<?php
/**
 * Version-keyed upgrades.
 *
 * @package AcidStudios\AEO
 */

declare(strict_types=1);

namespace AcidStudios\AEO;

defined( 'ABSPATH' ) || exit;

/**
 * Runs once per plugin version, on the first request after an update.
 *
 * Activation hooks do not run on in-place updates, so anything an update
 * needs — a cron entry that went missing, a rewrite flush for a changed
 * rule, a settings value whose meaning changed — has to be done here, keyed
 * on the version the site last ran.
 */
final class Upgrader {
	/**
	 * Option holding the last version that ran its upgrade.
	 *
	 * @var string
	 */
	public const OPTION = 'acid_aeo_version';

	/**
	 * Daily task hook name.
	 *
	 * @var string
	 */
	public const DAILY_HOOK = 'acid_aeo_daily';

	/**
	 * How far ahead the first run of a re-created daily event is placed.
	 *
	 * @var int
	 */
	public const CRON_DELAY = 3600;

	/**
	 * Runs the upgrade when the stored version is older than the code.
	 *
	 * A site with no stored version predates the stamp (1.0.0–1.0.4) and is
	 * treated as an upgrade; activation stamps the version, so a fresh site
	 * never gets here with an empty value.
	 *
	 * @return void
	 */
	public static function maybe_upgrade(): void {
		$stored = (string) get_option( self::OPTION, '' );

		if ( '' !== $stored && version_compare( $stored, ACID_AEO_VERSION, '>=' ) ) {
			return;
		}

		self::migrate( $stored );

		update_option( self::OPTION, ACID_AEO_VERSION, false );
	}

	/**
	 * Re-creates the daily event when it is missing.
	 *
	 * @return void
	 */
	public static function ensure_daily_cron(): void {
		if ( false === wp_next_scheduled( self::DAILY_HOOK ) ) {
			wp_schedule_event( time() + self::CRON_DELAY, 'daily', self::DAILY_HOOK );
		}
	}

	/**
	 * The steps every upgrade takes, then the version-specific ones.
	 *
	 * The cache version is bumped too: an update can change how any generated
	 * file renders, and the version stamp is the right moment to discard them.
	 *
	 * @param string $from The version the site ran before, or '' when unknown.
	 * @return void
	 */
	private static function migrate( string $from ): void {
		self::ensure_daily_cron();

		// Rewrite rules may have changed between versions; the flush itself
		// is deferred to the next `init` by `Plugin::maybe_flush_rewrites()`.
		update_option( 'acid_aeo_flush_needed', 1 );

		// An update can change any generated body, so drop the cached ones.
		Cache::invalidate_all();

		unset( $from ); // No version-specific step yet; 1.0.5 needs none.
	}
}