add-context - SKILL.md Agent Skill

name: add-context description: Create a new business domain context

Add a New Context (Business Domain)

Guide for creating a new context following clean architecture with Domain-Driven Design.

Required Information

Ask the user for:

Context name (e.g., PopcornWatchlist, PopcornReviews)
Domain entities needed
Core use cases to implement

Steps

1. Create Context Package Structure

Contexts/Popcorn{Context}/
├── Package.swift
├── Sources/
│   ├── {Context}Domain/           # Layer 1: Pure business logic
│   │   ├── Entities/
│   │   ├── Repositories/
│   │   └── DataSources/
│   ├── {Context}Application/      # Layer 2: Use cases
│   │   ├── UseCases/
│   │   └── {Context}ApplicationFactory.swift
│   ├── {Context}Infrastructure/   # Layer 3: Data sources
│   │   ├── DataSources/
│   │   │   ├── Local/
│   │   │   │   ├── Models/
│   │   │   │   └── Mappers/
│   │   │   └── Protocols/
│   │   ├── Repositories/
│   │   └── {Context}InfrastructureFactory.swift
│   └── {Context}Composition/      # Layer 4: Wiring
│       └── Popcorn{Context}Factory.swift
└── Tests/
    └── {Context}ApplicationTests/

2. Create Package.swift

// swift-tools-version: 6.2

import PackageDescription

let package = Package(
    name: "Popcorn{Context}",
    platforms: [
        .iOS(.v26),
        .macOS(.v26),
        .visionOS(.v26)
    ],
    products: [
        .library(name: "{Context}Domain", targets: ["{Context}Domain"]),
        .library(name: "{Context}Application", targets: ["{Context}Application"]),
        .library(name: "{Context}Infrastructure", targets: ["{Context}Infrastructure"]),
        .library(name: "{Context}Composition", targets: ["{Context}Composition"])
    ],
    dependencies: [
        .package(path: "../../Core/CoreDomain")
    ],
    targets: [
        // Domain - NO dependencies (pure business logic)
        .target(name: "{Context}Domain"),

        // Application - depends on Domain only
        .target(
            name: "{Context}Application",
            dependencies: ["{Context}Domain"]
        ),

        // Infrastructure - depends on Domain only
        .target(
            name: "{Context}Infrastructure",
            dependencies: ["{Context}Domain"]
        ),

        // Composition - depends on all above
        .target(
            name: "{Context}Composition",
            dependencies: [
                "{Context}Domain",
                "{Context}Application",
                "{Context}Infrastructure"
            ]
        ),

        // Tests
        .testTarget(
            name: "{Context}ApplicationTests",
            dependencies: ["{Context}Application", "{Context}Domain"]
        )
    ]
)

3. Create Domain Layer

Entities/{Entity}.swift:

public struct {Entity}: Identifiable, Equatable, Sendable {
    public let id: Int
    public let name: String
    // Add properties

    public init(id: Int, name: String) {
        self.id = id
        self.name = name
    }
}

Repositories/{Entity}Repository.swift:

public protocol {Entity}Repository: Sendable {
    func {entity}(withID id: Int) async throws({Entity}RepositoryError) -> {Entity}
}

public enum {Entity}RepositoryError: Error, Equatable, Sendable {
    case notFound
    case unknown(Error? = nil)
}

4. Create Application Layer

Follow the add-use-case workflow for each use case.

{Context}ApplicationFactory.swift:

public final class {Context}ApplicationFactory: Sendable {
    private let {entity}Repository: any {Entity}Repository

    public init({entity}Repository: some {Entity}Repository) {
        self.{entity}Repository = {entity}Repository
    }

    public func makeFetch{Entity}UseCase() -> some Fetch{Entity}UseCase {
        DefaultFetch{Entity}UseCase({entity}Repository: {entity}Repository)
    }
}

5. Create Infrastructure Layer

DataSources/Protocols/Remote/{Entity}RemoteDataSource.swift:

public protocol {Entity}RemoteDataSource: Sendable {
    func {entity}(withID id: Int) async throws({Entity}RemoteDataSourceError) -> {Entity}
}

public enum {Entity}RemoteDataSourceError: Error {
    case notFound
    case unauthorised
    case unknown(Error? = nil)
}

Repositories/Default{Entity}Repository.swift:

final class Default{Entity}Repository: {Entity}Repository {
    private let remoteDataSource: any {Entity}RemoteDataSource
    private let localDataSource: any {Entity}LocalDataSource

    func {entity}(withID id: Int) async throws({Entity}RepositoryError) -> {Entity} {
        // Cache-first strategy
    }
}

