Source

NContracts / NContracts / Contract.cs

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 //Copyright 2011 Felice Pollano

 //  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.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;
using System.Collections.ObjectModel;

namespace NContracts
{
    public interface IContract<T>
    {
        IContract<T> Is<TT>();
        IContract<T> IsEqual<TT>(TT of) where TT : T,IEquatable<TT>;
        IContract<T> IsGreatherThan<TT>(TT of) where TT : T,IComparable;
        IContract<T> IsGreatherThanOrEqual<TT>(TT of) where TT :T, IComparable;
        IContract<T> IsLessThan<TT>(TT of) where TT : T,IComparable;
        IContract<T> IsLessThanOrEq<TT>(TT of) where TT : T,IComparable;
        IContract<T> IsNot<TT>();
        IContract<T> IsNotEqual<TT>(TT of) where TT : T,IEquatable<TT>;
        IContract<T> IsNotNull();
        IContract<T> IsNotTheSameOf(object of);
        IContract<T> IsNull();
        IContract<T> IsTheSameOf(object of);
        IContract<T> Meet(Expression<Predicate<T>> predicate);
    }
    
    public class Contract
    {
        class ContractOn<T> : Contract, IContract<T>
        {
            Func<T> accessor;
            public string Name { get; private set; }
            public ContractOn(Func<T> accessor, string name)
            {
                this.accessor = accessor;
                this.Name = name;
            }
            public IContract<T> IsNotNull()
            {
                if (accessor() == null)
                    throw new ArgumentNullException(Name);
                return this;
            }
            public IContract<T> Is<TT>()
            {
                if (!typeof(TT).IsAssignableFrom(accessor().GetType()))
                    throw new ArgumentException("Type not expected, must be: " + typeof(TT).Name,Name);
                return this;
            }
            public IContract<T> Meet(Expression<Predicate<T>> predicate)
            {
                if (false == (bool)predicate.Compile().DynamicInvoke(accessor()))
                {
                    throw new ArgumentException("Precondition not verified:" + Rename(predicate),Name);
                }
                return this;
            }

            private string Rename(Expression<Predicate<T>> predicate)
            {
                var l = predicate as LambdaExpression;
                if (l != null && l.Parameters.Count > 0)
                {
                    var pnew = PredicateRewriter.Rewrite(predicate, Name);
                    return (pnew as LambdaExpression).Body.ToString();
                }
                else
                {
                    return string.Empty;
                }
            }
            public IContract<T> IsNot<TT>()
            {
                if (typeof(TT).IsAssignableFrom(accessor().GetType()))
                    throw new ArgumentException( "Type not expected, must not be: " + typeof(TT).Name,Name);
                return this;
            }
            public IContract<T> IsTheSameOf(object of)
            {
                if ( !object.ReferenceEquals(accessor(),of) )
                    throw new ArgumentOutOfRangeException(Name, "Not the same as expected");
                return this;
            }
            public IContract<T> IsNotTheSameOf(object of)
            {
                if (object.ReferenceEquals(accessor(), of))
                    throw new ArgumentOutOfRangeException(Name, "Is expected to be different");
                return this;
            }
            public IContract<T> IsNull()
            {
                if (accessor() != null)
                    throw new ArgumentOutOfRangeException(Name, "Must be null");
                return this;
            }
            public IContract<T> IsGreatherThan<TT>(TT of) where TT :T,IComparable
            {
                TT actual = (TT)accessor();
                if (actual.CompareTo(of) <= 0)
                {
                    throw new ArgumentOutOfRangeException(Name, "Must be greather than" + of.ToString());
                }
                return this;
            }

            public IContract<T> IsEqual<TT>(TT of) where TT : T,IEquatable<TT>
            {
                TT actual = (TT)accessor();
                if (!actual.Equals(of))
                {
                    throw new ArgumentOutOfRangeException(Name, "Must be equal to" + of.ToString());
                }
                return this;
            }

            public IContract<T> IsNotEqual<TT>(TT of) where TT : T,IEquatable<TT>
            {
                TT actual = (TT)accessor();
                if (actual.Equals(of))
                {
                    throw new ArgumentOutOfRangeException(Name, "Must not be equal to" + of.ToString());
                }
                return this;
            }

            public IContract<T> IsGreatherThanOrEqual<TT>(TT of) where TT : T,IComparable
            {
                TT actual = (TT)accessor();
                if (actual.CompareTo(of) < 0)
                {
                    throw new ArgumentOutOfRangeException(Name, "Must be greather than or equal" + of.ToString());
                }
                return this;
            }
            public IContract<T> IsLessThan<TT>(TT of) where TT : T,IComparable
            {
                TT actual = (TT)accessor();
                if (actual.CompareTo(of) >= 0)
                {
                    throw new ArgumentOutOfRangeException(Name, "Must be less than" + of.ToString());
                }
                return this;
            }
            public IContract<T> IsLessThanOrEq<TT>(TT of) where TT :T, IComparable
            {
                TT actual = (TT)accessor();
                if (actual.CompareTo(of) > 0)
                {
                    throw new ArgumentOutOfRangeException(Name, "Must be less than or equal" + of.ToString());
                }
                return this;
            }


