from collections import defaultdict
import logging
import time
import urllib
from datetime import datetime

from django.contrib.auth.models import User
from django.core.urlresolvers import reverse
from django.db import connection
from django.http import HttpResponse
from django.utils import simplejson
from django_comment_client.models import Role
from django_comment_client.permissions import check_permissions_by_view
from mitxmako import middleware
import pystache_custom as pystache

from xmodule.modulestore import Location
from xmodule.modulestore.django import modulestore
from xmodule.modulestore.search import path_to_location

log = logging.getLogger(__name__)

# TODO these should be cached via django's caching rather than in-memory globals
_FULLMODULES = None
_DISCUSSIONINFO = defaultdict(dict)

def extract(dic, keys):
    return {k: dic.get(k) for k in keys}

def strip_none(dic):
    return dict([(k, v) for k, v in dic.iteritems() if v is not None])

def strip_blank(dic):
    def _is_blank(v):
        return isinstance(v, str) and len(v.strip()) == 0
    return dict([(k, v) for k, v in dic.iteritems() if not _is_blank(v)])

# TODO should we be checking if d1 and d2 have the same keys with different values?
def merge_dict(dic1, dic2):
    return dict(dic1.items() + dic2.items())

def get_role_ids(course_id):
    roles = Role.objects.filter(course_id=course_id)
    staff = list(User.objects.filter(is_staff=True).values_list('id', flat=True))
    roles_with_ids = {'Staff': staff}
    for role in roles:
        roles_with_ids[role.name] = list(role.users.values_list('id', flat=True))
    return roles_with_ids

def has_forum_access(uname, course_id, rolename):
    try:
        role = Role.objects.get(name=rolename, course_id=course_id)
    except Role.DoesNotExist:
        return False
    return role.users.filter(username=uname).exists()

def get_full_modules():
    global _FULLMODULES
    if not _FULLMODULES:
        _FULLMODULES = modulestore().modules
    return _FULLMODULES

def get_discussion_id_map(course):
    """
        return a dict of the form {category: modules}
    """
    global _DISCUSSIONINFO
    initialize_discussion_info(course)
    return _DISCUSSIONINFO[course.id]['id_map']

def get_discussion_title(course, discussion_id):
    global _DISCUSSIONINFO
    initialize_discussion_info(course)
    title = _DISCUSSIONINFO[course.id]['id_map'].get(discussion_id, {}).get('title', '(no title)')
    return title

def get_discussion_category_map(course):

    global _DISCUSSIONINFO
    initialize_discussion_info(course)
    return filter_unstarted_categories(_DISCUSSIONINFO[course.id]['category_map'])

def filter_unstarted_categories(category_map):

    now = time.gmtime()

    result_map = {}

    unfiltered_queue = [category_map]
    filtered_queue   = [result_map]

    while len(unfiltered_queue) > 0:

        unfiltered_map = unfiltered_queue.pop()
        filtered_map   = filtered_queue.pop()

        filtered_map["children"] = []
        filtered_map["entries"] = {}
        filtered_map["subcategories"] = {}

        for child in unfiltered_map["children"]:
            if child in unfiltered_map["entries"]:
                if unfiltered_map["entries"][child]["start_date"] <= now:
                    filtered_map["children"].append(child)
                    filtered_map["entries"][child] = {}
                    for key in unfiltered_map["entries"][child]:
                        if key != "start_date":
                            filtered_map["entries"][child][key] = unfiltered_map["entries"][child][key]
                else:
                    print "filtering %s" % child, unfiltered_map["entries"][child]["start_date"]
            else:
                if unfiltered_map["subcategories"][child]["start_date"] < now:
                    filtered_map["children"].append(child)
                    filtered_map["subcategories"][child] = {}
                    unfiltered_queue.append(unfiltered_map["subcategories"][child])
                    filtered_queue.append(filtered_map["subcategories"][child])

    return result_map

def sort_map_entries(category_map):
    things = []
    for title, entry in category_map["entries"].items():
        things.append((title, entry))
    for title, category in category_map["subcategories"].items():
        things.append((title, category))
        sort_map_entries(category_map["subcategories"][title])
    category_map["children"] = [x[0] for x in sorted(things, key=lambda x: x[1]["sort_key"])]


def initialize_discussion_info(course):

    global _DISCUSSIONINFO

    # only cache in-memory discussion information for 10 minutes
    # this is because we need a short-term hack fix for
    # mongo-backed courseware whereby new discussion modules can be added
    # without LMS service restart

    if _DISCUSSIONINFO[course.id]:
        timestamp = _DISCUSSIONINFO[course.id].get('timestamp', datetime.now())
        age = datetime.now() - timestamp
        # expire every 5 minutes
        if age.seconds < 300:
            return

    course_id = course.id

    discussion_id_map = {}
    unexpanded_category_map = defaultdict(list)

