<?php
namespace Activitypub;

use WP_Post;
use WP_Comment;
use Activitypub\Activity\Activity;
use Activitypub\Collection\Users;
use Activitypub\Collection\Followers;
use Activitypub\Transformer\Factory;
use Activitypub\Transformer\Post;
use Activitypub\Transformer\Comment;

use function Activitypub\get_rest_url_by_path;
use function Activitypub\is_single_user;
use function Activitypub\is_user_disabled;
use function Activitypub\safe_remote_post;

/**
 * ActivityPub Activity_Dispatcher Class
 *
 * @author Matthias Pfefferle
 *
 * @see https://www.w3.org/TR/activitypub/
 */
class Activity_Dispatcher {
	/**
	 * Initialize the class, registering WordPress hooks.
	 */
	public static function init() {
		\add_action( 'activitypub_send_activity', array( self::class, 'send_activity' ), 10, 2 );
		\add_action( 'activitypub_send_activity', array( self::class, 'send_activity_or_announce' ), 10, 2 );
		\add_action( 'activitypub_send_update_profile_activity', array( self::class, 'send_profile_update' ), 10, 1 );
	}

	/**
	 * Send Activities to followers and mentioned users or `Announce` (boost) a blog post.
	 *
	 * @param mixed  $wp_object The ActivityPub Post.
	 * @param string $type      The Activity-Type.
	 *
	 * @return void
	 */
	public static function send_activity_or_announce( $wp_object, $type ) {
		// check if a migration is needed before sending new posts
		Migration::maybe_migrate();

		if ( is_user_type_disabled( 'blog' ) ) {
			return;
		}

		if ( is_single_user() ) {
			self::send_activity( $wp_object, $type, Users::BLOG_USER_ID );
			self::send_announce( $wp_object, $type, Users::APPLICATION_USER_ID );
		} else {
			self::send_announce( $wp_object, $type, Users::BLOG_USER_ID );
			self::send_announce( $wp_object, $type, Users::APPLICATION_USER_ID );
		}
	}

	/**
	 * Send Activities to followers and mentioned users.
	 *
	 * @param mixed  $wp_object The ActivityPub Post.
	 * @param string $type      The Activity-Type.
	 *
	 * @return void
	 */
	public static function send_activity( $wp_object, $type, $user_id = null ) {
		$transformer = Factory::instance()->get_transformer( $wp_object );

		if ( null !== $user_id ) {
			$transformer->change_wp_user_id( $user_id );
		}

		$user_id = $transformer->get_wp_user_id();

		if ( is_user_disabled( $user_id ) ) {
			return;
		}

		$activity = $transformer->to_activity( $type );

		self::send_activity_to_inboxes( $activity, $user_id );
	}

	/**
	 * Send Announces to followers and mentioned users.
	 *
	 * @param mixed  $wp_object The ActivityPub Post.
	 * @param string $type      The Activity-Type.
	 *
	 * @return void
	 */
	public static function send_announce( $wp_object, $type, $user_id = null ) {
		if ( ! in_array( $type, array( 'Create', 'Update' ), true ) ) {
			return;
		}

		$transformer = Factory::instance()->get_transformer( $wp_object );

		if ( null !== $user_id && Users::APPLICATION_USER_ID !== $user_id ) {
			$transformer->change_wp_user_id( $user_id );
		}

		if ( ! $user_id ) {
			$user_id  = $transformer->get_wp_user_id();
		}

		if ( is_user_disabled( $user_id ) ) {
			return;
		}

		$activity = $transformer->to_activity( 'Announce' );

		// TODO: properly fix this for the instance-to-instance federation with Mobilizon.
		// Error:
		//      Failed to map identity from signature (payload actor mismatch)
		//  	key_id=http://wp.lan/wp-json/activitypub/1.0/application, actor=http://wp.lan/@blog
        // Of course, the announce must be sent as the Application actor because he also signed it!
		if ( Users::APPLICATION_USER_ID === $user_id ) {
			$activity->set_actor( get_rest_url_by_path( 'application' ) );
		}

		self::send_activity_to_inboxes( $activity, $user_id );
	}

	/**
	 * Send a "Update" Activity when a user updates their profile.
	 *
	 * @param int $user_id The user ID to send an update for.
	 *
	 * @return void
	 */
	public static function send_profile_update( $user_id ) {
		$user = Users::get_by_various( $user_id );

		// bail if that's not a good user
		if ( is_wp_error( $user ) ) {
			return;
		}

		// build the update
		$activity = new Activity();
		$activity->set_id( $user->get_url() . '#update' );
		$activity->set_type( 'Update' );
		$activity->set_actor( $user->get_url() );
		$activity->set_object( $user->get_url() );
		$activity->set_to( 'https://www.w3.org/ns/activitystreams#Public' );

		// send the update
		self::send_activity_to_inboxes( $activity, $user_id );
	}

	/**
	 * Send an Activity to all followers and mentioned users.
	 *
	 * @param Activity $activity The ActivityPub Activity.
	 * @param int      $user_id  The user ID.
	 *
	 * @return void
	 */
	private static function send_activity_to_inboxes( $activity, $user_id ) {
		$follower_inboxes = Followers::get_inboxes( $user_id );

		$mentioned_inboxes = array();
		$cc = $activity->get_cc();
		if ( $cc ) {
			$mentioned_inboxes = Mention::get_inboxes( $cc );
		}

		$inboxes = array_merge( $follower_inboxes, $mentioned_inboxes );
		$inboxes = array_unique( $inboxes );

		if ( empty( $inboxes ) ) {
			return;
		}

		$json = $activity->to_json();

		foreach ( $inboxes as $inbox ) {
			safe_remote_post( $inbox, $json, $user_id );
		}
	}
}