utils.py

# pylint: disable=cyclic-import # only occurring in dev env

import json
import mimetypes
import os
import random
import shutil
import tempfile
import uuid
import zipfile
from collections import OrderedDict
from collections.abc import MutableMapping  # pylint: disable=no-name-in-module,deprecated-class
from threading import local
from urllib import parse

import requests
from celery_once.helpers import queue_once_key
from dateutil import parser
from django.conf import settings
from django.urls import NoReverseMatch, reverse, get_resolver
from djqscsv import csv_file_for
from elasticsearch_dsl import Q as es_Q
from pydash import flatten, compact, get
from requests.auth import HTTPBasicAuth
from rest_framework.utils import encoders

from core.common.constants import UPDATED_SINCE_PARAM, BULK_IMPORT_QUEUES_COUNT, CURRENT_USER, REQUEST_URL, \
    TEMP_PREFIX
from core.settings import EXPORT_SERVICE


def get_latest_dir_in_path(path):  # pragma: no cover
    all_sub_dirs = [path + d for d in os.listdir(path) if os.path.isdir(path + d)]
    return max(all_sub_dirs, key=os.path.getmtime)


def cd_temp():  # pragma: no cover
    cwd = os.getcwd()
    tmpdir = tempfile.mkdtemp()
    os.chdir(tmpdir)
    return cwd


def write_csv_to_s3(data, is_owner, **kwargs):  # pragma: no cover
    cwd = cd_temp()
    csv_file = csv_file_for(data, **kwargs)
    csv_file.close()
    zip_file_name = csv_file.name + '.zip'
    with zipfile.ZipFile(zip_file_name, 'w', zipfile.ZIP_DEFLATED) as zip_file:
        zip_file.write(csv_file.name)

    key = get_downloads_path(is_owner) + zip_file.filename
    get_export_service().upload_file(
        key=key, file_path=os.path.abspath(zip_file.filename), binary=True,
        metadata=dict(ContentType='application/zip'), headers={'content-type': 'application/zip'}
    )
    os.chdir(cwd)
    return get_export_service().url_for(key)


def compact_dict_by_values(_dict):
    copied_dict = _dict.copy()
    for key, value in copied_dict.copy().items():
        if not value:
            copied_dict.pop(key)

    return copied_dict


def get_downloads_path(is_owner):  # pragma: no cover
    return 'downloads/creator/' if is_owner else 'downloads/reader/'


def get_csv_from_s3(filename, is_owner):  # pragma: no cover
    filename = get_downloads_path(is_owner) + filename + '.csv.zip'

    export_service = get_export_service()
    if export_service.exists(filename):
        return export_service.url_for(filename)

    return None


def reverse_resource(resource, viewname, args=None, kwargs=None, **extra):
    """
    Generate the URL for the view specified as viewname of the object specified as resource.
    """
    kwargs = kwargs or {}
    parent = resource
    while parent is not None:
        if not hasattr(parent, 'get_url_kwarg'):
            return NoReverseMatch(f'Cannot get URL kwarg for {resource}')  # pragma: no cover

        if parent.is_versioned and not parent.is_head:
            from core.collections.models import Collection
            from core.sources.models import Source
            if isinstance(parent, (Source, Collection)):
                head = parent.get_latest_version()
            else:
                head = parent.head

            if head:
                kwargs.update({head.get_url_kwarg(): head.mnemonic})

            kwargs.update({parent.get_url_kwarg(): parent.version})
            parent_resource_url_kwarg = parent.get_resource_url_kwarg()
            if parent_resource_url_kwarg not in kwargs:
                kwargs.update({parent_resource_url_kwarg: parent.mnemonic})
        else:
            kwargs.update({parent.get_url_kwarg(): parent.mnemonic})
        parent = parent.parent if hasattr(parent, 'parent') else None
        allowed_kwargs = get_kwargs_for_view(viewname)
        for key in kwargs.copy():
            if key not in allowed_kwargs:
                kwargs.pop(key)

    return reverse(viewname=viewname, args=args, kwargs=kwargs, **extra)


def reverse_resource_version(resource, viewname, args=None, kwargs=None, **extra):
    """
    Generate the URL for the view specified as viewname of the object that is
    versioned by the object specified as resource.
    Assumes that resource extends ResourceVersionMixin, and therefore has a versioned_object attribute.
    """
    from core.collections.models import Collection
    from core.sources.models import Source
    if isinstance(resource, (Source, Collection)):
        head = resource.get_latest_version()
    else:
        head = resource.head

