Planning System (zentral_systems)¶

Central data layer and browser UI for project planning in PlantDesign. Manages ProjectContainers with hierarchical ProjectItems, providing CRUD, search, validation, version control integration, and a full browser widget.

Sub-packages¶

Directory	Purpose
`models/`	Dataclasses: `ProjectContainer`, `ProjectItem`, enums
`controllers/`	`PlanningController` -- CRUD, search, validation for one project
`persistence/`	`ContainerSerializer` (msgpack / msgpack.gz)
`validation/`	`ConsistencyChecker` (5 rules + auto-repair)
`constants/`	`PlanningPaths`, `Stylesheets`, schema versions
`widgets/`	`PlanningBrowserWidget` and all bound subsystems

Key Files (root level)¶

File	Purpose
`exceptions.py`	Domain exceptions (`PlanningSystemError` hierarchy)
`project_item.py`	Backward-compat re-export of `models.project_item`

Architecture¶

Flat dict storage for O(1) item access by instance_id
QAbstractItemModel for tree display (not QTreeWidget)
Session-based undo/redo via version_control_system commands
Bound subsystems pattern for browser UI components
Library integration for drag-drop from library and export back

Data Flow¶

PlanningController (business logic, signals)
    |
    v
PlanningBrowserController (orchestration, session commands)
    |
    +-- CrudHandler (rename, delete, copy, paste)
    +-- DragDropHandler (moves, reorder, library drops)
    +-- ContextMenuHandler (FluentContextMenu building)
    +-- SessionHandler (undo/redo, save, auto-persist)
    +-- LibraryExportController (export subtree to user library)