<?php

namespace App\Services;

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

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

    /**
     * 搜索终端关联知识库中的文档
     *
     * @param Terminal $terminal
     * @param string $query
     * @return array{context: string, sources: array}
     */
    public function search(Terminal $terminal, string $query): array
    {
        $knowledgeBaseIds = $terminal->knowledgeBases->pluck('id')->toArray();

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

        try {
            // 使用 Scout/Meilisearch 原生过滤（与 DocumentSearchService 一致）
            $documents = Document::search($query)
                ->whereIn('knowledge_base_id', $knowledgeBaseIds)
                ->take(self::TOP_K)
                ->get();
        } catch (\Exception $e) {
            Log::warning('Knowledge search failed', [
                'query' => $query,
                'error' => $e->getMessage(),
            ]);

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

        if ($documents->isEmpty()) {
            return [
                'context' => '',
                'sources' => [],
            ];
        }

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

        foreach ($documents as $document) {
            $snippet = $this->extractSnippet($document);

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

            $context .= $snippet . "\n\n";
            $sources[] = [
                'id' => $document->id,
                'title' => $document->title,
                'knowledge_base' => $document->knowledgeBase?->name,
            ];
        }

        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) . '...';
    }
}