# AGENTS.md

This file is the working guide for AI coding agents contributing to BEdit.
Its instructions apply to the entire repository.

## Project purpose

BEdit is a Python/PySide6 graphical editor for hierarchical block and bond-graph
models. A document contains reusable components, typed and oriented ports,
connections, nested graphs, and editable vector icons.

The application is evolving quickly. Prefer small, coherent changes that improve
the architecture without introducing compatibility layers unless compatibility is
explicitly requested.

## Architecture

The main boundary is strict:

```text
src/bedit/
├── __main__.py
├── core/                   # Pure Python; must not import PySide6
│   ├── model.py            # Document, component, graph, port, icon data
│   ├── port_types.py       # Port type definitions and compatibility
│   ├── serializer.py       # JSON persistence
│   ├── libraries.py        # Library file discovery and parsing
│   └── simulation/         # Qt-free composition and OpenModelica interface code
└── gui/                    # All Qt-dependent code
    ├── app.py              # QApplication startup and palette
    ├── main_window.py      # Top-level UI orchestration
    ├── preferences.py      # Explicit disk-backed QSettings factory
    ├── controllers/        # Document controller and undo commands
    ├── dialogs/            # Dialog behavior
    ├── graphics/           # Workspace, icon editor, vector rendering
    ├── models/             # Qt tree models and repository adapters
    └── generated/          # Generated UI/resource Python; never hand-edit
```

Dependency direction:

- `bedit.core` may depend only on the Python standard library.
- `bedit.gui` may depend on `bedit.core` and PySide6.
- `bedit.core` must never import `bedit.gui` or PySide6.
- Data parsing and validation belong in `core`.
- Signals, widgets, painting, Qt models, undo integration, and settings UI belong
  in `gui`.

Keep the root of `src/bedit` minimal. New UI modules should go into the relevant
`gui` subpackage rather than the package root.

