/// <summary>
    /// A model for configuring controllers in an MVC application.
    /// </summary>
    [DebuggerDisplay("ApplicationModel: Controllers: {Controllers.Count}, Filters: {Filters.Count}")]
    public class ApplicationModel : IPropertyModel, IFilterModel, IApiExplorerModel
    {
        /// <summary>
        /// Initializes a new instance of <see cref="ApplicationModel"/>.
        /// </summary>
        public ApplicationModel()
        {
            ApiExplorer = new ApiExplorerModel();
            Controllers = new List<ControllerModel>();
            Filters = new List<IFilterMetadata>();
            Properties = new Dictionary<object, object>();
        }

        /// <summary>
        /// Gets or sets the <see cref="ApiExplorerModel"/> for the application.
        /// </summary>
        /// <remarks>
        /// <see cref="ApplicationModel.ApiExplorer"/> allows configuration of default settings
        /// for ApiExplorer that apply to all actions unless overridden by 
        /// <see cref="ControllerModel.ApiExplorer"/> or <see cref="ActionModel.ApiExplorer"/>.
        /// 
        /// If using <see cref="ApplicationModel.ApiExplorer"/> to set <see cref="ApiExplorerModel.IsVisible"/> to
        /// <c>true</c>, this setting will only be honored for actions which use attribute routing.
        /// </remarks>
        public ApiExplorerModel ApiExplorer { get; set; }

        /// <summary>
        /// Gets the <see cref="ControllerModel"/> instances.
        /// </summary>
        public IList<ControllerModel> Controllers { get; }

        /// <summary>
        /// Gets the global <see cref="IFilterMetadata"/> instances.
        /// </summary>
        public IList<IFilterMetadata> Filters { get; }

        /// <summary>
        /// Gets a set of properties associated with all actions.
        /// These properties will be copied to <see cref="Abstractions.ActionDescriptor.Properties"/>.
        /// </summary>
        public IDictionary<object, object> Properties { get; }
    }

public void OnProvidersExecuting(ApplicationModelProviderContext context)
        {
            if (context == null)
            {
                throw new ArgumentNullException(nameof(context));
            }

            foreach (var filter in _mvcOptions.Filters)
            {
                context.Result.Filters.Add(filter);
            }

            foreach (var controllerType in context.ControllerTypes)
            {
                var controllerModel = CreateControllerModel(controllerType);
                if (controllerModel == null)
                {
                    continue;
                }

                context.Result.Controllers.Add(controllerModel);
                controllerModel.Application = context.Result;

                foreach (var propertyHelper in PropertyHelper.GetProperties(controllerType.AsType()))
                {
                    var propertyInfo = propertyHelper.Property;
                    var propertyModel = CreatePropertyModel(propertyInfo);
                    if (propertyModel != null)
                    {
                        propertyModel.Controller = controllerModel;
                        controllerModel.ControllerProperties.Add(propertyModel);
                    }
                }

                foreach (var methodInfo in controllerType.AsType().GetMethods())
                {
                    var actionModel = CreateActionModel(controllerType, methodInfo);
                    if (actionModel == null)
                    {
                        continue;
                    }

                    actionModel.Controller = controllerModel;
                    controllerModel.Actions.Add(actionModel);

                    foreach (var parameterInfo in actionModel.ActionMethod.GetParameters())
                    {
                        var parameterModel = CreateParameterModel(parameterInfo);
                        if (parameterModel != null)
                        {
                            parameterModel.Action = actionModel;
                            actionModel.Parameters.Add(parameterModel);
                        }
                    }
                }
            }
        }

internal ControllerModel CreateControllerModel(TypeInfo typeInfo)
        {
            if (typeInfo == null)
            {
                throw new ArgumentNullException(nameof(typeInfo));
            }

            // For attribute routes on a controller, we want to support 'overriding' routes on a derived
            // class. So we need to walk up the hierarchy looking for the first class to define routes.
            //
            // Then we want to 'filter' the set of attributes, so that only the effective routes apply.
            var currentTypeInfo = typeInfo;
            var objectTypeInfo = typeof(object).GetTypeInfo();

            IRouteTemplateProvider[] routeAttributes;

            do
            {
                routeAttributes = currentTypeInfo
                    .GetCustomAttributes(inherit: false)
                    .OfType<IRouteTemplateProvider>()
                    .ToArray();

                if (routeAttributes.Length > 0)
                {
                    // Found 1 or more route attributes.
                    break;
                }

                currentTypeInfo = currentTypeInfo.BaseType.GetTypeInfo();
            }
            while (currentTypeInfo != objectTypeInfo);

