add backend support for listing moderation

backend/config/__init__.py

@@ -0,0 +1,4 @@
+from .celery import app as celery_app
+
+
+__all__ = ("celery_app",)

backend/config/celery.py

@@ -0,0 +1,10 @@
+import os
+
+from celery import Celery
+
+
+os.environ.setdefault("DJANGO_SETTINGS_MODULE", "config.settings.development")
+
+app = Celery("penn_marketplace")
+app.config_from_object("django.conf:settings", namespace="CELERY")
+app.autodiscover_tasks()

backend/config/settings/base.py

@@ -124,3 +124,35 @@
 TWILIO_AUTH_TOKEN = os.environ.get("TWILIO_AUTH_TOKEN", "")
 TWILIO_PHONE_NUMBER = os.environ.get("TWILIO_PHONE_NUMBER", "")
 PHONE_VERIFICATION_CODE_EXPIRY_MINUTES = 10
+
+OPENAI_API_KEY = os.environ.get("OPENAI_API_KEY", "")
+
+# Celery
+CELERY_BROKER_URL = os.environ.get("REDIS_URL", "redis://redis:6379/0")
+CELERY_RESULT_BACKEND = os.environ.get("REDIS_URL", "redis://redis:6379/0")
+CELERY_ACCEPT_CONTENT = ["json"]
+CELERY_TASK_SERIALIZER = "json"
+CELERY_RESULT_SERIALIZER = "json"
+CELERY_BROKER_CONNECTION_RETRY_ON_STARTUP = True
+
+# Logging
+LOGGING = {
+    "version": 1,
+    "disable_existing_loggers": False,
+    "formatters": {
+        "verbose": {
+            "format": "[{asctime}] {levelname} {name}: {message}",
+            "style": "{",
+        },
+    },
+    "handlers": {
+        "console": {
+            "class": "logging.StreamHandler",
+            "formatter": "verbose",
+        },
+    },
+    "root": {
+        "handlers": ["console"],
+        "level": "INFO",
+    },
+}

backend/market/migrations/0006_listing_status_listing_market_list_status_0933cf_idx.py

@@ -0,0 +1,31 @@
+# Generated by Django 5.0.2 on 2026-03-29 18:52
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("market", "0005_sublet_true_latitude_sublet_true_longitude"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="listing",
+            name="status",
+            field=models.CharField(
+                choices=[
+                    ("PENDING", "Pending"),
+                    ("APPROVED", "Approved"),
+                    ("REJECTED", "Rejected"),
+                ],
+                db_index=True,
+                default="PENDING",
+                max_length=10,
+            ),
+        ),
+        migrations.AddIndex(
+            model_name="listing",
+            index=models.Index(fields=["status"], name="market_list_status_0933cf_idx"),
+        ),
+    ]

backend/market/migrations/0007_set_existing_listings_approved.py

@@ -0,0 +1,19 @@
+# Generated by Django 5.0.2 on 2026-03-29 18:57
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("market", "0006_listing_status_listing_market_list_status_0933cf_idx"),
+    ]
+
+    operations = [
+        migrations.RunPython(
+            lambda apps, schema_editor: apps.get_model("market", "Listing")
+            .objects.all()
+            .update(status="APPROVED"),
+            migrations.RunPython.noop,
+        ),
+    ]

backend/market/models.py

@@ -47,6 +47,7 @@ class Meta:
     def __str__(self):
         return f"Offer for {self.listing} made by {self.user}"
 
+
 class Category(models.Model):
     name = models.CharField(max_length=100, unique=True)
 
@@ -72,8 +73,14 @@ class Meta:
             models.Index(fields=["created_at"]),
             models.Index(fields=["expires_at"]),
             models.Index(fields=["negotiable"]),
+            models.Index(fields=["status"]),
         ]
 
