from django.contrib.auth import get_user_model
from django.utils.timezone import now
from django.utils.translation import gettext_lazy as _
from .models import AuditLog, Notification, Risk, ResidualRisk

def model_diff(old, new, fields=None):
    """
    Compare two model instances and return a dict of changed fields.
    - old: previous model instance (from DB)
    - new: updated model instance (unsaved)
    - fields: optional list of fields to check
    """
    changes = {}
    opts = new._meta

    if fields is None:
        fields = [f.name for f in opts.fields]

    for field_name in fields:
        old_value = getattr(old, field_name, None)
        new_value = getattr(new, field_name, None)

        if old_value != new_value:
            changes[field_name] = {"old": old_value, "new": new_value}

    return changes

def check_risk_followups():
    """
    Check if follow ups need attention and create notifications.
    Ensures no duplicate notifications per risk per day
    """
    today = now().date()
    risks = Risk.objects.filter(follow_up__lte=today).select_related("owner")

    for risk in risks:
        # Risk-Status auf review_required setzen (nicht überschreiben, wenn bereits closed)
        if risk.status != "closed" and risk.status != "review_required":
            Risk.objects.filter(pk=risk.pk).update(status="review_required")

        # ResidualRisk-Objekt sicherstellen und Review-Flag setzen
        resid, created = ResidualRisk.objects.get_or_create(risk=risk)
        if not resid.review_required:
            resid.review_required = True
            resid.save()

        # Notification an Stakeholder
        message = _("Follow-up reached: review required for risk '{t}'").format(t=risk.title)
        notification, created = Notification.objects.get_or_create(
            user=risk.owner,
            message=message,
            defaults={"read": False, "sent": False},
        )
        if created:
            AuditLog.objects.create(
                user=None, action="create", model="Notification", object_id=notification.pk,
                changes={"message": notification.message, "user": risk.owner.username if risk.owner else None},
            )