# -*- coding: utf-8 -*-
from __future__ import unicode_literals

from importlib import import_module
from django.conf import settings
from django.core.exceptions import PermissionDenied
from django.http import Http404

from . import servers


def get_class(import_path=None):
    """
    Largely based on django.core.files.storage's get_storage_class
    """
    from django.core.exceptions import ImproperlyConfigured
    if import_path is None:
        raise ImproperlyConfigured('No class path specified.')
    try:
        dot = import_path.rindex('.')
    except ValueError:
        raise ImproperlyConfigured("%s isn't a module." % import_path)
    module, classname = import_path[:dot], import_path[dot + 1:]
    try:
        mod = import_module(module)
    except ImportError as e:
        raise ImproperlyConfigured('Error importing module %s: "%s"' % (module, e))
    try:
        return getattr(mod, classname)
    except AttributeError:
        raise ImproperlyConfigured('Module "%s" does not define a "%s" class.' % (module, classname))


server = get_class(settings.PROTECTED_MEDIA_SERVER)(**getattr(settings, 'PROTECTED_MEDIA_SERVER_OPTIONS', {}))
if hasattr(settings,'PROTECTED_MEDIA_PERMISSIONS'):
    permissions = get_class(settings.PROTECTED_MEDIA_PERMISSIONS)(**getattr(settings, 'PROTECTED_MEDIA_PERMISSIONS_OPTIONS', {}))
else:
    from .permissions import DefaultProtectedPermissions
    permissions = DefaultProtectedPermissions()


def serve_protected_file(request, path):
    """
    Serve private files to users with read permission.
    """
    if not permissions.has_read_permission(request, path):
        if settings.DEBUG:
            raise PermissionDenied
        else:
            raise Http404('File not found')
    return server.serve(request, relative_path=path)