+    class Status(models.TextChoices):
+        PENDING = "PENDING", "Pending"
+        APPROVED = "APPROVED", "Approved"
+        REJECTED = "REJECTED", "Rejected"
+
     seller = models.ForeignKey(
         User, on_delete=models.CASCADE, related_name="listings_created"
     )
@@ -94,6 +101,9 @@ class Meta:
     negotiable = models.BooleanField(default=True)
     created_at = models.DateTimeField(auto_now_add=True)
     expires_at = models.DateTimeField(null=True, blank=True)
+    status = models.CharField(
+        max_length=10, choices=Status.choices, default=Status.PENDING, db_index=True
+    )
 
     def __str__(self):
         return f"{self.title} by {self.seller}"
@@ -170,7 +180,8 @@ def _calculate_approximate_location(self, latitude, longitude):
     def approximate_location(self):
         if self.latitude is not None and self.longitude is not None:
             approximate_location = self._calculate_approximate_location(
-                self.latitude, self.longitude)
+                self.latitude, self.longitude
+            )
             return approximate_location
         return None, None
 

backend/market/serializers.py

@@ -1,4 +1,3 @@
-
 from django.contrib.auth import get_user_model
 from django.core.exceptions import ValidationError as ModelValidationError
 from profanity_check import predict
@@ -126,6 +125,7 @@ def get_longitude(self, obj):
             return float(approx_lon)
         return None
 
+
 # Unified serializer for all listing types (Items and Sublets); used for CRUD operations
 class ListingSerializer(ListingTypeMixin, ModelSerializer):
     LISTING_TYPE_CONFIG = {
@@ -176,6 +176,7 @@ class Meta:
             "negotiable",
             "created_at",
             "expires_at",
+            "status",
             "images",
             "listing_type",
             "additional_data",
@@ -188,6 +189,7 @@ class Meta:
             "buyers",
             "images",
             "favorites",
+            "status",
         ]
 
     def validate(self, attrs):
@@ -254,12 +256,19 @@ def create(self, validated_data):
             raise ValidationError({"listing_type": f"Must be one of: {valid_types}"})
 
         try:
-            return create_method(validated_data, additional_data)
+            instance = create_method(validated_data, additional_data)
         except ModelValidationError as e:
             raise ValidationError(
                 e.message_dict if hasattr(e, "message_dict") else e.messages
             ) from e
 
+        from django.db import transaction
+
+        from market.tasks import moderate_listing_task
+
+        transaction.on_commit(lambda: moderate_listing_task.delay(instance.id))
+        return instance
+
     def _create_item(self, validated_data, additional_data):
         category_name = additional_data.get("category")
         category = Category.objects.filter(name=category_name).first()
@@ -291,7 +300,6 @@ def _create_sublet(self, validated_data, additional_data):
         latitude = additional_data.get("latitude")
         longitude = additional_data.get("longitude")
 
-
         if latitude is not None:
             latitude = float(latitude)
         if longitude is not None:
@@ -314,6 +322,8 @@ def _create_sublet(self, validated_data, additional_data):
         return sublet
 
     def update(self, instance, validated_data):
+        old_title = instance.title
+        old_description = instance.description
         listing_type = self.initial_data.get("listing_type")
         additional_data = self.initial_data.get("additional_data", {})
 
@@ -336,6 +346,20 @@ def update(self, instance, validated_data):
                     self._update_sublet(instance, additional_data)
 
             instance.save()
+
+            # TODO: needs to also validate images when implemented
+            content_changed = (
+                instance.title != old_title or instance.description != old_description
+            )
+            if content_changed:
+                from django.db import transaction
+
+                from market.tasks import moderate_listing_task
+
+                instance.status = Listing.Status.PENDING
+                instance.save(update_fields=["status"])
+                transaction.on_commit(lambda: moderate_listing_task.delay(instance.id))
+
             return instance
 
         except ModelValidationError as e:
@@ -395,6 +419,7 @@ class Meta:
             "price",
             "negotiable",
             "expires_at",
+            "status",
             "images",
             "favorite_count",
             "listing_type",
@@ -434,6 +459,7 @@ class Meta:
             "title",
             "price",
             "expires_at",
+            "status",
             "images",
             "favorite_count",
             "listing_type",

