<?php

declare(strict_types=1);

namespace App\Libraries;

/**
 * "Related tools" recommendation engine.
 *
 * Scoring signals (highest first):
 *   1. Curated related_slugs authored in the registry
 *   2. Same primary input format   (mp4 -> mp3 implies mp4 -> wav)
 *   3. Same primary output format  (jpg -> png implies webp -> png)
 *   4. Same category, weighted by popularity
 */
final class RelatedTools
{
    public const LIMIT = 8;

    public function forTool(array $tool, int $limit = self::LIMIT): array
    {
        $finder = service('finder');
        $result = [];

        // 1) curated picks always lead
        foreach (($tool['related_slugs'] ?? []) as $slug) {
            if ($related = $finder->tool((string) $slug)) {
                $result[$related['slug']] = $related + ['_score' => 1000];
            }
        }

        foreach ($finder->all() as $candidate) {
            if ($candidate['id'] === $tool['id'] || isset($result[$candidate['slug']])) {
                continue;
            }

            $score = 0;
            if ($tool['primary_input_format'] !== null && $candidate['primary_input_format'] === $tool['primary_input_format']) {
                $score += 50;
            }
            if ($tool['primary_output_format'] !== null && $candidate['primary_output_format'] === $tool['primary_output_format']) {
                $score += 40;
            }
            if ((int) $candidate['category_id'] === (int) $tool['category_id']) {
                $score += 25;
            }
            // small popularity tiebreaker keeps ordering stable and useful
            $score += min(10, (int) round(((int) $candidate['popularity']) / 500));

            if ($score >= 25) {
                $candidate['_score'] = $score;
                $result[$candidate['slug']] = $candidate;
            }
        }

        usort($result, static fn (array $a, array $b): int => $b['_score'] <=> $a['_score']);

        return array_slice(array_map(static function (array $t): array {
            unset($t['_score']);

            return $t;
        }, $result), 0, $limit);
    }

    /**
     * Format-conversion cross links: for a converter like mp4-to-mp3,
     * surface sibling conversions from the same input (mp4-to-wav,
     * mp4-to-webm ...) and to the same output from other inputs.
     *
     * @return list<array>
     */
    public function conversionsAround(array $tool, int $limit = 6): array
    {
        if ($tool['kind'] !== 'upload' || $tool['operation'] !== 'convert') {
            return [];
        }

        $finder = service('finder');
        $sameInput  = [];
        $sameOutput = [];

        foreach ($finder->all() as $candidate) {
            if ($candidate['id'] === $tool['id'] || $candidate['operation'] !== 'convert') {
                continue;
            }
            if ($tool['primary_input_format'] !== null && $candidate['primary_input_format'] === $tool['primary_input_format']) {
                $sameInput[] = $candidate;
            } elseif ($tool['primary_output_format'] !== null && $candidate['primary_output_format'] === $tool['primary_output_format']) {
                $sameOutput[] = $candidate;
            }
        }

        usort($sameInput, static fn ($a, $b) => $b['popularity'] <=> $a['popularity']);
        usort($sameOutput, static fn ($a, $b) => $b['popularity'] <=> $a['popularity']);

        return array_slice([...$sameInput, ...$sameOutput], 0, $limit);
    }
}