    kwargs = kwargs or {}
    if head:
        kwargs.update({head.get_url_kwarg(): head.mnemonic})

    kwargs.update({resource.get_url_kwarg(): resource.version})
    resource_url_kwarg = resource.get_resource_url_kwarg()

    if resource_url_kwarg not in kwargs:
        kwargs[resource_url_kwarg] = resource.mnemonic

    return reverse_resource(resource, viewname, args, kwargs, **extra)


def get_kwargs_for_view(view_name):
    resolver = get_resolver()
    patterns = resolver.reverse_dict.getlist(view_name)
    return list(set(flatten([p[0][0][1] for p in patterns])))


def parse_updated_since_param(params):
    return from_string_to_date(params.get(UPDATED_SINCE_PARAM))


def from_string_to_date(updated_since):  # pragma: no cover
    if updated_since:
        try:
            return parser.parse(updated_since)
        except ValueError:
            pass
    return None


def parse_boolean_query_param(request, param, default=None):
    val = request.query_params.get(param, default)
    if val is None:
        return None
    for boolean in [True, False]:
        if str(boolean).lower() == val.lower():
            return boolean
    return None  # pragma: no cover


def get_query_params_from_url_string(url):
    try:
        return dict(parse.parse_qsl(parse.urlsplit(url).query))
    except:  # pylint: disable=bare-except  # pragma: no cover
        return {}


def get_class(kls):
    parts = kls.split('.')
    module = ".".join(parts[:-1])
    _module = __import__(module)
    for comp in parts[1:]:
        _module = getattr(_module, comp)
    return _module


def write_export_file(
        version, resource_type, resource_serializer_type, logger
):  # pylint: disable=too-many-statements,too-many-locals,too-many-branches
    from core.concepts.models import Concept
    from core.mappings.models import Mapping
    cwd = cd_temp()
    logger.info(f'Writing export file to tmp directory: {cwd}')

    logger.info(f'Found {resource_type} version {version.version}.  Looking up resource...')
    logger.info(f'Found {resource_type} {version.mnemonic}.  Serializing attributes...')

    resource_serializer = get_class(resource_serializer_type)(version)
    data = resource_serializer.data
    resource_string = json.dumps(data, cls=encoders.JSONEncoder)
    logger.info('Done serializing attributes.')

    batch_size = 100
    is_collection = resource_type == 'collection'

    concepts_qs = Concept.objects.none()
    mappings_qs = Mapping.objects.none()

    if is_collection:
        if version.expansion_uri:
            concepts_qs = Concept.expansion_set.through.objects.filter(expansion_id=version.expansion.id)
            mappings_qs = Mapping.expansion_set.through.objects.filter(expansion_id=version.expansion.id)
    else:
        concepts_qs = Concept.sources.through.objects.filter(source_id=version.id)
        mappings_qs = Mapping.sources.through.objects.filter(source_id=version.id)

    filters = {}

    if not is_collection:
        filters['is_active'] = True
        if version.is_head:
            filters['is_latest_version'] = True

    with open('export.json', 'w') as out:
        out.write(f'{resource_string[:-1]}, "concepts": [')

    resource_name = resource_type.title()

    if concepts_qs.exists():
        logger.info(f'{resource_name} has concepts. Getting them in batches of {batch_size:d}...')
        concept_serializer_class = get_class('core.concepts.serializers.ConceptVersionExportSerializer')
        start = 0
        end = batch_size
        batch_queryset = concepts_qs.order_by('-concept_id')[start:end]

        while batch_queryset.exists():
            logger.info(f'Serializing concepts {start + 1:d} - {end:d}...')
            queryset = Concept.objects.filter(
                id__in=batch_queryset.values_list('concept_id')).filter(**filters).order_by('-id')
            if queryset.exists():
                if start > 0:
                    with open('export.json', 'a') as out:
                        out.write(', ')
                concept_versions = queryset.prefetch_related('names', 'descriptions')
                data = concept_serializer_class(concept_versions, many=True).data
                concept_string = json.dumps(data, cls=encoders.JSONEncoder)
                concept_string = concept_string[1:-1]

                with open('export.json', 'a') as out:
                    out.write(concept_string)

            start += batch_size
            end += batch_size
            batch_queryset = concepts_qs.order_by('-concept_id')[start:end]

        logger.info('Done serializing concepts.')
    else:
        logger.info(f'{resource_name} has no concepts to serialize.')

