Catalog - Improving Clarity of Business Logic

EventSourcingEcommerce.sln

@@ -61,6 +61,8 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Retail", "Retail", "{91DC34
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "shopping-cart", "shopping-cart", "{E8D6C05C-F653-42AA-BB9B-6E57251C7E99}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Ecommerce.Eventuous", "src\Core\Ecommerce.Eventuous\Ecommerce.Eventuous.csproj", "{3C54979E-C2BB-448E-86EE-08F366B973DF}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -135,6 +137,10 @@ Global
 		{F42EAACF-D74A-4646-A311-AB9EB131AE8A}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{F42EAACF-D74A-4646-A311-AB9EB131AE8A}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{F42EAACF-D74A-4646-A311-AB9EB131AE8A}.Release|Any CPU.Build.0 = Release|Any CPU
+		{3C54979E-C2BB-448E-86EE-08F366B973DF}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{3C54979E-C2BB-448E-86EE-08F366B973DF}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{3C54979E-C2BB-448E-86EE-08F366B973DF}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{3C54979E-C2BB-448E-86EE-08F366B973DF}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(NestedProjects) = preSolution
 		{9CD0617F-6555-4F29-9C3E-211DC9A92CD5} = {5C748417-563A-41A4-AC92-67A815C5A929}
@@ -155,5 +161,6 @@ Global
 		{090F1820-19D9-464B-A0B0-415182075D9D} = {E8FE7001-AFB6-4FB2-B922-BB6A203A652E}
 		{F42EAACF-D74A-4646-A311-AB9EB131AE8A} = {E8FE7001-AFB6-4FB2-B922-BB6A203A652E}
 		{E8D6C05C-F653-42AA-BB9B-6E57251C7E99} = {91DC34A2-E5DC-4BDD-9BAE-6B9D1E8E0769}
+		{3C54979E-C2BB-448E-86EE-08F366B973DF} = {5C748417-563A-41A4-AC92-67A815C5A929}
 	EndGlobalSection
 EndGlobal

src/Catalog/Catalog.Api/Commands/ProductCommandService.cs

@@ -23,6 +23,7 @@ public ProductCommandService(
                 cmd.Sku,
                 cmd.Name,
                 cmd.Description,
+                cmd.Brand,
                 DateTimeOffset.Now,
                 cmd.CreatedBy,
                 isSkuAvailable,
@@ -35,6 +36,7 @@ public ProductCommandService(
                 cmd.Sku,
                 cmd.Name,
                 cmd.Description,
+                cmd.Brand,
                 DateTimeOffset.Now,
                 cmd.CreatedBy,
                 isSkuAvailable,

src/Catalog/Catalog.Api/Commands/ProductCommands.cs

@@ -7,13 +7,15 @@ public record DraftWithProvidedId(
         string Sku,
         string Name,
         string Description,
+        string Brand,
         string CreatedBy
     );
 
     public record Draft(
         string Sku,
         string Name,
         string Description,
+        string Brand,
         string CreatedBy
     );
 
@@ -44,4 +46,10 @@ public record AdjustDescription(
         string Description,
         string AdjustedBy
     );
+
+    public record AdjustBrand(
+        string ProductId,
+        string Brand,
+        string AdjustedBy
+    );
 }

src/Catalog/Catalog.Api/HttpApi/CommandApi.cs

@@ -43,4 +43,9 @@ public Task<ActionResult<Result>> AdjustName([FromBody] AdjustName cmd, Cancella
     [Route("adjust-description")]
     public Task<ActionResult<Result>> AdjustDescription([FromBody] AdjustDescription cmd, CancellationToken ct)
         => Handle(cmd, ct);
+
+    [HttpPost]
+    [Route("adjust-brand")]
+    public Task<ActionResult<Result>> AdjustBrand([FromBody] AdjustBrand cmd, CancellationToken ct)
+        => Handle(cmd, ct);
 }

src/Catalog/Catalog.Api/Queries/ProductDocument.cs

@@ -14,4 +14,5 @@ public ProductDocument(string Id) : base(Id)
     public string Name { get; set; } = null!;
     public string Sku { get; set; } = null!;
     public string Description { get; set; } = null!;
+    public string Brand { get; set; } = null!;
 }

