Refactor: nearly done phase 5

core/communication/messages.py

@@ -3,7 +3,7 @@ Message types, constants, and validation functions for WebSocket communication.
 """
 import json
 import logging
-from typing import Dict, Any, Optional
+from typing import Dict, Any, Optional, Union
 from .models import (
     IncomingMessage, OutgoingMessage,
     SetSubscriptionListMessage, SetSessionIdMessage, SetProgressionStageMessage,
@@ -161,14 +161,14 @@ def create_state_report(cpu_usage: float, memory_usage: float,
     )
 
 
-def create_image_detection(subscription_identifier: str, detection_data: Dict[str, Any],
+def create_image_detection(subscription_identifier: str, detection_data: Union[Dict[str, Any], None],
                           model_id: int, model_name: str) -> ImageDetectionMessage:
     """
     Create an image detection message.
 
     Args:
         subscription_identifier: Camera subscription identifier
-        detection_data: Flat dictionary of detection results
+        detection_data: Detection results - Dict for data, {} for empty, None for abandonment
         model_id: Model identifier
         model_name: Model name
 
@@ -176,6 +176,12 @@ def create_image_detection(subscription_identifier: str, detection_data: Dict[st
         ImageDetectionMessage object
     """
     from .models import DetectionData
+    from typing import Union
+
+    # Handle three cases:
+    # 1. None = car abandonment (detection: null)
+    # 2. {} = empty detection (triggers session creation)
+    # 3. {...} = full detection data (updates session)
 
     data = DetectionData(
         detection=detection_data,

core/communication/models.py

@@ -35,10 +35,23 @@ class CameraConnection(BaseModel):
 
 
 class DetectionData(BaseModel):
-    """Detection result data structure."""
-    model_config = {"json_encoders": {type(None): lambda v: None}}
+    """
+    Detection result data structure.
 
-    detection: Optional[Dict[str, Any]] = Field(None, description="Flat key-value detection results, null for abandonment")
+    Supports three cases:
+    1. Empty detection: detection = {} (triggers session creation)
+    2. Full detection: detection = {"carBrand": "Honda", ...} (updates session)
+    3. Null detection: detection = None (car abandonment)
+    """
+    model_config = {
+        "json_encoders": {type(None): lambda v: None},
+        "arbitrary_types_allowed": True
+    }
+
+    detection: Union[Dict[str, Any], None] = Field(
+        default_factory=dict,
+        description="Detection results: {} for empty, {...} for data, None/null for abandonment"
+    )
     modelId: int
     modelName: str