AbstractComparisonValidator.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.Validators
{
    using System;
    using System.Linq.Expressions;
    using System.Reflection;
    using Attributes;
    using Internal;
    using Results;

    public abstract class AbstractComparisonValidator : PropertyValidator, IComparisonValidator {

        readonly Func<object, object> valueToCompareFunc;

        protected AbstractComparisonValidator(IComparable value, Expression<Func<string>> errorMessageSelector, string errorCode) : base(errorMessageSelector, errorCode) {
            value.Guard("value must not be null.");
            ValueToCompare = value;
        }

        protected AbstractComparisonValidator(Func<object, object> valueToCompareFunc, MemberInfo member, Expression<Func<string>> errorMessageSelector, string errorCode)
            : base(errorMessageSelector, errorCode) {
            this.valueToCompareFunc = valueToCompareFunc;
            this.MemberToCompare = member;
        }

        protected sealed override bool IsValid(PropertyValidatorContext context) {
            if(context.PropertyValue == null) {
                // If we're working with a nullable type then this rule should not be applied.
                // If you want to ensure that it's never null then a NotNull rule should also be applied. 
                return true;
            }
            
            var value = GetComparisonValue(context);

            if (!IsValid((IComparable)context.PropertyValue, value)) {
                context.MessageFormatter.AppendArgument("ComparisonValue", value);
                return false;
            }

            return true;
        }

        private IComparable GetComparisonValue(PropertyValidatorContext context) {
            if(valueToCompareFunc != null) {
                return (IComparable)valueToCompareFunc(context.Instance);
            }

            return (IComparable)ValueToCompare;
        }

        public abstract bool IsValid(IComparable value, IComparable valueToCompare);
        public abstract Comparison Comparison { get; }
        public MemberInfo MemberToCompare { get; private set; }
        public object ValueToCompare { get; private set; }
    }

    public interface IComparisonValidator : IPropertyValidator {
        Comparison Comparison { get; }
        MemberInfo MemberToCompare { get; }
        object ValueToCompare { get; }
    }

    public enum Comparison {
        Equal,
        NotEqual,
        LessThan,
        GreaterThan,
        GreaterThanOrEqual,
        LessThanOrEqual
    }
}