# Controllers

Controllers extend `MagicController` (a `ChangeNotifier`) to hold reactive state, run validation, and dispatch navigation, keeping business logic out of the widget tree.

- [Introduction](#introduction)
- [Writing Controllers](#writing-controllers)
    - [Basic Controllers](#basic-controllers)
    - [Single Action Controllers](#single-action-controllers)
- [Controller State Management](#controller-state-management)
    - [The MagicStateMixin](#the-magicstatemixin)
    - [Rendering State](#rendering-state)
    - [Fetch Helpers](#fetch-helpers)
- [Validation Handling](#validation-handling)
- [Controller Lifecycle](#controller-lifecycle)
- [Generating Controllers](#generating-controllers)

<a name="introduction"></a>
## Introduction

Instead of defining all of your request handling logic as closures in your route files, you may wish to organize this behavior using "controller" classes. Controllers can group related request handling logic into a single class. Controllers are stored in the `lib/app/controllers` directory.

<a name="writing-controllers"></a>
## Writing Controllers

<a name="basic-controllers"></a>
### Basic Controllers

To generate a new controller, use the `make:controller` Magic CLI command:

```bash
dart run magic:artisan make:controller User
```

A basic controller extends `MagicController` and contains action methods that return widgets:

```dart
import 'package:flutter/material.dart';
import 'package:magic/magic.dart';
import '../../resources/views/users/user_list_view.dart';
import '../../resources/views/users/user_show_view.dart';

class UserController extends MagicController {
  /// Singleton accessor - the Magic way!
  static UserController get instance => Magic.findOrPut(UserController.new);

  /// Display a listing of users.
  Widget index() => const UserListView();

  /// Display the specified user.
  Widget show(String id) => UserShowView(userId: id);
  
  /// Show the form for creating a new user.
  Widget create() => const CreateUserView();
}
```

Register the controller's methods as routes:

```dart
MagicRoute.page('/users', () => UserController.instance.index());
MagicRoute.page('/users/create', () => UserController.instance.create());
MagicRoute.page('/users/:id', (id) => UserController.instance.show(id));
```

> [!NOTE]
> The `Magic.findOrPut()` pattern ensures a single controller instance exists, similar to Laravel's service container.

<a name="single-action-controllers"></a>
### Single Action Controllers

If a controller action is particularly complex, you may dedicate an entire controller class to that single action:

```dart
class ExportReportController extends MagicController {
  static ExportReportController get instance => 
      Magic.findOrPut(ExportReportController.new);

  Widget invoke() {
    return const ExportReportView();
  }
}
```

<a name="controller-state-management"></a>
## Controller State Management

<a name="the-magicstatemixin"></a>
### The MagicStateMixin

Controllers may use `MagicStateMixin<T>` to manage async data and loading states:

```dart
class UserController extends MagicController 
    with MagicStateMixin<List<User>> {
  
  static UserController get instance => Magic.findOrPut(UserController.new);

  Widget index() {
    if (isEmpty) loadUsers();
    return const UserListView();
  }

  Future<void> loadUsers() async {
    setLoading();
    
    try {
      final users = await User.all();
      setSuccess(users);
    } catch (e) {
      setError('Failed to load users: $e');
    }
  }
}
```

#### State Methods

| Method | Description |
|--------|-------------|
| `setLoading()` | Set loading state |
| `setSuccess(T data)` | Set success state with data |
| `setError(String message)` | Set error state with message |
| `setEmpty()` | Set empty state (no data) |

#### State Properties

| Property | Type | Description |
|----------|------|-------------|
| `isLoading` | bool | Currently loading |
| `isSuccess` | bool | Successfully loaded |
| `isError` | bool | Error occurred |
| `isEmpty` | bool | Empty/no data |
| `rxState` | T? | The current data |

<a name="fetch-helpers"></a>
### Fetch Helpers

`MagicStateMixin` ships two convenience methods that handle the full loading → success/error/empty cycle without boilerplate. Both delegate to `Http.get()` internally.

#### `fetchList<E>`

Fetch a paginated or collection endpoint. The response body must contain a JSON array under `dataKey` (default: `'data'`).

```dart
Future<void> fetchList<E>(
  String url,
  E Function(Map<String, dynamic>) fromMap, {
  String dataKey = 'data',
  Map<String, dynamic>? query,
  Map<String, String>? headers,
})
```

```dart
class ProjectController extends MagicController
    with MagicStateMixin<List<Project>> {

  static ProjectController get instance =>
      Magic.findOrPut(ProjectController.new);

  Future<void> loadProjects(String teamId) =>
      fetchList('teams/$teamId/projects', Project.fromMap);

  // With query parameters
  Future<void> search(String q) =>
      fetchList('projects', Project.fromMap, query: {'q': q});
}
```

