Detection Engine

app.application.managers.detection_engine

Centralizes detection engine lifecycle (create / update / remove) per session.

`DetectionEngineManager`

Manages the lifecycle of DetectionEngine instances on a per-session basis.

Responsibilities

Create a new DetectionEngine when none exists for a session.
Update the loaded model in an existing DetectionEngine.
Remove (clear) the engine reference from a session.

This manager centralises the engine-creation logic that previously lived inside DetectionService._create_or_update_detection_engine_from_model_name_for_session_id, giving DetectionService a narrower single responsibility.

The session repository is injected, so the manager is independently unit-testable without a live Application instance.

PARAMETER	DESCRIPTION
`session_repo`	Interface used to find a session and assign its detection engine. TYPE: `UIApplicationInterface`

`init(session_repo: UIApplicationInterface) -> None`

`create_or_update(s_id: SessionId, model_name: str) -> None`

Create a new engine or update the model in an existing engine for s_id.

PARAMETER	DESCRIPTION
`s_id`	Session ID of the target session. TYPE: `SessionId`
`model_name`	YOLO model name to load (e.g. `"yolov8n"`). TYPE: `str`

Note

If the session has no engine yet, a new DetectionEngine is instantiated and assigned to session.detection_engine. If an engine already exists, its model is updated via DetectionEngine.set_model() to avoid unnecessary re-creation.

DetectionEngine is imported lazily to keep this module free of heavy infrastructure dependencies at import time.

`remove(s_id: SessionId) -> None`

Remove (clear) the detection engine reference for s_id.

PARAMETER	DESCRIPTION
`s_id`	Session ID of the target session. TYPE: `SessionId`

Note

Sets session.detection_engine to None. Any in-flight worker using that engine must be stopped before calling this.

Detection Engine