<?php
/**
 * Class responsible for initializing ActivityPub Event Extensions.
 *
 * The setup class provides function for checking if this plugin should be activated.
 * It detects supported event plugins and provides all setup hooks and filters.
 *
 * @package Activitypub_Event_Extensions
 * @since 1.0.0
 */

namespace Activitypub_Event_Extensions;

// Exit if accessed directly.
defined( 'ABSPATH' ) || exit; // @codeCoverageIgnore

require_once ABSPATH . 'wp-admin/includes/plugin.php';

/**
 * Class Setup.
 *
 * This class is responsible for initializing ActivityPub Event Extensions.
 *
 * @since 1.0.0
 */
class Setup {
	const SUPPORTED_EVENT_PLUGINS = array(
		'events_manager'      => array(
			'plugin_file'       => 'events-manager/events-manager.php',
			'post_type'         => 'event',
			'settings_page'     => 'options-general.php?page=vsel',
			'transformer_class' => 'Events_Manager',
		),
		'gatherpress'         => array(
			'plugin_file'       => 'gatherpress/gatherpress.php',
			'post_type'         => 'gatherpress_event',
			'transformer_class' => 'GatherPress',
			'settings_page_id'  => 'gatherpress_general',
		),
		'the_events_calendar' => array(
			'plugin_file'       => 'the-events-calendar/the-events-calendar.php',
			'post_type'         => 'tribe_events',
			'transformer_class' => 'Tribe_Events',
			'settings_page_id'  => 'tribe_general',
		),
		'vsel'                => array(
			'plugin_file'       => 'very-simple-event-list/vsel.php',
			'post_type'         => 'event',
			'settings_page_id'  => 'settings_page_vsel',
			'transformer_class' => 'VS_Event',
		),
	);

	/**
	 * Holds an array of the currently activated supported event plugins.
	 *
	 * @var array
	 */
	protected $active_event_plugins = array();

	/**
	 * Constructor for the Setup class.
	 *
	 * Initializes and sets up various components of the plugin.
	 *
	 * @since 1.0.0
	 */
	protected function __construct() {
		$this->active_event_plugins = self::detect_supported_event_plugins();
		if ( empty( $this->active_event_plugins ) ) {
			return;
		}
		$this->setup_hooks();
	}

	/**
	 * The single instance of the class.
	 *
	 * @since 1.0.0
	 * @var ?self|null The instance of the class.
	 */
	private static $instance = null;

	/**
	 * Get the instance of the Singleton class.
	 *
	 * If an instance does not exist, it creates one; otherwise, it returns the existing instance.
	 *
	 * @since 1.0.0
	 *
	 * @return self The instance of the class.
	 */
	public static function get_instance(): self {
		if ( null === self::$instance ) {
			self::$instance = new self();
		}

		return self::$instance;
	}

	/**
	 * Function that checks for supported activated event plugins.
	 *
	 * @return array List of supported event plugins as keys from the SUPPORTED_EVENT_PLUGINS const.
	 */
	public static function detect_supported_event_plugins(): array {
		$active_event_plugins = array();
		foreach ( self::SUPPORTED_EVENT_PLUGINS as $event_plugin_key => $event_plugin ) {
			if ( \is_plugin_active( $event_plugin['plugin_file'] ) ) {
				$active_event_plugins[ $event_plugin_key ] = $event_plugin;
			}
		}
		return $active_event_plugins;
	}

	/**
	 * Set up hooks for various purposes.
	 *
	 * This method adds hooks for different purposes as needed.
	 *
	 * @since 1.0.0
	 *
	 * @return void
	 */
	protected function setup_hooks(): void {
		register_activation_hook( ACTIVITYPUB_EVENT_EXTENSIONS_PLUGIN_FILE, array( $this, 'activate' ) );

		add_action( 'admin_init', array( $this, 'do_admin_notices' ) );

		add_filter( 'activitypub_transformer', array( $this, 'register_activitypub_event_transformer' ), 10, 3 );
	}

	/**
	 * Fires the initialization of admin notices for all active supported event plugins.s
	 */
	public function do_admin_notices(): void {
		foreach ( $this->active_event_plugins as $event_plugin ) {
			new Admin_Notices( $event_plugin );
		}
	}

	/**
	 * Add the custom transformers for the events of several WordPress event plugins.
	 *
	 * @param Activitypub\Transformer\Base $transformer  The transformer to use.
	 * @param mixed                        $wp_object    The WordPress object to transform.
	 * @param string                       $object_class The class of the object to transform.
	 *
	 * @returns \Activitypub\Transformer\Base
	 */
	public function register_activitypub_event_transformer( $transformer, $wp_object, $object_class ): \Activitypub\Transformer\Base {
		// If the current WordPress object is not a post (e.g., a WP_Comment), don't change the transformer.
		if ( 'WP_Post' !== $object_class ) {
			return $transformer;
		}

		// Get the transformer for a specific event plugins event-post type.
		foreach ( $this->active_event_plugins as $event_plugin ) {
			if ( $wp_object->post_type === $event_plugin['post_type'] ) {
				$transformer_class = 'Activitypub_Event_Extensions\Activitypub\Transformer\\' . $event_plugin['transformer_class'];
				return new $transformer_class( $wp_object );
			}
		}

		// Return the default transformer.
		return $transformer;
	}

	/**
	 * Activates the ActivityPub Event Extensions plugin.
	 *
	 * This method handles the activation of the ActivityPub Event Extensions plugin.
	 *
	 * @since 1.0.0
	 *
	 * @return void
	 */
	public function activate() {
		// Don't allow plugin activation, when the ActivityPub plugin is not activated yet.
		if ( ! is_plugin_active( 'activitypub/activitypub.php' ) ) {
			deactivate_plugins( plugin_basename( ACTIVITYPUB_EVENT_EXTENSIONS_PLUGIN_FILE ) );
			wp_die(
				esc_html_e(
					'Please install and activate the <a href="https://wordpress.org/plugins/activitypub/">ActivityPub plugin</a> first.',
					'activitypub-event-extensions',
				),
				'Plugin dependency check',
				array( 'back_link' => true ),
			);
		}
		// If someone installs this plugin, we simply enable ActivityPub support for the event post type, without asking.
		$activitypub_supported_post_types = get_option( 'activitypub_support_post_types', array() );
		foreach ( $this->active_event_plugins as $event_plugin ) {
			if ( ! in_array( $event_plugin['post_type'], $activitypub_supported_post_types, true ) ) {
				$activitypub_supported_post_types[] = $event_plugin['post_type'];
			}
		}
		update_option( 'activitypub_support_post_types', $activitypub_supported_post_types );
	}
}