/* ****************************************************************************
 *
 * Copyright (c) Microsoft Corporation. All rights reserved.
 *
 * This software is subject to the Microsoft Public License (Ms-PL). 
 * A copy of the license can be found in the license.htm file included 
 * in this distribution.
 *
 * You must not remove this notice, or any other, from this software.
 *
 * ***************************************************************************/

namespace System.Web.Mvc {
    using System;
    using System.Collections.Generic;
    using System.Globalization;
    using System.Linq;
    using System.Reflection;
    using System.Web.Mvc.Resources;

    public class ReflectedActionDescriptor : ActionDescriptor {

        private readonly static ActionMethodDispatcherCache _staticDispatcherCache = new ActionMethodDispatcherCache();
        private ActionMethodDispatcherCache _instanceDispatcherCache;

        private readonly string _actionName;
        private readonly ControllerDescriptor _controllerDescriptor;
        private ParameterDescriptor[] _parametersCache;

        public ReflectedActionDescriptor(MethodInfo methodInfo, string actionName, ControllerDescriptor controllerDescriptor)
            : this(methodInfo, actionName, controllerDescriptor, true /* validateMethod */) {
        }

        internal ReflectedActionDescriptor(MethodInfo methodInfo, string actionName, ControllerDescriptor controllerDescriptor, bool validateMethod) {
            if (methodInfo == null) {
                throw new ArgumentNullException("methodInfo");
            }
            if (String.IsNullOrEmpty(actionName)) {
                throw new ArgumentException(MvcResources.Common_NullOrEmpty, "actionName");
            }
            if (controllerDescriptor == null) {
                throw new ArgumentNullException("controllerDescriptor");
            }

            if (validateMethod) {
                string failedMessage = VerifyActionMethodIsCallable(methodInfo);
                if (failedMessage != null) {
                    throw new ArgumentException(failedMessage, "methodInfo");
                }
            }

            MethodInfo = methodInfo;
            _actionName = actionName;
            _controllerDescriptor = controllerDescriptor;
        }

        public override string ActionName {
            get {
                return _actionName;
            }
        }

        public override ControllerDescriptor ControllerDescriptor {
            get {
                return _controllerDescriptor;
            }
        }

        internal ActionMethodDispatcherCache DispatcherCache {
            get {
                if (_instanceDispatcherCache == null) {
                    _instanceDispatcherCache = _staticDispatcherCache;
                }
                return _instanceDispatcherCache;
            }
            set {
                _instanceDispatcherCache = value;
            }
        }

        public MethodInfo MethodInfo {
            get;
            private set;
        }

        public override object Execute(ControllerContext controllerContext, IDictionary<string, object> parameters) {
            if (controllerContext == null) {
                throw new ArgumentNullException("controllerContext");
            }
            if (parameters == null) {
                throw new ArgumentNullException("parameters");
            }

            ParameterInfo[] parameterInfos = MethodInfo.GetParameters();
            var rawParameterValues = from parameterInfo in parameterInfos
                                     select ExtractParameterFromDictionary(parameterInfo, parameters, MethodInfo);
            object[] parametersArray = rawParameterValues.ToArray();

            ActionMethodDispatcher dispatcher = DispatcherCache.GetDispatcher(MethodInfo);
            object actionReturnValue = dispatcher.Execute(controllerContext.Controller, parametersArray);
            return actionReturnValue;
        }

        private static object ExtractParameterFromDictionary(ParameterInfo parameterInfo, IDictionary<string, object> parameters, MethodInfo methodInfo) {
            object value;

            if (!parameters.TryGetValue(parameterInfo.Name, out value)) {
                // the key should always be present, even if the parameter value is null
                string message = String.Format(CultureInfo.CurrentUICulture, MvcResources.ReflectedActionDescriptor_ParameterNotInDictionary,
                    parameterInfo.Name, parameterInfo.ParameterType, methodInfo, methodInfo.DeclaringType);
                throw new ArgumentException(message, "parameters");
            }

            if (value == null && !TypeHelpers.TypeAllowsNullValue(parameterInfo.ParameterType)) {
                // tried to pass a null value for a non-nullable parameter type
                string message = String.Format(CultureInfo.CurrentUICulture, MvcResources.ReflectedActionDescriptor_ParameterCannotBeNull,
                    parameterInfo.Name, parameterInfo.ParameterType, methodInfo, methodInfo.DeclaringType);
                throw new ArgumentException(message, "parameters");
            }

            if (value != null && !parameterInfo.ParameterType.IsInstanceOfType(value)) {
                // value was supplied but is not of the proper type
                string message = String.Format(CultureInfo.CurrentUICulture, MvcResources.ReflectedActionDescriptor_ParameterValueHasWrongType,
                    parameterInfo.Name, methodInfo, methodInfo.DeclaringType, value.GetType(), parameterInfo.ParameterType);
                throw new ArgumentException(message, "parameters");
            }

