{
  "module": "layering_rules",
  "content": {
    "path": "layering_rules",
    "docstring": "# Layering Rules\n\n## Summary\n\nThe dependency direction is fixed. Violating it is a design defect.\n\n---\n\n## Allowed imports\n\n```\ninterfaces/*      ->  domain/*            (services, ports, models)\ninterfaces/*      ->  infra/adapters/*    (only read-only value objects)\ndomain/*          ->  domain/*            (same layer)\ndomain/*          ->  pipelines/*         (call a pipeline via a port)\ninfra/adapters/*  ->  domain/ports/*      (implement the interface)\nmain.py/init.py   ->  everything          (composition root only)\n```\n\n## Forbidden imports\n\n```\ndomain/*          ->  interfaces/*        (never)\ndomain/*          ->  fastapi/starlette   (never)\ninfra/adapters/*  ->  interfaces/*        (never)\ninterfaces/*      ->  infra/db/*          (state lives in resources, not imports)\n```\n\n## Why\n\n- A pure domain is testable without a server, a database, or an event loop.\n- Adapters can be swapped (in-memory fake, real database) without touching\n  business logic.\n- The HTTP edge stays thin and replaceable.\n\n## The port/adapter contract\n\nA **port** is an abstract class or protocol declared in `domain/<x>/ports/`.\nAn **adapter** implements it in `infra/adapters/`. The composition root binds\nthe two.\n\n```\ndomain/<resource>/ports/db.py       -> repository port + document model\ndomain/<resource>/ports/service.py  -> service + factory\ninfra/db/repos/<vendor>.py          -> repository adapter factory\ninfra/adapters/service.py           -> generic CRUD service base\n```\n\n## Enforcement\n\n- Keep every domain module importable with only the standard library and\n  Pydantic. If a domain import pulls in `fastapi`, the layering is broken.\n- Reviewers (and CI) reject `import fastapi` inside `domain/` or `infra/`.\n",
    "objects": {}
  }
}