import logging
from django.db.models.signals import post_save
from django.dispatch import receiver
from apps.chat.models import ChatMessage, RoomMessage
from apps.account.models import User
from apps.account.notification_service import create_and_send_notification
from apps.course.models.course import get_localized_field
from apps.course.models.participant import Participant

logger = logging.getLogger(__name__)

def get_message_preview(instance, lang='fa'):
    if instance.content_type == 'text':
        preview = instance.content or ''
        if len(preview) > 50:
            return preview[:50] + '...'
        return preview
    elif instance.content_type == 'image':
        return 'تصویر' if lang == 'fa' else 'Image'
    elif instance.content_type == 'audio':
        return 'صدا' if lang == 'fa' else 'Audio'
    else:
        return 'فایل ضمیمه' if lang == 'fa' else 'Attachment'

@receiver(post_save, sender=ChatMessage)
def notify_on_new_chat_message(sender, instance, created, **kwargs):
    if not created:
        return
        
    sender_user = instance.sender
    room = instance.room
    
    # 1. Check if the message is in a PRIVATE room
    if room.room_type == RoomMessage.RoomTypeChoices.PRIVATE:
        # Determine the recipient user (the other person in the private room)
        recipient_user = None
        if room.initiator == sender_user:
            recipient_user = room.recipient
        else:
            recipient_user = room.initiator
            
        if not recipient_user:
            return
            
        # Case A: Teacher Replied in a Private Chat
        if sender_user.user_type == User.UserType.PROFESSOR:
            if recipient_user.user_type in [User.UserType.STUDENT, User.UserType.CLIENT]:
                preview_en = get_message_preview(instance, 'en')
                preview_fa = get_message_preview(instance, 'fa')
                
                create_and_send_notification(
                    user=recipient_user,
                    title_en="New Message from Teacher",
                    body_en=f"Teacher {sender_user.fullname or sender_user.username} replied: {preview_en}",
                    title_fa="پیام جدید از طرف استاد",
                    body_fa=f"استاد {sender_user.fullname or sender_user.username} پاسخ داد: {preview_fa}",
                    service='imam-javad',
                    data={'type': 'teacher_reply_private', 'message_id': instance.id, 'room_id': room.id}
                )
                
        # Case B: Support Replied
        elif sender_user.user_type in [User.UserType.ADMIN, User.UserType.SUPER_ADMIN, User.UserType.CONSULTANT]:
            if recipient_user.user_type in [User.UserType.STUDENT, User.UserType.CLIENT]:
                preview_en = get_message_preview(instance, 'en')
                preview_fa = get_message_preview(instance, 'fa')
                
                create_and_send_notification(
                    user=recipient_user,
                    title_en="New Message from Support",
                    body_en=f"Support agent {sender_user.fullname or sender_user.username} replied to your message: {preview_en}",
                    title_fa="پاسخ پشتیبانی",
                    body_fa=f"پشتیبان {sender_user.fullname or sender_user.username} به پیام شما پاسخ داد: {preview_fa}",
                    service='imam-javad',
                    data={'type': 'support_reply', 'message_id': instance.id, 'room_id': room.id}
                )

    # 2. Check if the message is in a GROUP/COURSE room
    elif room.room_type == RoomMessage.RoomTypeChoices.GROUP and room.course:
        # Case A: Teacher Replied in a Course Chat
        if sender_user.user_type == User.UserType.PROFESSOR:
            course = room.course
            course_title_en = get_localized_field('en', course.title)
            course_title_fa = get_localized_field('fa', course.title)
            
            preview_en = get_message_preview(instance, 'en')
            preview_fa = get_message_preview(instance, 'fa')
            
            # Notify all active enrolled students of the course
            participants = Participant.objects.filter(course=course, is_active=True).select_related('student')
            for p in participants:
                if p.student != sender_user: # Exclude sender
                    create_and_send_notification(
                        user=p.student,
                        title_en="Teacher Post in Course Chat",
                        body_en=f"Teacher {sender_user.fullname or sender_user.username} posted in '{course_title_en}': {preview_en}",
                        title_fa="پیام استاد در گفتگوی دوره",
                        body_fa=f"استاد {sender_user.fullname or sender_user.username} در گفتگوی دوره «{course_title_fa}» پیام جدیدی فرستاد: {preview_fa}",
                        service='imam-javad',
                        data={'type': 'teacher_reply_course', 'message_id': instance.id, 'room_id': room.id}
                    )