<?php
/**
 * Short-lived cache for a session's context preview.
 *
 * @package MazeAi
 * @since   0.1.2
 */

declare(strict_types=1);

namespace MazeAi\Chat;

defined('ABSPATH') || exit;

use Illuminate\MazeAssistant\WordPress\Settings\SettingsRepository;

/**
 * Stores one transient per session. The caller supplies a fingerprint of all context inputs, so a changed
 * transcript, run, permission mode, settings or user invalidates the cached preview without a separate delete.
 *
 * @since 0.1.2
 */
final class SessionContextPreviewCache
{
    public const TTL_SECONDS = 120;

    public function __construct(protected SettingsRepository $store)
    {
    }

    /**
     * Return a matching preview, if one is still fresh.
     *
     * @return array<string, mixed>|null
     */
    public function get(int $sessionId, string $fingerprint): ?array
    {
        $cached = $this->store->getTransient($this->key($sessionId));
        if (!is_array($cached) || !is_string($cached['fingerprint'] ?? null) || !hash_equals($fingerprint, $cached['fingerprint']) || !is_array($cached['data'] ?? null)) {
            return null;
        }

        return $cached['data'];
    }

    /**
     * Save a preview until its context changes or the short TTL expires.
     *
     * @param array<string, mixed> $data
     */
    public function put(int $sessionId, string $fingerprint, array $data): void
    {
        $this->store->setTransient($this->key($sessionId), ['fingerprint' => $fingerprint, 'data' => $data], self::TTL_SECONDS);
    }

    protected function key(int $sessionId): string
    {
        return 'session-context-' . max(0, $sessionId);
    }
}