backend/market/tasks.py

@@ -0,0 +1,53 @@
+import logging
+
+from celery import shared_task
+
+
+logger = logging.getLogger(__name__)
+
+
+@shared_task(
+    bind=True,
+    max_retries=3,
+    default_retry_delay=10,
+    autoretry_for=(Exception,),
+    retry_backoff=True,
+)
+def moderate_listing_task(self, listing_id):
+    from market.models import Listing
+    from utils.moderation import moderate_content
+
+    try:
+        listing = Listing.objects.get(id=listing_id)
+    except Listing.DoesNotExist:
+        logger.warning("Listing %s not found for moderation, skipping.", listing_id)
+        return
+
+    if listing.status != Listing.Status.PENDING:
+        logger.info(
+            "Listing %s status is %s (not PENDING), skipping.",
+            listing_id,
+            listing.status,
+        )
+        return
+
+    text = f"{listing.title} {listing.description or ''}"
+
+    image_urls = []
+    for img in listing.images.all():
+        if img.image and img.image.url.startswith("http"):
+            image_urls.append(img.image.url)
+
+    logger.info(
+        "Moderating listing %s: text=%r, image_count=%d",
+        listing_id,
+        text[:100],
+        len(image_urls),
+    )
+
+    is_safe = moderate_content(text, image_urls)
+
+    status = Listing.Status.APPROVED if is_safe else Listing.Status.REJECTED
+    logger.info("Listing %s moderation result: %s", listing_id, status)
+    listing.status = status
+    listing.save(update_fields=["status"])

backend/market/views.py

@@ -169,10 +169,11 @@ def list(self, request, *args, **kwargs):
         if request.query_params.get("seller", "false").lower() == "true":
             queryset = queryset.filter(seller=request.user)
         else:
-            # Show listings that are not expired, or have no expiration
+            # Show only approved listings that are not expired
             now = timezone.now()
             queryset = queryset.filter(
-                Q(expires_at__gte=now) | Q(expires_at__isnull=True)
+                Q(expires_at__gte=now) | Q(expires_at__isnull=True),
+                status=Listing.Status.APPROVED,
             )
 
         page = self.paginate_queryset(queryset)
@@ -188,6 +189,8 @@ def retrieve(self, request, *args, **kwargs):
         if instance.seller == request.user:
             serializer_class = ListingSerializer
         else:
+            if instance.status != Listing.Status.APPROVED:
+                raise exceptions.NotFound()
             serializer_class = ListingSerializerPublic
         serializer = serializer_class(instance, context={"request": request})
         return Response(serializer.data)

backend/pyproject.toml

@@ -36,6 +36,7 @@ dependencies = [
     "inflection",
     "firebase-admin",
     "twilio",
+    "requests",
 ]
 
 [dependency-groups]

backend/utils/moderation.py

@@ -0,0 +1,45 @@
+import logging
+
+import requests
+from django.conf import settings
+
+
+logger = logging.getLogger(__name__)
+
+OPENAI_MODERATION_API_URL = "https://api.openai.com/v1/moderations"
+
+
+def moderate_content(text, image_urls=None):
+    """
+    Call OpenAI's Moderation API with text and optional image URLs.
+    Returns True if ALL content is safe, False if any is flagged.
+    """
+    api_key = settings.OPENAI_API_KEY
+    if not api_key:
+        logger.warning("OPENAI_API_KEY not set, skipping moderation")
+        return True
+
+    inputs = [{"type": "text", "text": text}]
+    for url in image_urls or []:
+        inputs.append({"type": "image_url", "image_url": {"url": url}})
+
+    try:
+        response = requests.post(
+            OPENAI_MODERATION_API_URL,
+            headers={"Authorization": f"Bearer {api_key}"},
+            json={"model": "omni-moderation-latest", "input": inputs},
+            timeout=30,
+        )
+        response.raise_for_status()
+        result = response.json()
+        flagged = any(r["flagged"] for r in result["results"])
+        logger.info("Moderation API response: flagged=%s", flagged)
+        for r in result["results"]:
+            scores = r.get("category_scores", {})
+            high_scores = {k: v for k, v in scores.items() if v > 0.01}
+            if high_scores:
+                logger.info("  high scores: %s", high_scores)
+        return not flagged
+    except Exception:
+        logger.exception("Moderation API call failed, defaulting to approved")
+        return True