import uuid

from django.conf import settings
from django.db.models.signals import post_delete, post_save
from django.dispatch import receiver

from .models import ModelChangeLog, SecurityEvent
from .signals import security_event_occurred


def _get_excluded_models():
    config = getattr(settings, "INFRASYNTH_AUDIT", {})
    return set(config.get("EXCLUDED_MODELS", []))


def _get_excluded_fields():
    config = getattr(settings, "INFRASYNTH_AUDIT", {})
    return set(config.get("EXCLUDED_FIELDS", []))


def _get_request_id(request=None):
    if request:
        return getattr(request, "request_id", "") or str(uuid.uuid4())[:8]
    return str(uuid.uuid4())[:8]


@receiver(post_save)
def track_model_change(sender, instance, created, raw, **kwargs):
    if raw:
        return
    label = sender._meta.label
    if label in _get_excluded_models():
        return
    config = getattr(settings, "INFRASYNTH_AUDIT", {})
    if not config.get("ENABLE_MODEL_CHANGE_TRACKING", True):
        return

    if created:
        ModelChangeLog.objects.create(
            model_label=label,
            object_id=str(instance.pk),
            action="create",
            changes=_get_created_changes(instance),
            actor=_get_actor_from_instance(instance),
            request_id=_get_request_id(),
        )
    else:
        if hasattr(instance, "_previous_state"):
            changes = _compute_changes(instance._previous_state, instance)
            if changes:
                ModelChangeLog.objects.create(
                    model_label=label,
                    object_id=str(instance.pk),
                    action="update",
                    changes=changes,
                    actor=_get_actor_from_instance(instance),
                    request_id=_get_request_id(),
                )


@receiver(post_delete)
def track_model_delete(sender, instance, **kwargs):
    label = sender._meta.label
    if label in _get_excluded_models():
        return
    config = getattr(settings, "INFRASYNTH_AUDIT", {})
    if not config.get("ENABLE_MODEL_CHANGE_TRACKING", True):
        return

    ModelChangeLog.objects.create(
        model_label=label,
        object_id=str(instance.pk),
        action="delete",
        changes={},
        actor=_get_actor_from_instance(instance),
        request_id=_get_request_id(),
    )


def _get_actor_from_instance(instance):
    for field in ["actor", "user", "usuario_creacion", "created_by", "uploaded_by"]:
        val = getattr(instance, field, None)
        if val is not None:
            return val
    return None


def _get_created_changes(instance):
    excluded = _get_excluded_fields()
    changes = {}
    for field in instance._meta.get_fields():
        if field.name in excluded:
            continue
        if hasattr(field, "serialize") and field.serialize:
            val = getattr(instance, field.name, None)
            if val is not None:
                changes[field.name] = [None, str(val)]
    return changes


def _compute_changes(old, new):
    excluded = _get_excluded_fields()
    changes = {}
    for field in new._meta.get_fields():
        if field.name in excluded:
            continue
        if not hasattr(field, "column") or field.column is None:
            continue
        old_val = getattr(old, field.name, None)
        new_val = getattr(new, field.name, None)
        if old_val != new_val:
            changes[field.name] = [
                str(old_val) if old_val is not None else None,
                str(new_val) if new_val is not None else None,
            ]
    return changes


@receiver(security_event_occurred)
def log_security_event(sender, **kwargs):
    config = getattr(settings, "INFRASYNTH_AUDIT", {})
    if not config.get("ENABLE_SECURITY_EVENTS", True):
        return
    SecurityEvent.objects.create(
        event_type=kwargs.get("event_type", "unknown"),
        actor=kwargs.get("actor"),
        ip_address=kwargs.get("ip_address"),
        metadata=kwargs.get("metadata", {}),
        request_id=_get_request_id(),
    )