"""Common utility methods."""


def flatten_json(nested_json):
    """Flatten json object with nested keys into a single level."""
    output = {}

    def flatten(json, name=''):
        if type(json) is dict:
            for key in json:
                flatten(json[key], name + key + '_')
        elif type(json) is list:
            i = 0
            for key in json:
                flatten(key, name + str(i) + '_')
                i += 1
        else:
            output[name[:-1]] = json

    flatten(nested_json)
    return output


def filter_keys_from_list_of_dict(list_of_dicts, keys):
    """Filter keys from a list of dicts."""
    return [
        {key: item[key] for key in keys}
        for item in list_of_dicts
    ]


def iterate_all(iterable, return_value='key'):
    """Iterates an interable and returns all keys or values."""
    if isinstance(iterable, dict):
        for key, value in iterable.items():
            if return_value == 'key':
                yield key
            elif return_value == 'value':
                if not (isinstance(value, dict) or isinstance(value, list)):
                    yield value
            for ret in iterate_all(value, return_value=return_value):
                yield ret
    elif isinstance(iterable, list):
        for el in iterable:
            for ret in iterate_all(el, return_value=return_value):
                yield ret