"""
This module contains helper functions and helper classes.
"""
import time
import hmac

from django.core.cache import cache
from django.db.models import Model

from django.utils import timezone

from neboard import settings


CACHE_KEY_DELIMITER = '_'
PERMISSION_MODERATE = 'moderation'

def get_client_ip(request):
    x_forwarded_for = request.META.get('HTTP_X_FORWARDED_FOR')
    if x_forwarded_for:
        ip = x_forwarded_for.split(',')[-1].strip()
    else:
        ip = request.META.get('REMOTE_ADDR')
    return ip


# TODO The output format is not epoch because it includes microseconds
def datetime_to_epoch(datetime):
    return int(time.mktime(timezone.localtime(
        datetime,timezone.get_current_timezone()).timetuple())
               * 1000000 + datetime.microsecond)


def get_websocket_token(user_id='', timestamp=''):
    """
    Create token to validate information provided by new connection.
    """

    sign = hmac.new(settings.CENTRIFUGE_PROJECT_SECRET.encode())
    sign.update(settings.CENTRIFUGE_PROJECT_ID.encode())
    sign.update(user_id.encode())
    sign.update(timestamp.encode())
    token = sign.hexdigest()

    return token


def cached_result(key_method=None):
    """
    Caches method result in the Django's cache system, persisted by object name,
    object name and model id if object is a Django model.
    """
    def _cached_result(function):
        def inner_func(obj, *args, **kwargs):
            # TODO Include method arguments to the cache key
            cache_key_params = [obj.__class__.__name__, function.__name__]
            if isinstance(obj, Model):
                cache_key_params.append(str(obj.id))

            if key_method is not None:
                cache_key_params += [str(arg) for arg in key_method(obj)]

            cache_key = CACHE_KEY_DELIMITER.join(cache_key_params)

            persisted_result = cache.get(cache_key)
            if persisted_result is not None:
                result = persisted_result
            else:
                result = function(obj, *args, **kwargs)
                cache.set(cache_key, result)

            return result

        return inner_func
    return _cached_result


def is_moderator(request):
    try:
        moderate = request.user.has_perm(PERMISSION_MODERATE)
    except AttributeError:
        moderate = False

    return moderate