    # get all discussion models within this course_id
    all_modules = modulestore().get_items(['i4x', course.location.org, course.location.course, 'discussion', None], course_id=course_id)

    for module in all_modules:
        skip_module = False
        for key in ('id', 'discussion_category', 'for'):
            if key not in module.metadata:
                log.warning("Required key '%s' not in discussion %s, leaving out of category map" % (key, module.location))
                skip_module = True

        if skip_module:
            continue

        id = module.metadata['id']
        category = module.metadata['discussion_category']
        title = module.metadata['for']
        sort_key = module.metadata.get('sort_key', title)
        category = " / ".join([x.strip() for x in category.split("/")])
        last_category = category.split("/")[-1]
        discussion_id_map[id] = {"location": module.location, "title": last_category + " / " + title}
        unexpanded_category_map[category].append({"title": title, "id": id,
            "sort_key": sort_key, "start_date": module.start})

    category_map = {"entries": defaultdict(dict), "subcategories": defaultdict(dict)}
    for category_path, entries in unexpanded_category_map.items():
        node = category_map["subcategories"]
        path = [x.strip() for x in category_path.split("/")]

        # Find the earliest start date for the entries in this category
        category_start_date = None
        for entry in entries:
            if category_start_date is None or entry["start_date"] < category_start_date:
                category_start_date = entry["start_date"]

        for level in path[:-1]:
            if level not in node:
                node[level] = {"subcategories": defaultdict(dict),
                               "entries": defaultdict(dict),
                               "sort_key": level,
                               "start_date": category_start_date}
            else:
                if node[level]["start_date"] > category_start_date:
                    node[level]["start_date"] = category_start_date
            node = node[level]["subcategories"]

        level = path[-1]
        if level not in node:
            node[level] = {"subcategories": defaultdict(dict),
                            "entries": defaultdict(dict),
                            "sort_key": level,
                            "start_date": category_start_date}
        else:
            if node[level]["start_date"] > category_start_date:
                node[level]["start_date"] = category_start_date

        for entry in entries:
            node[level]["entries"][entry["title"]] = {"id": entry["id"],
                                                      "sort_key": entry["sort_key"],
                                                      "start_date": entry["start_date"]}

    # TODO.  BUG! : course location is not unique across multiple course runs!
    # (I think Kevin already noticed this)  Need to send course_id with requests, store it
    # in the backend.
    default_topics = {'General': {'id' :course.location.html_id()}}
    discussion_topics = course.metadata.get('discussion_topics', default_topics)
    for topic, entry in discussion_topics.items():
        category_map['entries'][topic] = {"id": entry["id"],
                                          "sort_key": entry.get("sort_key", topic),
                                          "start_date": time.gmtime()}
    sort_map_entries(category_map)

    _DISCUSSIONINFO[course.id]['id_map'] = discussion_id_map
    _DISCUSSIONINFO[course.id]['category_map'] = category_map
    _DISCUSSIONINFO[course.id]['timestamp'] = datetime.now()

class JsonResponse(HttpResponse):
    def __init__(self, data=None):
        content = simplejson.dumps(data)
        super(JsonResponse, self).__init__(content,
                                           mimetype='application/json; charset=utf-8')

class JsonError(HttpResponse):
    def __init__(self, error_messages=[], status=400):
        if isinstance(error_messages, str):
            error_messages = [error_messages]
        content = simplejson.dumps({'errors': error_messages},
                                   indent=2,
                                   ensure_ascii=False)
        super(JsonError, self).__init__(content,
                                        mimetype='application/json; charset=utf-8', status=status)

class HtmlResponse(HttpResponse):
    def __init__(self, html=''):
        super(HtmlResponse, self).__init__(html, content_type='text/plain')

class ViewNameMiddleware(object):
    def process_view(self, request, view_func, view_args, view_kwargs):
        request.view_name = view_func.__name__

class QueryCountDebugMiddleware(object):
    """
    This middleware will log the number of queries run
    and the total time taken for each request (with a
    status code of 200). It does not currently support
    multi-db setups.
    """
    def process_response(self, request, response):
        if response.status_code == 200:
            total_time = 0

            for query in connection.queries:
                query_time = query.get('time')
                if query_time is None:
                    # django-debug-toolbar monkeypatches the connection
                    # cursor wrapper and adds extra information in each
                    # item in connection.queries. The query time is stored
                    # under the key "duration" rather than "time" and is
                    # in milliseconds, not seconds.
                    query_time = query.get('duration', 0) / 1000
                total_time += float(query_time)

            log.info('%s queries run, total %s seconds' % (len(connection.queries), total_time))
        return response

