# MercadoDeVida backend — modular monolith skeleton

TypeScript + Fastify modular monolith. Simple code, clear modules, small changes, no magic.

## Requirements

- Node.js >= 22
- npm

## Commands

```bash
npm install           # install dependencies
npm run build         # compile to dist/
npm start             # run compiled server (PORT, HOST env vars)
npm test              # vitest unit tests (no database needed)
npm run typecheck     # tsc --noEmit
npm run lint          # eslint + prettier check
npm run lint:boundaries  # module boundary check
```

## Configuration

Startup is fail-fast: `src/infrastructure/config` parses env once and refuses to boot
on missing/invalid required vars. `DATABASE_URL` is required; `PORT`, `HOST`,
`LOG_LEVEL`, `NODE_ENV`, `REDIS_URL` are optional with defaults. `COOKIE_SECURE`
defaults to `true` (set `false` only for local http dev). Errors name variable
NAMES only, never values.

Feature flags: `FLAG_<NAME>=true|false` env vars seed the flag store at boot. Unknown
flags default to OFF (fail-safe). Flags flip at runtime through the store — activation
is separate from deployment (no redeploy). Copy `.env.example` to `.env` to start.

## HTTP contract

- Every response carries an `x-request-id` header (propagated from a safe incoming
  `x-request-id`, or a fresh UUID). Every JSON log line for a request carries the same id.
- Errors always use one envelope:
  `{ "error": { "statusCode", "code", "message", "details?" }, "requestId" }`
  Codes: `NOT_FOUND`, `VALIDATION_ERROR`, `BAD_REQUEST`/Fastify 4xx codes, `INTERNAL_ERROR`.
  5xx messages are always generic; stack traces stay in server logs only.
- Input validation is explicit per route: `parseJson(schema, body)` (zod) in the handler.
- Auth codes: `UNAUTHORIZED` (401, missing/invalid/revoked session),
  `FORBIDDEN` (403, role or ownership check failed), `INVALID_CREDENTIALS` (401),
  `EMAIL_ALREADY_REGISTERED` (409), `TOO_MANY_ATTEMPTS` (429, with `Retry-After` header).
- Log level via `LOG_LEVEL` env var (default `info`); logs are JSON only.

## Authentication (identity module)

The server is the only authority for identity; the frontend is never trusted with
session or credential state.

| Route               | Result                                                    |
| ------------------- | --------------------------------------------------------- |
| POST /auth/register | `201` + `{ id, email, role, createdAt }`                  |
| POST /auth/login    | `200` + `{ id, email, role }` + `Set-Cookie: mdv_session` |
| POST /auth/logout   | `204`, cookie cleared, session revoked (idempotent)       |

- Passwords: argon2id (OWASP parameters). Only the PHC hash is stored, never
  plaintext or anything reversible.
- Sessions: opaque 512-bit token in the cookie; the DB stores only its SHA-256
  hash (`identity_sessions.token_hash`). TTL 7 days; logout revokes server-side.
- Cookie: `HttpOnly`, `Secure` (`COOKIE_SECURE`, default true), `SameSite=Lax`,
  `Path=/`, `Max-Age=604800`.
- Login failures: identical generic 401 for unknown email and wrong password (no
  enumeration; timing equalized via dummy hash). After 10 consecutive failures per
  email, further attempts get `429` with `Retry-After` for 15 minutes. The limiter
  is in-memory per instance behind a `LoginRateLimiter` interface (Redis-backed
  swap later without touching use cases).
- Identity routes are wired only when the app is built with a DB pool.

## Users and RBAC (users module)

Every route resolves the session cookie against the DB first (expired/revoked
sessions and missing cookies get `401 UNAUTHORIZED`). Roles are `customer`
(default) and `admin`; the role is read from `identity_users` on every request,
so promotions/demotions apply immediately. Role changes are an out-of-band DB
operation in this slice (no admin API yet).

| Route                                  | Access         | Result                             |
| -------------------------------------- | -------------- | ---------------------------------- |
| GET /users                             | admin only     | `200` + `{ items: [profile] }`     |
| GET /users/:id                         | owner or admin | `200` profile, `404` if none yet   |
| PATCH /users/:id                       | owner or admin | `200` upserted profile             |
| GET /users/:id/addresses               | owner or admin | `200` + `{ items: [address] }`     |
| POST /users/:id/addresses              | owner or admin | `201` address                      |
| PATCH /users/:id/addresses/:addressId  | owner or admin | `200` address, `404` if not theirs |
| DELETE /users/:id/addresses/:addressId | owner or admin | `204`, `404` if not theirs         |

- Authorization is checked before existence: a non-owner gets `403 FORBIDDEN`
  regardless of whether the target resource exists (no enumeration).
- Address queries are scoped by `user_id` in SQL, so a valid foreign address id
  is unreachable.
- `GET /users` lists users that have a profile row (users who have patched their
  profile at least once).
- The users module never imports identity: session resolution arrives as an
  injected `Authenticate` function from the composition root.

## Database (local dev)

```bash
cp .env.example .env  # once
npm run docker:up     # start PostgreSQL 16 + Redis 7
npm run db:up         # apply migrations
npm run db:status     # list applied migrations
npm run db:down       # revert last migration
npm run test:integration  # integration tests (need TEST_DATABASE_URL from .env)
npm run docker:down   # stop services (add -v to wipe volumes)
```

### Table naming convention

```text
<module>_<table>          e.g. catalog_products, inventory_stock, orders_orders
```

- Every table is prefixed with its owning module.
- A module never queries tables without its own prefix; data flows through module interfaces.
- Migrations are immutable once merged: fixes ship as new migrations.
- No schema change without migration.

## Layout

```text
src/
├── app/             # composition root (only place that wires modules)
├── infrastructure/  # http server, db pool, config, logging
├── modules/         # business modules, one folder each
│   ├── health/      # exemplar module: public API only via index.ts
│   ├── flags/       # feature flags (unknown default OFF, runtime flip)
│   ├── identity/    # register/login/logout, argon2, sessions, rate limit
│   └── users/       # profile + address CRUD, owner-or-admin RBAC
└── shared/          # cross-cutting helpers (error envelope, input parsing)
```

## Module rules

- A module exposes its public API only through its `index.ts`.
- Files inside a module may import: own subtree, `src/shared`, Node builtins, npm packages.
- Code outside modules (app/infrastructure) may import a module only via its `index.ts`.
- `npm run lint:boundaries` enforces these rules.