            // CoreCLR returns IEnumerable<Attribute> from GetCustomAttributes - the OfType<object>
            // is needed to so that the result of ToArray() is object
            var attributes = typeInfo.GetCustomAttributes(inherit: true);

            // This is fairly complicated so that we maintain referential equality between items in
            // ControllerModel.Attributes and ControllerModel.Attributes[*].Attribute.
            var filteredAttributes = new List<object>();
            foreach (var attribute in attributes)
            {
                if (attribute is IRouteTemplateProvider)
                {
                    // This attribute is a route-attribute, leave it out.
                }
                else
                {
                    filteredAttributes.Add(attribute);
                }
            }

            filteredAttributes.AddRange(routeAttributes);

            attributes = filteredAttributes.ToArray();

            var controllerModel = new ControllerModel(typeInfo, attributes);

            AddRange(controllerModel.Selectors, CreateSelectors(attributes));

            controllerModel.ControllerName =
                typeInfo.Name.EndsWith("Controller", StringComparison.OrdinalIgnoreCase) ?
                    typeInfo.Name.Substring(0, typeInfo.Name.Length - "Controller".Length) :
                    typeInfo.Name;

            AddRange(controllerModel.Filters, attributes.OfType<IFilterMetadata>());

            foreach (var routeValueProvider in attributes.OfType<IRouteValueProvider>())
            {
                controllerModel.RouteValues.Add(routeValueProvider.RouteKey, routeValueProvider.RouteValue);
            }

            var apiVisibility = attributes.OfType<IApiDescriptionVisibilityProvider>().FirstOrDefault();
            if (apiVisibility != null)
            {
                controllerModel.ApiExplorer.IsVisible = !apiVisibility.IgnoreApi;
            }

            var apiGroupName = attributes.OfType<IApiDescriptionGroupNameProvider>().FirstOrDefault();
            if (apiGroupName != null)
            {
                controllerModel.ApiExplorer.GroupName = apiGroupName.GroupName;
            }

            // Controllers can implement action filter and result filter interfaces. We add
            // a special delegating filter implementation to the pipeline to handle it.
            //
            // This is needed because filters are instantiated before the controller.
            if (typeof(IAsyncActionFilter).GetTypeInfo().IsAssignableFrom(typeInfo) ||
                typeof(IActionFilter).GetTypeInfo().IsAssignableFrom(typeInfo))
            {
                controllerModel.Filters.Add(new ControllerActionFilter());
            }
            if (typeof(IAsyncResultFilter).GetTypeInfo().IsAssignableFrom(typeInfo) ||
                typeof(IResultFilter).GetTypeInfo().IsAssignableFrom(typeInfo))
            {
                controllerModel.Filters.Add(new ControllerResultFilter());
            }

            return controllerModel;
        }

internal PropertyModel CreatePropertyModel(PropertyInfo propertyInfo)
        {
            if (propertyInfo == null)
            {
                throw new ArgumentNullException(nameof(propertyInfo));
            }

            var attributes = propertyInfo.GetCustomAttributes(inherit: true);

            // BindingInfo for properties can be either specified by decorating the property with binding specific attributes.
            // ModelMetadata also adds information from the property's type and any configured IBindingMetadataProvider.
            var modelMetadata = _modelMetadataProvider.GetMetadataForProperty(propertyInfo.DeclaringType, propertyInfo.Name);
            var bindingInfo = BindingInfo.GetBindingInfo(attributes, modelMetadata);

            if (bindingInfo == null)
            {
                // Look for BindPropertiesAttribute on the handler type if no BindingInfo was inferred for the property.
                // This allows a user to enable model binding on properties by decorating the controller type with BindPropertiesAttribute.
                var declaringType = propertyInfo.DeclaringType;
                var bindPropertiesAttribute = declaringType.GetCustomAttribute<BindPropertiesAttribute>(inherit: true);
                if (bindPropertiesAttribute != null)
                {
                    var requestPredicate = bindPropertiesAttribute.SupportsGet ? _supportsAllRequests : _supportsNonGetRequests;
                    bindingInfo = new BindingInfo
                    {
                        RequestPredicate = requestPredicate,
                    };
                }
            }

            var propertyModel = new PropertyModel(propertyInfo, attributes)
            {
                PropertyName = propertyInfo.Name,
                BindingInfo = bindingInfo,
            };

            return propertyModel;
        }

internal ActionModel CreateActionModel(
            TypeInfo typeInfo,
            MethodInfo methodInfo)
        {
            if (typeInfo == null)
            {
                throw new ArgumentNullException(nameof(typeInfo));
            }

            if (methodInfo == null)
            {
                throw new ArgumentNullException(nameof(methodInfo));
            }

            if (!IsAction(typeInfo, methodInfo))
            {
                return null;
            }