    if is_collection:
        references_qs = version.references
        total_references = references_qs.count()

        with open('export.json', 'a') as out:
            out.write('], "references": [')
        if total_references:
            logger.info(
                f'{resource_name} has {total_references:d} references. Getting them in batches of {batch_size:d}...'
            )
            reference_serializer_class = get_class('core.collections.serializers.CollectionReferenceSerializer')
            for start in range(0, total_references, batch_size):
                end = min(start + batch_size, total_references)
                logger.info(f'Serializing references {start + 1:d} - {end:d}...')
                references = references_qs.order_by('-id').filter()[start:end]
                reference_serializer = reference_serializer_class(references, many=True)
                reference_string = json.dumps(reference_serializer.data, cls=encoders.JSONEncoder)
                reference_string = reference_string[1:-1]
                with open('export.json', 'a') as out:
                    out.write(reference_string)
                    if end != total_references:
                        out.write(', ')
            logger.info('Done serializing references.')
        else:
            logger.info(f'{resource_name} has no references to serialize.')

    with open('export.json', 'a') as out:
        out.write('], "mappings": [')

    if mappings_qs.exists():
        logger.info(f'{resource_name} has mappings. Getting them in batches of {batch_size:d}...')
        mapping_serializer_class = get_class('core.mappings.serializers.MappingDetailSerializer')
        start = 0
        end = batch_size
        batch_queryset = mappings_qs.order_by('-mapping_id')[start:end]

        while batch_queryset.exists():
            logger.info(f'Serializing mappings {start + 1:d} - {start + batch_size:d}...')
            queryset = Mapping.objects.filter(
                id__in=batch_queryset.values_list('mapping_id')).filter(**filters).order_by('-id')
            if queryset.exists():
                if start > 0:
                    with open('export.json', 'a') as out:
                        out.write(', ')

                data = mapping_serializer_class(queryset, many=True).data
                mapping_string = json.dumps(data, cls=encoders.JSONEncoder)
                mapping_string = mapping_string[1:-1]
                with open('export.json', 'a') as out:
                    out.write(mapping_string)

            start += batch_size
            end += batch_size
            batch_queryset = mappings_qs.order_by('-mapping_id')[start:end]

        logger.info('Done serializing mappings.')
    else:
        logger.info(f'{resource_name} has no mappings to serialize.')

    with open('export.json', 'a') as out:
        out.write(']}')

    with zipfile.ZipFile('export.zip', 'w', zipfile.ZIP_DEFLATED) as _zip:
        _zip.write('export.json')

    file_path = os.path.abspath('export.zip')
    logger.info(file_path)
    logger.info('Done compressing.  Uploading...')

    s3_key = version.export_path
    export_service = get_export_service()
    if version.is_head:
        export_service.delete_objects(version.generic_export_path(suffix=None))

    upload_status_code = export_service.upload_file(
        key=s3_key, file_path=file_path, binary=True, metadata=dict(ContentType='application/zip'),
        headers={'content-type': 'application/zip'}
    )
    logger.info(f'Upload response status: {str(upload_status_code)}')
    uploaded_path = export_service.url_for(s3_key)
    logger.info(f'Uploaded to {uploaded_path}.')

    if not get(settings, 'TEST_MODE', False):
        tmp_dir_path = file_path.replace('/export.zip', '')
        logger.info(f'Removing tmp {tmp_dir_path}.')
        shutil.rmtree(tmp_dir_path, ignore_errors=True)

    os.chdir(cwd)


def get_api_base_url():
    return settings.API_BASE_URL


def get_api_internal_base_url():
    return settings.API_INTERNAL_BASE_URL


def to_snake_case(string):
    # from https://www.geeksforgeeks.org/python-program-to-convert-camel-case-string-to-snake-case/
    return ''.join(['_' + i.lower() if i.isupper() else i for i in string]).lstrip('_')


def to_camel_case(string):
    # from https://www.geeksforgeeks.org/python-convert-snake-case-string-to-camel-case/?ref=rp
    temp = string.split('_')
    return str(temp[0] + ''.join(ele.title() for ele in temp[1:]))


