from django.db.models.signals import post_save, post_delete, pre_save
from django.dispatch import receiver
from django.contrib.contenttypes.models import ContentType
from .models import ActivityLog, AuditLog
import json
from django.core.serializers.json import DjangoJSONEncoder
import inspect

# Try to import models dynamically to avoid circular imports during startup
# We'll use get_model where possible, but for signals we need the actual models
from projects.models import Project, Task

def get_current_request():
    """
    A hacky way to get the current request in signals. 
    In a real production app, you'd use a middleware like django-crum
    or pass the user explicitly.
    For this prototype, we'll try to find the request in the stack.
    """
    for f in inspect.stack():
        if 'request' in f[0].f_locals:
            return f[0].f_locals['request']
    return None

def get_user_and_tenant_from_instance_or_request(instance):
    request = get_current_request()
    user = getattr(request, 'user', None) if request else None
    
    # If user is anonymous, try to get from instance
    if user and user.is_authenticated:
        pass
    elif hasattr(instance, 'created_by') and instance.created_by:
        user = instance.created_by
    elif hasattr(instance, 'user') and instance.user:
        user = instance.user
        
    tenant = getattr(request, 'tenant', None) if request else getattr(instance, 'tenant', None)
    
    return user, tenant

@receiver(post_save, sender=Project)
@receiver(post_save, sender=Task)
def log_activity_on_save(sender, instance, created, **kwargs):
    user, tenant = get_user_and_tenant_from_instance_or_request(instance)
    
    if not tenant:
        return # Cannot log without tenant

    action = "created" if created else "updated"
    target_type = sender.__name__
    
    metadata = {}
    if hasattr(instance, 'name'):
        metadata['name'] = instance.name
    elif hasattr(instance, 'title'):
        metadata['title'] = instance.title

    ActivityLog.objects.create(
        tenant=tenant,
        user=user if (user and user.is_authenticated) else None,
        action=action,
        target_type=target_type,
        target_id=str(instance.id),
        metadata=metadata
    )

@receiver(post_delete, sender=Project)
@receiver(post_delete, sender=Task)
def log_activity_on_delete(sender, instance, **kwargs):
    user, tenant = get_user_and_tenant_from_instance_or_request(instance)
    
    if not tenant:
        return

    action = "deleted"
    target_type = sender.__name__
    
    metadata = {}
    if hasattr(instance, 'name'):
        metadata['name'] = instance.name
    elif hasattr(instance, 'title'):
        metadata['title'] = instance.title

    ActivityLog.objects.create(
        tenant=tenant,
        user=user if (user and user.is_authenticated) else None,
        action=action,
        target_type=target_type,
        target_id=str(instance.id),
        metadata=metadata
    )

# --- Audit Logs ---

# Small hack: Store the original state before saving
@receiver(pre_save, sender=Project)
@receiver(pre_save, sender=Task)
def store_original_state(sender, instance, **kwargs):
    if instance.pk:
        try:
            old_instance = sender.objects.get(pk=instance.pk)
            # Store it on the instance for the post_save signal
            instance._old_state = {f.name: getattr(old_instance, f.name) for f in sender._meta.fields}
        except sender.DoesNotExist:
            pass

@receiver(post_save, sender=Project)
@receiver(post_save, sender=Task)
def log_audit_on_save(sender, instance, created, **kwargs):
    user, tenant = get_user_and_tenant_from_instance_or_request(instance)
    request = get_current_request()
    
    if not tenant:
        return
        
    action = "created" if created else "updated"
    
    changes = {}
    if not created and hasattr(instance, '_old_state'):
        for f in sender._meta.fields:
            old_val = instance._old_state.get(f.name)
            new_val = getattr(instance, f.name)
            if old_val != new_val:
                # Basic stringification for JSON serialization
                changes[f.name] = {
                    'old': str(old_val),
                    'new': str(new_val)
                }
    elif created:
        for f in sender._meta.fields:
            changes[f.name] = {'new': str(getattr(instance, f.name))}

    AuditLog.objects.create(
        tenant=tenant,
        user=user if (user and user.is_authenticated) else None,
        action=action,
        model_name=sender.__name__,
        object_id=str(instance.id),
        changes=changes,
        ip_address=request.META.get('REMOTE_ADDR') if request else None
    )

@receiver(post_delete, sender=Project)
@receiver(post_delete, sender=Task)
def log_audit_on_delete(sender, instance, **kwargs):
    user, tenant = get_user_and_tenant_from_instance_or_request(instance)
    request = get_current_request()
    
    if not tenant:
        return
        
    changes = {f.name: {'old': str(getattr(instance, f.name))} for f in sender._meta.fields}

    AuditLog.objects.create(
        tenant=tenant,
        user=user if (user and user.is_authenticated) else None,
        action="deleted",
        model_name=sender.__name__,
        object_id=str(instance.id),
        changes=changes,
        ip_address=request.META.get('REMOTE_ADDR') if request else None
    )