## Important behavior and design decisions

- Components may contain nested graph or text implementations.
- Ports retain stable IDs. Display names, types, orientation, positions, and icon
  anchors may change without changing IDs.
- Parameters belong to `Component` rather than a particular implementation kind,
  so graph and text components share stable-ID name/type/value records.
- Port orientation is presented as one unified list in the UI, while the model
  indexes inputs and outputs separately for connection semantics.
- Port types are registered in `core/port_types.py`. Only compatible types may be
  connected. `signal` is currently the only type.
- Port removal or reorientation must be rejected when it would invalidate an
  existing connection.
- Connections reference port IDs, never port names.
- Connection junctions are explicit typed graph objects. Splitting a connection
  creates one incoming and one outgoing segment; the junction can source further
  branches without overlapping full connection paths.
- Graph interaction has separate Pointer and Connect modes. Port hints are only
  visible in Connect mode. Connecting two blocks opens the compatible port-pair
  chooser; explicit port clicks determine its default selection. Connections
  use one freely angled polyline format with absolute `properties.waypoints`.
  Semantic ports choose compatibility, while each rendered endpoint is the
  intersection of the owning hitbox and its center-to-adjacent-route-point ray.
- Connection appearance is configured per port type in
  `gui/graphics/connection_styles.py`, including color, width, pen style, and
  source/target arrowheads. Do not scatter those constants through painters.
- Graph annotations are `box`, `line`, or `text` objects in `Graph.annotations`.
  They use integer layers below or above graph layer 0. Annotation lines reuse
  connection polyline and absolute `properties.waypoints` semantics. Graph
  annotations and icon elements share `ShapeOptionsDialog` and `shape_pen` so
  their style fields and rendering must remain aligned.
- Icon editing uses a fixed 128×128 coordinate space.
- The visible/selectable component hitbox is calculated from vector elements,
  not from the complete 128×128 icon canvas.
- New component icons default to a centered 64×64 shape.
- Vector elements include rectangles, circles, ellipses, lines, triangles, and
  text. Shape styling and geometry are stored in document JSON.
- Icon port anchors are stored in `Port.properties["iconPosition"]`.
- Workspace grid size, workspace snapping size, and icon grid size are separate
  persisted settings.
- Settings use `gui.preferences.application_settings()` and are stored under the
  explicit `BEdit/BEdit` identity. Do not create anonymous `QSettings()` objects.
- Avoid the QSettings group name `general`; Qt treats `General` specially in INI
  files. Autosave keys live under `autosave/`.
- User-visible document edits should participate in undo/redo.
- The text-definition editor uses OpenModelica highlighting and completion from
  `src/bedit/data/syntax/openmodelica.json`. Keep keywords, types, built-ins, and
  named BEdit `$name$` macro completions editable there; arbitrary `$name$`
  expressions are highlighted as BEvalues. Highlight colors and bold/italic
  styles are persisted under `syntax/<category>/` in application settings.
- Application-wide messages use `core.application_log.get_logger()`. The main
  window installs the Qt log-panel handler; core code must only use standard
  Python logging and must not import the GUI handler.
- File → Reload Simulation Code (`Ctrl+F5`) reloads modules under
  `bedit.core.simulation`, replaces the shared application/controller service,
  and preserves the previous instance attributes where possible.
- Modelica composition lives in `core/simulation/composer.py`; the simulation
  service only owns application state and delegates composition. Ports with
  `multipleConnections` are emitted as Modelica arrays. Their size is inferred
  per component instance from graph connections and exposed while compiling as
  `$portname_N$`; array connection endpoints receive stable one-based indices in
  graph connection order.
- OpenModelica integration belongs in `core/simulation/openmodelica.py`. Its
  persistent worker and OMC session start lazily on the first queued request.
  Never perform OMPython work directly on the Qt GUI thread. Result and error
  callbacks run on background threads and must use a Qt signal before touching UI.
  One lazy temporary working directory is shared by all requests in the session.
  Explicit application shutdown closes OMC and removes that directory plus the
  current session's OMPython log and port files; `__del__` is only a fallback.
- Simulation runs start an ephemeral localhost TCP listener before launching the
  generated model through OMC's `system()` function. OpenModelica's newline-delimited
  `xmltcp` status and message records are parsed in the core and forwarded through
  callbacks; the simulation service retains the latest progress for polling.
- The application owns one reusable `SimulationWindow`. Starting a run clears its
  progress, log, and future result views. Extend graph presentation through its
  Designer-owned `resultsLayout` and the `clear_results()`/`load_results()` hooks.
- The optional OpenModelica executable is persisted as
  `simulation/openModelicaPath`. The GUI passes it into `Simulation`; core must
  not read `QSettings`. An empty path uses OMPython/PATH discovery, while an
  explicit `.../bin/omc` path is converted to the OpenModelica home directory.

## Qt Designer and generated files

Editable Designer sources are in `ui/`. Resources are defined in
`resources/resources.qrc`.

Never hand-edit files in `src/bedit/gui/generated/`. Modify the corresponding
`.ui` or `.qrc` source and regenerate instead.

Use the configured VS Code task **Qt: Build Designer Files**, or run the relevant
commands directly:

```bash
pyside6-rcc resources/resources.qrc \
  -o src/bedit/gui/generated/resources_rc.py

pyside6-uic --from-imports ui/main_window.ui \
  -o src/bedit/gui/generated/ui_main_window.py

pyside6-uic --from-imports ui/settings_dialog.ui \
  -o src/bedit/gui/generated/ui_settings_dialog.py

pyside6-uic --from-imports ui/component_options_dialog.ui \
  -o src/bedit/gui/generated/ui_component_options_dialog.py

pyside6-uic --from-imports ui/port_options_dialog.ui \
  -o src/bedit/gui/generated/ui_port_options_dialog.py

pyside6-uic --from-imports ui/shape_options_dialog.ui \
  -o src/bedit/gui/generated/ui_shape_options_dialog.py

pyside6-uic --from-imports ui/icon_editor_dialog.ui \
  -o src/bedit/gui/generated/ui_icon_editor_dialog.py

pyside6-uic --from-imports ui/text_definition_editor.ui \
  -o src/bedit/gui/generated/ui_text_definition_editor.py

pyside6-uic --from-imports ui/simulation_settings_dialog.ui \
  -o src/bedit/gui/generated/ui_simulation_settings_dialog.py

pyside6-uic --from-imports ui/simulation_window.ui \
  -o src/bedit/gui/generated/ui_simulation_window.py

pyside6-uic --from-imports ui/graph_parameters_dialog.ui \
  -o src/bedit/gui/generated/ui_graph_parameters_dialog.py

pyside6-uic --from-imports ui/parameter_options_dialog.ui \
  -o src/bedit/gui/generated/ui_parameter_options_dialog.py
```

