"""
Django-native notification service.

This service provides a fully Django-native notification system. Supports:
- In-app notifications
- Email notifications (via Django email backend)
- Real-time notifications (ready for Django Channels integration)
"""

import logging
from typing import Any

from django.conf import settings
from django.contrib.auth import get_user_model
from django.contrib.contenttypes.models import ContentType
from django.core.mail import send_mail
from django.db.models import QuerySet
from django.template.loader import render_to_string
from django.utils import timezone
from django.utils.html import strip_tags

from .models import Notification, NotificationLog, NotificationPreference, SystemAnnouncement

logger = logging.getLogger(__name__)
User = get_user_model()


class NotificationService:
    """
    Django-native notification service using django-notifications-hq.
    
    This replaces the Novu-based service with a fully Django-native approach.
    """

    # Notification workflow types
    WORKFLOW_SUBMISSION_STATUS = "submission_status"
    WORKFLOW_MODERATION_ALERT = "moderation_alert"
    WORKFLOW_SYSTEM_ANNOUNCEMENT = "system_announcement"
    WORKFLOW_ADMIN_ALERT = "admin_alert"
    WORKFLOW_WELCOME = "welcome"
    WORKFLOW_COMMENT_REPLY = "comment_reply"
    WORKFLOW_MENTION = "mention"
    WORKFLOW_FOLLOW = "follow"

    def __init__(self):
        self.from_email = getattr(
            settings, "DEFAULT_FROM_EMAIL", "noreply@thrillwiki.com"
        )
        self.site_name = getattr(settings, "SITE_NAME", "ThrillWiki")
        self.site_url = getattr(settings, "SITE_URL", "https://thrillwiki.com")

    def send_notification(
        self,
        recipient: User,
        actor: User | None,
        verb: str,
        action_object: Any = None,
        target: Any = None,
        description: str = "",
        level: str = "info",
        data: dict | None = None,
        send_email: bool = True,
        email_template: str | None = None,
    ) -> bool:
        """
        Send a notification to a user.
        
        Args:
            recipient: The user to notify
            actor: The user who performed the action (can be None for system notifications)
            verb: Description of the action (e.g., "approved your submission")
            action_object: The object that was acted upon
            target: The target of the action
            description: Additional description text
            level: Notification level (info, success, warning, error)
            data: Additional data to store with the notification
            send_email: Whether to also send an email notification
            email_template: Template path for email (optional)
            
        Returns:
            True if notification was sent successfully
        """
        try:
            # Check user preferences
            if self._is_user_opted_out(recipient):
                logger.debug(f"User {recipient.id} opted out of notifications")
                return False

            # Create in-app notification using our native model
            notification_data = {
                "recipient": recipient,
                "actor": actor,
                "verb": verb,
                "description": description,
                "level": level,
                "data": data or {},
            }

            # Add generic foreign key for action_object if provided
            if action_object:
                notification_data["action_object_content_type"] = ContentType.objects.get_for_model(action_object)
                notification_data["action_object_id"] = action_object.pk

            # Add generic foreign key for target if provided
            if target:
                notification_data["target_content_type"] = ContentType.objects.get_for_model(target)
                notification_data["target_id"] = target.pk

            Notification.objects.create(**notification_data)

            # Log the notification
            self._log_notification(
                user=recipient,
                workflow_id=data.get("workflow_id", "general") if data else "general",
                notification_type=level,
                channel="in_app",
                status=NotificationLog.Status.SENT,
                payload=data or {},
            )

            # Optionally send email
            if send_email and self._should_send_email(recipient, data):
                self._send_email_notification(
                    recipient=recipient,
                    verb=verb,
                    actor=actor,
                    action_object=action_object,
                    target=target,
                    description=description,
                    template=email_template,
                    data=data,
                )

            return True

        except Exception as e:
            logger.exception(f"Failed to send notification to {recipient.id}: {e}")
            self._log_notification(
                user=recipient,
                workflow_id=data.get("workflow_id", "general") if data else "general",
                notification_type=level,
                channel="in_app",
                status=NotificationLog.Status.FAILED,
                payload=data or {},
                error_message=str(e),
            )
            return False

    def send_to_group(
        self,
        recipients: QuerySet | list,
        actor: User | None,
        verb: str,
        action_object: Any = None,
        target: Any = None,
        description: str = "",
        level: str = "info",
        data: dict | None = None,
        send_email: bool = False,
    ) -> dict:
        """
        Send a notification to multiple users.
        
