mills

Purpose: Business logic and services — framework-free.

mills is where domain rules live. It has no knowledge of HTTP, ORM models, or any specific framework. It operates entirely on the contracts defined in pacts and calls repositories through the protocols defined there.

Depends on / depended on by

Depends on	pacts
Depended on by	gates, inits

mills must never import from Django, SQLAlchemy, or any ORM. If a service needs data access, it receives a UoW or repository via constructor injection.

What it contains

• Service classes implementing business use cases
• Domain logic (validation, computation, orchestration)
• Nothing that touches HTTP, templates, forms, ORM models, or framework internals

Services take UoW via constructor

class InvoiceService:
    def __init__(self, uow: UnitOfWorkProtocol) -> None:
        self._uow = uow

    def generate(self, data: CreateInvoiceDict) -> InvoiceDTO:
        ...

The UoW is passed in by inits — never imported directly from links.

Slicing axis

Files are sliced by subdomain, then bounded context when the subdomain grows. This axis must mirror pacts/ exactly — if pacts splits a subdomain into contexts, mills must do the same.

mills/billing.py
mills/billing/invoicing.py       # only after pacts/billing/invoicing.py exists
mills/billing/subscriptions.py
mills/auth.py

Red flags

• mills importing from Django or any ORM — absolute violation
• mills/web/... or any port axis — mills has no delivery-mechanism axis
• mills/{entity}.py holding context-specific write logic — entity-level mills are only for entity-level invariants
• mills/ sliced differently than pacts/ — axes must mirror
• A single mills.py file — mills must be a package