src/Catalog/Catalog.Api/Queries/ProductStateProjection.cs

@@ -1,5 +1,4 @@
 using Catalog.Products;
-using Eventuous;
 using Eventuous.Projections.MongoDB;
 using Eventuous.Subscriptions.Context;
 using MongoDB.Driver;
@@ -32,7 +31,9 @@ private static UpdateDefinition<ProductDocument> Handle(
                 .Set(x => x.CreatedBy, evt.CreatedBy)
                 .Set(x => x.Status, nameof(ProductStatus.Drafted))
                 .Set(x => x.Name, evt.Name)
-                .Set(x => x.Sku, evt.Sku);
+                .Set(x => x.Sku, evt.Sku)
+                .Set(x => x.Description, evt.Description)
+                .Set(x => x.Brand, evt.Brand);
     }
 
     private static UpdateDefinition<ProductDocument> Handle(
@@ -79,4 +80,13 @@ private static UpdateDefinition<ProductDocument> Handle(
 
         return update.Set(x => x.Description, evt.Description);
     }
+
+    private static UpdateDefinition<ProductDocument> Handle(
+        IMessageConsumeContext<V1.ProductBrandAdjusted> ctx,
+        UpdateDefinition<ProductDocument> update)
+    {
+        var evt = ctx.Message;
+
+        return update.Set(x => x.Brand, evt.Brand);
+    }
 }

src/Catalog/Catalog/Brand.cs

@@ -0,0 +1,30 @@
+using Eventuous;
+
+namespace Catalog;
+
+public class Brand
+{
+    public string Value { get; internal init; } = string.Empty;
+
+    internal Brand() { }
+
+    public Brand(string value)
+    {
+        if (string.IsNullOrWhiteSpace(value))
+            throw new DomainException("Brand value cannot be empty");
+
+        if (value.Length <= 2)
+            throw new DomainException("A brand's name must exceed 2 characters");
+
+        if (value.Length > 64)
+            throw new DomainException("A brand's name cannot exceed 64 characters");
+
+        Value = value;
+    }
+
+    public bool HasSameValue(string another)
+        => string.Compare(Value, another, StringComparison.CurrentCulture) != 0;
+
+    public static implicit operator string(Brand brand)
+        => brand.Value;
+}

src/Catalog/Catalog/Catalog.csproj

@@ -1,21 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
-    <ItemGroup>
-        <PackageReference Include="Eventuous.Domain" Version="$(EventuousVersion)" />
-        <PackageReference Include="Eventuous.Shared" Version="$(EventuousVersion)" />
-    </ItemGroup>
-
     <ItemGroup>
         <ProjectReference Include="..\..\Core\Ecommerce.Core\Ecommerce.Core.csproj" />
-    </ItemGroup>
-
-    <ItemGroup>
-        <AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleTo">
-            <_Parameter1>$(AssemblyName).Tests</_Parameter1>
-        </AssemblyAttribute>
-        <AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleTo">
-            <_Parameter1>$(AssemblyName).WebApi.Tests</_Parameter1>
-        </AssemblyAttribute>
+        <ProjectReference Include="..\..\Core\Ecommerce.Eventuous\Ecommerce.Eventuous.csproj" />
     </ItemGroup>
 
 </Project>

src/Catalog/Catalog/Name.cs

@@ -13,11 +13,13 @@ public Name(string value)
         if (string.IsNullOrWhiteSpace(value))
             throw new DomainException("Name value cannot be empty");
 
-        if (value.Length <= 4)
-            throw new DomainException("A product's name must exceed 4 characters");
+        if (value.Length <= 3)
+            throw new DomainException("A product's name must exceed 3 characters");
 
