Drop dead code, page through PageRequest, and give the version and clock one home each

.agents/skills/data-access-ef-core/SKILL.md

@@ -14,9 +14,9 @@ One repository, `EntityFrameworkMovieReviewsRepository` in `src/Infrastructure/D
 ## Steps
 
 1. Add the method to the Application interface first (`IMoviesRepository` and friends), taking a `CancellationToken` last.
-2. Implement it in the matching `#region` of the repository, as `public virtual async Task<...>` like every other method.
+2. Implement it in the matching `#region` of the repository, as `public async Task<...>` like every other method.
 3. Reads: start from `this.context.<Set>`, filter, then either
-   - **a list**: count, order (ending with the id), skip, take, and `Select` the summary fields so SQL does the counting and averaging (`paging`), or
+   - **a list**: take a `PageRequest page`, count, order (ending with the id), `Skip(page.Offset)`, `Take(page.Limit)`, `Select` the summary fields so SQL does the counting and averaging, and return `new Page<T>(items, page.Offset, page.Limit, totalCount)` (`paging`), or
    - **one entity**: `Include` what the entity needs, `FirstOrDefaultAsync`, then map with `this.mapper.ToDomain(...)` (`mapping-with-mapperly`).
 4. Writes:
    - **create**: build the model, set `DateCreated` and `DateModified` from `this.timeProvider.GetUtcNow().UtcDateTime`, `Add`, `SaveChangesAsync`, then read it back with its includes.
@@ -31,7 +31,7 @@ One repository, `EntityFrameworkMovieReviewsRepository` in `src/Infrastructure/D
 
 ```csharp
 // src/Infrastructure/Databases/MovieReviews/EntityFrameworkMovieReviewsRepository.cs
-public virtual async Task<ApplicationReview?> UpdateReview(Guid id, int stars, CancellationToken cancellationToken)
+public async Task<ApplicationReview?> UpdateReview(Guid id, int stars, CancellationToken cancellationToken)
 {
     var now = this.timeProvider.GetUtcNow().UtcDateTime;
 

.agents/skills/mapping-with-mapperly/SKILL.md

@@ -9,7 +9,7 @@ metadata:
 
 ## The rule
 
-Mapping code is generated at compile time by Mapperly (`Riok.Mapperly`), never written by hand and never done by reflection. Infrastructure's `MovieReviewsMapper` (`src/Infrastructure/Databases/MovieReviews/Mapping/MovieReviewsMapper.cs`) maps database models to Application entities and back. Presentation layers that need their own response models have their own mapper beside them.
+Mapping code is generated at compile time by Mapperly (`Riok.Mapperly`), never written by hand and never done by reflection. Infrastructure's `MovieReviewsMapper` (`src/Infrastructure/Databases/MovieReviews/Mapping/MovieReviewsMapper.cs`) maps database models to Application entities. It only maps that way, because writes build the database model directly (`data-access-ef-core`). Add a mapping in the other direction only when something calls it. Presentation layers that need their own response models have their own mapper beside them.
 
 Mapperly reports unmapped members as `RMG` warnings, and warnings fail the build, so every member is either mapped or explicitly ignored.
 

.agents/skills/mediator/SKILL.md

@@ -36,7 +36,6 @@ Behaviours run in the order they're registered. The first one registered is the
 ```csharp
 // src/Application/DependencyInjection.cs
 _ = services.AddValidatorsFromAssembly(Assembly.GetExecutingAssembly(), ServiceLifetime.Transient);
-services.TryAddSingleton(TimeProvider.System);
 
 _ = services.AddScoped(typeof(IPipelineBehavior<,>), typeof(LoggingBehaviour<,>));
 _ = services.AddScoped(typeof(IPipelineBehavior<,>), typeof(ValidationBehaviour<,>));

.agents/skills/paging/SKILL.md

@@ -9,17 +9,19 @@ metadata:
 
 ## The rule
 
-Every list is paged with an offset and a limit, and no endpoint returns an unbounded list. A page is `Page<T>(Items, Offset, Limit, TotalCount)` from `src/Application/Common/Paging/Page.cs`. The default limit is `Paging.DefaultLimit` (10) and the maximum is `Paging.MaxLimit` (50). To get the next page, a caller adds the limit to the offset.
+Every list is paged with an offset and a limit, and no endpoint returns an unbounded list. A repository is asked for a `PageRequest(Offset, Limit)` and returns a `Page<T>(Items, Offset, Limit, TotalCount)`, both from `src/Application/Common/Paging/`. Application owns that contract; Infrastructure turns it into `Skip` and `Take`, and each presentation maps it to and from its own wire shape. The default limit is `Paging.DefaultLimit` (10) and the maximum is `Paging.MaxLimit` (50). To get the next page, a caller adds the limit to the offset.
 
