<?php
/**
 * Records the installed data version and is where later versions migrate it.
 *
 * @package Tagsmith
 */

declare(strict_types=1);

namespace Tagsmith\Migration;

use Tagsmith\Settings;

defined( 'ABSPATH' ) || exit;

/**
 * Runs as early as possible in Plugin::boot(). It records which data version
 * the site is on; a version that changes how its data is stored adds a step
 * (upgrade_NNN(), named for the version) to maybe_upgrade(), guarded by that
 * recorded version, so each step runs once.
 *
 * It only ever touches options this plugin created. The options of any other
 * plugin are never read, moved or deleted.
 */
class Upgrader {

	/**
	 * The option recording the installed schema/data version. Autoloaded,
	 * since maybe_upgrade() reads it on every request and must stay cheap.
	 * The settings row is the only other autoloaded Tagsmith option.
	 *
	 * @var string
	 */
	public const DB_VERSION_OPTION = 'tagsmith_db_version';

	/**
	 * The version maybe_upgrade() brings the site to.
	 *
	 * @var string
	 */
	public const CURRENT_VERSION = '2.1.0';

	/**
	 * Brings the site's data to the current version if it is not there yet.
	 * Cheap on every request: a single get_option() call when already current.
	 */
	public function maybe_upgrade(): void {
		$current = get_option( self::DB_VERSION_OPTION );

		if ( is_string( $current ) && version_compare( $current, self::CURRENT_VERSION, '>=' ) ) {
			return;
		}

		// A site with no recorded version runs every step: each one is safe on
		// data that is already in its final shape.
		if ( ! is_string( $current ) || version_compare( $current, '2.1.0', '<' ) ) {
			$this->upgrade_210();
		}

		update_option( self::DB_VERSION_OPTION, self::CURRENT_VERSION, true );
	}

	/**
	 * 2.1.0: the settings row is autoloaded, because the front-end tags read
	 * it on every request. A row saved by 2.0.0 was not, and update_option()
	 * leaves the autoload flag alone when a save changes nothing, so the flag
	 * is set here. A site with no row gets one holding the defaults, so
	 * reading the settings never queries for an option that does not exist.
	 */
	private function upgrade_210(): void {
		if ( null === get_option( Settings::OPTION, null ) ) {
			add_option( Settings::OPTION, Settings::defaults(), '', true );

			return;
		}

		wp_set_option_autoload( Settings::OPTION, true );
	}
}