<?php

declare(strict_types=1);

namespace App\Support;

use App\Models\Setting;
use Illuminate\Database\Eloquent\Model;

/**
 * A number that changes whenever published content does.
 *
 * The public API is cached with `s-maxage` and a long
 * `stale-while-revalidate`, which is right for an SSR frontend and wrong for
 * an urgent correction: a fix can sit behind a stale copy for minutes. The
 * frontend cannot know something changed without asking, and asking is the
 * thing the cache exists to avoid.
 *
 * So it is told. `/site` carries this number, the frontend keeps it as part of
 * its cache key, and the moment it moves everything downstream is stale by
 * definition — no purge webhook, no shared secret, nothing to deploy.
 */
final class ContentVersion
{
    public const KEY = 'content.version';

    public static function current(): int
    {
        return (int) Setting::get(self::KEY, 0);
    }

    /**
     * Move it on. Cheap on purpose: this runs on every content save.
     */
    public static function bump(): void
    {
        Setting::set(self::KEY, self::current() + 1);
    }

    /**
     * Whether a change to this record is one a visitor could notice.
     *
     * A draft nobody can see moving does not invalidate anybody's cache, and
     * bumping on every keystroke of a half-written page would make the number
     * meaningless.
     */
    public static function shouldBumpFor(Model $record): bool
    {
        if (method_exists($record, 'isPublishedNow')) {
            // Either it is on the site now, or it was a moment ago — going
            // away is exactly as visible as arriving.
            return $record->isPublishedNow() || (bool) $record->getOriginal('published_at');
        }

        return true;
    }
}