Update the App class documentation with a detailed overview, including methods, properties, and a usage example, to improve clarity and understanding of the functionality.

Author: BottyIvan

docs/guide/app.md

@@ -1,3 +1,158 @@
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+---
+
+:::danger Important
+Certain features of the `App` class are either under development or may undergo significant changes in future updates. Please refer to the official documentation regularly to stay informed about the latest updates and modifications.
+:::
+
+# App Class Overview
+
+The `App` class is the cornerstone of the **Fire Framework**, designed to streamline application management. It handles configuration, routing, middleware, services, and orchestrates the entire application lifecycle with a robust and cohesive structure.
+
+---
+
+## 📖 Overview
+
+### Namespace
+
+```php
+Framework\Fire
+```
+
+### Description
+
+The `App` class is implemented as a singleton to ensure a single instance of the application is maintained. It orchestrates environment configuration, routing, middleware, and database connections, providing a cohesive structure for application management.
+
+---
+
+## 🛠️ Properties
+
+### `static ?App $instance`
+
+- **Description**: Holds the singleton instance of the `App` class.
+- **Visibility**: Protected.
+
+### `IRouter $router`
+
+- **Description**: Manages HTTP request routing.
+- **Visibility**: Protected.
+
+### `string $envPath`
+
+- **Description**: Specifies the path to the `.env` file.
+- **Visibility**: Protected.
+
+### `string $basePath`
+
+- **Description**: Defines the base directory of the application.
+- **Visibility**: Protected.
+
+### `IEnvironmentLoader $environmentLoader`
+
+- **Description**: Handles the loading of environment variables.
+- **Visibility**: Protected.
+
+### `IDatabaseManager $databaseManager`
+
+- **Description**: Manages database connections and interactions.
+- **Visibility**: Protected.
+
+---
+
+## 🔧 Methods
+
+### `static getInstance(): self`
+
+- **Description**: Retrieves the singleton instance of the `App` class.
+- **Throws**: `RuntimeException` if the instance is not initialized.
+- **Returns**: `App`.
+
+---
+
+### `static configure(string $basePath, ?IEnvironmentLoader $environmentLoader = null, ?IRouter $router = null, ?IDatabaseManager $databaseManager = null): self`
+
+- **Description**: Configures the application with essential components such as the base path, environment loader, router, and database manager.
+- **Parameters**:
+  - `string $basePath`: The base directory of the application.
+  - `?IEnvironmentLoader $environmentLoader`: (Optional) The environment loader instance.
+  - `?IRouter $router`: (Optional) The router instance.
+  - `?IDatabaseManager $databaseManager`: (Optional) The database manager instance.
+- **Returns**: `App`.
+
+---
+
+### `loadRoutes(): self`
+
+- **Description**: Loads application routes from the `/routes` directory.
+- **Throws**: `RuntimeException` if the routes directory is missing.
+- **Returns**: `App`.
+
+---
+
+### `loadMiddlewares(): self`
+
+- **Description**: Loads middleware components from the `/app/middlewares` directory.
+- **Returns**: `App`.
+
+---
+
+### `loadServices(): self`
+
+- **Description**: Loads additional services from a specified directory (to be implemented).
+- **Returns**: `App`.
+
+---
+
+### `getBasePath(): string`
+
+- **Description**: Retrieves the base directory of the application.
+- **Returns**: `string`.
+
+---
+
+### `setNotFoundHandler(callable $handler): self`
+
+- **Description**: Configures a custom handler for "404 Not Found" errors.
+- **Parameters**:
+  - `callable $handler`: The callback function to handle 404 errors.
+- **Returns**: `App`.
+
+---
+
+### `run(): void`
+
+- **Description**: Executes the application by resolving the current HTTP request through the router. Handles exceptions by returning a 500 error response.
+- **Returns**: `void`.
+
+---
+
+## 📂 Usage Example
+
+```php
+use Framework\Fire\App;
+use Framework\Fire\Environment\EnvironmentLoader;
+use Framework\Fire\Routing\Router;
+
+// Configure the application
+$app = App::configure(
+        __DIR__,
+        new EnvironmentLoader(__DIR__),
+        new Router()
+);
+
+// Load routes and middleware
+$app->loadRoutes()
+        ->loadMiddlewares();
+
+// Run the application
+$app->run();
+```
+
+---
+
+## 🔗 Notes
+
+- The `App` class employs a singleton pattern to ensure a single instance is used throughout the application lifecycle.
+- Additional functionality can be integrated by utilizing the `loadServices()` method.
+- Comprehensive error handling is implemented to manage runtime exceptions effectively, ensuring application stability.