// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Diagnostics.CodeAnalysis;
 
namespace System.Reflection
{
    /// <summary>
    /// DispatchProxy provides a mechanism for the instantiation of proxy objects and handling of
    /// their method dispatch.
    /// </summary>
    public abstract class DispatchProxy
    {
        protected DispatchProxy()
        {
        }
 
        /// <summary>
        /// Whenever any method on the generated proxy type is called, this method
        /// will be invoked to dispatch control.
        /// </summary>
        /// <param name="targetMethod">The method the caller invoked</param>
        /// <param name="args">The arguments the caller passed to the method</param>
        /// <returns>The object to return to the caller, or <c>null</c> for void methods</returns>
        protected abstract object? Invoke(MethodInfo? targetMethod, object?[]? args);
 
        /// <summary>
        /// Creates an object instance that derives from class <typeparamref name="TProxy"/>
        /// and implements interface <typeparamref name="T"/>.
        /// </summary>
        /// <typeparam name="T">The interface the proxy should implement.</typeparam>
        /// <typeparam name="TProxy">The base class to use for the proxy class.</typeparam>
        /// <returns>An object instance that implements <typeparamref name="T"/>.</returns>
        /// <exception cref="System.ArgumentException"><typeparamref name="T"/> is a class,
        /// or <typeparamref name="TProxy"/> is sealed or does not have a parameterless constructor</exception>
        //
        // https://github.com/dotnet/runtime/issues/73136 - we can remove the RequiresDynamicCode annotation.
        // This has been done AOT-safely with .NET Native in the past.
        [RequiresDynamicCode("Creating a proxy instance requires generating code at runtime")]
        public static T Create<[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.All)] T, [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)] TProxy>()
            where TProxy : DispatchProxy
        {
            return (T)DispatchProxyGenerator.CreateProxyInstance(typeof(TProxy), typeof(T), "T", "TProxy");
        }
 
        /// <summary>
        /// Creates an object instance that derives from class <paramref name="proxyType"/>
        /// and implements interface <paramref name="interfaceType"/>.
        /// </summary>
        /// <param name="interfaceType">The interface the proxy should implement.</param>
        /// <param name="proxyType">The base class to use for the proxy class.</param>
        /// <returns>An object instance that implements <paramref name="interfaceType"/>.</returns>
        /// <exception cref="System.ArgumentNullException"><paramref name="interfaceType"/> or <paramref name="proxyType"/> is null</exception>
        /// <exception cref="System.ArgumentException"><paramref name="interfaceType"/> is a class,
        /// or <paramref name="proxyType"/> is sealed or abstract or does not inherited from the <see cref="System.Reflection.DispatchProxy"/>
        /// type or have a parameterless constructor</exception>
        [RequiresDynamicCode("Creating a proxy instance requires generating code at runtime")]
        public static object Create([DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.All)] Type interfaceType, [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)] Type proxyType)
        {
            ArgumentNullException.ThrowIfNull(interfaceType);
            ArgumentNullException.ThrowIfNull(proxyType);
 
            if (!proxyType.IsAssignableTo(typeof(DispatchProxy)))
            {
                throw new ArgumentException(SR.Format(SR.ProxyType_Must_Be_Derived_From_DispatchProxy, proxyType.Name), nameof(proxyType));
            }
 
            return DispatchProxyGenerator.CreateProxyInstance(proxyType, interfaceType, "interfaceType", "proxyType");
        }
    }
}