def parse_bulk_import_task_id(task_id):
    """
    Used to parse bulk import task id, which is in format '{uuid}-{username}~{queue}'.
    :param task_id:
    :return: dictionary with uuid, username, queue
    """
    task = dict(uuid=task_id[:37])
    username = task_id[37:]
    queue_index = username.find('~')
    if queue_index != -1:
        queue = username[queue_index + 1:]
        username = username[:queue_index]
    else:
        queue = 'default'

    task['username'] = username
    task['queue'] = queue
    return task


def flower_get(url, **kwargs):
    """
    Returns a flower response from the given endpoint url.
    :param url:
    :return:
    """
    return requests.get(
        f'http://{settings.FLOWER_HOST}:{settings.FLOWER_PORT}/{url}',
        auth=HTTPBasicAuth(settings.FLOWER_USER, settings.FLOWER_PASSWORD),
        **kwargs
    )


def es_get(url, **kwargs):
    """
    Returns a flower response from the given endpoint url.
    :param url:
    :return:
    """
    return requests.get(
        f'http://{settings.ES_HOST}:{settings.ES_PORT}/{url}',
        **kwargs
    )


def task_exists(task_id):
    """
    This method is used to check Celery Task validity when state is PENDING. If task exists in
    Flower then it's considered as Valid task otherwise invalid task.
    """
    flower_response = flower_get('api/task/info/' + task_id)
    return bool(flower_response and flower_response.status_code == 200 and flower_response.text)


def queue_bulk_import(  # pylint: disable=too-many-arguments
        to_import, import_queue, username, update_if_exists, threads=None, inline=False, sub_task=False
):
    """
    Used to queue bulk imports. It assigns a bulk import task to a specified import queue or a random one.
    If requested by the root user, the bulk import goes to the priority queue.

    :param to_import:
    :param import_queue:
    :param username:
    :param update_if_exists:
    :param threads:
    :param inline:
    :param sub_task:
    :return: task
    """
    task_id = str(uuid.uuid4()) + '-' + username

    if username in ['root', 'ocladmin'] and import_queue != 'concurrent':
        queue_id = 'bulk_import_root'
        task_id += '~priority'
    elif import_queue == 'concurrent':
        queue_id = import_queue
        task_id += '~' + import_queue
    elif import_queue:
        # assigning to one of 5 queues processed in order
        queue_id = 'bulk_import_' + str(hash(username + import_queue) % BULK_IMPORT_QUEUES_COUNT)
        task_id += '~' + import_queue
    else:
        # assigning randomly to one of 5 queues processed in order
        queue_id = 'bulk_import_' + str(random.randrange(0, BULK_IMPORT_QUEUES_COUNT))
        task_id += '~default'

    if inline:
        if sub_task:
            from core.common.tasks import bulk_import_parts_inline
            return bulk_import_parts_inline.apply_async(
                (to_import, username, update_if_exists), task_id=task_id, queue=queue_id
            )

        if threads:
            from core.common.tasks import bulk_import_parallel_inline
            return bulk_import_parallel_inline.apply_async(
                (to_import, username, update_if_exists, threads), task_id=task_id, queue=queue_id
            )
        from core.common.tasks import bulk_import_inline
        return bulk_import_inline.apply_async(
            (to_import, username, update_if_exists), task_id=task_id, queue=queue_id
        )

    from core.common.tasks import bulk_import
    return bulk_import.apply_async((to_import, username, update_if_exists), task_id=task_id, queue=queue_id)


def drop_version(expression):
    if not expression:
        return expression

    parts = expression.split('/')

    if len(parts) <= 4:
        return expression

    resource = parts[-4]
    name = parts[-3]
    version = parts[-2]
    if resource in ['concepts', 'mappings', 'sources', 'collections'] and name and version:
        return '/'.join(parts[:-2]) + '/'

    return expression


def is_versioned_uri(expression):
    return expression != drop_version(expression)


def to_parent_uri(expression):
    splitter = None
    if '/concepts/' in expression:
        splitter = '/concepts/'
    elif '/mappings/' in expression:
        splitter = '/mappings/'

    if splitter:
        return expression.split(splitter)[0] + '/'

    return expression


def to_owner_uri(expression):
    return '/' + '/'.join(compact(expression.split('/'))[:2]) + '/'


