# Classes Backend

## Purpose

`classes` is the per-organization roster of teaching classes (a named, sectioned group of
students, optionally tied to an academic year, grade, campus and homeroom teacher). It is a
generic-CRUD slice assembled from the shared factories; the backend is the source of truth for
class records.

## Slice Files (by layer)

- Route: `src/routes/classes.ts` — `createCrudRouter(controller, { permission: 'classes' })`.
- Controller: `src/api/controllers/classes.controller.ts` — `createCrudController(service, { csvFields })`.
- Service (BLL): `src/services/classes.ts` — `createCrudService(DbApi, { notFoundCode: 'classesNotFound' })`.
- Repository (DAL): `src/db/api/classes.ts` (`ClassesDBApi`) — entity-specific
  `create`/`bulkImport`/`update`/`findBy`/`findAll`; `remove`/`deleteByIds`/`findAllAutocomplete`
  delegate to `db/api/shared/repository.ts`.
- Model: `src/db/models/classes.ts`.
- Shared used: CRUD factories (`services/shared/crud-service.ts`,
  `api/controllers/shared/crud-controller.ts`, `api/http/crud-router.ts`), repository helpers
  (`db/api/shared/repository.ts`), `shared/constants/pagination.ts` (`resolvePagination`),
  `shared/constants/database.ts` (`BULK_IMPORT_TIMESTAMP_STEP_MS`), `db/utils.ts` (`Utils`).

## API

The standard generic-CRUD surface (all under `/api/classes`, JWT + `${METHOD}_CLASSES`
permission, all `200`) — see `backend-architecture.md` for the shared contract:

- `POST /` — body `{ data }`, returns `true`.
- `POST /bulk-import` — multipart CSV file, returns `true`.
- `PUT /:id` — body `{ data, id }` (the service reads the id from the **body**), returns `true`.
- `DELETE /:id` — returns `true`.
- `POST /deleteByIds` — body `{ data: string[] }`, returns `true`.
- `GET /` — query filters, returns `{ rows, count }`; `?filetype=csv` streams a CSV of `csvFields`.
- `GET /count` — returns `{ rows: [], count }`.
- `GET /autocomplete` — `?query&limit&offset`, returns `[{ id, label }]` where `label` is `name`.
- `GET /:id` — returns the record with eager associations (see Data Contract).

`csvFields`: `id`, `name`, `section`, `capacity`.

## Access Rules

- JWT required; the whole router is guarded by `checkCrudPermissions('classes')`, deriving
  `READ_CLASSES` / `CREATE_CLASSES` / `UPDATE_CLASSES` / `DELETE_CLASSES` per HTTP method.
- Access is granted by role permission or per-user `custom_permissions` (see `permissions.md`).

## Tenant Scope

- `findAll` scopes `where.organizationId` to `currentUser.organizationId`; a `globalAccess`
  role clears the org filter (sees all tenants).
- `create` assigns the organization from `currentUser.organizationId`; `update` only reassigns
  organization for `globalAccess` users (otherwise it stays the caller's org).

## Data Contract

Model columns (`paranoid`, soft-delete via `deletedAt`):

- `id` (UUID PK).
- `name`, `section` — TEXT, nullable.
- `capacity` — INTEGER, nullable.
- `status` — ENUM `active` | `archived`.
- `importHash` (unique), `academic_yearId`, `campusId`, `organizationId`, `gradeId`,
  `homeroom_teacherId`, `createdById`, `updatedById`, timestamps.

Associations: `belongsTo` organization, campus, academic_year (academic_years), grade (grades),
homeroom_teacher (staff), createdBy/updatedBy (users); `hasMany` `class_enrollments_class`,
`class_subjects_class`, `attendance_sessions_class`. `findBy`/`GET /:id` eager-load
class_enrollments_class, class_subjects_class, attendance_sessions_class, organization, campus,
academic_year, grade and homeroom_teacher in a single `Promise.all`.

List filters (`ClassesFilter`): `id`, `name` (ilike), `section` (ilike), `capacityRange`,
`status`, `campus` (id or name, `|`-separated), `academic_year` (id or name, `|`-separated),
`grade` (id or name, `|`-separated), `homeroom_teacher` (id or `employee_number`, `|`-separated),
`organization`, `createdAtRange`, plus `field`/`sort` ordering and `limit`/`page` pagination.

## Behavior / Notes

- `create`/`update` wire the organization, campus, academic_year, grade and homeroom_teacher
  relations via the `set*` association mixins; `bulkImport` does not set these relations.
- `bulkImport` offsets `createdAt` per row by `BULK_IMPORT_TIMESTAMP_STEP_MS` to preserve order.
- List pagination uses the shared `resolvePagination` defaults (page size 10, capped at 100).
- Note: `ClassesFilter` accepts an `active` flag the model has no column for; it is currently
  inert (kept for source accuracy).

## Tests

None yet.

## Related

- Generic-CRUD contract: `backend-architecture.md`; related slices: `class_enrollments`,
  `class_subjects`, `campuses`, `academic_years`, `grades`, `staff`, `attendance_sessions`,
  `permissions.md`.