Issue-293: Create Structure for Features

plugin.php

@@ -63,6 +63,11 @@ function () {
  * Instantiate the plugin.
  */
 function main(): void {
-	// ...
+	// This should be an array with keys set to feature classnames and arguments.
+	$features = [
+		// Add initial features here.
+	];
+	$features = apply_filters( 'create_wordpress_plugin_features', $features );
+	Feature_Manager::add_features( $features );
 }
 main();

src/class-feature-manager.php

@@ -0,0 +1,80 @@
+<?php
+/**
+ * Class to manage plugin features.
+ *
+ * @package create-wordpress-plugin
+ */
+
+namespace Create_WordPress_Plugin;
+
+use Alley\WP\Types\Feature;
+
+/**
+ * The Feature Manager class.
+ */
+class Feature_Manager {
+	/**
+	 * Collected features.
+	 *
+	 * @var object[]
+	 */
+	private static array $features = [];
+
+	/**
+	 * Set up.
+	 *
+	 * @param array $features_to_create Array of feature classnames and arguments.
+	 *
+	 * @phpstan-param array{string: array{string?: mixed}}|array{} $features_to_create
+	 */
+	public static function add_features( array $features_to_create = [] ): void {
+		foreach ( $features_to_create as $feature_class => $args ) {
+			self::add_feature( $feature_class, $args );
+		}
+	}
+
+	/**
+	 * Return the plugin features.
+	 *
+	 * @return object[] The plugin features.
+	 */
+	public static function get_features(): array {
+		return self::$features;
+	}
+
+	/**
+	 * Add a feature to the plugin.
+	 *
+	 * @param string $feature_class The feature class to add.
+	 * @param array  $args          The arguments to pass to the feature constructor.
+	 *
+	 * @phpstan-param array{string?: mixed} $args
+	 *
+	 * @return object The instatiated feature that was added.
+	 * @throws \Exception If the feature class does not implement Feature.
+	 */
+	public static function add_feature( string $feature_class, array $args = [] ): object {
+		if ( ! in_array( Feature::class, class_implements( $feature_class ) ?: [], true ) ) {
+			throw new \Exception( 'Feature class must implement Feature interface.' );
+		}
+		$feature = new $feature_class( ...$args );
+		$feature->boot(); // @phpstan-ignore-line
+		self::$features[] = $feature;
+		return $feature;
+	}
+
+	/**
+	 * Get a feature by class name.
+	 *
+	 * @param string $feature_name The name of the feature to get.
+	 * @return object|null The feature or null if it doesn't exist.
+	 */
+	public static function get_feature( string $feature_name ): ?object {
+		foreach ( self::$features as $feature ) {
+			if ( get_class( $feature ) === $feature_name ) {
+				return $feature;
+			}
+		}
+		return null;
+	}
+}

src/features/README.md

@@ -0,0 +1,150 @@
+# Features
+Features should be PHP classes that implement the [Alley\WP\Types\Feature interface](https://github.com/alleyinteractive/wp-type-extensions/blob/main/src/alley/wp/types/interface-feature.php).
+
+Features should be located in the `src/features` directory of the plugin and have namespace `Create_WordPress_Plugin\Features;`
+
+Files in the features directory will be autoloaded, but features will not be instantiated. Features are instantiated via the `Feature_Manager` static class.
+
+The following variable is passed to the `Class_Hello` feature in each of the following examples. This shows how we can remove any business logic from the feature and pass it in when the feature is added.
+
+```
+$lyrics = "Hello, Dolly
+    Well, hello, Dolly
+    It's so nice to have you back where you belong
+    You're lookin' swell, Dolly
+    I can tell, Dolly
+    You're still glowin', you're still crowin'
+    You're still goin' strong
+    I feel the room swayin'
+    While the band's playin'
+    One of our old favorite songs from way back when
+    So, take her wrap, fellas
+    Dolly, never go away again";
+```
+
+## There are two ways to add a feature:
+### Add a feature using the `add_features` method
+```
+$features = [
+    'Create_WordPress_Plugin\Features\Hello' => [ 'lyrics' => $lyrics ],
+];
+
+Feature_Manager::add_features( $features );
+```
+
+> 💡 If you `apply_filters` to the features array before passing it to `add_features`, you can modify it with a filter.
+```
+$features = apply_filters( 'create_wordpress_plugin_features', $features );
+```
+
+### Add a feature using the `add_feature` method
+```
+Feature_Manager::add_feature( 'Create_WordPress_Plugin\Features\Hello', [ 'lyrics' => $lyrics ] );
+```
+## Get the instance of an added feature with the `get_feature` method
+```
+$hello_feature = Feature_Manager::get_feature( 'Create_WordPress_Plugin\Features\Hello' );
+```
+## Once we have the instance, we can remove hooks from inside the instance
+```
+remove_action( 'admin_head', [ $hello_feature, 'dolly_css' ] );
+```
+
+## Example feature class:
+This is a port of the infamous WordPress `hello.php` plugin to a feature. The lyrics would be passed in when the feature was called, as shown above.
+```
+<?php
+/**
+ * Feature implementation of hello.php
+ *
+ * @package Create_WordPress_Plugin
+ */
+
+namespace Create_WordPress_Plugin\Features;
+
+use Alley\WP\Types\Feature;
+
+/**
+ * Hello class file
+ */
+final class Hello implements Feature {
+	/**
+	 * Set up.
+	 *
+	 * @param string $lyrics The lyrics to Hello Dolly.
+	 */
+	public function __construct(
+		private readonly string $lyrics,
+	) {}
+
+	/**
+	 * Boot the feature.
+	 */
+	public function boot(): void {
+		add_action( 'admin_notices', [ $this, 'hello_dolly' ] );
+		add_action( 'admin_head', [ $this, 'dolly_css' ] );
+	}
+
+	/**
+	 * Gets a random lyric from the lyric string.
+	 *
+	 * @return string
+	 */
+	public function hello_dolly_get_lyric(): string {
+		// Here we split the lyrics into lines.
+		$lyrics = explode( "\n", $this->lyrics );
+
+		// And then randomly choose a line.
+		return wptexturize( $lyrics[ wp_rand( 0, count( $lyrics ) - 1 ) ] );
+	}
+
+	/**
+	 * Echos the chosen line.
+	 */
+	public function hello_dolly(): void {
+		$chosen = $this->hello_dolly_get_lyric();
+		$lang   = '';
+		if ( 'en_' !== substr( get_user_locale(), 0, 3 ) ) {
+			$lang = ' lang="en"';
+		}
+
+		printf(
+			'<p id="dolly"><span class="screen-reader-text">%s </span><span dir="ltr"%s>%s</span></p>',
+			esc_html__( 'Quote from Hello Dolly song, by Jerry Herman:' ),
+			esc_attr( $lang ),
+			esc_html( $chosen )
+		);
+	}
+
+	/**
+	 * Output css to position the paragraph.
+	 */
+	public function dolly_css(): void {
+		echo "
+		<style type='text/css'>
+		#dolly {
+			float: right;
+			padding: 5px 10px;
+			margin: 0;
+			font-size: 12px;
+			line-height: 1.6666;
+		}
+		.rtl #dolly {
+			float: left;
+		}
+		.block-editor-page #dolly {
+			display: none;
+		}
+		@media screen and (max-width: 782px) {
+			#dolly,
+			.rtl #dolly {
+				float: none;
+				padding-left: 0;
+				padding-right: 0;
+			}
+		}
+		</style>
+		";
+	}
+}
+```