            // CoreCLR returns IEnumerable<Attribute> from GetCustomAttributes - the OfType<object>
            // is needed to so that the result of ToArray() is object
            var attributes = methodInfo.GetCustomAttributes(inherit: true);

            var actionModel = new ActionModel(methodInfo, attributes);

            AddRange(actionModel.Filters, attributes.OfType<IFilterMetadata>());

            var actionName = attributes.OfType<ActionNameAttribute>().FirstOrDefault();
            if (actionName?.Name != null)
            {
                actionModel.ActionName = actionName.Name;
            }
            else
            {
                actionModel.ActionName = CanonicalizeActionName(methodInfo.Name);
            }

            var apiVisibility = attributes.OfType<IApiDescriptionVisibilityProvider>().FirstOrDefault();
            if (apiVisibility != null)
            {
                actionModel.ApiExplorer.IsVisible = !apiVisibility.IgnoreApi;
            }

            var apiGroupName = attributes.OfType<IApiDescriptionGroupNameProvider>().FirstOrDefault();
            if (apiGroupName != null)
            {
                actionModel.ApiExplorer.GroupName = apiGroupName.GroupName;
            }

            foreach (var routeValueProvider in attributes.OfType<IRouteValueProvider>())
            {
                actionModel.RouteValues.Add(routeValueProvider.RouteKey, routeValueProvider.RouteValue);
            }

            // Now we need to determine the action selection info (cross-section of routes and constraints)
            //
            // For attribute routes on a action, we want to support 'overriding' routes on a
            // virtual method, but allow 'overriding'. So we need to walk up the hierarchy looking
            // for the first definition to define routes.
            //
            // Then we want to 'filter' the set of attributes, so that only the effective routes apply.
            var currentMethodInfo = methodInfo;

            IRouteTemplateProvider[] routeAttributes;

            while (true)
            {
                routeAttributes = currentMethodInfo
                    .GetCustomAttributes(inherit: false)
                    .OfType<IRouteTemplateProvider>()
                    .ToArray();

                if (routeAttributes.Length > 0)
                {
                    // Found 1 or more route attributes.
                    break;
                }

                // GetBaseDefinition returns 'this' when it gets to the bottom of the chain.
                var nextMethodInfo = currentMethodInfo.GetBaseDefinition();
                if (currentMethodInfo == nextMethodInfo)
                {
                    break;
                }

                currentMethodInfo = nextMethodInfo;
            }

            // This is fairly complicated so that we maintain referential equality between items in
            // ActionModel.Attributes and ActionModel.Attributes[*].Attribute.
            var applicableAttributes = new List<object>();
            foreach (var attribute in attributes)
            {
                if (attribute is IRouteTemplateProvider)
                {
                    // This attribute is a route-attribute, leave it out.
                }
                else
                {
                    applicableAttributes.Add(attribute);
                }
            }

            applicableAttributes.AddRange(routeAttributes);
            AddRange(actionModel.Selectors, CreateSelectors(applicableAttributes));

            return actionModel;
        }

internal ParameterModel CreateParameterModel(ParameterInfo parameterInfo)
        {
            if (parameterInfo == null)
            {
                throw new ArgumentNullException(nameof(parameterInfo));
            }

            var attributes = parameterInfo.GetCustomAttributes(inherit: true);

            BindingInfo bindingInfo;
            if (_modelMetadataProvider is ModelMetadataProvider modelMetadataProviderBase)
            {
                var modelMetadata = modelMetadataProviderBase.GetMetadataForParameter(parameterInfo);
                bindingInfo = BindingInfo.GetBindingInfo(attributes, modelMetadata);
            }
            else
            {
                // GetMetadataForParameter should only be used if the user has opted in to the 2.1 behavior.
                bindingInfo = BindingInfo.GetBindingInfo(attributes);
            }

            var parameterModel = new ParameterModel(parameterInfo, attributes)
            {
                ParameterName = parameterInfo.Name,
                BindingInfo = bindingInfo,
            };

            return parameterModel;
        }