def get_ability(course_id, content, user):
    return {
            'editable': check_permissions_by_view(user, course_id, content, "update_thread" if content['type'] == 'thread' else "update_comment"),
            'can_reply': check_permissions_by_view(user, course_id, content, "create_comment" if content['type'] == 'thread' else "create_sub_comment"),
            'can_endorse': check_permissions_by_view(user, course_id, content, "endorse_comment") if content['type'] == 'comment' else False,
            'can_delete': check_permissions_by_view(user, course_id, content, "delete_thread" if content['type'] == 'thread' else "delete_comment"),
            'can_openclose': check_permissions_by_view(user, course_id, content, "openclose_thread") if content['type'] == 'thread' else False,
            'can_vote': check_permissions_by_view(user, course_id, content, "vote_for_thread" if content['type'] == 'thread' else "vote_for_comment"),
    }

#TODO: RENAME
def get_annotated_content_info(course_id, content, user, user_info):
    """
    Get metadata for an individual content (thread or comment)
    """
    voted = ''
    if content['id'] in user_info['upvoted_ids']:
        voted = 'up'
    elif content['id'] in user_info['downvoted_ids']:
        voted = 'down'
    return {
        'voted': voted,
        'subscribed': content['id'] in user_info['subscribed_thread_ids'],
        'ability': get_ability(course_id, content, user),
    }

#TODO: RENAME
def get_annotated_content_infos(course_id, thread, user, user_info):
    """
    Get metadata for a thread and its children
    """
    infos = {}
    def annotate(content):
        infos[str(content['id'])] = get_annotated_content_info(course_id, content, user, user_info)
        for child in content.get('children', []):
            annotate(child)
    annotate(thread)
    return infos

def get_metadata_for_threads(course_id, threads, user, user_info):
    def infogetter(thread):
        return get_annotated_content_infos(course_id, thread, user, user_info)

    metadata = reduce(merge_dict, map(infogetter, threads), {})
    return metadata

# put this method in utils.py to avoid circular import dependency between helpers and mustache_helpers
def url_for_tags(course_id, tags):
    return reverse('django_comment_client.forum.views.forum_form_discussion', args=[course_id]) + '?' + urllib.urlencode({'tags': tags})

def render_mustache(template_name, dictionary, *args, **kwargs):
    template = middleware.lookup['main'].get_template(template_name).source
    return pystache.render(template, dictionary)

def permalink(content):
    if content['type'] == 'thread':
        return reverse('django_comment_client.forum.views.single_thread',
                       args=[content['course_id'], content['commentable_id'], content['id']])
    else:
        return reverse('django_comment_client.forum.views.single_thread',
                       args=[content['course_id'], content['commentable_id'], content['thread_id']]) + '#' + content['id']

def extend_content(content):
    roles = {}
    if content.get('user_id'):
        try:
            user = User.objects.get(pk=content['user_id'])
            roles = dict(('name', role.name.lower()) for role in user.roles.filter(course_id=content['course_id']))
        except user.DoesNotExist:
            log.error('User ID {0} in comment content {1} but not in our DB.'.format(content.get('user_id'), content.get('id')))

    content_info = {
        'displayed_title': content.get('highlighted_title') or content.get('title', ''),
        'displayed_body': content.get('highlighted_body') or content.get('body', ''),
        'raw_tags': ','.join(content.get('tags', [])),
        'permalink': permalink(content),
        'roles': roles,
        'updated': content['created_at']!=content['updated_at'],
    }
    return merge_dict(content, content_info)

def get_courseware_context(content, course):
    id_map = get_discussion_id_map(course)
    id = content['commentable_id']
    content_info = None
    if id in id_map:
        location = id_map[id]["location"].url()
        title = id_map[id]["title"]
        (course_id, chapter, section, position) = path_to_location(modulestore(), course.id, location)
        url = reverse('courseware_position', kwargs={"course_id":course_id,
                                                     "chapter":chapter,
                                                     "section":section,
                                                     "position":position})
        content_info = {"courseware_url": url, "courseware_title": title}
    return content_info

def safe_content(content):
    fields = [
        'id', 'title', 'body', 'course_id', 'anonymous', 'anonymous_to_peers',
        'endorsed', 'parent_id', 'thread_id', 'votes', 'closed', 'created_at',
        'updated_at', 'depth', 'type', 'commentable_id', 'comments_count',
        'at_position_list', 'children', 'highlighted_title', 'highlighted_body',
        'courseware_title', 'courseware_url', 'tags', 'unread_comments_count',
        'read',
    ]

    if (content.get('anonymous') is False) and (content.get('anonymous_to_peers') is False):
        fields += ['username', 'user_id']

    if 'children' in content:
        safe_children = [safe_content(child) for child in content['children']]
        content['children'] = safe_children

    return strip_none(extract(content, fields))
