<?php

declare(strict_types=1);

namespace App\Support;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Support\Facades\Crypt;

/**
 * A shareable link to a draft on the public site.
 *
 * The shared `SITE_PREVIEW_TOKEN` still exists, but it is one secret, never
 * rotated, that has to be pasted into a curl command. This is the same idea
 * made usable: a link somebody can send to whoever needs to look, scoped to
 * one record and one language, and useless a few hours later.
 *
 * The token carries the record it points at rather than being a bearer of
 * "show me anything", so passing it around leaks one draft rather than every
 * unpublished thing on the site.
 */
final class PreviewLink
{
    /**
     * How long a link stays good. Long enough to send it and get an answer,
     * short enough that one forwarded in an e-mail thread stops working.
     */
    public const HOURS = 8;

    public static function for(Model $record, string $type, string $locale): ?string
    {
        $slug = $record->getTranslation('slug', $locale, useFallbackLocale: false);

        // No slug in this language means no address to preview.
        if (blank($slug)) {
            return null;
        }

        $path = SiteUrls::path($type, $locale, (string) $slug);

        $token = Crypt::encryptString(json_encode([
            'type' => $type,
            'id' => $record->getKey(),
            'locale' => $locale,
            'expires' => now()->addHours(self::HOURS)->timestamp,
        ], JSON_THROW_ON_ERROR));

        return rtrim((string) config('site.url'), '/').$path.'?preview='.urlencode($token);
    }

    /**
     * What a token says, or null when it is expired, forged or unreadable.
     *
     * @return array{type: string, id: int|string, locale: string}|null
     */
    public static function open(string $token): ?array
    {
        try {
            $payload = json_decode(Crypt::decryptString($token), true, flags: JSON_THROW_ON_ERROR);
        } catch (\Throwable) {
            return null;
        }

        if (! is_array($payload) || ($payload['expires'] ?? 0) < now()->timestamp) {
            return null;
        }

        return [
            'type' => (string) $payload['type'],
            'id' => $payload['id'],
            'locale' => (string) $payload['locale'],
        ];
    }
}