        Returns:
            Dict with success/failure counts
        """
        results = {"success": 0, "failed": 0, "skipped": 0}
        
        for recipient in recipients:
            if self._is_user_opted_out(recipient):
                results["skipped"] += 1
                continue
                
            success = self.send_notification(
                recipient=recipient,
                actor=actor,
                verb=verb,
                action_object=action_object,
                target=target,
                description=description,
                level=level,
                data=data,
                send_email=send_email,
            )
            
            if success:
                results["success"] += 1
            else:
                results["failed"] += 1
                
        return results

    def notify_moderators(
        self,
        verb: str,
        action_object: Any = None,
        description: str = "",
        data: dict | None = None,
    ) -> dict:
        """
        Send a notification to all moderators.
        """
        from django.contrib.auth import get_user_model
        User = get_user_model()
        
        # Get users with moderator permissions
        moderators = User.objects.filter(
            is_active=True,
            is_staff=True,  # Or use a specific permission check
        ).exclude(
            novu_notification_prefs__is_opted_out=True
        )
        
        return self.send_to_group(
            recipients=moderators,
            actor=None,
            verb=verb,
            action_object=action_object,
            description=description,
            level="info",
            data={**(data or {}), "workflow_id": self.WORKFLOW_MODERATION_ALERT},
            send_email=True,
        )

    def notify_admins(
        self,
        verb: str,
        description: str = "",
        level: str = "warning",
        data: dict | None = None,
    ) -> dict:
        """
        Send a notification to all admins.
        """
        admins = User.objects.filter(is_superuser=True, is_active=True)
        
        return self.send_to_group(
            recipients=admins,
            actor=None,
            verb=verb,
            description=description,
            level=level,
            data={**(data or {}), "workflow_id": self.WORKFLOW_ADMIN_ALERT},
            send_email=True,
        )

    def send_system_announcement(
        self,
        title: str,
        message: str,
        severity: str = "info",
        action_url: str = "",
        target_users: QuerySet | None = None,
        created_by: User | None = None,
    ) -> SystemAnnouncement:
        """
        Create and broadcast a system announcement.
        """
        # Create the announcement
        announcement = SystemAnnouncement.objects.create(
            title=title,
            message=message,
            severity=severity,
            action_url=action_url,
            created_by=created_by,
            is_active=True,
        )
        
        # Notify users
        recipients = target_users or User.objects.filter(is_active=True)
        
        self.send_to_group(
            recipients=recipients,
            actor=created_by,
            verb=f"System announcement: {title}",
            action_object=announcement,
            description=message,
            level=severity,
            data={
                "workflow_id": self.WORKFLOW_SYSTEM_ANNOUNCEMENT,
                "announcement_id": str(announcement.id),
                "action_url": action_url,
            },
            send_email=severity in ["warning", "critical"],
        )
        
        return announcement

    def get_user_notifications(
        self,
        user: User,
        unread_only: bool = False,
        limit: int = 50,
    ):
        """
        Get notifications for a user.
        """
        qs = Notification.objects.filter(recipient=user)
        
        if unread_only:
            qs = qs.unread()
            
        return qs[:limit]

    def mark_as_read(self, user: User, notification_id: int | None = None):
        """
        Mark notification(s) as read.
        """
        if notification_id:
            try:
                notification = Notification.objects.get(recipient=user, id=notification_id)
                notification.mark_as_read()
            except Notification.DoesNotExist:
                pass
        else:
            # Mark all as read
            Notification.objects.filter(recipient=user).mark_all_as_read()

    def get_unread_count(self, user: User) -> int:
        """
        Get count of unread notifications.
        """
        return Notification.objects.filter(recipient=user, unread=True).count()

    def _is_user_opted_out(self, user: User) -> bool:
        """Check if user has opted out of notifications."""
        try:
            prefs = NotificationPreference.objects.get(user=user)
            return prefs.is_opted_out
        except NotificationPreference.DoesNotExist:
            return False

    def _should_send_email(self, user: User, data: dict | None) -> bool:
        """Check if email should be sent based on user preferences."""
        try:
            prefs = NotificationPreference.objects.get(user=user)
            
            # Check channel preferences
            channel_prefs = prefs.channel_preferences or {}
            email_enabled = channel_prefs.get("email", True)
            
            if not email_enabled:
                return False
                
            # Check workflow-specific preferences
            if data and "workflow_id" in data:
                workflow_prefs = prefs.workflow_preferences or {}
                workflow_email = workflow_prefs.get(data["workflow_id"], {}).get("email", True)
                return workflow_email
                
            return True
            
        except NotificationPreference.DoesNotExist:
            # Default to sending email if no preferences set
            return True

    def _send_email_notification(
        self,
        recipient: User,
        verb: str,
        actor: User | None,
        action_object: Any,
        target: Any,
        description: str,
        template: str | None,
        data: dict | None,
    ):
        """Send an email notification."""
        try:
            # Build context
            context = {
                "recipient": recipient,
                "actor": actor,
                "verb": verb,
                "action_object": action_object,
                "target": target,
                "description": description,
                "site_name": self.site_name,
                "site_url": self.site_url,
                "data": data or {},
            }
            
            # Render email
            if template:
                html_content = render_to_string(template, context)
                text_content = strip_tags(html_content)
            else:
                # Default simple email
                actor_name = actor.username if actor else self.site_name
                subject = f"{actor_name} {verb}"
                text_content = description or f"{actor_name} {verb}"
                html_content = f"<p>{text_content}</p>"
                
                if data and data.get("action_url"):
                    html_content += f'<p><a href="{data["action_url"]}">View details</a></p>'
            
            subject = f"[{self.site_name}] {verb[:50]}"
            
            send_mail(
                subject=subject,
                message=text_content,
                from_email=self.from_email,
                recipient_list=[recipient.email],
                html_message=html_content,
                fail_silently=True,
            )
            
