Add UI to select an offline page

pwa-wp.php

@@ -41,7 +41,12 @@
 /** Amend default filters */
 require PWAWP_PLUGIN_DIR . '/wp-includes/default-filters.php';
 
+/** WP_Offline_Page Class */
+require PWAWP_PLUGIN_DIR . '/wp-includes/class-wp-offline-page.php';
+
 $wp_web_app_manifest = new WP_Web_App_Manifest();
 $wp_web_app_manifest->init();
 $wp_https_detection = new WP_HTTPS_Detection();
 $wp_https_detection->init();
+$wp_offline_page = new WP_Offline_Page();
+$wp_offline_page->init();

tests/test-class-wp-offline-page.php

@@ -0,0 +1,170 @@
+<?php
+/**
+ * Tests for class WP_Offline_Page.
+ *
+ * @package PWA
+ */
+
+/**
+ * Tests for class WP_Offline_Page.
+ */
+class Test_WP_Offline_Page extends WP_UnitTestCase {
+
+	/**
+	 * Tested instance.
+	 *
+	 * @var WP_Offline_Page
+	 */
+	public $instance;
+
+	/**
+	 * Setup.
+	 *
+	 * @inheritdoc
+	 */
+	public function setUp() {
+		parent::setUp();
+		$this->instance = new WP_Offline_Page();
+	}
+
+	/**
+	 * Test init.
+	 *
+	 * @covers WP_Offline_Page::init()
+	 */
+	public function test_init() {
+		$this->instance->init();
+		$this->assertEquals( 10, has_action( 'admin_init', array( $this->instance, 'register_setting' ) ) );
+		$this->assertEquals( 10, has_action( 'admin_init', array( $this->instance, 'settings_field' ) ) );
+	}
+
+	/**
+	 * Test register_setting.
+	 *
+	 * @covers WP_Offline_Page::register_setting()
+	 */
+	public function test_register_setting() {
+		global $new_whitelist_options, $wp_registered_settings;
+
+		$this->instance->register_setting();
+		$this->assertTrue( in_array( WP_Offline_Page::OPTION_NAME, $new_whitelist_options['reading'], true ) );
+		$this->assertEquals(
+			array(
+				'type'              => 'integer',
+				'group'             => WP_Offline_Page::OPTION_GROUP,
+				'description'       => '',
+				'sanitize_callback' => array( $this->instance, 'sanitize_callback' ),
+				'show_in_rest'      => false,
+			),
+			$wp_registered_settings[ WP_Offline_Page::OPTION_NAME ]
+		);
+	}
+
+	/**
+	 * Test sanitize_callback.
+	 *
+	 * @covers WP_Offline_Page::sanitize_callback()
+	 */
+	public function test_sanitize_callback() {
+		global $wp_settings_errors;
+
+		$settings_error = array(
+			'setting' => WP_Offline_Page::OPTION_NAME,
+			'code'    => WP_Offline_Page::OPTION_NAME,
+			'type'    => 'error',
+		);
+
+		// The option isn't a post, so this should add a settings error.
+		$this->assertEquals( null, $this->instance->sanitize_callback( true ) );
+		$this->assertEquals(
+			array_merge(
+				$settings_error,
+				array(
+					'message' => 'The current offline page does not exist. Please select or create one.',
+				)
+			),
+			reset( $wp_settings_errors )
+		);
+		$wp_settings_errors = array(); // WPCS: global override OK.
+
+		// The option isn't a post, so this should add a settings error.
+		$trashed_post_id = $this->factory()->post->create( array( 'post_status' => 'trash' ) );
+		$this->assertEquals( null, $this->instance->sanitize_callback( $trashed_post_id ) );
+		$this->assertEquals(
+			array_merge(
+				$settings_error,
+				array(
+					'message' => 'The current offline page is in the trash. Please select or create one.',
+				)
+			),
+			reset( $wp_settings_errors )
+		);
+		$wp_settings_errors = array(); // WPCS: global override OK.
+
+		// The argument passed to the sanitize_callback() is a valid page ID, so it should return it.
+		$valid_post_id = $this->factory()->post->create( array( 'post_type' => 'page' ) );
+		$this->assertEquals( $valid_post_id, $this->instance->sanitize_callback( $valid_post_id ) );
+		$this->assertEquals( array(), $wp_settings_errors );
+	}
+
+	/**
+	 * Test settings_field.
+	 *
+	 * @covers WP_Offline_Page::settings_field()
+	 */
+	public function test_settings_field() {
+		global $wp_settings_fields;
+
+		$this->instance->settings_field();
+		$this->assertEquals(
+			array(
+				'id'       => WP_Offline_Page::SETTING_ID,
+				'title'    => 'Progressive Web App Offline Page',
+				'callback' => array( $this->instance, 'settings_callback' ),
+				'args'     => array(),
+			),
+			$wp_settings_fields[ WP_Offline_Page::OPTION_GROUP ]['default'][ WP_Offline_Page::SETTING_ID ]
+		);
+	}
+
+	/**
+	 * Test settings_callback.
+	 *
+	 * @covers WP_Offline_Page::settings_callback()
+	 */
+	public function test_settings_callback() {
+		$number_pages = 10;
+		$page_ids     = array();
+		for ( $i = 0; $i < $number_pages; $i++ ) {
+			$page_ids[] = $this->factory()->post->create( array( 'post_type' => 'page' ) );
+		}
+		ob_start();
+		$this->instance->settings_callback();
+		$output = ob_get_clean();
+		$this->assertContains( 'Select an existing page:', $output );
+
+		// All of the pages should appear in the <select> element from wp_dropdown_pages().
+		foreach ( $page_ids as $page_id ) {
+			$this->assertContains( strval( $page_id ), $output );
+		}
+	}
+
+	/**
+	 * Test has_pages.
+	 *
+	 * @covers WP_Offline_Page::has_pages()
+	 */
+	public function test_has_pages() {
+		$this->assertFalse( $this->instance->has_pages() );
+
+		// There is a post, but this needs a post type of 'page'.
+		$this->factory()->post->create();
+		$this->assertFalse( $this->instance->has_pages() );
+
+		// There's a post with the type of 'page,' so this should be true.
+		$this->factory()->post->create( array(
+			'post_type' => 'page',
+		) );
+		$this->assertTrue( $this->instance->has_pages() );
+	}
+}