def separate_version(expression):
    versionless_expression = drop_version(expression)
    if expression != versionless_expression:
        return expression.replace(versionless_expression, '').replace('/', ''), versionless_expression

    return None, expression


def generate_temp_version():
    return f"{TEMP_PREFIX}{str(uuid.uuid4())[:8]}"


def startswith_temp_version(value):
    return value.startswith(TEMP_PREFIX)


def jsonify_safe(value):
    if isinstance(value, dict):
        return value

    try:
        return json.loads(value)
    except:  # pylint: disable=bare-except
        return value


def web_url():
    env = settings.ENV
    if not env or env in ['development', 'ci']:
        return 'http://localhost:4000'

    if env == 'production':
        return "https://app.openconceptlab.org"

    return f"https://app.{env}.openconceptlab.org"


def get_resource_class_from_resource_name(resource):  # pylint: disable=too-many-return-statements
    if not resource:
        return resource

    name = resource.lower()
    if name in ['concepts', 'concept']:
        from core.concepts.models import Concept
        return Concept
    if name in ['mappings', 'mapping']:
        from core.mappings.models import Mapping
        return Mapping
    if name in ['users', 'user', 'user_profiles', 'user_profile', 'userprofiles', 'userprofile']:
        from core.users.models import UserProfile
        return UserProfile
    if name in ['orgs', 'org', 'organizations', 'organization']:
        from core.orgs.models import Organization
        return Organization
    if name in ['sources', 'source']:
        from core.sources.models import Source
        return Source
    if name in ['collections', 'collection']:
        from core.collections.models import Collection
        return Collection

    return None


def get_content_type_from_resource_name(resource):
    model = get_resource_class_from_resource_name(resource)
    if model:
        from django.contrib.contenttypes.models import ContentType
        return ContentType.objects.get_for_model(model)

    return None


def flatten_dict(dikt, parent_key='', sep='__'):
    items = []
    for key, val in dikt.items():
        new_key = parent_key + sep + key if parent_key else key

        if isinstance(val, MutableMapping):
            items.extend(flatten_dict(val, new_key, sep=sep).items())
        # elif isinstance(val, list):
        #     for i, _v in enumerate(val, start=0):
        #         if isinstance(_v, dict):
        #             items.extend(flatten_dict(_v, "{}__{}".format(key, i)).items())
        #         else:
        #             items.append(("{}__{}".format(key, i), str(_v)))
        else:
            items.append((new_key, str(val)))
    return dict(items)


def get_bulk_import_celery_once_lock_key(async_result):
    result_args = async_result.args
    args = [('to_import', result_args[0]), ('username', result_args[1]), ('update_if_exists', result_args[2])]

    if async_result.name == 'core.common.tasks.bulk_import_parallel_inline':
        args.append(('threads', result_args[3]))

    return get_celery_once_lock_key(async_result.name, args)


def get_celery_once_lock_key(name, args):
    return queue_once_key(name, OrderedDict(args), None)


def guess_extension(file=None, name=None):
    if not file and not name:
        return None
    if file:
        name = file.name
    _, extension = os.path.splitext(name)

    if not extension:
        extension = mimetypes.guess_extension(name)
    return extension


def is_csv_file(file=None, name=None):
    if not file and not name:
        return None

    extension = guess_extension(file=file, name=name)

    return extension and extension.endswith('csv')


def is_url_encoded_string(string, lower=True):
    encoded_string = encode_string(decode_string(string), safe=' ')

    if lower:
        return string.lower() == encoded_string.lower()

    return string == encoded_string


def decode_string(string, plus=True):
    return parse.unquote_plus(string) if plus else parse.unquote(string)


def encode_string(string, **kwargs):
    return parse.quote(string, **kwargs)


def to_parent_uri_from_kwargs(params):
    if not params:
        return None

    owner_type, owner, parent_type, parent = None, None, None, None

    if 'org' in params:
        owner_type = 'orgs'
        owner = params.get('org')
    elif 'user' in params:
        owner_type = 'users'
        owner = params.get('user')

    if 'source' in params:
        parent_type = 'sources'
        parent = params.get('source')
    elif 'collection' in params:
        parent_type = 'collections'
        parent = params.get('collection')

    return '/' + '/'.join(compact([owner_type, owner, parent_type, parent, params.get('version', None)])) + '/'


