<?php

declare(strict_types=1);

namespace App\Knowledge\Retrieval;

use Psr\Cache\CacheItemPoolInterface;
use Psr\Cache\InvalidArgumentException;

final readonly class CachedRetriever implements RetrieverInterface
{
    public function __construct(
        private RetrieverInterface $inner,
        private CacheItemPoolInterface $cache,
        private int $ttlSeconds = 300,
    ) {
    }

    /**
     * @return string[]
     * @throws InvalidArgumentException
     */
    public function retrieve(string $prompt): array
    {
        $key = $this->buildCacheKey($prompt);

        $item = $this->cache->getItem($key);
        if ($item->isHit()) {
            $cached = $item->get();

            return is_array($cached) ? $cached : [];
        }

        $result = $this->inner->retrieve($prompt);

        $item->set($result);
        $item->expiresAfter($this->ttlSeconds);
        $this->cache->save($item);

        return $result;
    }

    private function buildCacheKey(string $prompt): string
    {
        $normalized = mb_strtolower(trim($prompt));
        $normalized = preg_replace('/\s+/u', ' ', $normalized) ?? $normalized;

        return 'rag_retrieval_' . sha1($normalized);
    }
}