When adding a promoted/custom widget in Designer, its header must use the real
Python module path, for example `bedit.gui.graphics.workspace`.

Substantial windows and dialogs must have a Designer `.ui` source. Python classes
bind behavior and data but must not reconstruct or replace those layouts at
runtime. A tiny generic prompt with one field and OK/Cancel may remain code-only.

## Editing conventions

- Preserve stable document IDs and existing connections.
- Validate candidate document changes before pushing an undo command.
- Keep model serialization symmetrical: additions to `to_dict()` require matching
  handling in `from_dict()` and cloning where relevant.
- Use descriptive domain names; avoid generic `utils.py` modules.
- Prefer focused classes and helpers over growing `main_window.py` further.
- Shared vector calculations that do not require Qt belong in `core`; Qt painter
  code belongs in `gui/graphics`.
- Do not silently swallow malformed document data. Raise a useful `ValueError` in
  `core`, then present it through the GUI layer.
- Preserve unrelated user changes. The worktree may already be dirty.
- Do not delete or overwrite library/document JSON unless the requested workflow
  explicitly calls for it.

## Document and library files

- Documents use the `bedit-document` JSON format.
- Documents can be stored as human-readable `.bedit.json`/`.json` through
  `JsonDocumentSerializer`, or as compressed MessagePack `.beb` through
  `BebDocumentSerializer`. UI document I/O dispatches via `DocumentSerializer`.
- `test.bedit.json` is a useful manually created example during development.
- Library documents use the same recursive document model.
- Library parsing belongs in `core/libraries.py`; Qt change notifications belong
  in `gui/models/library_repository.py`.
- Package library data, if present, belongs under `src/bedit/data/libraries/`.

## Validation

There is not yet a complete automated test suite. For every change, run at least:

```bash
python3 -m compileall -q src
git diff --check
```

Run imports with the source tree explicitly available:

```bash
PYTHONPATH=src python3 -c "import bedit.core; import bedit.gui.app"
```

Verify the backend remains Qt-free after core changes:

```bash
PYTHONPATH=src python3 - <<'PY'
import sys
import bedit.core
assert not any(name.startswith("PySide6") for name in sys.modules)
PY
```

For model changes, add a focused in-memory round-trip check using
`GraphDocument.to_dict()` and `GraphDocument.from_dict()`. For controller changes,
exercise undo and redo when applicable.

GUI smoke tests may fail in headless environments because the system Qt platform
theme tries to access a display even with an offscreen platform. Do not claim an
interactive GUI test passed unless a display-capable environment was actually
used. Compilation, imports, and pure model/controller checks remain useful.

If Ruff is installed, also run:

```bash
ruff check src
```

## Running the application

Install the package in editable mode or run it from the source tree:

```bash
PYTHONPATH=src python3 -m bedit
```

The installed GUI entry point is `bedit.gui.app:main`.

## Completion checklist

Before handing off a change:

1. Confirm the `core`/`gui` dependency boundary is intact.
2. Confirm generated files were not hand-edited.
3. Check serialization and cloning for model changes.
4. Check undo/redo for document mutations.
5. Run compilation and `git diff --check`.
6. Report any GUI behavior that could not be tested interactively.
7. Update README or this file if the architecture or workflow changed.