specifications:

samples/SimplestApp/Program.cs

@@ -7,6 +7,7 @@
 using System;
 using SimplestApp.Operations;
 using SimplestApp.Services;
+using SimplestApp.Specifications;
 
 namespace SimplestApp
 {
@@ -16,7 +17,8 @@ static void Main(string[] args)
         {
             Console.WriteLine("== Simple App to Create a User");
 
-            UserService us = new UserService();
+            var spec = new UserValidSpecification();
+            UserService us = new UserService(spec);
 
             var user = us.Add(new AddUser {Name = "My name", Mail = "[email protected]"});
 

samples/SimplestApp/Services/UserService.cs

@@ -5,6 +5,7 @@
 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
 
 using System;
+using DFlow.Domain.Specifications;
 using DFlow.Samples.BusinessObjects.Domain.BusinessObjects;
 using DFlow.Samples.Domain.Aggregates;
 using DFlow.Samples.Domain.BusinessObjects;
@@ -14,13 +15,19 @@ namespace SimplestApp.Services
 {
     public class UserService:IUserService
     {
+        private ISpecification<UserEntityBasedAggregationRoot> _specification;
+        public UserService(ISpecification<UserEntityBasedAggregationRoot> specification)
+        {
+            _specification = specification;
+        }
+
         public User Add(AddUser user)
         {
             var agg = UserEntityBasedAggregationRoot.CreateFrom(Name.From(user.Name), Email.From(user.Mail));
 
-            if (!agg.IsValid)
+            if (!_specification.IsSatisfiedBy(agg))
             {
-                throw new ArgumentException("One or more parameters informed to create a user are not valid.");
+                throw new ArgumentException(agg.Failures[0].ErrorMessage);
             }
 
             return agg.GetChange();

samples/SimplestApp/Specifications/UserService.cs

@@ -0,0 +1,44 @@
+// Copyright (C) 2020  Road to Agility
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+using System;
+using DFlow.Domain.Specifications;
+using DFlow.Samples.Domain.Aggregates;
+using DFlow.Samples.Domain.BusinessObjects;
+using FluentValidation.Results;
+using SimplestApp.Operations;
+using SimplestApp.Services;
+
+namespace SimplestApp.Specifications
+{
+    public class UserValidSpecification:CompositeSpecification<UserEntityBasedAggregationRoot>
+    {
+
+        public User Add(AddUser user)
+        {
+            var agg = UserEntityBasedAggregationRoot.CreateFrom(Name.From(user.Name), Email.From(user.Mail));
+
+            if (!agg.IsValid)
+            {
+                throw new ArgumentException("One or more parameters informed to create a user are not valid.");
+            }
+
+            return agg.GetChange();
+        }
+
+        public override bool IsSatisfiedBy(UserEntityBasedAggregationRoot candidate)
+        {
+            if (!candidate.IsValid)
+            {
+                candidate.AppendValidationResult(new ValidationFailure("InvalidUser",
+                    "One or more parameters informed to create a user are not valid."));
+                return false;
+            }
+
+            return true;
+        }
+    }
+}

src/DFlow.Business.Cqrs/CommandHandlers/CommandResult.cs

@@ -5,6 +5,7 @@
 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
 
 using System.Collections.Generic;
+using DFlow.Domain.Validation;
 using FluentValidation.Results;
 
 namespace DFlow.Business.Cqrs.CommandHandlers

src/DFlow.Domain/Specifications/AndSpecification.cs

@@ -0,0 +1,22 @@
+// Copyright (C) 2021  Road to Agility
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+namespace DFlow.Domain.Specifications
+{
+    public class AndSpecification<TBusinessObject>:LogicalSpecification<TBusinessObject>
+    {
+        public AndSpecification(ISpecification<TBusinessObject> leftCondition, ISpecification<TBusinessObject> rightCondition) 
+            : base(leftCondition, rightCondition)
+        {
+        }
+
+        public override bool IsSatisfiedBy(TBusinessObject candidate)
+        {
+            return LeftCondition.IsSatisfiedBy(candidate) 
+                   && RightCondition.IsSatisfiedBy(candidate);
+        }
+    }
+}