-Lists return summaries (`MovieSummary`, `AuthorSummary`) worked out in SQL, not full entities with their children. A by-id query returns the full entity.
+Lists return summaries (`MovieSummary`, `AuthorSummary`) worked out in SQL, not full entities with their children. A by-id query returns the full entity with all its children. That is a deliberate limit of the sample data model: when a parent can have many children, return its summary and page the children through their own list query instead.
+
+When one response holds a page of parents and each one needs its children, ask for the children of the whole page in one trip with `GetReviewsForMoviesQuery` or `GetReviewsForAuthorsQuery`. They take at most `Paging.MaxLimit` ids, which is one page, and return an entry for every id. GraphQL uses them in its DataLoaders and MCP uses them for `includeReviews`. The REST templates don't call them, because their lists return summaries and a by-id query loads its children with the parent, but they stay in Application so the shared layers match in every template.
 
 ## Steps
 
 1. Give the query `Offset` (default 0) and `Limit` (default `Paging.DefaultLimit`) properties, plus an optional `Query` search term if the list can be searched.
 2. Validate them with `ValidOffset()`, `ValidLimit()` and `ValidSearchTerm()` (`validation`).
-3. Have the repository return `(List<T> Items, int TotalCount)`; `Page<T>` exposes the items as an `IReadOnlyList<T>`. Count before you skip and take.
+3. Give the repository method a `PageRequest page` parameter after any filters, and have it return `Page<T>`. Count before you skip and take.
 4. Order by something that makes a stable order, ending with the id, so a row never shows up on two pages.
-5. Build the page in the handler: `new Page<T>(items, request.Offset, request.Limit, totalCount)`.
+5. The handler passes the page through: `return await repository.GetMovies(request.Query, new PageRequest(request.Offset, request.Limit), cancellationToken);`
 
