from django.db.models.signals import post_save, post_delete
from django.dispatch import receiver
from channels.layers import get_channel_layer
from asgiref.sync import async_to_sync
from django.template.loader import render_to_string
from .models import Expense

@receiver(post_save, sender=Expense)
def expense_saved(sender, instance, created, **kwargs):
    channel_layer = get_channel_layer()
    
    # Renderizamos la fila parcial
    html = render_to_string('expenses/partials/expense_row.html', {'expense': instance})
    
    # Envolvemos el HTML con las directivas OOB (Out-of-Band) de HTMX
    if created:
        # Si es nuevo, lo insertamos al principio del tbody con id "expenses-tbody"
        payload = f'<tbody id="expenses-tbody" hx-swap-oob="afterbegin">{html}</tbody>'
    else:
        # Si ya existe, HTMX reemplazará automáticamente el tr con el mismo ID si usamos hx-swap-oob="true"
        payload = html.replace('<tr ', '<tr hx-swap-oob="true" ')

    async_to_sync(channel_layer.group_send)(
        'expenses_updates',
        {
            'type': 'expense_update',
            'html': payload
        }
    )

@receiver(post_delete, sender=Expense)
def expense_deleted(sender, instance, **kwargs):
    channel_layer = get_channel_layer()
    # Para borrar, mandamos un elemento vacío con swap out-of-band que reemplace la fila eliminada
    payload = f'<tr id="expense-{instance.id}" hx-swap-oob="outerHTML"></tr>'
    
    async_to_sync(channel_layer.group_send)(
        'expenses_updates',
        {
            'type': 'expense_update',
            'html': payload
        }
    )