# Implementer — F-007 Categories module

done -> work/artifacts/F-007/implementer.md

## Summary
Implemented the categories module as a hexagonal backend slice with PostgreSQL persistence, Fastify routes, validation, tree handling, slug public URLs, and tests.

## Changed files
- `project/src/modules/categories/domain/category.ts`
- `project/src/modules/categories/domain/errors.ts`
- `project/src/modules/categories/domain/ports.ts`
- `project/src/modules/categories/application/category-use-cases.ts`
- `project/src/modules/categories/infrastructure/pg-category-repository.ts`
- `project/src/modules/categories/api/categories.routes.ts`
- `project/src/modules/categories/index.ts`
- `project/migrations/005_categories.js`
- `project/src/app/build-app.ts`
- `project/src/modules/categories/tests/category-use-cases.test.ts`
- `project/src/app/tests/categories.itest.ts`
- `backlog/features.json`
- `work/current.md`
- `work/artifacts/F-007/architect.md`

## Acceptance traceability
1. Duplicate slug returns HTTP 409
   - Implemented through `categories_categories.slug UNIQUE` and `CATEGORY_SLUG_EXISTS` mapping.
   - Covered by `project/src/app/tests/categories.itest.ts` (`returns HTTP 409 for duplicate slug`).
2. Category tree supports parent/child and blocks cycles
   - Implemented with adjacency list `parent_id`, tree builder, self-parent guard, recursive descendant check.
   - Covered by unit and integration tests.
3. Public URL is `/categoria/<slug>`, never internal id
   - Implemented `GET /categoria/:slug` and serialized `url: /categoria/<slug>`.
   - Covered by integration test.
4. `verify.sh` green
   - Verified after implementation.

## Commands run
- `cd project && npm run typecheck` — PASS
- `cd project && npm test` — PASS: 55 passed, 25 skipped (DB integration skipped without `TEST_DATABASE_URL`)
- `cd project && npm run lint` — PASS after Prettier normalization
- `cd project && npm run build` — PASS
- `cd project && npm run lint:boundaries` — PASS: 61 files checked
- `./scripts/verify.sh` — PASS

## Notes
- No new npm dependencies.
- Category mutation routes are admin-only using the existing shared auth contract injected from the composition root.
- Public reads (`GET /categories/tree`, `GET /categoria/:slug`) are unauthenticated.
- Corrected delete behavior during review preparation: missing category now maps to `404 NOT_FOUND`; category with children maps to `409 CATEGORY_HAS_CHILDREN`.
- Documentation stage should update README/API notes because new user-facing endpoints were added.
