import numpy as np

try:
    import importlib.resources as pkg_resources
except ImportError:
    # Try backported to PY<37 'importlib_resources'
    import importlib_resources as pkg_resources


class Telescope(object):
    def __init__(self, param=None, optEffCurve_path=None):
        self.diameter = 2.0  # in unit of meter
        if param is not None:
            self.diameter = param["diameter"]
        self.pupil_area = np.pi * (0.5 * self.diameter)**2
        if optEffCurve_path is not None:
            self.efficiency = self._get_efficiency(optEffCurve_path)
        else:
            try:
                with pkg_resources.files('observation_sim.instruments.data').joinpath('mirror_ccdnote.txt') as optEffCurve_path:
                    self.efficiency = self._get_efficiency(optEffCurve_path)
            except AttributeError:
                with pkg_resources.path('observation_sim.instruments.data', 'mirror_ccdnote.txt') as optEffCurve_path:
                    self.efficiency = self._get_efficiency(optEffCurve_path)

    def _get_efficiency(self, effCurve_path):
        """ Read in the efficiency of optics
                for each band
        Parameters:
                effCurve_path:	the path for efficiency file
        Returns:
                opticsEff:		a dictionary of efficiency (a scalar) for each band
        """
        f = open(effCurve_path, 'r')
        for _ in range(2):
            header = f.readline()

        iline = 0
        opticsEff = {}
        for line in f:
            line = line.strip()
            columns = line.split()
            opticsEff[str(columns[0])] = float(columns[2])
        f.close()
        return opticsEff