State transitions:

| Condition | Resulting State |
|-----------|----------------|
| Request fails (4xx/5xx) | `isError` with `response.errorMessage` |
| `dataKey` list is null or empty | `isEmpty` |
| List has items | `isSuccess` with `List<E>` cast to `T` |

#### `fetchOne`

Fetch a single resource. The response body must contain the resource object under `dataKey` (default: `'data'`).

```dart
Future<void> fetchOne(
  String url,
  T Function(Map<String, dynamic>) fromMap, {
  String dataKey = 'data',
  Map<String, dynamic>? query,
  Map<String, String>? headers,
})
```

```dart
class ProjectDetailController extends MagicController
    with MagicStateMixin<Project> {

  static ProjectDetailController get instance =>
      Magic.findOrPut(ProjectDetailController.new);

  Future<void> loadProject(String id) =>
      fetchOne('projects/$id', Project.fromMap);
}
```

State transitions:

| Condition | Resulting State |
|-----------|----------------|
| Request fails (4xx/5xx) | `isError` with `response.errorMessage` |
| `dataKey` value is null | `isError` with `'Resource not found'` |
| Data present | `isSuccess` with parsed `T` |

> [!TIP]
> Both helpers accept optional `query` and `headers` parameters, forwarded directly to `Http.get()`. Use `query` for pagination or filtering parameters.

<a name="rendering-state"></a>
### Rendering State

Use `renderState` in your view to declaratively handle different states—like Blade's `@if` directives:

```dart
class UserListView extends MagicView {
  @override
  Widget build(BuildContext context) {
    final controller = UserController.instance;
    
    return controller.renderState(
      (users) => ListView.builder(
        itemCount: users.length,
        itemBuilder: (_, i) => UserCard(user: users[i]),
      ),
      onLoading: Center(child: CircularProgressIndicator()),
      onError: (msg) => ErrorWidget(message: msg),
      onEmpty: EmptyState(message: 'No users yet'),
    );
  }
}
```

<a name="validation-handling"></a>
## Validation Handling

Controllers can handle server-side validation errors using the `ValidatesRequests` mixin:

```dart
class AuthController extends MagicController 
    with MagicStateMixin<bool>, ValidatesRequests {
  
  static AuthController get instance => Magic.findOrPut(AuthController.new);

  Future<void> register(Map<String, dynamic> data) async {
    setLoading();
    clearErrors();  // Clear previous validation errors
    
    final response = await Http.post('/register', data: data);
    
    if (response.successful) {
      setSuccess(true);
      Magic.success('Success', 'Account created!');
      MagicRoute.to('/dashboard');
    } else {
      // Automatically handles 422 validation errors
      handleApiError(response, fallback: 'Registration failed');
    }
  }
}
```

### ValidatesRequests Methods

| Method | Description |
|--------|-------------|
| `handleApiError(response)` | Handle 422 and other API errors automatically |
| `setErrorsFromResponse(response)` | Populate errors from 422 validation response |
| `hasError('field')` | Check if a field has an error |
| `getError('field')` | Get error message for a field |
| `hasErrors` | Check if any validation errors exist |
| `clearErrors()` | Clear all validation errors |

> [!TIP]
> Use `MagicFormData` in your view to collect form data. The validation errors automatically bind to form fields.

<a name="controller-lifecycle"></a>
## Controller Lifecycle

Controllers have lifecycle methods you can override:

```dart
class UserController extends MagicController {
  @override
  void onInit() {
    super.onInit();
    // Called when controller is first created
    // Initialize data, start listeners, etc.
  }

  @override
  void onClose() {
    // Called when controller is disposed
    // Cancel subscriptions, clean up resources
    super.onClose();
  }
}
```

<a name="generating-controllers"></a>
## Generating Controllers

The Magic CLI can generate controllers with various options:

```bash
# Basic controller
dart run magic:artisan make:controller User

# Resource controller with CRUD actions and views
dart run magic:artisan make:controller Product --resource

# Nested in subfolder
dart run magic:artisan make:controller Admin/Dashboard

# Resource controller with model binding
dart run magic:artisan make:controller Post --resource --model=Post
```

### Command Options

| Option | Alias | Description |
|--------|-------|-------------|
| `--resource` | `-r` | Generate CRUD controller with associated views |

### Resource Controllers

When using `--resource`, the command generates a full resource controller with:

**Controller actions:**
- `index()` - Display a listing
- `create()` - Show creation form
- `store(data)` - Handle creation
- `show(id)` - Display single item
- `edit(id)` - Show edit form
- `update(id, data)` - Handle update
- `destroy(id)` - Handle deletion

**Views:**
- `lib/resources/views/<name>/index_view.dart`
- `lib/resources/views/<name>/show_view.dart`
- `lib/resources/views/<name>/create_view.dart`
- `lib/resources/views/<name>/edit_view.dart`

Example:

```bash
dart run magic:artisan make:controller Task --resource
```

This generates a TaskController with all CRUD actions and four corresponding views.