src/DFlow.Domain/Specifications/CompositeSpecification.cs

@@ -0,0 +1,32 @@
+// Copyright (C) 2021  Road to Agility
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+using System.Collections.Generic;
+using System.Collections.Immutable;
+
+namespace DFlow.Domain.Specifications
+{
+    public abstract class CompositeSpecification<TBusinessObject>:ISpecification<TBusinessObject>
+    {
+        public ISpecification<TBusinessObject> And(ISpecification<TBusinessObject> candidate)
+        {
+            return new AndSpecification<TBusinessObject>(this,candidate);
+        }
+
+        public ISpecification<TBusinessObject> Or(ISpecification<TBusinessObject> candidate)
+        {
+            return new OrSpecification<TBusinessObject>(this,candidate);
+
+        }
+
+        public ISpecification<TBusinessObject> Not()
+        {
+            return new NotSpecification<TBusinessObject>(this);
+        }
+
+        public abstract bool IsSatisfiedBy(TBusinessObject candidate);
+    }
+}

src/DFlow.Domain/Specifications/ISpecification.cs

@@ -0,0 +1,18 @@
+// Copyright (C) 2021  Road to Agility
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+using System.Collections.Generic;
+
+namespace DFlow.Domain.Specifications
+{
+    public interface ISpecification<TBusinessObject>
+    {
+        bool IsSatisfiedBy(TBusinessObject candidate);
+        ISpecification<TBusinessObject> And(ISpecification<TBusinessObject> other);
+        ISpecification<TBusinessObject> Or(ISpecification<TBusinessObject> other);
+        ISpecification<TBusinessObject> Not();
+    }
+}

src/DFlow.Domain/Specifications/LinqExpressionSpecification.cs

@@ -0,0 +1,20 @@
+// Copyright (C) 2021  Road to Agility
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+using System;
+using System.Linq.Expressions;
+
+namespace DFlow.Domain.Specifications
+{
+    public abstract class LinqExpressionSpecification<TBusinessObject>
+        :CompositeSpecification<TBusinessObject>
+    {
+        protected abstract Expression<Func<TBusinessObject, bool>> AsExpression();
+
+        public override bool IsSatisfiedBy(TBusinessObject candidate) 
+            => AsExpression().Compile()(candidate);
+    }
+}

src/DFlow.Domain/Specifications/LogicalSpecification.cs

@@ -0,0 +1,22 @@
+// Copyright (C) 2021  Road to Agility
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+namespace DFlow.Domain.Specifications
+{
+    public abstract class LogicalSpecification<TBusinessObject>:CompositeSpecification<TBusinessObject>
+    {
+        protected ISpecification<TBusinessObject> LeftCondition { get; }
+
+        protected ISpecification<TBusinessObject> RightCondition { get; }
+
+        protected LogicalSpecification(ISpecification<TBusinessObject> leftCondition,
+            ISpecification<TBusinessObject> rightCondition)
+        {
+            LeftCondition = leftCondition;
+            RightCondition = rightCondition;
+        }
+    }
+}

src/DFlow.Domain/Specifications/NotSpecification.cs

@@ -0,0 +1,23 @@
+// Copyright (C) 2021  Road to Agility
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+namespace DFlow.Domain.Specifications
+{
+    public class NotSpecification<TBusinessObject>:CompositeSpecification<TBusinessObject>
+    {
+        protected ISpecification<TBusinessObject> Condition { get; }
+
+        public NotSpecification(ISpecification<TBusinessObject> condition)
+        {
+            Condition = condition;
+        }
+
+        public override bool IsSatisfiedBy(TBusinessObject candidate)
+        {
+            return !Condition.IsSatisfiedBy(candidate);
+        }
+    }
+}

src/DFlow.Domain/Specifications/OrSpecification.cs

@@ -0,0 +1,22 @@
+// Copyright (C) 2021  Road to Agility
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+namespace DFlow.Domain.Specifications
+{
+    public class OrSpecification<TBusinessObject>:LogicalSpecification<TBusinessObject>
+    {
+        public OrSpecification(ISpecification<TBusinessObject> leftCondition, ISpecification<TBusinessObject> rightCondition) 
+            : base(leftCondition, rightCondition)
+        {
+        }
+
+        public override bool IsSatisfiedBy(TBusinessObject candidate)
+        {
+            return LeftCondition.IsSatisfiedBy(candidate) 
+                   || RightCondition.IsSatisfiedBy(candidate);
+        }
+    }
+}

