(OpCodes.Call, pi.GetGetMethod());
        // g.Emit(OpCodes.Ret);

        // propertyBuilder.SetGetMethod(builder);


        /*
        Label callModified = g.DefineLabel();
        Label exitMethod = g.DefineLabel();


         //   IL_0000: ldarg.0
            //IL_0001: call instance class [Esiur]Esiur.Resource.Instance [Esiur]Esiur.Resource.Resource::get_Instance()
            //// (no C# code)
            //IL_0006: dup
            //IL_0007: brtrue.s IL_000c
            //IL_0009: pop
            //// }
            //IL_000a: br.s IL_0017
            //// (no C# code)
            //IL_000c: ldstr "Level3"
            //IL_0011: call instance void [Esiur]Esiur.Resource.Instance::Modified(string)
            //IL_0016: nop
            //IL_0017: ret


        // Add IL code for set method
        g.Emit(OpCodes.Nop);
        g.Emit(OpCodes.Ldarg_0);
        g.Emit(OpCodes.Ldarg_1);
        g.Emit(OpCodes.Call, pi.GetSetMethod());


         //   IL_0000: ldarg.0
           // IL_0001: call instance class [Esiur]Esiur.Resource.Instance [Esiur]Esiur.Resource.Resource::get_Instance()
           // IL_0006: ldstr "Level3"
            //IL_000b: callvirt instance void [Esiur]Esiur.Resource.Instance::Modified(string)
            //IL_0010: ret


        // Call property changed for object
        g.Emit(OpCodes.Nop);
        g.Emit(OpCodes.Ldarg_0);
        g.Emit(OpCodes.Call, instanceGet);

        g.Emit(OpCodes.Dup);
        g.Emit(OpCodes.Brtrue_S, callModified);
        g.Emit(OpCodes.Pop);
        g.Emit(OpCodes.Br_S, exitMethod);

        g.MarkLabel(callModified);
        g.Emit(OpCodes.Ldstr, pi.Name);
        g.Emit(OpCodes.Callvirt, modifyMethod);
        g.Emit(OpCodes.Nop);
        g.MarkLabel(exitMethod);
        g.Emit(OpCodes.Ret);
        propertyBuilder.SetSetMethod(builder);


        // create get method

        */
    }

}