-        if (value.Length > 200)
-            throw new DomainException("A product's name cannot exceed 200 characters");
+        if (value.Length > 100)
+            throw new DomainException("A product's name cannot exceed 100 characters");
+
+        Value = value;
     }
 
     public bool HasSameValue(string another)

src/Catalog/Catalog/Products/Product.cs

@@ -11,6 +11,7 @@ public async Task Draft(
         string sku,
         string name,
         string description,
+        string brand,
         DateTimeOffset createdAt,
         string createdBy,
         IsSkuAvailable isSkuAvailable,
@@ -26,6 +27,7 @@ public async Task Draft(
                 sku,
                 name,
                 description,
+                brand,
                 createdAt,
                 createdBy
             )
@@ -101,6 +103,20 @@ public void AdjustName(string name, DateTimeOffset adjustedAt, string adjustedBy
         );
     }
 
+    public void AdjustBrand(string name, DateTimeOffset adjustedAt, string adjustedBy)
+    {
+        EnsureExists();
+
+        Apply(
+            new V1.ProductBrandAdjusted(
+                State.Id.Value,
+                name,
+                adjustedAt,
+                adjustedBy
+            )
+        );
+    }
+
     private static async Task ValidateSkuAvailability(Sku sku, IsSkuAvailable isSkuAvailable)
     {
         var skuAvailable = await isSkuAvailable(sku);

src/Catalog/Catalog/Products/ProductEvents.cs

@@ -12,6 +12,7 @@ public record ProductDrafted(
             string Sku,
             string Name,
             string Description,
+            string Brand,
             DateTimeOffset CreatedAt,
             string CreatedBy
         );
@@ -53,5 +54,13 @@ public record ProductDescriptionAdjusted(
             DateTimeOffset AdjustedAt,
             string AdjustedBy
         );
+
+        [EventType("V1.ProductBrandAdjusted")]
+        public record ProductBrandAdjusted(
+            string ProductId,
+            string Brand,
+            DateTimeOffset AdjustedAt,
+            string AdjustedBy
+        );
     }
 }

src/Catalog/Catalog/Products/ProductState.cs

@@ -1,3 +1,4 @@
+using Ecommerce.Eventuous.Exceptions;
 using Eventuous;
 
 using static Catalog.Products.ProductEvents;
@@ -36,50 +37,85 @@ private static ProductState Handle(
         Sku = new Sku(@event.Sku)
     };
 
-    private static ProductState Handle(ProductState state, V1.ProductActivated @event)
+    private static ProductState Handle(ProductState state, V1.ProductActivated @event) => state.Status switch
     {
-        if (state.Status != ProductStatus.Drafted)
-            throw new DomainException($"Product must be be {nameof(ProductStatus.Drafted)} status to be activated");
-
-        return state with { Status = ProductStatus.Activated };
-    }
+        ProductStatus.Archived => throw InvalidStateChangeException.For<Product, V1.ProductDescriptionAdjusted>(state.Id, ProductStatus.Archived),
+        ProductStatus.Cancelled => throw InvalidStateChangeException.For<Product, V1.ProductDescriptionAdjusted>(state.Id, ProductStatus.Cancelled),
+        _ => state with { Status = ProductStatus.Activated }
+    };
 
-    private static ProductState Handle(ProductState state, V1.ProductArchived @event)
+    private static ProductState Handle(ProductState state, V1.ProductArchived @event) => state.Status switch
     {
-        if (state.Status != ProductStatus.Activated)
-            throw new DomainException($"Product can only be set to {nameof(ProductStatus.Archived)} while in {nameof(ProductStatus.Activated)}");
-
-        return state with { Status = ProductStatus.Archived };
-    }
+        ProductStatus.Archived => throw InvalidStateChangeException.For<Product, V1.ProductArchived>(state.Id, ProductStatus.Archived),
+        ProductStatus.Cancelled => throw InvalidStateChangeException.For<Product, V1.ProductArchived>(state.Id, ProductStatus.Cancelled),
+        _ => state with { Status = ProductStatus.Archived }
+    };
 
     private static ProductState Handle(ProductState state, V1.ProductDraftCancelled @event)
     {
-        if (state.Status != ProductStatus.Drafted)
-            throw new DomainException($"Product can only be set to {nameof(ProductStatus.Cancelled)} from {nameof(ProductStatus.Drafted)}");
+        ////////// Thoughts regarding modeling state //////////
+        // Does the business really need Archived and Cancelled?
+        // Can we model things to be more reflective of how the
+        // business actually handles, models, or mentally models
+        // these operations?
+        // What if we split this single model (AKA entity, aggregate,
+        // or stream) into two?
+        // Where there's a process for submitting the initial draft
+        // and any changes (rough drafts), and then one that has been
+        // approved and is now "live" or "active"?
+
+        if (state.Status is not ProductStatus.Drafted)
+            throw InvalidStateChangeException.For<Product, V1.ProductDraftCancelled>(state.Id, ProductStatus.Drafted);
 