wp-includes/class-wp-offline-page.php

@@ -0,0 +1,157 @@
+<?php
+/**
+ * WP_Offline_Page class.
+ *
+ * @package PWA
+ */
+
+/**
+ * WP_Offline_Page class.
+ * Much of this is taken from wp-admin/privacy.php.
+ */
+class WP_Offline_Page {
+
+	/**
+	 * The option group for the offline page option.
+	 *
+	 * @var string
+	 */
+	const OPTION_GROUP = 'reading';
+
+	/**
+	 * The option name.
+	 *
+	 * @var string
+	 */
+	const OPTION_NAME = 'wp_offline_page';
+
+	/**
+	 * The ID of the settings section.
+	 *
+	 * @var string
+	 */
+	const SETTING_ID = 'pwa_offline_page';
+
+	/**
+	 * Inits the class.
+	 */
+	public function init() {
+		add_action( 'admin_init', array( $this, 'register_setting' ) );
+		add_action( 'admin_init', array( $this, 'settings_field' ) );
+	}
+
+	/**
+	 * Registers the offline page setting.
+	 */
+	public function register_setting() {
+		register_setting(
+			self::OPTION_GROUP,
+			self::OPTION_NAME,
+			array(
+				'type'              => 'integer',
+				'sanitize_callback' => array( $this, 'sanitize_callback' ),
+			)
+		);
+	}
+
+	/**
+	 * Sanitize callback for the setting.
+	 * Mainly taken from wp-admin/privacy.php.
+	 *
+	 * @todo: Ensure this is stored with a custom post status.
+	 * @param string $raw_setting The setting before sanitizing it.
+	 * @return string|null The sanitized setting, or null if it's invalid.
+	 */
+	public function sanitize_callback( $raw_setting ) {
+		$sanitized_post_id = sanitize_text_field( $raw_setting );
+		$offline_page      = get_post( $sanitized_post_id );
+		if ( ! $offline_page instanceof WP_Post ) {
+			add_settings_error(
+				self::OPTION_NAME,
+				self::OPTION_NAME,
+				__( 'The current offline page does not exist. Please select or create one.', 'pwa' )
+			);
+		} elseif ( 'trash' === $offline_page->post_status ) {
+			add_settings_error(
+				self::OPTION_NAME,
+				self::OPTION_NAME,
+				__( 'The current offline page is in the trash. Please select or create one.', 'pwa' )
+			);
+		} else {
+			return $sanitized_post_id;
+		}
+	}
+
+	/**
+	 * Adds a settings field to the 'Reading Settings' page.
+	 */
+	public function settings_field() {
+		add_settings_field(
+			self::SETTING_ID,
+			__( 'Progressive Web App Offline Page', 'pwa' ),
+			array( $this, 'settings_callback' ),
+			self::OPTION_GROUP
+		);
+	}
+
+	/**
+	 * Outputs the settings section.
+	 * Mainly taken from wp-admin/privacy.php.
+	 */
+	public function settings_callback() {
+		if ( $this->has_pages() ) :
+			?>
+			<label for="<?php echo esc_attr( self::OPTION_NAME ); ?>">
+				<?php esc_html_e( 'Select an existing page:', 'pwa' ); ?>
+			</label>
+			<?php
+			wp_dropdown_pages(
+				array(
+					'name'              => esc_html( self::OPTION_NAME ),
+					/* Translators: %1$s: A long dash */
+					'show_option_none'  => sprintf( esc_html__( '%1$s Select %1$s', 'pwa' ), '&mdash;' ),
+					'option_none_value' => '0',
+					'selected'          => intval( get_option( self::OPTION_NAME ) ),
+					'post_status'       => array( 'draft', 'publish' ),
+				)
+			);
+		endif;
+		?>
+		<p>
+			<span>
+				<?php
+				// @todo: Add the href value, to allow creating a new page.
+				if ( $this->has_pages() ) {
+					printf(
+						// Translators: %s: A link to create a new page.
+						esc_html__( 'or %s a new one.', 'pwa' ),
+						sprintf( '<a href="%s">%s</a>', '#', esc_html__( 'create', 'pwa' ) )
+					);
+				} else {
+					esc_html_e( 'There are no pages.', 'pwa' );
+				}
+				?>
+			</span>
+		</p>
+		<?php
+	}
+
+	/**
+	 * Whether the there are pages to display in the <select>
+	 * Mainly taken from wp-admin/privacy.php
+	 *
+	 * @todo: Handle a case where there are no pages.
+	 * @return boolean
+	 */
+	public function has_pages() {
+		$query = new WP_Query( array(
+			'post_type'      => 'page',
+			'posts_per_page' => 1,
+			'post_status'    => array(
+				'publish',
+				'draft',
+			),
+		) );
+		return $query->found_posts > 0;
+	}
+}