           
        }

        private Contract()
        {
            
        }

       
       
        public static IContract<T> Expect<T>(Expression<Func<T>> exp)
        {
            if (exp.Body.NodeType == ExpressionType.MemberAccess)
            {
                var name = (exp.Body as MemberExpression).Member.Name;
                return new ContractOn<T>(exp.Compile(), name);
            }
            throw new Exception("Unexpected expression");
        }

        static class  PredicateRewriter
        {
            public static Expression<Predicate<T>> Rewrite<T>(Expression<Predicate<T>> exp, string newParamName)
            {
                var param = Expression.Parameter(exp.Parameters[0].Type, newParamName);
                var newExpression = new PredicateRewriterVisitor(param).Visit(exp);

                return (Expression<Predicate<T>>)newExpression;
            }

            private class PredicateRewriterVisitor : ExpressionVisitor
            {
                private readonly ParameterExpression _parameterExpression;

                public PredicateRewriterVisitor(ParameterExpression parameterExpression)
                {
                    _parameterExpression = parameterExpression;
                }

                protected override Expression VisitParameter(ParameterExpression node)
                {
                    return _parameterExpression;
                }
            }
        }
        //Expression visitor implementation for framework 3.5
        // code from Matt Warren
        // http://blogs.msdn.com/b/mattwar/archive/2007/07/31/linq-building-an-iqueryable-provider-part-ii.aspx
        public abstract class ExpressionVisitor
        {

            protected ExpressionVisitor()
            {

            }

            public virtual Expression Visit(Expression exp)
            {

                if (exp == null)

                    return exp;

                switch (exp.NodeType)
                {

                    case ExpressionType.Negate:

                    case ExpressionType.NegateChecked:

                    case ExpressionType.Not:

                    case ExpressionType.Convert:

                    case ExpressionType.ConvertChecked:

                    case ExpressionType.ArrayLength:

                    case ExpressionType.Quote:

                    case ExpressionType.TypeAs:

                        return this.VisitUnary((UnaryExpression)exp);

                    case ExpressionType.Add:

                    case ExpressionType.AddChecked:

                    case ExpressionType.Subtract:

                    case ExpressionType.SubtractChecked:

                    case ExpressionType.Multiply:

                    case ExpressionType.MultiplyChecked:

                    case ExpressionType.Divide:

                    case ExpressionType.Modulo:

                    case ExpressionType.And:

                    case ExpressionType.AndAlso:

                    case ExpressionType.Or:

                    case ExpressionType.OrElse:

                    case ExpressionType.LessThan:

                    case ExpressionType.LessThanOrEqual:

                    case ExpressionType.GreaterThan:

                    case ExpressionType.GreaterThanOrEqual:

                    case ExpressionType.Equal:

                    case ExpressionType.NotEqual:

                    case ExpressionType.Coalesce:

                    case ExpressionType.ArrayIndex:

                    case ExpressionType.RightShift:

                    case ExpressionType.LeftShift:

                    case ExpressionType.ExclusiveOr:

                        return this.VisitBinary((BinaryExpression)exp);

                    case ExpressionType.TypeIs:

                        return this.VisitTypeIs((TypeBinaryExpression)exp);

                    case ExpressionType.Conditional:

                        return this.VisitConditional((ConditionalExpression)exp);

                    case ExpressionType.Constant:

                        return this.VisitConstant((ConstantExpression)exp);

                    case ExpressionType.Parameter:

                        return this.VisitParameter((ParameterExpression)exp);

                    case ExpressionType.MemberAccess:

                        return this.VisitMemberAccess((MemberExpression)exp);

                    case ExpressionType.Call:

                        return this.VisitMethodCall((MethodCallExpression)exp);

                    case ExpressionType.Lambda:

                        return this.VisitLambda((LambdaExpression)exp);

                    case ExpressionType.New:

                        return this.VisitNew((NewExpression)exp);

                    case ExpressionType.NewArrayInit:

                    case ExpressionType.NewArrayBounds:

                        return this.VisitNewArray((NewArrayExpression)exp);

                    case ExpressionType.Invoke:

