<?php

namespace App\Services;

use App\Models\Document;
use App\Models\KnowledgeBase;
use Illuminate\Support\Facades\Log;

class KnowledgeContextService
{
    private const MAX_CONTEXT_LENGTH = 2000;
    private const TOP_K = 5;

    /**
     * 搜索所有知识库中的文档
     *
     * @param string $query
     * @return array{context: string, sources: array}
     */
    public function search(string $query): array
    {
        $knowledgeBaseIds = KnowledgeBase::where('status', 'active')->pluck('id')->toArray();

        if (empty($knowledgeBaseIds)) {
            return [
                'context' => '',
                'sources' => [],
            ];
        }

        try {
            // 使用 Scout/Meilisearch 搜索并获取排名分数
            $rawResults = Document::search($query, function ($meilisearch, $query, $options) use ($knowledgeBaseIds) {
                $options['showRankingScore'] = true;
                $filter = collect($knowledgeBaseIds)
                    ->map(fn($id) => "knowledge_base_id = {$id}")
                    ->implode(' OR ');
                $options['filter'] = $filter;
                $options['limit'] = self::TOP_K;
                return $meilisearch->search($query, $options);
            })->raw();

            $hits = $rawResults['hits'] ?? [];
        } catch (\Exception $e) {
            Log::warning('Knowledge search failed', [
                'query' => $query,
                'error' => $e->getMessage(),
            ]);

            return [
                'context' => '',
                'sources' => [],
            ];
        }

        if (empty($hits)) {
            return [
                'context' => '',
                'sources' => [],
            ];
        }

        // 取出文档 ID 并加载 Eloquent 模型
        $hitIds = collect($hits)->pluck('id')->toArray();
        $documents = Document::whereIn('id', $hitIds)->get()->keyBy('id');

        // 构建排名分数映射
        $rankingScores = collect($hits)->pluck('_rankingScore', 'id');

        $context = '';
        $sources = [];

        foreach ($hits as $hit) {
            $document = $documents->get($hit['id']);
            if (!$document) {
                continue;
            }

            $snippet = $this->extractSnippet($document);

            if (mb_strlen($context) + mb_strlen($snippet) > self::MAX_CONTEXT_LENGTH) {
                break;
            }

            $context .= $snippet . "\n\n";
            $sources[] = [
                'title' => $document->title,
                'id' => 'kb-doc-' . str_pad($document->id, 3, '0', STR_PAD_LEFT),
                'relevance' => round($rankingScores->get($document->id, 0), 2),
            ];
        }

        return [
            'context' => trim($context),
            'sources' => $sources,
        ];
    }

    /**
     * 从文档中提取摘要片段
     */
    private function extractSnippet($document): string
    {
        $content = $document->markdown_preview ?? $document->description ?? '';

        if (mb_strlen($content) <= 500) {
            return "【{$document->title}】\n{$content}";
        }

        return "【{$document->title}】\n" . mb_substr($content, 0, 500) . '...';
    }
}