<?php

declare(strict_types=1);

namespace FreshetBackup;

/**
 * One run at a time: a cron run and a Run-now click must not dump into the
 * same folder at once.
 *
 * The lock is an options row taken with a plain INSERT, which the unique key
 * on option_name makes atomic. A lock older than STALE belongs to a run that
 * died, and is taken over with a compare-and-set UPDATE so two takers cannot
 * both win.
 *
 * phpcs:disable WordPress.DB.DirectDatabaseQuery -- the atomicity is the point; the options API cannot give it.
 */
class Lock
{
    public const NAME = 'freshet_backup_lock';
    public const STALE = 6 * HOUR_IN_SECONDS;

    public function acquire(): bool
    {
        global $wpdb;
        $now = (string) time();

        $taken = $wpdb->query($wpdb->prepare(
            'INSERT IGNORE INTO %i (option_name, option_value, autoload) VALUES (%s, %s, %s)',
            $wpdb->options,
            self::NAME,
            $now,
            'off'
        ));
        if ($taken === 1) {
            return true;
        }

        $held = (string) $wpdb->get_var($wpdb->prepare('SELECT option_value FROM %i WHERE option_name = %s', $wpdb->options, self::NAME));
        if ($held !== '' && (int) $held > time() - self::STALE) {
            return false;
        }

        return $wpdb->query($wpdb->prepare(
            'UPDATE %i SET option_value = %s WHERE option_name = %s AND option_value = %s',
            $wpdb->options,
            $now,
            self::NAME,
            $held
        )) === 1;
    }

    public function release(): void
    {
        global $wpdb;
        $wpdb->query($wpdb->prepare('DELETE FROM %i WHERE option_name = %s', $wpdb->options, self::NAME));
    }
}