            # Log email notification
            self._log_notification(
                user=recipient,
                workflow_id=data.get("workflow_id", "general") if data else "general",
                notification_type="email",
                channel="email",
                status=NotificationLog.Status.SENT,
                payload=data or {},
            )
            
        except Exception as e:
            logger.exception(f"Failed to send email to {recipient.email}: {e}")
            self._log_notification(
                user=recipient,
                workflow_id=data.get("workflow_id", "general") if data else "general",
                notification_type="email",
                channel="email",
                status=NotificationLog.Status.FAILED,
                payload=data or {},
                error_message=str(e),
            )

    def _log_notification(
        self,
        user: User,
        workflow_id: str,
        notification_type: str,
        channel: str,
        status: str,
        payload: dict,
        error_message: str = "",
    ):
        """Log a notification to the audit trail."""
        NotificationLog.objects.create(
            user=user,
            workflow_id=workflow_id,
            notification_type=notification_type,
            channel=channel,
            status=status,
            payload=payload,
            error_message=error_message,
        )


# Singleton instance
notification_service = NotificationService()


# ============================================================================
# Backward compatibility - keep old NovuService interface but delegate to native
# ============================================================================

class NovuServiceSync:
    """
    Backward-compatible wrapper that delegates to the new notification service.
    
    This maintains the old API signature for existing code while using
    the new Django-native implementation.
    """

    def __init__(self):
        self._service = notification_service

    @property
    def is_configured(self) -> bool:
        """Always configured since we're using Django-native system."""
        return True

    def create_subscriber(self, subscriber_id: str, **kwargs) -> dict[str, Any]:
        """Create subscriber - now a no-op as django-notifications-hq uses User directly."""
        logger.info(f"Subscriber creation not needed for django-notifications-hq: {subscriber_id}")
        return {"subscriberId": subscriber_id, "status": "native"}

    def update_subscriber(self, subscriber_id: str, **kwargs) -> dict[str, Any]:
        """Update subscriber - now a no-op."""
        logger.info(f"Subscriber update not needed for django-notifications-hq: {subscriber_id}")
        return {"subscriberId": subscriber_id, "status": "native"}

    def trigger_notification(
        self,
        workflow_id: str,
        subscriber_id: str,
        payload: dict | None = None,
        overrides: dict | None = None,
    ) -> dict[str, Any]:
        """Trigger a notification using the new native service."""
        try:
            user = User.objects.get(pk=subscriber_id)
            
            verb = payload.get("message", f"Notification: {workflow_id}") if payload else f"Notification: {workflow_id}"
            description = payload.get("description", "") if payload else ""
            
            success = self._service.send_notification(
                recipient=user,
                actor=None,
                verb=verb,
                description=description,
                data={**(payload or {}), "workflow_id": workflow_id},
            )
            
            return {
                "status": "sent" if success else "failed",
                "workflow_id": workflow_id,
            }
        except User.DoesNotExist:
            logger.error(f"User not found for notification: {subscriber_id}")
            return {"status": "failed", "error": "User not found"}

    def trigger_topic_notification(
        self,
        workflow_id: str,
        topic_key: str,
        payload: dict | None = None,
    ) -> dict[str, Any]:
        """Trigger topic notification - maps to group notification."""
        logger.info(f"Topic notification: {workflow_id} -> {topic_key}")
        
        # Map topic keys to user groups
        if topic_key == "moderators":
            result = self._service.notify_moderators(
                verb=payload.get("message", "New moderation task") if payload else "New moderation task",
                data={**(payload or {}), "workflow_id": workflow_id},
            )
        elif topic_key == "admins":
            result = self._service.notify_admins(
                verb=payload.get("message", "Admin notification") if payload else "Admin notification",
                data={**(payload or {}), "workflow_id": workflow_id},
            )
        else:
            logger.warning(f"Unknown topic key: {topic_key}")
            result = {"success": 0, "failed": 0, "skipped": 0}
            
        return {
            "status": "sent",
            "workflow_id": workflow_id,
            "result": result,
        }

    def update_preferences(
        self,
        subscriber_id: str,
        preferences: dict[str, Any],
    ) -> dict[str, Any]:
        """Update notification preferences."""
        try:
            user = User.objects.get(pk=subscriber_id)
            prefs, _ = NotificationPreference.objects.get_or_create(user=user)
            
            if "channel_preferences" in preferences:
                prefs.channel_preferences = preferences["channel_preferences"]
            if "workflow_preferences" in preferences:
                prefs.workflow_preferences = preferences["workflow_preferences"]
            if "is_opted_out" in preferences:
                prefs.is_opted_out = preferences["is_opted_out"]
                
            prefs.save()
            
            return {"status": "updated"}
        except User.DoesNotExist:
            return {"status": "failed", "error": "User not found"}


# Keep old name for backward compatibility
novu_service = NovuServiceSync()