# Developer Guide: GUI Internals

This document provides technical details about the implementation of the Graphical User Interface (GUI) for developers.

## Framework

The GUI is built using `PySide6`, which provides Python bindings for the Qt framework.

## Main Window (`gui/main_window.py`)

The `MainWindow` class is the central component of the GUI application. It is responsible for:

*   Defining the main application window structure and layout using PySide6 widgets.
*   Arranging the Preset Editor panel (left) and the **Unified Hierarchical View** (right).
*   Setting up the menu bar, including the "View" menu for toggling the Log Console.
*   Connecting user interactions (button clicks, drag-and-drop events, edits in the Unified View) to corresponding methods (slots) within the `MainWindow` or other handler classes.
*   Managing the display of application logs in the UI console using a custom `QtLogHandler`.
*   Interacting with background handlers (`ProcessingHandler`, `PredictionHandler`) via Qt signals and slots to ensure thread-safe updates to the UI during long-running operations.
*   Receiving the initial `SourceRule` hierarchy from the `PredictionHandler` and populating the `UnifiedViewModel`.
*   Sending the final, potentially user-modified, `SourceRule` list to `main.py` to initiate processing via the `ProcessingEngine`.

## Threading and Background Tasks

To keep the UI responsive during intensive operations like asset processing and rule prediction, the GUI utilizes background threads managed by `QThread`.

*   **`ProcessingHandler` (`gui/processing_handler.py`):** This class is designed to run in a separate `QThread`. It manages the execution of the main asset processing pipeline using the **`ProcessingEngine`** for multiple assets concurrently using `concurrent.futures.ProcessPoolExecutor`. It submits individual asset processing tasks to the pool, passing the relevant `SourceRule` object and `Configuration` instance to the `ProcessingEngine`. It monitors task completion and communicates progress, status updates, and results back to the `MainWindow` on the main UI thread using Qt signals. It also handles the execution of optional Blender scripts via subprocess calls after processing.
*   **`PredictionHandler` (`gui/prediction_handler.py`):** This class also runs in a separate `QThread`. It is responsible for generating the initial `SourceRule` hierarchy with predicted values based on the input files and the selected preset. It uses logic (including accessing preset rules and `config.py`'s allowed types) to analyze files and predict initial values for overridable fields in the `SourceRule`, `AssetRule`, and `FileRule` objects (e.g., asset type, item type, target asset name). It constructs the complete `SourceRule` hierarchy based on these predictions and emits a signal (`rule_hierarchy_ready`) with the generated `List[SourceRule]` to the `MainWindow` to populate the Unified Hierarchical View.

## Communication (Signals and Slots)

Communication between the main UI thread (`MainWindow`) and the background threads (`ProcessingHandler`, `PredictionHandler`) relies heavily on Qt's signals and slots mechanism. This is a thread-safe way for objects in different threads to communicate.

*   Background handlers emit signals to indicate events (e.g., progress updated, file status changed, task finished).
*   The `MainWindow` connects slots (methods) to these signals. When a signal is emitted, the connected slot is invoked on the thread that owns the receiving object (the main UI thread for `MainWindow`), ensuring UI updates happen safely.

## Preset Editor

The GUI includes an integrated preset editor panel. This allows users to interactively create, load, modify, and save preset `.json` files directly within the application. The editor typically uses standard UI widgets to display and edit the key fields of the preset structure.

## Unified Hierarchical View (`gui/unified_view_model.py`, `gui/delegates.py`)

The core of the GUI's rule editing interface is the Unified Hierarchical View, implemented using a `QTreeView` with a custom model and delegates.

*   **`Unified View Model` (`gui/unified_view_model.py`):** This class implements a `QAbstractItemModel` to expose the structure of a list of `SourceRule` objects (Source -> Asset -> File) to the `QTreeView`. It holds the `SourceRule` data that is the single source of truth for the GUI's processing rules. It provides data and flags for display in multiple columns and supports inline editing of specific rule attributes (e.g., asset type, item type override, target asset name override) by interacting with delegates.
*   **`Delegates` (`gui/delegates.py`):** This module contains custom `QStyledItemDelegate` implementations used by the `QTreeView` to provide inline editors for specific data types or rule attributes. Examples include delegates for `QComboBox` (for selecting from allowed types sourced from `config.py`) and `QLineEdit` (for free-form text editing). These delegates handle the presentation and editing of data within the tree view cells, interacting with the `UnifiedViewModel` to get and set data.

The `PredictionHandler` generates the initial `SourceRule` hierarchy, which is then set on the `UnifiedViewModel`. The `QTreeView` displays this model, allowing users to navigate the hierarchy and make inline edits to the rule attributes. Edits made in the view directly modify the attributes of the underlying rule objects in the `SourceRule` hierarchy held by the model.

**Data Flow Diagram (GUI Rule Management):**

```mermaid
graph LR
    A[User Input (Drag/Drop, Preset Select)] --> B(MainWindow);
    B -- Calls --> C(PredictionHandler);
    C -- Generates SourceRule Hierarchy with Predictions --> D(UnifiedViewModel);
    B -- Sets Model --> E(QTreeView - Unified View);
    E -- Displays Data from --> D;
    E -- Uses Delegates from --> F(Delegates);
    F -- Interact with --> D;
    User -- Edits Rules via --> E;
    E -- Updates Data in --> D;
    B -- Triggers Processing with Final SourceRule List --> G(main.py / ProcessingHandler);
```

## Application Styling

The application style is explicitly set to 'Fusion' in `gui/main_window.py` to provide a more consistent look and feel across different operating systems. A custom `QPalette` is also applied to the application to adjust default colors within the 'Fusion' style.

## Logging

A custom `QtLogHandler` is used to redirect log messages from the standard Python `logging` module to a text area or console widget within the GUI, allowing users to see detailed application output and errors.

## Cancellation

The GUI provides a "Cancel" button to stop ongoing processing. The `ProcessingHandler` implements logic to handle cancellation requests. This typically involves setting an internal flag and attempting to shut down the `ProcessPoolExecutor`. However, it's important to note that this does not immediately terminate worker processes that are already executing; it primarily prevents new tasks from starting and stops processing results from completed futures once the cancellation flag is checked.

These key components work together to provide the tool's functionality, separating concerns and utilizing concurrency for performance and responsiveness. The Unified Hierarchical View centralizes rule management in the GUI, and the `SourceRule` object serves as a clear data contract passed to the processing engine.