from netCDF4 import Dataset

import xarray as xr
import numpy as np


def read_data(sensor: str, l1b_filename: str, geo_filename: str):

    data = xr.open_dataset(l1b_filename, group='observation_data', decode_cf=False)
    in_data = xr.Dataset()
    if sensor.lower() == 'viirs':
        for band in list(data.variables):
            if 'reflectance' in data[band].long_name:
                if hasattr(data[band], 'VCST_scale_factor'):
                    scale_factor = data[band].VCST_scale_factor * data[band].bias_correction
                else:
                    scale_factor = data[band].radiance_scale_factor
                in_data[band] = (('number_of_lines', 'number_of_pixels'),
                                 data[band].values * scale_factor)

            elif 'radiance' in data[band].long_name:
                in_data[band] = (('number_of_lines', 'number_of_pixels'),
                                 data[f'{band}_brightness_temperature_lut'].values[data[band].values])
            else:
                pass

    data = xr.open_dataset(geo_filename, group='geolocation_data')

    in_data = in_data.merge(data)

    return in_data