                        return this.VisitInvocation((InvocationExpression)exp);

                    case ExpressionType.MemberInit:

                        return this.VisitMemberInit((MemberInitExpression)exp);

                    case ExpressionType.ListInit:

                        return this.VisitListInit((ListInitExpression)exp);

                    default:

                        throw new Exception(string.Format("Unhandled expression type: '{0}'", exp.NodeType));

                }

            }



            protected virtual MemberBinding VisitBinding(MemberBinding binding)
            {

                switch (binding.BindingType)
                {

                    case MemberBindingType.Assignment:

                        return this.VisitMemberAssignment((MemberAssignment)binding);

                    case MemberBindingType.MemberBinding:

                        return this.VisitMemberMemberBinding((MemberMemberBinding)binding);

                    case MemberBindingType.ListBinding:

                        return this.VisitMemberListBinding((MemberListBinding)binding);

                    default:

                        throw new Exception(string.Format("Unhandled binding type '{0}'", binding.BindingType));

                }

            }



            protected virtual ElementInit VisitElementInitializer(ElementInit initializer)
            {

                ReadOnlyCollection<Expression> arguments = this.VisitExpressionList(initializer.Arguments);

                if (arguments != initializer.Arguments)
                {

                    return Expression.ElementInit(initializer.AddMethod, arguments);

                }

                return initializer;

            }



            protected virtual Expression VisitUnary(UnaryExpression u)
            {

                Expression operand = this.Visit(u.Operand);

                if (operand != u.Operand)
                {

                    return Expression.MakeUnary(u.NodeType, operand, u.Type, u.Method);

                }

                return u;

            }



            protected virtual Expression VisitBinary(BinaryExpression b)
            {

                Expression left = this.Visit(b.Left);

                Expression right = this.Visit(b.Right);

                Expression conversion = this.Visit(b.Conversion);

                if (left != b.Left || right != b.Right || conversion != b.Conversion)
                {

                    if (b.NodeType == ExpressionType.Coalesce && b.Conversion != null)

                        return Expression.Coalesce(left, right, conversion as LambdaExpression);

                    else

                        return Expression.MakeBinary(b.NodeType, left, right, b.IsLiftedToNull, b.Method);

                }

                return b;

            }



            protected virtual Expression VisitTypeIs(TypeBinaryExpression b)
            {

                Expression expr = this.Visit(b.Expression);

                if (expr != b.Expression)
                {

                    return Expression.TypeIs(expr, b.TypeOperand);

                }

                return b;

            }



            protected virtual Expression VisitConstant(ConstantExpression c)
            {

                return c;

            }



            protected virtual Expression VisitConditional(ConditionalExpression c)
            {

                Expression test = this.Visit(c.Test);

                Expression ifTrue = this.Visit(c.IfTrue);

                Expression ifFalse = this.Visit(c.IfFalse);

                if (test != c.Test || ifTrue != c.IfTrue || ifFalse != c.IfFalse)
                {

                    return Expression.Condition(test, ifTrue, ifFalse);

                }

                return c;

            }



            protected virtual Expression VisitParameter(ParameterExpression p)
            {

                return p;

            }



            protected virtual Expression VisitMemberAccess(MemberExpression m)
            {

                Expression exp = this.Visit(m.Expression);

                if (exp != m.Expression)
                {

                    return Expression.MakeMemberAccess(exp, m.Member);

                }

                return m;

            }



            protected virtual Expression VisitMethodCall(MethodCallExpression m)
            {

                Expression obj = this.Visit(m.Object);

                IEnumerable<Expression> args = this.VisitExpressionList(m.Arguments);

                if (obj != m.Object || args != m.Arguments)
                {

                    return Expression.Call(obj, m.Method, args);

                }

                return m;

            }



            protected virtual ReadOnlyCollection<Expression> VisitExpressionList(ReadOnlyCollection<Expression> original)
            {

                List<Expression> list = null;

                for (int i = 0, n = original.Count; i < n; i++)
                {

                    Expression p = this.Visit(original[i]);

                    if (list != null)
                    {

                        list.Add(p);

                    }

                    else if (p != original[i])
                    {

                        list = new List<Expression>(n);

                        for (int j = 0; j < i; j++)
                        {

                            list.Add(original[j]);

                        }

                        list.Add(p);

                    }

                }

                if (list != null)
                {

                    return list.AsReadOnly();

                }

                return original;

            }



            protected virtual MemberAssignment VisitMemberAssignment(MemberAssignment assignment)
            {

                Expression e = this.Visit(assignment.Expression);

                if (e != assignment.Expression)
                {

                    return Expression.Bind(assignment.Member, e);

                }

                return assignment;

