import os

from haystack.nodes import PreProcessor, WebRetriever


def return_retriever():
    """
    Returns the retriever.
    :return: the retriever
    """
    preprocessor = PreProcessor(
        split_by='word',
        split_length=4096,
        split_respect_sentence_boundary=True,
        split_overlap=40,
    )

    return WebRetriever(
        api_key=os.environ['SERPERDEV_API_KEY'],
        allowed_domains=['docs.haystack.deepset.ai'],
        mode='preprocessed_documents',
        preprocessor=preprocessor,
        top_search_results=40,
        top_k=20,
    )