"""
Signals for monitoring system
"""
import logging
from django.db.models.signals import post_save, post_delete
from django.dispatch import receiver
from django.utils import timezone

from monitoring.models import Alert, SystemStatus
from monitoring.services.alerting import AlertingService

logger = logging.getLogger(__name__)


@receiver(post_save, sender=Alert)
def alert_created_handler(sender, instance, created, **kwargs):
    """Handle alert creation"""
    if created:
        logger.info(f"New alert created: {instance.title} ({instance.severity})")
        
        # Send notifications for new alerts
        try:
            alerting_service = AlertingService()
            alert_data = {
                'rule_id': str(instance.rule.id),
                'title': instance.title,
                'description': instance.description,
                'severity': instance.severity,
                'current_value': float(instance.triggered_value) if instance.triggered_value else None,
                'threshold_value': float(instance.threshold_value) if instance.threshold_value else None
            }
            
            notification_results = alerting_service.notification_service.send_alert_notifications(alert_data)
            logger.info(f"Alert notifications sent: {notification_results}")
            
        except Exception as e:
            logger.error(f"Failed to send alert notifications: {e}")


@receiver(post_save, sender=SystemStatus)
def system_status_changed_handler(sender, instance, created, **kwargs):
    """Handle system status changes"""
    if created or instance.tracker.has_changed('status'):
        logger.info(f"System status changed to: {instance.status}")
        
        # Update system status in cache or external systems
        try:
            # This could trigger notifications to external systems
            # or update status pages
            pass
        except Exception as e:
            logger.error(f"Failed to update system status: {e}")


# Add tracker to SystemStatus model for change detection
from django.db import models

class SystemStatusTracker:
    """Track changes to SystemStatus model"""
    
    def __init__(self, instance):
        self.instance = instance
        self._initial_data = {}
        if instance.pk:
            self._initial_data = {
                'status': instance.status,
                'message': instance.message
            }
    
    def has_changed(self, field):
        """Check if a field has changed"""
        if not self.instance.pk:
            return True
        return getattr(self.instance, field) != self._initial_data.get(field)

# Monkey patch the SystemStatus model to add tracker
def add_tracker_to_system_status():
    """Add tracker to SystemStatus instances"""
    original_init = SystemStatus.__init__
    
    def new_init(self, *args, **kwargs):
        original_init(self, *args, **kwargs)
        self.tracker = SystemStatusTracker(self)
    
    SystemStatus.__init__ = new_init

# Call the function to add tracker
add_tracker_to_system_status()