            return value;
        }

        public override object[] GetCustomAttributes(bool inherit) {
            return MethodInfo.GetCustomAttributes(inherit);
        }

        public override object[] GetCustomAttributes(Type attributeType, bool inherit) {
            return MethodInfo.GetCustomAttributes(attributeType, inherit);
        }

        public override FilterInfo GetFilters() {
            // Enumerable.OrderBy() is a stable sort, so this method preserves scope ordering.
            FilterAttribute[] typeFilters = (FilterAttribute[])MethodInfo.ReflectedType.GetCustomAttributes(typeof(FilterAttribute), true /* inherit */);
            FilterAttribute[] methodFilters = (FilterAttribute[])MethodInfo.GetCustomAttributes(typeof(FilterAttribute), true /* inherit */);
            List<FilterAttribute> orderedFilters = typeFilters.Concat(methodFilters).OrderBy(attr => attr.Order).ToList();

            FilterInfo filterInfo = new FilterInfo();
            MergeFiltersIntoList(orderedFilters, filterInfo.ActionFilters);
            MergeFiltersIntoList(orderedFilters, filterInfo.AuthorizationFilters);
            MergeFiltersIntoList(orderedFilters, filterInfo.ExceptionFilters);
            MergeFiltersIntoList(orderedFilters, filterInfo.ResultFilters);
            return filterInfo;
        }

        public override ParameterDescriptor[] GetParameters() {
            ParameterDescriptor[] parameters = LazilyFetchParametersCollection();

            // need to clone array so that user modifications aren't accidentally stored
            return (ParameterDescriptor[])parameters.Clone();
        }

        public override ICollection<ActionSelector> GetSelectors() {
            ActionMethodSelectorAttribute[] attrs = (ActionMethodSelectorAttribute[])MethodInfo.GetCustomAttributes(typeof(ActionMethodSelectorAttribute), true /* inherit */);
            ActionSelector[] selectors = Array.ConvertAll(attrs, attr => (ActionSelector)(controllerContext => attr.IsValidForRequest(controllerContext, MethodInfo)));
            return selectors;
        }

        public override bool IsDefined(Type attributeType, bool inherit) {
            return MethodInfo.IsDefined(attributeType, inherit);
        }

        private ParameterDescriptor[] LazilyFetchParametersCollection() {
            return DescriptorUtil.LazilyFetchOrCreateDescriptors<ParameterInfo, ParameterDescriptor>(
                ref _parametersCache /* cacheLocation */,
                MethodInfo.GetParameters /* initializer */,
                parameterInfo => new ReflectedParameterDescriptor(parameterInfo, this) /* converter */);
        }

        private static void MergeFiltersIntoList<TFilter>(IList<FilterAttribute> allFilters, IList<TFilter> destFilters) where TFilter : class {
            foreach (FilterAttribute filter in allFilters) {
                TFilter castFilter = filter as TFilter;
                if (castFilter != null) {
                    destFilters.Add(castFilter);
                }
            }
        }

        internal static ReflectedActionDescriptor TryCreateDescriptor(MethodInfo methodInfo, string name, ControllerDescriptor controllerDescriptor) {
            ReflectedActionDescriptor descriptor = new ReflectedActionDescriptor(methodInfo, name, controllerDescriptor, false /* validateMethod */);
            string failedMessage = VerifyActionMethodIsCallable(methodInfo);
            return (failedMessage == null) ? descriptor : null;
        }

        private static string VerifyActionMethodIsCallable(MethodInfo methodInfo) {
            // we can't call instance methods where the 'this' parameter is a type other than ControllerBase
            if (!methodInfo.IsStatic && !typeof(ControllerBase).IsAssignableFrom(methodInfo.ReflectedType)) {
                return String.Format(CultureInfo.CurrentUICulture, MvcResources.ReflectedActionDescriptor_CannotCallInstanceMethodOnNonControllerType,
                    methodInfo, methodInfo.ReflectedType.FullName);
            }

            // we can't call methods with open generic type parameters
            if (methodInfo.ContainsGenericParameters) {
                return String.Format(CultureInfo.CurrentUICulture, MvcResources.ReflectedActionDescriptor_CannotCallOpenGenericMethods,
                    methodInfo, methodInfo.ReflectedType.FullName);
            }

            // we can't call methods with ref/out parameters
            ParameterInfo[] parameterInfos = methodInfo.GetParameters();
            foreach (ParameterInfo parameterInfo in parameterInfos) {
                if (parameterInfo.IsOut || parameterInfo.ParameterType.IsByRef) {
                    return String.Format(CultureInfo.CurrentUICulture, MvcResources.ReflectedActionDescriptor_CannotCallMethodsWithOutOrRefParameters,
                        methodInfo, methodInfo.ReflectedType.FullName, parameterInfo);
                }
            }

            // we can call this method
            return null;
        }

    }
}