Extensions.cs

#region License
// Copyright (c) Jeremy Skinner (http://www.jeremyskinner.co.uk)
// 
// Licensed under the Apache License, Version 2.0 (the "License"); 
// you may not use this file except in compliance with the License. 
// You may obtain a copy of the License at 
// 
// http://www.apache.org/licenses/LICENSE-2.0 
// 
// Unless required by applicable law or agreed to in writing, software 
// distributed under the License is distributed on an "AS IS" BASIS, 
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
// See the License for the specific language governing permissions and 
// limitations under the License.
// 
// The latest version of this file can be found at http://www.codeplex.com/FluentValidation
#endregion

namespace ServiceStack.FluentValidation.Internal
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Linq.Expressions;
    using System.Reflection;
    using System.Text.RegularExpressions;
    using Validators;

    /// <summary>
    /// Useful extensions
    /// </summary>
    public static class Extensions {
        internal static void Guard(this object obj, string message) {
            if (obj == null) {
                throw new ArgumentNullException(message);
            }
        }

        internal static void Guard(this string str, string message) {
            if (string.IsNullOrEmpty(str)) {
                throw new ArgumentNullException(message);
            }
        }

        /// <summary>
        /// Gets a MemberInfo from a member expression.
        /// </summary>
        public static MemberInfo GetMember(this LambdaExpression expression) {
            var memberExp = RemoveUnary(expression.Body);

            if (memberExp == null) {
                return null;
            }

            return memberExp.Member;
        }

        /// <summary>
        /// Gets a MemberInfo from a member expression.
        /// </summary>
        public static MemberInfo GetMember<T, TProperty>(this Expression<Func<T, TProperty>> expression) {
            var memberExp = RemoveUnary(expression.Body);

            if (memberExp == null) {
                return null;
            }

            return memberExp.Member;
        }

        private static MemberExpression RemoveUnary(Expression toUnwrap) {
            if (toUnwrap is UnaryExpression) {
                return ((UnaryExpression)toUnwrap).Operand as MemberExpression;
            }

            return toUnwrap as MemberExpression;
        }


        /// <summary>
        /// Splits pascal case, so "FooBar" would become "Foo Bar"
        /// </summary>
        public static string SplitPascalCase(this string input) {
            if (string.IsNullOrEmpty(input)) {
                return input;
            }
            return Regex.Replace(input, "([A-Z])", " $1").Trim();
        }
        /// <summary>
        /// Helper method to construct a constant expression from a constant.
        /// </summary>
        /// <typeparam name="T">Type of object being validated</typeparam>
        /// <typeparam name="TProperty">Type of property being validated</typeparam>
        /// <param name="valueToCompare">The value being compared</param>
        /// <returns></returns>
        internal static Expression<Func<T, TProperty>> GetConstantExpresionFromConstant<T, TProperty>(TProperty valueToCompare) {
            Expression constant = Expression.Constant(valueToCompare, typeof(TProperty));
            ParameterExpression parameter = Expression.Parameter(typeof(T), "t");
            return Expression.Lambda<Func<T, TProperty>>(constant, parameter);
        }

        internal static void ForEach<T>(this IEnumerable<T> source, Action<T> action) {
            foreach(var item in source) {
                action(item);	
            }
        }

        /// <summary>
        /// Based on a child validator and a propery rule, infers whether the validator should be wrapped in a ChildValidatorAdaptor or a CollectionValidatorAdaptor
        /// </summary>
        internal static IPropertyValidator InferPropertyValidatorForChildValidator(PropertyRule rule, IValidator childValidator) {
            // If the property implements IEnumerable<T> and the validator validates T, assume it's a collection property validator
            // This is here for backwards compatibility with v2. V3 uses the new SetCollectionValidator method.
            if (DoesImplementCompatibleIEnumerable(rule.TypeToValidate, childValidator)) {
                return new ChildCollectionValidatorAdaptor(childValidator);
            }

            // Otherwise if the validator is allowed to validate the type, assume child validator
            if (childValidator.CanValidateInstancesOfType(rule.TypeToValidate)) {
                return new ChildValidatorAdaptor(childValidator);
            }

            throw new InvalidOperationException(string.Format("The validator '{0}' cannot validate members of type '{1}' - the types are not compatible.", childValidator.GetType().Name, rule.TypeToValidate.Name));
        }

        private static bool DoesImplementCompatibleIEnumerable(Type propertyType, IValidator childValidator) {
            //concatenate the property type itself, incase we're using IEnumerable directly (typeof(IEnumerable).GetInterfaces() obviously doesn't include IEnumerable)
            var interfaces = from i in propertyType.GetInterfaces().Concat(new[] { propertyType })
                             where i.IsGenericType
                             where i.GetGenericTypeDefinition() == typeof(IEnumerable<>)
                             let enumerableType = i.GetGenericArguments()[0]
                             where childValidator.CanValidateInstancesOfType(enumerableType)
                             select i;

            return interfaces.Any();
        }

        public static Func<object, object> CoerceToNonGeneric<T, TProperty>(this Func<T, TProperty> func) {
            return x => func((T)x);
        } 

        public static Func<object, bool> CoerceToNonGeneric<T>(this Func<T, bool> func) {
            return x => func((T)x);
        }

        public static Action<object> CoerceToNonGeneric<T>(this Action<T> action) {
            return x => action((T)x);
        }

#if WINDOWS_PHONE
        // WP7 doesn't support expression tree compilation.
        // As a workaround, this extension method falls back to delegate compilation. 
        // However, it only supports simple property references, ie x => x.SomeProperty

        internal static TDelegate Compile<TDelegate>(this Expression<TDelegate> expression) {
            var compiledDelegate = CompilePropertyGetterExpression(expression, typeof(TDelegate));
            return (TDelegate)compiledDelegate;
        }

        static object CompilePropertyGetterExpression(LambdaExpression expression, Type delegateType) {
            var member = expression.GetMember() as PropertyInfo;

            if (member == null) {
                throw new NotSupportedException("FluentValidation for WP7 can only be used with expressions that reference public properties, ie x => x.SomeProperty");
            }

            var compiledDelegate = Delegate.CreateDelegate(delegateType, member.GetGetMethod());
            return compiledDelegate;
        }
#endif
    }
}