Add data access helpers

We need an API that looks the same for online and offline data analysis of Bliss data.

Proposal: streamline API on top of Bliss or HDF5

from numbers import Integral, Number
from typing import Callable, Dict, Iterable, Optional, Sequence


def get_reader(url) -> "DataReader":
    pass


class DataReader:
    def __init__(
        self,
        point_multipliers: Optional[Dict[str, Integral]],
        time_multipliers: Optional[Dict[str, Integral]]
    ) -> None:
        """Some channels produce 2*n, 3*n, ... points"""
        self._point_multipliers = point_multipliers
        self._time_multipliers = time_multipliers

    def iter_data(
        self,
        period: Optional[Number] = None,
        npoints: Optional[Integral] = None,
        channel_filter: Optional[Callable[[str], bool]] = None,
    ) -> Iterable[Dict[str, Sequence]]:
        """Yield data every `period` seconds or every `npoints` points.

        Returns a dictionary with a sequence of data points per channel.
        """
        raise NotImplementedError

    def get_channel_metadata(
        self, channel_filter: Optional[Callable[[str], bool]]
    ) -> Dict:
        """Return metadata of the channels (e.g. detector pixel size)"""
        raise NotImplementedError

    def get_metadata(self) -> Dict:
        """Return non-channel metadata (e.g. SR current)"""
        raise NotImplementedError


class BlissReader(DataReader):
    """Data comes from Redis, Lima server or HDF5 files"""

    def __init__(self, url: str, **kwargs) -> None:
        """For example

        url="redis://localhost:25002/1?key=demo_session:tmp:scans:inhouse:id002205:sample:sample_0001:1_loopscan"

        """
        super().__init__(**kwargs)


class HDF5Reader(DataReader):
    """Data comes from the HDF5 file"""

    def __init__(self, url: str, **kwargs) -> None:
        """For example

        url="hdf5:///tmp/scans/inhouse/id002205/id00/20220501/sample/sample_0001/sample_0001.h5"

        """
        super().__init__(**kwargs)

Usage:

reader = get_reader("redis://localhost:25002/1?key=demo_session:tmp:scans:inhouse:id002205:sample:sample_0001:1_loopscan")

for data in reader.iter_data(period=5):
    pass