def api_get(url, user, **kwargs):
    response = requests.get(
        settings.API_BASE_URL + url, headers=user.auth_headers,
        **kwargs
    )
    return response.json()


thread_locals = local()


def set_current_user(func):
    setattr(thread_locals, CURRENT_USER, func.__get__(func, local))  # pylint: disable=unnecessary-dunder-call


def set_request_url(func):
    setattr(thread_locals, REQUEST_URL, func.__get__(func, local))  # pylint: disable=unnecessary-dunder-call


def get_current_user():
    current_user = getattr(thread_locals, CURRENT_USER, None)
    if callable(current_user):
        current_user = current_user()  # pylint: disable=not-callable

    return current_user


def get_request_url():
    request_url = getattr(thread_locals, REQUEST_URL, None)
    if callable(request_url):
        request_url = request_url()  # pylint: disable=not-callable

    return request_url


def named_tuple_fetchall(cursor):
    """Return all rows from a cursor as a namedtuple"""
    from collections import namedtuple
    desc = cursor.description
    nt_result = namedtuple('Result', [col[0] for col in desc])
    return [nt_result(*row) for row in cursor.fetchall()]


def nested_dict_values(_dict):
    for value in _dict.values():
        if isinstance(value, dict):
            yield from nested_dict_values(value)
        else:
            yield value


def chunks(lst, size):
    """Yield successive n-sized chunks from lst."""
    for i in range(0, len(lst), size):
        yield lst[i:i + size]


def es_id_in(search, ids):
    if ids:
        return search.query("terms", _id=ids)
    return search


def get_es_wildcard_search_criterion(search_str, name_attr='name'):
    def get_query(_str):
        return es_Q(
            "wildcard", id=dict(value=_str, boost=2)
        ) | es_Q(
            "wildcard", **{name_attr: dict(value=_str, boost=5)}
        ) | es_Q(
            "query_string", query=f"*{_str}*"
        )

    if search_str:
        words = search_str.split()
        criterion = get_query(words[0])
        for word in words[1:]:
            criterion |= get_query(word)
    else:
        criterion = get_query(search_str)

    return criterion


def get_es_exact_search_criterion(search_str, fields):
    def get_query(attr):
        words = search_str.split(' ')
        criteria = es_Q('match', **{attr: words[0]})
        for word in words[1:]:
            criteria &= es_Q('match', **{attr: word})
        return criteria

    criterion = get_query(fields.pop())
    for field in fields:
        criterion |= get_query(field)

    return criterion


def es_wildcard_search(search, search_str, exact_search_fields, name_attr='name'):
    if not search_str:
        return search

    return search.query(
        get_es_wildcard_search_criterion(
            search_str, name_attr) | get_es_exact_search_criterion(search_str, exact_search_fields))


def es_exact_search(search, search_str, exact_search_fields):
    if not search_str:
        return search

    return search.query(get_es_exact_search_criterion(search_str, exact_search_fields))


def get_exact_search_fields(klass):
    return [field for field, config in get(klass, 'es_fields', {}).items() if config.get('exact', False)]


def es_to_pks(search):
    # doesn't care about the order
    default_limit = 25
    limit = default_limit
    offset = 0
    result_count = 25
    pks = []
    while result_count > 0:
        hits = search[offset:limit].execute().hits
        result_count = len(hits)
        if result_count:
            pks += [hit.meta.id for hit in hits]
        offset += default_limit
        limit += default_limit
    return pks


def batch_qs(qs, batch_size=1000):
    """
    Returns a sub-queryset for each batch in the given queryset.

    Usage:
        # Make sure to order your querset
        article_qs = Article.objects.order_by('id')
        for qs in batch_qs(article_qs):
            for article in qs:
                print article.body
    """
    total = qs.count()
    for start in range(0, total, batch_size):
        end = min(start + batch_size, total)
        yield qs[start:end]


def split_list_by_condition(items, predicate):
    include, exclude = [], []
    for item in items:
        (exclude, include)[predicate(item)].append(item)

    return include, exclude


def is_canonical_uri(string):
    return ':' in string


def get_export_service():
    parts = EXPORT_SERVICE.split('.')
    klass = parts[-1]
    mod = __import__('.'.join(parts[0:-1]), fromlist=[klass])
    return getattr(mod, klass)