// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Linq;
using System.Reflection;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Mvc.Core;
using Microsoft.Extensions.DependencyInjection;
 
namespace Microsoft.AspNetCore.Mvc.Filters;
 
/// <summary>
/// Calls into user provided 'Configure' methods for configuring a middleware pipeline. The semantics of finding
/// the 'Configure' methods is similar to the application Startup class.
/// </summary>
internal sealed class MiddlewareFilterConfigurationProvider
{
    public static Action<IApplicationBuilder> CreateConfigureDelegate(Type configurationType)
    {
        ArgumentNullException.ThrowIfNull(configurationType);
 
        if (!HasParameterlessConstructor(configurationType))
        {
            throw new InvalidOperationException(
                Resources.FormatMiddlewareFilterConfigurationProvider_CreateConfigureDelegate_CannotCreateType(configurationType, nameof(configurationType)));
        }
 
        var instance = Activator.CreateInstance(configurationType)!;
        var configureDelegateBuilder = GetConfigureDelegateBuilder(configurationType);
        return configureDelegateBuilder.Build(instance);
    }
 
    private static ConfigureBuilder GetConfigureDelegateBuilder(Type startupType)
    {
        var configureMethod = FindMethod(startupType, typeof(void));
        return new ConfigureBuilder(configureMethod);
    }
 
    private static MethodInfo FindMethod(Type startupType, Type returnType)
    {
        var methodName = "Configure";
 
        var methods = startupType.GetMethods(BindingFlags.Public | BindingFlags.Instance | BindingFlags.Static);
        var selectedMethods = methods.Where(method => method.Name.Equals(methodName)).ToList();
        if (selectedMethods.Count > 1)
        {
            throw new InvalidOperationException(
                Resources.FormatMiddewareFilter_ConfigureMethodOverload(methodName));
        }
 
        var methodInfo = selectedMethods.FirstOrDefault();
        if (methodInfo == null)
        {
            throw new InvalidOperationException(
                Resources.FormatMiddewareFilter_NoConfigureMethod(
                    methodName,
                    startupType.FullName));
        }
 
        if (methodInfo.ReturnType != returnType)
        {
            throw new InvalidOperationException(
                Resources.FormatMiddlewareFilter_InvalidConfigureReturnType(
                    methodInfo.Name,
                    startupType.FullName,
                    returnType.Name));
        }
        return methodInfo;
    }
 
    private static bool HasParameterlessConstructor(Type modelType)
    {
        return !modelType.IsAbstract && modelType.GetConstructor(Type.EmptyTypes) != null;
    }
 
    private sealed class ConfigureBuilder
    {
        public ConfigureBuilder(MethodInfo configure)
        {
            MethodInfo = configure;
        }
 
        public MethodInfo MethodInfo { get; }
 
        public Action<IApplicationBuilder> Build(object instance)
        {
            return (applicationBuilder) => Invoke(instance, applicationBuilder);
        }
 
        private void Invoke(object instance, IApplicationBuilder builder)
        {
            var serviceProvider = builder.ApplicationServices;
            var parameterInfos = MethodInfo.GetParameters();
            var parameters = new object[parameterInfos.Length];
            for (var index = 0; index < parameterInfos.Length; index++)
            {
                var parameterInfo = parameterInfos[index];
                if (parameterInfo.ParameterType == typeof(IApplicationBuilder))
                {
                    parameters[index] = builder;
                }
                else
                {
                    try
                    {
                        parameters[index] = serviceProvider.GetRequiredService(parameterInfo.ParameterType);
                    }
                    catch (Exception ex)
                    {
                        throw new InvalidOperationException(
                            Resources.FormatMiddlewareFilter_ServiceResolutionFail(
                                parameterInfo.ParameterType.FullName,
                                parameterInfo.Name,
                                MethodInfo.Name,
                                MethodInfo.DeclaringType!.FullName),
                            ex);
                    }
                }
            }
            MethodInfo.Invoke(instance, parameters);
        }
    }
}