<?php

/**
 * Class ActionScheduler_Versions
 */
class ActionScheduler_Versions {
	/**
	 * @var ActionScheduler_Versions
	 */
	private static $instance = null;

	private $versions = array();

	public function register( $version_string, $initialization_callback ) {
		if ( isset( $this->versions[ $version_string ] ) ) {
			return false;
		}
		$this->versions[ $version_string ] = $initialization_callback;
		return true;
	}

	public function get_versions() {
		return $this->versions;
	}

	public function latest_version() {
		$keys = array_keys( $this->versions );
		if ( empty( $keys ) ) {
			return false;
		}
		uasort( $keys, 'version_compare' );
		return end( $keys );
	}

	public function latest_version_callback() {
		$latest = $this->latest_version();
		if ( empty( $latest ) || ! isset( $this->versions[ $latest ] ) ) {
			return '__return_null';
		}
		return $this->versions[ $latest ];
	}

	/**
	 * @return ActionScheduler_Versions
	 * @codeCoverageIgnore
	 */
	public static function instance() {
		if ( empty( self::$instance ) ) {
			self::$instance = new self();
		}
		return self::$instance;
	}

	/**
	 * @codeCoverageIgnore
	 */
	public static function initialize_latest_version() {
		$self = self::instance();
		call_user_func( $self->latest_version_callback() );
	}
}

