from google.protobuf.message import Message
from typing import Dict, Optional

from frostfs_sdk.models.mappers.meta_header_mapper import MetaHeaderMapper
from frostfs_sdk.models.mappers.session_mapper import SessionMapper
from frostfs_sdk.models.dto.meta_header import MetaHeader
from frostfs_sdk.protos.models.session import types_pb2 as types_pb2_session


META_HEADER_FIELD_NAME = "meta_header"


class RequestConstructor:
    @staticmethod
    def add_meta_header(request: Message, x_headers: Optional[Dict[str, str]] = None, session_token: types_pb2_session.SessionToken = None):
        """
        Adds a meta header to the request.

        :param request: A Protobuf Message.Builder object.
        :param x_headers: Optional dictionary of custom headers.
        :param session_token: Optional session token.
        :raises ValueError: If the request or required fields are missing.
        """
        if request is None:
            return

        descriptor = request.DESCRIPTOR
        if getattr(descriptor, META_HEADER_FIELD_NAME) is None:
            raise ValueError(f"Required Protobuf field is missing: {META_HEADER_FIELD_NAME}")

        meta_header = getattr(request, META_HEADER_FIELD_NAME)
        if meta_header.ByteSize() > 0:
            return

        meta_header_builder = MetaHeaderMapper.to_grpc_message(MetaHeader())

        if session_token and session_token.ByteSize() > 0:
            meta_header_builder.session_token = session_token

        if x_headers:
            grpc_x_headers = [
                types_pb2_session.XHeader(key=key, value=value)
                for key, value in x_headers.items()
            ]
            meta_header_builder.x_headers.extend(grpc_x_headers)

        setattr(request, META_HEADER_FIELD_NAME, meta_header_builder.build())