 ## Example
 
@@ -30,8 +32,8 @@ var totalCount = await movies.CountAsync(cancellationToken);
 var result = await movies
     .OrderBy(m => m.Title)
     .ThenBy(m => m.Id)
-    .Skip(offset)
-    .Take(limit)
+    .Skip(page.Offset)
+    .Take(page.Limit)
     .Select(m => new
     {
         m.Id,
@@ -40,12 +42,15 @@ var result = await movies
         AverageStars = m.Reviews.Average(r => (double?)r.Stars)
     })
     .ToListAsync(cancellationToken);
+
+return new([.. result.Select(m => new ApplicationMovieSummary(m.Id, m.Title, m.ReviewCount, RoundStars(m.AverageStars)))], page.Offset, page.Limit, totalCount);
 ```
 
 ## Don't
 
 - Add an endpoint or query that returns every row.
 - Use cursors or page numbers. Offset and limit everywhere; a presentation layer that needs cursors (GraphQL connections) wraps the offset.
+- Return a tuple or a bare list and build the page in the handler.
 - Order only by a column that can repeat, such as a title.
 - `Include` child collections on a list just to count or average them. Project the numbers in SQL.
 

.agents/skills/time-provider/SKILL.md

@@ -9,7 +9,7 @@ metadata:
 
 ## The rule
 
-Nothing reads the clock directly. Code that needs the time takes `TimeProvider` through its constructor and calls `GetUtcNow()`. Production gets `TimeProvider.System`, registered with `TryAddSingleton` in both `AddApplication` and `AddInfrastructure`, so either layer works on its own and the clock is only registered once. Tests pass a `FakeTimeProvider` (`Microsoft.Extensions.TimeProvider.Testing`) set to a fixed moment, so every date is known in advance.
+Nothing reads the clock directly. Code that needs the time takes `TimeProvider` through its constructor and calls `GetUtcNow()`. Production gets `TimeProvider.System`, registered with `TryAddSingleton` in `AddInfrastructure` only. The system clock is an outside dependency, and Infrastructure owns those; Application only uses the abstract `TimeProvider`, which is part of .NET and needs no package. Every host calls `AddInfrastructure`, and `TryAdd` lets a host or test register its own clock first. Tests pass a `FakeTimeProvider` (`Microsoft.Extensions.TimeProvider.Testing`) set to a fixed moment, so every date is known in advance.
 
 Times are stored and compared in UTC. Two things read the clock today. The repository stamps `DateCreated` and `DateModified` on writes, and `LoggingBehaviour` times each request with `GetTimestamp()` and `GetElapsedTime()`.
 

src/Application/Authors/IAuthorsRepository.cs

@@ -1,13 +1,13 @@
 namespace CleanLambdaFunction.Application.Authors;
 
+using Common.Paging;
 using Entities;
 
 public interface IAuthorsRepository
 {
-    public Task<(List<AuthorSummary> Items, int TotalCount)> GetAuthors(
+    public Task<Page<AuthorSummary>> GetAuthors(
         string? query,
-        int offset,
-        int limit,
+        PageRequest page,
         CancellationToken cancellationToken);
 
     public Task<Author?> GetAuthorById(Guid id, CancellationToken cancellationToken);

src/Application/Authors/Queries/GetAuthors/GetAuthorsHandler.cs

@@ -8,8 +8,6 @@ public class GetAuthorsHandler(IAuthorsRepository repository) : IRequestHandler<
 {
     public async ValueTask<Page<AuthorSummary>> Handle(GetAuthorsQuery request, CancellationToken cancellationToken)
     {
-        var (items, totalCount) = await repository.GetAuthors(request.Query, request.Offset, request.Limit, cancellationToken);
-
-        return new Page<AuthorSummary>(items, request.Offset, request.Limit, totalCount);
+        return await repository.GetAuthors(request.Query, new PageRequest(request.Offset, request.Limit), cancellationToken);
     }
 }

src/Application/Common/Paging/PageRequest.cs

@@ -0,0 +1,8 @@
+namespace CleanLambdaFunction.Application.Common.Paging;
+
+/// <summary>
+/// The slice of a list a use case asks a repository for.
+/// </summary>
+/// <param name="Offset">How many items to skip. 0 is the first page.</param>
+/// <param name="Limit">The most items to return.</param>
+public record PageRequest(int Offset, int Limit);

src/Application/DependencyInjection.cs

@@ -6,15 +6,13 @@ namespace CleanLambdaFunction.Application;
 using FluentValidation;
 using Mediator;
 using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.DependencyInjection.Extensions;
 
 [ExcludeFromCodeCoverage]
 public static class DependencyInjection
 {
     public static IServiceCollection AddApplication(this IServiceCollection services)
     {
         _ = services.AddValidatorsFromAssembly(Assembly.GetExecutingAssembly(), ServiceLifetime.Transient);
-        services.TryAddSingleton(TimeProvider.System);
 
         _ = services.AddScoped(typeof(IPipelineBehavior<,>), typeof(LoggingBehaviour<,>));
         _ = services.AddScoped(typeof(IPipelineBehavior<,>), typeof(ValidationBehaviour<,>));

src/Application/Movies/IMoviesRepository.cs

@@ -1,13 +1,13 @@
 namespace CleanLambdaFunction.Application.Movies;
 
