Add BC Contract

Create Contract for inter-BC communication using Provider pattern.

When to Use

• BC needs to read data from another BC
• Creating select options from another BC (TwigComponent)
• Exposing domain data to other contexts

Inputs/Outputs

Process

Structures

Contract (interface in ProviderBC/Contracts/):

interface ContractName {
    public function provide(string $uuid): EntityData; // throws
    public function provideAll(?array $ids = null): iterable;
}

Provider (readonly, uses Finder):

final readonly class ProviderBCContractName implements ContractName {
    public function __construct(private EntityFinder $finder) {} // Finder, NOT Repository

    public function provide(string $uuid): EntityData {
        $entity = $this->finder->find($uuid) ?? throw EntityNotFound::fromUuid($uuid);
        return $this->toData($entity);
    }

    public function provideAll(?array $ids = null): iterable {
        $entities = $ids ? $this->finder->findByUuids($ids) : $this->finder->findAll();
        foreach ($entities as $entity) {
            yield $this->toData($entity);
        }
    }

    private function toData(Entity $entity): EntityData { /* convert to DTO */ }
}

Config (ProviderBC/Frameworks/config/services.yaml):

ProviderBC\Contracts\ContractName:
    class: ProviderBC\Adapters\Contracts\ProviderBCContractName

Deptrac (ConsumerBC/Frameworks/deptrac.yaml):

ConsumerBC\Adapters:
    - ProviderBC\Contracts  # ONLY Contracts, NOT Entities/UseCases

See: docs/GLOSSARY.md#contract, #provider, #data-dto

Rules

CRITICAL:

• Provider uses Finder (NOT Repository) - providers are read-only
• Consumer depends ONLY on Contract interface (never Provider implementation)
• Deptrac allows ONLY Contracts namespace (not Entities/UseCases)

Locations:

• Contract: ProviderBC/Contracts/
• Provider: ProviderBC/Adapters/Contracts/
• Exception: ProviderBC/Contracts/Exception/ if needed
• DTO: ProviderBC/Contracts/DTO/ if complex data

Naming:

• Contract: {Entity}Provider (e.g., ArticleProvider)
• Provider: {BC}{Contract} (e.g., AdminArticleProvider)

Variants

Query Provider (data access):

public function provide(string $uuid): EntityData;
public function provideAll(?array $ids = null): iterable;

TwigComponent Provider (form select):

/** @return array<string, string> [uuid => label] */
public function getAllForChoice(): array;

Templates

• contract.php.tpl - Contract interface
• provider.php.tpl - Provider implementation

Location: .claude/templates/

References

• Contract/Provider pattern: docs/GLOSSARY.md#contract, #provider
• Inter-BC architecture: docs/architecture.md#inter-bc
• Detailed guide: docs/guides/bounded-contexts.md