class LLMS_Prevent_Concurrent_Logins {

	use LLMS_Trait_Singleton;

	/**
	 * Array of sessions for the current user.
	 *
	 * @var array
	 */
	private $user_sessions;

	/**
	 * Current user ID.
	 *
	 * @var int
	 */
	private $user_id;

	/**
	 * Private Constructor.
	 *
	 * @since 5.6.0
	 *
	 * @return void
	 */
	private function __construct() {

		if ( llms_parse_bool( get_option( 'lifterlms_prevent_concurrent_logins', 'no' ) ) &&
				! empty( get_option( 'lifterlms_prevent_concurrent_logins_roles', array( 'student' ) ) ) ) {

			add_action( 'init', array( $this, 'init' ) );
			add_action( 'init', array( $this, 'maybe_prevent_concurrent_logins' ) );
		}

	}

	/**
	 * Initialize.
	 *
	 * @since 5.6.0
	 *
	 * @return void
	 */
	public function init() {

		$this->user_id = get_current_user_id();

		if ( empty( $this->user_id ) ) {
			return;
		}

		$this->user_sessions = wp_get_all_sessions();

	}

	/**
	 * Maybe prevent current logins.
	 *
	 * @since 5.6.0
	 *
	 * @return bool `true` if concurrent login prevented, `false` otherwise.
	 */
	public function maybe_prevent_concurrent_logins() {

		// No logged in user or current user has only one active session: nothing to do.
		if ( empty( $this->user_sessions ) || count( $this->user_sessions ) < 2 ) {
			return false;
		}

		/**
		 * Filters whether or not allowing a specific user to have concurrent sessions.
		 *
		 * @since 5.6.0
		 *
		 * @param bool $allow   Whether or not the user should be allowed to have concurrent sessions.
		 * @param int  $user_id WP_User ID of the current use.
		 */
		if ( (bool) apply_filters( 'llms_allow_user_concurrent_logins', false, $this->user_id ) ) {
			return false;
		}

		// Current user doesn't have any restricted role: nothing to do.
		if ( empty( array_intersect( get_userdata( $this->user_id )->roles, (array) get_option( 'lifterlms_prevent_concurrent_logins_roles', array( 'student' ) ) ) ) ) {
			return false;
		}

		$this->destroy_all_sessions_but_newest();

		return true;

	}

	/**
	 * Prevent login by destroying all the user's sessions but the newest.
	 *
	 * @since 5.6.0
	 *
	 * @return int 1 if the kept session is the current one, 0 otherwise.
	 */
	private function destroy_all_sessions_but_newest() {

		$is_current_session_newest_session = $this->current_user_newest_session_login_time() === $this->current_user_current_session_login_time();

		$is_current_session_newest_session
			?
			wp_destroy_other_sessions()
			:
			wp_destroy_current_session();

		return (int) $is_current_session_newest_session;

	}

	/**
	 * Retrieve current session for the current user.
	 *
	 * @since 5.6.0
	 *
	 * @return int
	 */
	private function current_user_current_session_login_time() {

		$sessions = WP_Session_Tokens::get_instance( $this->user_id );
		return $sessions->get( wp_get_session_token() )['login'];

	}

	/**
	 * Retrieve newest session login time for the current user.
	 *
	 * The bigger the login time is the newest the session is.
	 *
	 * @since 5.6.0
	 *
	 * @return int
	 */
	private function current_user_newest_session_login_time() {

		return max( array_column( $this->user_sessions, 'login' ) );

	}

}