<?php
/**
 * Class Google\Site_Kit\Core\Admin\Screen
 *
 * @package   Google\Site_Kit
 * @copyright 2019 Google LLC
 * @license   https://www.apache.org/licenses/LICENSE-2.0 Apache License 2.0
 * @link      https://sitekit.withgoogle.com
 */

namespace Google\Site_Kit\Core\Admin;

use Google\Site_Kit\Context;
use Google\Site_Kit\Core\Assets\Assets;

/**
 * Class representing a single screen.
 *
 * @since 1.0.0
 * @access private
 * @ignore
 */
final class Screen {

	const MENU_SLUG = 'googlesitekit';

	/**
	 * Unique screen slug.
	 *
	 * @since 1.0.0
	 * @var string
	 */
	private $slug;

	/**
	 * Screen arguments.
	 *
	 * @since 1.0.0
	 * @var array
	 */
	private $args = array();

	/**
	 * Constructor.
	 *
	 * @since 1.0.0
	 *
	 * @param string $slug Unique screen slug.
	 * @param array  $args {
	 *     Associative array of screen arguments.
	 *
	 *     @type callable $render_callback     Required callback to render the page content.
	 *     @type string   $title               Required screen title.
	 *     @type string   $capability          Capability required to access the screen. Default is 'manage_options'.
	 *     @type string   $menu_title          Title to display in the menu (only if $add_to_menu is true). Default is
	 *                                         the value of $title.
	 *     @type string   $parent_slug         Slug of the parent menu screen (only if $add_to_menu is true). Default
	 *                                         empty string (which means it will be a top-level page).
	 *     @type callable $enqueue_callback    Callback to enqueue additional scripts or stylesheets. The base admin
	 *                                         script and stylesheet will always be enqueued. Default null.
	 *     @type callable $initialize_callback Callback to run actions when initializing the screen, before headers are
	 *                                         sent and markup is generated. Default null.
	 * }
	 */
	public function __construct( $slug, array $args ) {
		$this->slug = $slug;
		$this->args = wp_parse_args(
			$args,
			array(
				'render_callback'     => null,
				'title'               => '',
				'capability'          => 'manage_options',
				'menu_title'          => '',
				'parent_slug'         => self::MENU_SLUG,
				'enqueue_callback'    => null,
				'initialize_callback' => null,
			)
		);

		if ( empty( $this->args['menu_title'] ) ) {
			$this->args['menu_title'] = $this->args['title'];
		}

		$this->args['title'] = __( 'Site Kit by Google', 'google-site-kit' ) . ' ' . $this->args['title'];
	}

	/**
	 * Gets the unique screen slug.
	 *
	 * @since 1.0.0
	 *
	 * @return string Unique screen slug.
	 */
	public function get_slug() {
		return $this->slug;
	}

	/**
	 * Adds the screen to the WordPress admin backend.
	 *
	 * @since 1.0.0
	 *
	 * @param Context $context Plugin context, used for URL generation.
	 * @return string Hook suffix of the screen, or empty string if not added.
	 */
	public function add( Context $context ) {
		static $menu_slug = null;

		if ( ! $this->args['render_callback'] || ! $this->args['title'] ) {
			return '';
		}

		// A parent slug of null means the screen will not appear in the menu.
		$parent_slug = null;

		// If parent slug is provided, use it as parent.
		if ( ! empty( $this->args['parent_slug'] ) ) {
			$parent_slug = $this->args['parent_slug'];

			// If parent slug is 'googlesitekit', append to main Site Kit menu.
			if ( self::MENU_SLUG === $parent_slug ) {
				// If this is null, it means no menu has been added yet.
				if ( null === $menu_slug ) {
					add_menu_page(
						$this->args['title'],
						__( 'Site Kit', 'google-site-kit' ),
						$this->args['capability'],
						$this->slug,
						function() use ( $context ) {
							$this->render( $context );
						},
						$context->url( 'dist/assets/images/logo-g_white_small.png' )
					);
					$menu_slug = $this->slug;
				}

				// Set parent slug to actual slug of main Site Kit menu.
				$parent_slug = $menu_slug;
			}
		}

		// If submenu item or not in menu, use add_submenu_page().
		return (string) add_submenu_page(
			$parent_slug,
			$this->args['title'],
			$this->args['menu_title'],
			$this->args['capability'],
			$this->slug,
			function() use ( $context ) {
				$this->render( $context );
			}
		);
	}

	/**
	 * Runs actions when initializing the screen, before sending headers and generating markup.
	 *
	 * @since 1.0.0
	 *
	 * @param Context $context Plugin context.
	 */
	public function initialize( Context $context ) {
		if ( ! $this->args['initialize_callback'] ) {
			return;
		}

		call_user_func( $this->args['initialize_callback'], $context );
	}

	/**
	 * Enqueues assets for the screen.
	 *
	 * @since 1.0.0
	 *
	 * @param Assets $assets Assets instance to rely on for enqueueing assets.
	 */
	public function enqueue_assets( Assets $assets ) {
		// Enqueue fonts.
		$assets->enqueue_fonts();

		// Enqueue base admin screen stylesheet.
		$assets->enqueue_asset( 'googlesitekit_admin_css' );

		// Helps detection of enabled ad blockers to warn users before activating or setup AdSense module.
		if ( $this->is_ad_blocker_detection_required() ) {
			$assets->enqueue_asset( 'googlesitekit_ads_detect' );
		}

		if ( $this->args['enqueue_callback'] ) {
			call_user_func( $this->args['enqueue_callback'], $assets );
		}

		// Enqueue module hooks.
		$assets->enqueue_asset( 'googlesitekit_modules' );
	}

	/**
	 * Renders the screen content.
	 *
	 * @since 1.0.0
	 *
	 * @param Context $context Plugin context.
	 */
	private function render( Context $context ) {
		if ( ! $this->args['render_callback'] ) {
			return;
		}

		call_user_func( $this->args['render_callback'], $context );
	}

	/**
	 * Verifies if it's required to detect and warn user to disable ad blocker in the current screen.
	 *
	 * Required on dashboard and settings page if module is inactive.
	 * Required on adsense dashboard if module is active and not setup complete.
	 *
	 * @return bool True if ad blocker detection is required.
	 */
	private function is_ad_blocker_detection_required() {
		$screens = array(
			'googlesitekit-settings',
			'googlesitekit-dashboard',
			'googlesitekit-module-adsense',
			'googlesitekit-splash',
		);

		if ( in_array( $this->slug, $screens, true ) ) {
			return true;
		}

		return false;
	}
}