"""Read the MERSI-II relative spectral responses.

Data available from NSMC:
http://gsics.nsmc.org.cn/portal/en/fycv/srf.html
http://gsics.nsmc.org.cn/download/documents/SRF/FY3D_MERSI_SRF_Pub.zip
"""
import logging
import os

import numpy as np

from pyspectral.raw_reader import InstrumentRSR
from pyspectral.utils import INSTRUMENTS
from pyspectral.utils import convert2hdf5 as tohdf5

LOG = logging.getLogger(__name__)

MERSI2_BAND_NAMES = ['ch1', 'ch2', 'ch3', 'ch4', 'ch5', 'ch6', 'ch7', 'ch8',
                     'ch9', 'ch10', 'ch11', 'ch12', 'ch13', 'ch14', 'ch15', 'ch16',
                     'ch17', 'ch18', 'ch19', 'ch20', 'ch21', 'ch22', 'ch23', 'ch24',
                     'ch25']


class Mersi2RSR(InstrumentRSR):
    """Container for the FY3D MERSI-II RSR data."""

    def __init__(self, bandname, platform_name):
        """Initialize the MERSI-2 RSR class."""
        super(Mersi2RSR, self).__init__(bandname, platform_name, MERSI2_BAND_NAMES)

        self.instrument = INSTRUMENTS.get(platform_name, 'mersi-2')

        self._get_options_from_config()
        self._get_bandfilenames()

        LOG.debug("Filenames: %s", str(self.filenames))
        if self.filenames[bandname] and os.path.exists(self.filenames[bandname]):
            self.requested_band_filename = self.filenames[bandname]
            self._load()

        else:
            LOG.warning("Couldn't find an existing file for this band: %s",
                        str(self.bandname))

        # To be compatible with VIIRS....
        self.filename = self.requested_band_filename

    def _load(self, scale=0.001):
        """Load the MERSI-2 RSR data for the band requested.

        Wavelength is given in nanometers.
        """
        data = np.genfromtxt(self.requested_band_filename,
                             unpack=True,
                             names=['wavelength',
                                    'response'],
                             skip_header=0)

        wavelength = data['wavelength'] * scale
        response = data['response']

        self.rsr = {'wavelength': wavelength, 'response': response}


if __name__ == "__main__":
    for platform_name in ["FY-3D", ]:
        tohdf5(Mersi2RSR, platform_name, MERSI2_BAND_NAMES)
