langchain_service_impl.dart

class LangchainServicesImpl extends LangchainService {
  final Connection connection;
  final OpenAIEmbeddings embeddings;
  final OpenAI openAI;

  LangchainServicesImpl({
    required this.connection,
    required this.embeddings,
    required this.openAI,
  });
  
  // do something

  @override
  Future<String> queryNeonTable(String tableName, String query) async {
    final embedQuery = await embeddings.embedQuery(query);
    List<List<dynamic>> getSimilar = await connection.execute(
        "SELECT *, 1 - (embedding <=> '$embedQuery') AS cosine_similarity FROM $tableName WHERE (1 - (embedding <=> '$embedQuery')) BETWEEN 0.3 AND 1.00 ORDER BY cosine_similarity DESC LIMIT 10;");

    List<Metadata> pdfMetadata = getSimilar
        .map((item) => Metadata.fromJson(json.decode(item[1])))
        .toList();

    if (pdfMetadata.isNotEmpty) {
      final concatPageContent = pdfMetadata.map((e) {
        return e.pageContent;
      }).join(' ');
      final docChain = StuffDocumentsQAChain(llm: openAI);
      final response = await docChain.call({
        'input_documents': [
          Document(pageContent: concatPageContent),
        ],
        'question': query,
      });

      return response['output'];
    } else {
      return "Couldn't find anything on that topic";
    }
  }
}

void debugPrint(String message) {
  if (kDebugMode) {
    print(message);
  }
}