            }



            protected virtual MemberMemberBinding VisitMemberMemberBinding(MemberMemberBinding binding)
            {

                IEnumerable<MemberBinding> bindings = this.VisitBindingList(binding.Bindings);

                if (bindings != binding.Bindings)
                {

                    return Expression.MemberBind(binding.Member, bindings);

                }

                return binding;

            }



            protected virtual MemberListBinding VisitMemberListBinding(MemberListBinding binding)
            {

                IEnumerable<ElementInit> initializers = this.VisitElementInitializerList(binding.Initializers);

                if (initializers != binding.Initializers)
                {

                    return Expression.ListBind(binding.Member, initializers);

                }

                return binding;

            }



            protected virtual IEnumerable<MemberBinding> VisitBindingList(ReadOnlyCollection<MemberBinding> original)
            {

                List<MemberBinding> list = null;

                for (int i = 0, n = original.Count; i < n; i++)
                {

                    MemberBinding b = this.VisitBinding(original[i]);

                    if (list != null)
                    {

                        list.Add(b);

                    }

                    else if (b != original[i])
                    {

                        list = new List<MemberBinding>(n);

                        for (int j = 0; j < i; j++)
                        {

                            list.Add(original[j]);

                        }

                        list.Add(b);

                    }

                }

                if (list != null)

                    return list;

                return original;

            }



            protected virtual IEnumerable<ElementInit> VisitElementInitializerList(ReadOnlyCollection<ElementInit> original)
            {

                List<ElementInit> list = null;

                for (int i = 0, n = original.Count; i < n; i++)
                {

                    ElementInit init = this.VisitElementInitializer(original[i]);

                    if (list != null)
                    {

                        list.Add(init);

                    }

                    else if (init != original[i])
                    {

                        list = new List<ElementInit>(n);

                        for (int j = 0; j < i; j++)
                        {

                            list.Add(original[j]);

                        }

                        list.Add(init);

                    }

                }

                if (list != null)

                    return list;

                return original;

            }



            protected virtual Expression VisitLambda(LambdaExpression lambda)
            {

                Expression body = this.Visit(lambda.Body);

                if (body != lambda.Body)
                {

                    return Expression.Lambda(lambda.Type, body, lambda.Parameters);

                }

                return lambda;

            }



            protected virtual NewExpression VisitNew(NewExpression nex)
            {

                IEnumerable<Expression> args = this.VisitExpressionList(nex.Arguments);

                if (args != nex.Arguments)
                {

                    if (nex.Members != null)

                        return Expression.New(nex.Constructor, args, nex.Members);

                    else

                        return Expression.New(nex.Constructor, args);

                }

                return nex;

            }



            protected virtual Expression VisitMemberInit(MemberInitExpression init)
            {

                NewExpression n = this.VisitNew(init.NewExpression);

                IEnumerable<MemberBinding> bindings = this.VisitBindingList(init.Bindings);

                if (n != init.NewExpression || bindings != init.Bindings)
                {

                    return Expression.MemberInit(n, bindings);

                }

                return init;

            }



            protected virtual Expression VisitListInit(ListInitExpression init)
            {

                NewExpression n = this.VisitNew(init.NewExpression);

                IEnumerable<ElementInit> initializers = this.VisitElementInitializerList(init.Initializers);

                if (n != init.NewExpression || initializers != init.Initializers)
                {

                    return Expression.ListInit(n, initializers);

                }

                return init;

            }



            protected virtual Expression VisitNewArray(NewArrayExpression na)
            {

                IEnumerable<Expression> exprs = this.VisitExpressionList(na.Expressions);

                if (exprs != na.Expressions)
                {

                    if (na.NodeType == ExpressionType.NewArrayInit)
                    {

                        return Expression.NewArrayInit(na.Type.GetElementType(), exprs);

                    }

                    else
                    {

                        return Expression.NewArrayBounds(na.Type.GetElementType(), exprs);

                    }

                }

                return na;

            }



            protected virtual Expression VisitInvocation(InvocationExpression iv)
            {

                IEnumerable<Expression> args = this.VisitExpressionList(iv.Arguments);

                Expression expr = this.Visit(iv.Expression);

                if (args != iv.Arguments || expr != iv.Expression)
                {

                    return Expression.Invoke(expr, args);

                }

                return iv;

            }

        }

       
    }
}
Tip: Filter by directory path e.g. /media app.js to search for public/media/app.js.
Tip: Use camelCasing e.g. ProjME to search for ProjectModifiedEvent.java.
Tip: Filter by extension type e.g. /repo .js to search for all .js files in the /repo directory.
Tip: Separate your search with spaces e.g. /ssh pom.xml to search for src/ssh/pom.xml.
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