src/DFlow.Domain/Validation/BaseValidation.cs

@@ -7,14 +7,19 @@
 
 using System.Collections.Generic;
 using System.Collections.Immutable;
-using DFlow.Domain.BusinessObjects;
 using FluentValidation.Results;
 
 namespace DFlow.Domain.Validation
 {
     public abstract class BaseValidation: IValidable
     {
         private readonly List<ValidationFailure> _failures = new List<ValidationFailure>();
+
+        public void AppendValidationResult(ValidationFailure failure)
+        {
+            _failures.Add(failure);
+        }
+
         public void AppendValidationResult(IReadOnlyList<ValidationFailure> failures)
         {
             _failures.AddRange(failures);

src/DFlow.Domain/Validation/IValidable.cs

@@ -13,6 +13,8 @@ namespace DFlow.Domain.Validation
     public interface IValidable
     {
         bool IsValid { get; }
+        void AppendValidationResult(ValidationFailure failure);
+
         void AppendValidationResult(IReadOnlyList<ValidationFailure> failures);
     }
 }

src/DFlow.Specifications/DFlow.Specifications.csproj

@@ -0,0 +1,7 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFrameworks>net5.0;netcoreapp3.1</TargetFrameworks>
+  </PropertyGroup>
+
+</Project>

src/Directory.Build.props

@@ -1,6 +1,6 @@
 <Project>
   <PropertyGroup>
-    <VersionPrefix>0.3.0</VersionPrefix>
+    <VersionPrefix>0.4.0</VersionPrefix>
     <VersionSuffix>pre</VersionSuffix>
     <!-- <PackageProjectUrl>https://github.com/roadtoagility/dflow</PackageProjectUrl>
         <PackageIconUrl>https://github.com/roadtoagility/dflow/raw/master/docs/img/logodflow_200x200.png</PackageIconUrl> -->

tests/DFlow.Tests/Domain/EntityTests.cs

@@ -5,7 +5,6 @@
 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
 
 
-using System;
 using AutoFixture;
 using DFlow.Domain.BusinessObjects;
 using DFlow.Tests.Supporting.DomainObjects;

tests/DFlow.Tests/Domain/SpecificationTests.cs

@@ -0,0 +1,60 @@
+// Copyright (C) 2021  Road to Agility
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+
+using DFlow.Domain.BusinessObjects;
+using DFlow.Tests.Supporting.DomainObjects;
+using DFlow.Tests.Supporting.Specifications;
+using Xunit;
+
+namespace DFlow.Tests.Domain
+{
+    public class SpecificationForCreationEntityTests
+    {
+        [Fact]
+        public void BusinessEntityIsNew()
+        {
+            var bu = BusinessEntity.New();
+            var isNew = new BusinessEntityIsNew();
+
+            Assert.True(isNew.IsSatisfiedBy(bu));
+        }
+
+        [Fact]
+        public void BusinessEntityNotIsNew()
+        {
+            var buUpdated = BusinessEntity.From(EntityTestId.GetNext(), VersionId.Next(VersionId.New()));
+            var isNew = new BusinessEntityIsNew();
+
+            Assert.False(isNew.IsSatisfiedBy(buUpdated));
+        }
+
+        [Fact]
+        public void AnotherBusinessEntityNameIsRoad()
+        {
+            var bu = AnotherBusinessEntity
+                .New(Name.From("Road"), Email.From("[email protected]"));
+
+            var isRoad = new AnotherBusinessEntityNameIsRoad(Name.From("Road"));
+
+            Assert.True(isRoad.IsSatisfiedBy(bu));
+        }
+
+        [Fact]
+        public void AnotherBusinessEntityNameIsRoadAndEmailFromRoadCompany()
+        {
+            var bu = AnotherBusinessEntity
+                .New(Name.From("Road"), Email.From("[email protected]"));
+
+            var isRoad = new AnotherBusinessEntityNameIsRoad(Name.From("Road"));
+            var isFromCompany = new AnotherBusinessEntityEmailFromCompany(Email.From("[email protected]"));
+
+            isRoad.And(isFromCompany);
+
+            Assert.True(isRoad.IsSatisfiedBy(bu));
+        }
+    }
+}