from datetime import timedelta

from django.db import transaction

from common.utils import get_logger
from common.utils.timezone import local_now
from users.models import User
from .models import MessageContent, SiteMessage

logger = get_logger(__file__)


class SiteMessageUtil:

    @classmethod
    def send_msg(cls, subject, message, user_ids=(), group_ids=(),
                 sender=None, is_broadcast=False, display_mode=MessageContent.DisplayMode.default):
        if not any((user_ids, group_ids, is_broadcast)):
            raise ValueError('No recipient is specified')

        with transaction.atomic():
            site_msg = MessageContent(
                subject=subject, message=message,
                is_broadcast=is_broadcast, sender=sender,
                display_mode=display_mode
            )

            if is_broadcast:
                # 广播消息时只为在线用户创建，未登录的用户不创建消息，
                # 等用户登录后在 SiteMessage.create_site_msg_for_user_if_need 按需创建
                from audits.models import UserSession
                user_ids = UserSession.objects.all().values_list('user_id', flat=True).distinct()
            elif group_ids:
                site_msg.groups.add(*group_ids)

                user_ids_from_group = User.groups.through.objects.filter(
                    usergroup_id__in=group_ids
                ).values_list('user_id', flat=True)
                user_ids = [*user_ids, *user_ids_from_group]

            site_msg.users.add(*user_ids)
            # 只有调用 save 才能触发 post_save 信号
            site_msg.save()
        return site_msg

    @classmethod
    def get_user_all_msgs(cls, user_id):
        site_msg_rels = SiteMessage.objects \
            .filter(user=user_id) \
            .prefetch_related('content') \
            .order_by('-date_created')
        return site_msg_rels

    @classmethod
    def get_user_all_msgs_count(cls, user_id):
        site_msgs_count = SiteMessage.objects.filter(
            user_id=user_id
        ).distinct().count()
        return site_msgs_count

    @classmethod
    def filter_user_msgs(cls, user_id, has_read=False):
        return cls.get_user_all_msgs(user_id).filter(has_read=has_read)

    @classmethod
    def get_user_unread_msgs_count(cls, user_id):
        site_msgs_count = SiteMessage.objects \
            .filter(user=user_id, has_read=False) \
            .values_list('content', flat=True) \
            .distinct().count()
        return site_msgs_count
    
    @classmethod
    def get_user_display_msgs(cls, user_id):
        # 获取用户未读的且需要展示的消息
        msgs = SiteMessage.objects.filter(user_id=user_id, has_read=False).exclude(
            content__display_mode=MessageContent.DisplayMode.default
        ).prefetch_related('content')
        return msgs
    
    @classmethod
    def create_site_msgs_for_user_if_need(cls, user_id):
        '''
        创建用户未读的且需要展示的消息
        广播消息时只为在线用户创建，未登录的用户不创建消息，等用户登录后在这里按需创建
        只创建用户没有的、最近24小时内的、需要广播的消息
        '''
        contents = MessageContent.objects.filter(
            is_broadcast=True,
            date_created__gt=local_now() - timedelta(hours=24)
        ).exclude(display_mode=MessageContent.DisplayMode.default)
        content_ids = set(contents.values_list('id', flat=True))
        has_content_ids = SiteMessage.objects.filter(
            user_id=user_id, content_id__in=content_ids
        ).values_list('content_id', flat=True)
        to_create_content_ids = set(content_ids) - set(has_content_ids)
        site_msgs = [
            SiteMessage(user_id=user_id, content_id=cid) for cid in to_create_content_ids
        ]
        SiteMessage.objects.bulk_create(site_msgs)

    @classmethod
    def mark_msgs_as_read(cls, user_id, msg_ids=None):
        site_msgs = SiteMessage.objects.filter(user_id=user_id)
        if msg_ids:
            site_msgs = site_msgs.filter(id__in=msg_ids)
        site_msgs.update(has_read=True, read_at=local_now())