import collections
from importlib import import_module
import json
import logging

import six


logger = logging.getLogger(__name__)


def serialise_to_json(value):
    """ Safely serialise ``value`` to JSON formatted string
    """
    return json.dumps(safe_for_serialisation(value))


def serialise_to_string(value):
    """ Safely serialise ``value`` to string representation
    """
    return str(safe_for_serialisation(value))


def safe_for_serialisation(value):
    no_op_types = six.string_types + six.integer_types + (float,)
    if isinstance(value, no_op_types):
        return value
    if isinstance(value, bytes):
        return value.decode('utf-8', 'ignore')
    if isinstance(value, dict):
        return {
            safe_for_serialisation(key): safe_for_serialisation(val)
            for key, val in six.iteritems(value)}
    if isinstance(value, collections.Iterable):
        return list(map(safe_for_serialisation, value))
    try:
        return six.text_type(value)
    except Exception:
        logger.warning(
            'failed to get string representation', exc_info=True)
        return 'failed to get string representation'


def import_by_path(dotted_path):
    """
    Import a dotted module path and return the attribute/class designated by
    the last name in the path. Raise ImportError if the import failed.

    Borrowed from ``django.utils.module_loading.import_string``.

    """
    try:
        module_path, class_name = dotted_path.rsplit('.', 1)
    except ValueError:
        raise ImportError(
            "{} doesn't look like a module path".format(dotted_path))

    module = import_module(module_path)

    try:
        return getattr(module, class_name)
    except AttributeError:
        raise ImportError(
            'Module "{}" does not define a "{}" attribute/class'
            .format(module_path, class_name))
