# Module Generator Backend

The backend generator exposes authenticated schema-inspection and generation endpoints. It renders backend files from Handlebars templates and writes frontend files using a copied template plus source strings supplied by the admin app.

## Endpoints

Routes are registered in `apps/backend/start/routes.ts`.

| Method | Path                         | Controller method | Purpose                                            |
| ------ | ---------------------------- | ----------------- | -------------------------------------------------- |
| `GET`  | `/makeModule/tables`         | `tables`          | List eligible public PostgreSQL tables             |
| `GET`  | `/makeModule/columns/:table` | `columns`         | Return columns used to configure form/table fields |
| `POST` | `/makeModule/generate`       | `generate`        | Generate selected frontend and backend assets      |

All three endpoints use `middleware.auth()`.

## Database Inspection

`apps/backend/app/services/database_inspector.ts` reads PostgreSQL `information_schema`.

- Table discovery is limited to the `public` schema.
- framework, authentication, access-control, migration, and PostgreSQL system tables are excluded.
- columns provide `column_name`, `data_type`, and `is_nullable`.
- columns ending in `_id` are treated as belongs-to relationship candidates.
- tables containing a `<table>_id` column are treated as has-many relationship candidates.
- searchable string and numeric columns are derived for generated resource controllers.

Relationship inference is heuristic. Review generated model imports, related class names, property names, and module availability.

## Type Mapping

The controller maps database types separately for Lucid models, Vine validators, and frontend entities.

| Database category     | Lucid TypeScript type | Vine type | Frontend type   |
| --------------------- | --------------------- | --------- | --------------- |
| integer/numeric types | `number`              | `number`  | `number`        |
| boolean               | `boolean`             | `boolean` | `boolean`       |
| date/timestamp        | `DateTime`            | `date`    | `IsoDateString` |
| other values          | `string`              | `string`  | `string`        |

Nullable database columns receive `| null` in generated model/entity types and optional validation where applicable. `created_at`, `updated_at`, and `deleted_at` receive special handling.

## Backend Output

For module name `<name>`, table `<table>`, and derived module class `<ModuleName>`, selected assets are written under:

```txt
apps/backend/modules/<ModuleName>/
├── api/
│   ├── controllers/<entity>_api_controller.ts
│   ├── validators/<entity>_create_api_validator.ts
│   ├── validators/<entity>_update_api_validator.ts
│   └── routes.ts
├── config/permissions.ts
├── controller/<entity>_controller.ts
├── model/<entity>.ts
├── policy/<entity>_policy.ts
├── validators/<entity>_create_validator.ts
├── validators/<entity>_update_validator.ts
└── routes.ts
```

Tests are written under:

```txt
apps/backend/tests/modules/<ModuleName>/
├── <entity>.spec.ts
└── <entity>.api.spec.ts
```

`<entity>` is derived by removing the final character from the selected table name. This assumes a plural table name and must be reviewed for irregular plurals.

## Asset Behavior

### Model

Renders `apps/backend/app/templates/backend/model.hbs` with columns, inferred relationships, searchable fields, and optional password hashing.

### Controller and routes

Renders an authenticated resource controller with list/search/sort/pagination and CRUD actions. `routes.hbs` registers an `apiOnly` resource route and applies authentication.

### Validators

Creates separate create and update Vine validators. Primary keys and timestamp/deletion fields are excluded according to controller rules. Email, password, nullable, and string trimming behavior is inferred from column names and database metadata.

### Policy and permissions

Creates a Bouncer policy with view/create/update/delete checks, creates `config/permissions.ts`, and adds a lazy policy import to `apps/backend/app/policies/main.ts` when missing.

Permission slugs are derived from the module name, for example:

```txt
<name>s.view
<name>s.create
<name>s.update
<name>s.delete
```

Review names that are already plural because policy and frontend metadata derivation are not a general-purpose pluralization system.

### API subtree

Creates a second CRUD controller and route group under `/api/<entity>`, plus API-specific validators and a test. The controller imports the generated model and passes it to `modelToSchema` for Swagger response metadata.

API routes currently do not add authentication middleware in the generated API template. Add the required authentication and authorization explicitly before exposing the route.

## Frontend Writes Performed by the Backend

The backend copies `apps/admin/src/modules/_template` to `apps/admin/src/modules/<name>` and then writes:

- configured form component and form definition;
- configured datatable and list page;
- configured manage trigger, menu, and module manifest;
- generated `config/meta.ts`;
- database-derived `entities/Entity.ts`.

See [frontend.md](./frontend.md) for the complete frontend structure and payload ownership.

## Template Helpers

The controller registers Handlebars helpers for `eq`, `not`, `or`, and `and`. New templates should use the existing render function and receive an explicit context object from the controller.

## Extending the Backend Generator

1. Add or update a Handlebars template under `apps/backend/app/templates/`.
2. Add an explicit destination path in the controller `paths` object.
3. Create its parent directory through the existing path initialization.
4. Render only when the corresponding asset is selected.
5. Pass normalized metadata rather than querying the database inside templates.
6. Add generation tests for nullable values, dates, numeric types, passwords, and irregular names.
7. Verify both backend and frontend builds after generation.

Avoid adding hidden writes. Every generated or modified destination, including shared registries such as `app/policies/main.ts`, should remain visible in the controller flow and documented here.