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

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