from django.db.models.signals import post_save, pre_save
from django.dispatch import receiver
from django.db import transaction

from apps.transaction.models import TransactionParticipant
from apps.course.models import Participant


@receiver(pre_save, sender=TransactionParticipant)
def store_previous_status(sender, instance, **kwargs):
    """
    Store the previous status before saving to compare with new status
    """
    if instance.pk:
        try:
            previous_instance = TransactionParticipant.objects.get(pk=instance.pk)
            instance._previous_status = previous_instance.status
        except TransactionParticipant.DoesNotExist:
            instance._previous_status = None
    else:
        instance._previous_status = None


@receiver(post_save, sender=TransactionParticipant)
def create_participant_on_success(sender, instance, created, **kwargs):
    """
    Create course participant when transaction status changes to SUCCESS
    """
    # اگر تراکنش جدید ایجاد شده و وضعیت آن SUCCESS است
    if created and instance.status == TransactionParticipant.TransactionStatus.SUCCESS:
        create_course_participant(instance)
    
    # اگر تراکنش موجود بوده و وضعیت آن از حالت دیگری به SUCCESS تغییر کرده
    elif not created and hasattr(instance, '_previous_status'):
        if (instance._previous_status != TransactionParticipant.TransactionStatus.SUCCESS and 
            instance.status == TransactionParticipant.TransactionStatus.SUCCESS):
            create_course_participant(instance)


def create_course_participant(transaction_instance):
    """
    Create course participant for successful transaction
    """
    try:
        with transaction.atomic():
            # بررسی اینکه آیا کاربر نقش student دارد یا نه
            if not transaction_instance.user.has_role('student'):
                transaction_instance.user.add_role('student')
            
            # بررسی اینکه آیا قبلاً participant ایجاد شده یا نه
            existing_participant = Participant.objects.filter(
                student=transaction_instance.user, 
                course=transaction_instance.course
            ).first()
            
            if not existing_participant:
                # ایجاد participant جدید
                participant = Participant.objects.create(
                    student=transaction_instance.user,
                    course=transaction_instance.course
                )
                print(f"Course participant created: {participant}")
            else:
                print(f"Course participant already exists: {existing_participant}")
                
    except Exception as e:
        print(f"Error creating course participant: {e}")