+using Common.Paging;
 using Entities;
 
 public interface IMoviesRepository
 {
-    public Task<(List<MovieSummary> Items, int TotalCount)> GetMovies(
+    public Task<Page<MovieSummary>> GetMovies(
         string? query,
-        int offset,
-        int limit,
+        PageRequest page,
         CancellationToken cancellationToken);
 
     public Task<Movie?> GetMovieById(Guid id, CancellationToken cancellationToken);

src/Application/Movies/Queries/GetMovies/GetMoviesHandler.cs

@@ -8,8 +8,6 @@ public class GetMoviesHandler(IMoviesRepository repository) : IRequestHandler<Ge
 {
     public async ValueTask<Page<MovieSummary>> Handle(GetMoviesQuery request, CancellationToken cancellationToken)
     {
-        var (items, totalCount) = await repository.GetMovies(request.Query, request.Offset, request.Limit, cancellationToken);
-
-        return new Page<MovieSummary>(items, request.Offset, request.Limit, totalCount);
+        return await repository.GetMovies(request.Query, new PageRequest(request.Offset, request.Limit), cancellationToken);
     }
 }

src/Application/Reviews/IReviewsRepository.cs

@@ -1,5 +1,6 @@
 namespace CleanLambdaFunction.Application.Reviews;
 
+using Common.Paging;
 using Entities;
 
 public interface IReviewsRepository
@@ -12,11 +13,10 @@ public Task<Review> CreateReview(
 
     public Task<bool> DeleteReview(Guid id, CancellationToken cancellationToken);
 
-    public Task<(List<Review> Items, int TotalCount)> GetReviews(
+    public Task<Page<Review>> GetReviews(
         Guid? movieId,
         Guid? authorId,
-        int offset,
-        int limit,
+        PageRequest page,
         CancellationToken cancellationToken);
 
     public Task<List<Review>> GetReviewsForMovies(IReadOnlyCollection<Guid> movieIds, CancellationToken cancellationToken);

src/Application/Reviews/Queries/GetReviews/GetReviewsHandler.cs

@@ -8,8 +8,6 @@ public class GetReviewsHandler(IReviewsRepository repository) : IRequestHandler<
 {
     public async ValueTask<Page<Review>> Handle(GetReviewsQuery request, CancellationToken cancellationToken)
     {
-        var (items, totalCount) = await repository.GetReviews(request.MovieId, request.AuthorId, request.Offset, request.Limit, cancellationToken);
-
-        return new Page<Review>(items, request.Offset, request.Limit, totalCount);
+        return await repository.GetReviews(request.MovieId, request.AuthorId, new PageRequest(request.Offset, request.Limit), cancellationToken);
     }
 }

src/Application/Versions/Entities/VersionInfo.cs

@@ -1,5 +1,7 @@
 namespace CleanLambdaFunction.Application.Versions.Entities;
 
+using System.Reflection;
+
 /// <summary>
 /// The version details of the running application.
 /// </summary>
@@ -16,4 +18,18 @@ public class VersionInfo
     /// </summary>
     /// <example>1.1.0+e30eba8</example>
     public required string InformationalVersion { get; init; }
+
+    /// <summary>
+    /// Reads the version attributes of the assembly the host hands over, usually its own.
+    /// </summary>
+    /// <param name="assembly">The assembly to read, or null for empty versions.</param>
+    /// <returns>The assembly's file and informational versions.</returns>
+    public static VersionInfo FromAssembly(Assembly? assembly)
+    {
+        return new VersionInfo
+        {
+            FileVersion = $"{assembly?.GetCustomAttribute<AssemblyFileVersionAttribute>()?.Version}",
+            InformationalVersion = $"{assembly?.GetCustomAttribute<AssemblyInformationalVersionAttribute>()?.InformationalVersion}"
+        };
+    }
 }

src/Application/Versions/Queries/GetVersion/GetVersionHandler.cs

@@ -1,35 +1,12 @@
 namespace CleanLambdaFunction.Application.Versions.Queries.GetVersion;
 
-using System.Reflection;
 using Entities;
 using Mediator;
 
-public class GetVersionHandler : IRequestHandler<GetVersionQuery, VersionInfo>
+public class GetVersionHandler(VersionInfo version) : IRequestHandler<GetVersionQuery, VersionInfo>
 {
-    private readonly Assembly? assembly;
-
-    /// <summary>Reads the version of the app that's running.</summary>
-    public GetVersionHandler()
-        : this(Assembly.GetEntryAssembly())
-    {
-    }
-
-    /// <summary>Reads the version of the given assembly, so tests can choose one with known values.</summary>
-    internal GetVersionHandler(Assembly? assembly)
-    {
-        this.assembly = assembly;
-    }
-
     public ValueTask<VersionInfo> Handle(GetVersionQuery request, CancellationToken cancellationToken)
     {
-        var version = new VersionInfo
-        {
-            FileVersion =
-                $"{this.assembly?.GetCustomAttribute<AssemblyFileVersionAttribute>()?.Version}",
-            InformationalVersion =
-                $"{this.assembly?.GetCustomAttribute<AssemblyInformationalVersionAttribute>()?.InformationalVersion}"
-        };
-
         return ValueTask.FromResult(version);
     }
 }