         return state with { Status = ProductStatus.Cancelled };
     }
 
     private static ProductState Handle(ProductState state, V1.ProductDescriptionAdjusted @event)
     {
-        if (state.Status is not ProductStatus.Drafted or ProductStatus.Activated)
-            throw new DomainException($"Product must be set to {nameof(ProductStatus.Drafted)} or {nameof(ProductStatus.Activated)} to adjust {nameof(Description)}");
+        // Validation of the value is performed early in the process before overall state is checked.
+        var adjustedDescription = new Description(@event.Description);
 
-        return state with
+        // a switch expression
+        return state.Status switch
         {
-            Description = new Description(@event.Description)
+            ProductStatus.Unset => throw InvalidStateChangeException.For<Product, V1.ProductDescriptionAdjusted>(state.Id, ProductStatus.Unset),
+            ProductStatus.Archived => throw InvalidStateChangeException.For<Product, V1.ProductDescriptionAdjusted>(state.Id, ProductStatus.Archived),
+            ProductStatus.Cancelled => throw InvalidStateChangeException.For<Product, V1.ProductDescriptionAdjusted>(state.Id, ProductStatus.Cancelled),
+            _ => state with { Description = adjustedDescription }
         };
     }
 
     private static ProductState Handle(ProductState state, V1.ProductNameAdjusted @event)
     {
-        if (state.Status is not ProductStatus.Drafted or ProductStatus.Activated)
-            throw new DomainException($"Product must be set to {nameof(ProductStatus.Drafted)} or {nameof(ProductStatus.Activated)} to adjust {nameof(Name)}");
-
+        // Validation of the value is performed early in the process before overall state is checked.
         var adjustedName = new Name(@event.Name);
 
+        // a switch statement
+        switch (state.Status)
+        {
+            case ProductStatus.Unset:
+                throw InvalidStateChangeException.For<Product, V1.ProductNameAdjusted>(state.Id, ProductStatus.Unset);
+            case ProductStatus.Archived:
+                throw InvalidStateChangeException.For<Product, V1.ProductNameAdjusted>(state.Id, ProductStatus.Archived);
+            case ProductStatus.Cancelled:
+                throw InvalidStateChangeException.For<Product, V1.ProductNameAdjusted>(state.Id, ProductStatus.Cancelled);
+            case ProductStatus.Drafted:
+            case ProductStatus.Activated:
+            case ProductStatus.Closed:
+            default:
+                break;
+        }
+
+        ////////// Thoughts regarding event store immutability //////////
+        // Is this exception okay? It should be. However, when aggregating the
+        // state (events) in the future, and if the event stream was illegally
+        // modified (as it should be immutable), then there could be issues.
+        // This is why it's important an event store's log truly be immutable,
+        // as business logic / use cases are built around expecting it to be so.
+        // An event store is the source of truth. An audit log. A ledger of transactions.
+
         if (state.Name.HasSameValue(adjustedName))
-            throw new DomainException("Product name is the same");
+            throw InvalidStateChangeException.For<Product, V1.ProductNameAdjusted>(state.Id, "Incoming name value is the same as current name");
 
         return state with { Name = adjustedName };
     }

src/Core/Ecommerce.Eventuous/Ecommerce.Eventuous.csproj

@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <ItemGroup>
+        <PackageReference Include="Eventuous.Domain" Version="$(EventuousVersion)" />
+        <PackageReference Include="Eventuous.Shared" Version="$(EventuousVersion)" />
+    </ItemGroup>
+
+    <ItemGroup>
+        <ProjectReference Include="..\..\Core\Ecommerce.Core\Ecommerce.Core.csproj" />
+    </ItemGroup>
+
+</Project>