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

from zerver.models import UserProfile, UserActivity, UserActivityInterval, Message

from django.utils.timezone import utc

from datetime import timedelta
from itertools import chain

def median(data):
    data = sorted(data)

    size = len(data)
    if size % 2 == 1:
        return data[size//2]
    else:
        before = size//2 - 1
        after = size//2
        return (data[before] + data[after]) / 2.0

users_who_sent_query = Message.objects.select_related("sender") \
        .exclude(sending_client__name__contains="mirror") \
        .exclude(sending_client__name__contains="API")

def active_users():
    # Return a list of active users we want to count towards various
    # statistics.
    return UserProfile.objects.filter(is_bot=False, is_active=True).select_related()

def users_who_sent_between(begin, end):
    sender_objs = users_who_sent_query.filter(pub_date__gt=begin, pub_date__lt=end) \
        .values("sender__id")
    return set(s["sender__id"] for s in sender_objs)

def users_who_sent_ever():
    return set(s["sender__id"] for s in users_who_sent_query.values("sender__id"))

def active_users_to_measure():
    senders = users_who_sent_ever()
    return [u for u in active_users() if u.id in senders]

def active_users_who_sent_between(begin, end):
    senders = users_who_sent_between(begin, end)
    return [u for u in active_users() if u.id in senders]

# Return the amount of Zulip usage for this user between the two
# given dates
def seconds_usage_between(user_profile, begin, end):
    intervals = UserActivityInterval.objects.filter(user_profile=user_profile, end__gte=begin, start__lte=end)
    duration = timedelta(0)
    for interval in intervals:
        start = max(begin, interval.start)
        finish = min(end, interval.end)
        duration += finish-start
    return duration

# Return a list of how many seconds each user has been engaging with the app on a given day
def seconds_active_during_day(day):
    begin_day = day.replace(hour=0, minute=0, second=0, microsecond=0, tzinfo=utc)
    end_day = day.replace(hour=23, minute=59, second=59, microsecond=0, tzinfo=utc)
    active_users = active_users_to_measure()

    return [seconds_usage_between(user, begin_day, end_day).total_seconds() for user in active_users]

def users_active_nosend_during_day(day):
    begin_day = day.replace(hour=0, minute=0, second=0, microsecond=0, tzinfo=utc)
    end_day = day.replace(hour=23, minute=59, second=59, microsecond=0, tzinfo=utc)
    active_users = active_users_to_measure()
    today_senders = users_who_sent_between(begin_day, end_day)

    today_users = []
    for user_profile in active_users:
        intervals = UserActivityInterval.objects.filter(user_profile=user_profile,
                                                        end__gte=begin_day,
                                                        start__lte=end_day)
        if len(intervals) != 0:
            today_users.append(user_profile)
    return [u for u in today_users if not u.id in today_senders]

def calculate_stats(data, all_users):
    if len(data) == 0:
        return {"# data points": 0}

    active_user_count = len([x for x in data if x > 1])
    mean_data = sum(data) / active_user_count
    median_data = median([x for x in data if x > 1])

    return {'active users': active_user_count,
            'total users': len(all_users),
            'mean': str(timedelta(seconds=mean_data)),
            'median': str(timedelta(seconds=median_data)),
            '# data points': len(data)}

# Return an info dict {mean: , median} containing the mean/median seconds users were active on a given day
def activity_averages_during_day(day):
    users_to_measure = active_users_to_measure()
    seconds_active = seconds_active_during_day(day)
    return calculate_stats(seconds_active, all_users=users_to_measure)

# Returns an info dict {mean: , median} with engagement numbers for all users according
# to active_users_to_measure.
def activity_averages_between(begin, end, by_day=True):
    seconds_active = {}
    users_to_measure = active_users_to_measure()
    for i in range((end - begin).days):
        day = begin + timedelta(days=i)

        # Ignore weekends
        if day.weekday() in [5, 6]:
            continue

        seconds_active[day] = seconds_active_during_day(day)

    if by_day:
        return dict((day, calculate_stats(values, all_users=users_to_measure))
                    for day, values in seconds_active.iteritems())
    else:
        return calculate_stats(list(chain.from_iterable(seconds_active.values())),
                               all_users=users_to_measure)