6. Create Composition Layer

Popcorn{Context}Factory.swift — a concrete Sendable final class (there is no factory protocol; the concrete factory is the public API, like the adapter factories):

public final class Popcorn{Context}Factory: Sendable {
    private let applicationFactory: {Context}ApplicationFactory

    public init({entity}RemoteDataSource: some {Entity}RemoteDataSource, modelContainer: ModelContainer) {
        let infrastructure = {Context}InfrastructureFactory(
            remoteDataSource: {entity}RemoteDataSource,
            modelContainer: modelContainer
        )
        self.applicationFactory = {Context}ApplicationFactory(
            {entity}Repository: infrastructure.make{Entity}Repository()
        )
    }

    public func makeFetch{Entity}UseCase() -> some Fetch{Entity}UseCase {
        applicationFactory.makeFetch{Entity}UseCase()
    }
}

7. Create Adapters

The adapters package bridges external services (TMDb) to the context's ports — the *RemoteDataSource and provider protocols defined in the Domain/Infrastructure layers. Its factory exposes those adapters through make…() -> some Port methods.

It does not build Popcorn{Context}Factory, and it must not depend on {Context}Composition. Assembling the context factory from these adapters is the composition root's job (Step 8) — this keeps the adapters package a leaf in the dependency graph rather than reaching across into the context's composition layer.

Adapters/Contexts/Popcorn{Context}Adapters/
├── Package.swift
├── Sources/
│   └── Popcorn{Context}Adapters/
│       ├── DataSources/
│       │   ├── TMDb{Entity}RemoteDataSource.swift   # conforms to {Entity}RemoteDataSource (internal)
│       │   └── Mappers/                              # TMDb DTO → Domain mappers
│       └── Popcorn{Context}AdaptersFactory.swift
└── Tests/
    └── Popcorn{Context}AdaptersTests/

Package.swift — depend on the context's Domain and Infrastructure products (where the ports live) plus TMDb. Do not add {Context}Composition:

dependencies: [
    .product(name: "{Context}Domain", package: "Popcorn{Context}"),
    .product(name: "{Context}Infrastructure", package: "Popcorn{Context}"),
    "TMDb"
]

Popcorn{Context}AdaptersFactory.swift — return the port implementations, one make…() per port. Keep the concrete adapter types internal; the some Port return types hide them. Qualify the TMDb service type as TMDb.{Entity}Service to avoid ambiguity once {Context}Infrastructure is imported:

import {Context}Infrastructure
import TMDb

public final class Popcorn{Context}AdaptersFactory {

    private let {entity}Service: any TMDb.{Entity}Service

    public init({entity}Service: some TMDb.{Entity}Service) {
        self.{entity}Service = {entity}Service
    }

    public func make{Entity}RemoteDataSource() -> some {Entity}RemoteDataSource {
        TMDb{Entity}RemoteDataSource({entity}Service: {entity}Service)
    }

}

A provider adapter backed by another context's use case (e.g. an AppConfigurationProviding) takes that use case in the factory's init and is exposed via its own make…() method. Concerns that are not adapters — themeColorProvider, observability, a modelContainer — do not belong on this factory; the composition root passes them straight into the context factory (Step 8).

8. Wire in AppServices

AppServices (in AppDependencies/Sources/AppDependencies/Composition/) is the app's composition root: it builds the shared service and factory graph once, in dependency order. Add the new context factory there so features can reach its use cases:

AppServices.swift — declare the factory as a stored property, and add a matching field to the Graph struct + the init assignment:

public let {context}Factory: Popcorn{Context}Factory
// ...in Graph:
let {context}Factory: Popcorn{Context}Factory
// ...in init:
self.{context}Factory = graph.{context}Factory

AppServices+Composition.swift — in buildGraph, build the adapters factory from the shared TMDb services, then assemble Popcorn{Context}Factory from the adapters it produces (plus any non-adapter concerns like the model container or theme-colour provider), and pass it into the returned Graph. The composition root is the single place that assembles context factories from adapters:

let {context}Adapters = Popcorn{Context}AdaptersFactory(
    {entity}Service: domain.tmdb.{entities}
)
let {context}Factory = Popcorn{Context}Factory(
    {entity}RemoteDataSource: {context}Adapters.make{Entity}RemoteDataSource(),
    modelContainer: modelContainer
)

A feature then consumes these use cases in its Dependencies.live(services:) builder via services.{context}Factory.make{UseCaseName}UseCase() — see the add-use-case and add-feature workflows. There is no *+TCA.swift file and no per-use-case dependency registration.

9. Add to Xcode Project

Add the new package to the main Xcode project's package dependencies.

10. Register Tests in Test Plan

Add all new unit test targets to TestPlans/PopcornUnitTests.xctestplan so tests run as part of the test plan. Add an entry to the testTargets array for each test target:

{
  "target" : {
    "containerPath" : "container:Contexts\/Popcorn{Context}",
    "identifier" : "{Context}ApplicationTests",
    "name" : "{Context}ApplicationTests"
  }
}

Repeat for each test target (e.g., {Context}DomainTests, {Context}InfrastructureTests). Do NOT add snapshot test targets here — those belong in PopcornSnapshotTests.xctestplan.

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