#!/usr/bin/env python
# coding: utf8

""" Module that provides configuration loading function. """

import json

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

from os.path import exists

from .. import resources, SpleeterError


__email__ = 'research@deezer.com'
__author__ = 'Deezer Research'
__license__ = 'MIT License'

_EMBEDDED_CONFIGURATION_PREFIX = 'spleeter:'


def load_configuration(descriptor):
    """ Load configuration from the given descriptor. Could be
    either a `spleeter:` prefixed embedded configuration name
    or a file system path to read configuration from.

    :param descriptor: Configuration descriptor to use for lookup.
    :returns: Loaded description as dict.
    :raise ValueError: If required embedded configuration does not exists.
    :raise SpleeterError: If required configuration file does not exists.
    """
    # Embedded configuration reading.
    if descriptor.startswith(_EMBEDDED_CONFIGURATION_PREFIX):
        name = descriptor[len(_EMBEDDED_CONFIGURATION_PREFIX):]
        if not loader.is_resource(resources, f'{name}.json'):
            raise SpleeterError(f'No embedded configuration {name} found')
        with loader.open_text(resources, f'{name}.json') as stream:
            return json.load(stream)
    # Standard file reading.
    if not exists(descriptor):
        raise SpleeterError(f'Configuration file {descriptor} not found')
    with open(descriptor, 'r') as stream:
        return json.load(stream)