# Native OCCT history provider

This provider is compiled from the cached OCCT checkout selected by
`OCCT_SOURCE_DIR` and exposes the native Boolean history API through Emscripten
Embind. The provider keeps `TopoDS_Shape` handles and history queries in one
WASM instance. A handle from `@bitbybit-dev/occt` must never be passed directly
to this module because WebAssembly linear memories are independent.

Build and verify it with the project wrapper:

```bash
./npmw run build:occt-history
./npmw run test:occt-history
```

The build also publishes the JS/WASM pair to
`public/native/occt-history/`, which is the default URL used by
`NativeOcctHistoryWorkerProvider`. The generated artifacts remain ignored; a
clean checkout must run the build after restoring the pinned OCCT source and
Emscripten toolchain.

The exported `booleanHistory(object, tool, operation)` function supports
`fuse`, `cut`, and `common`. It returns the native result shape, per-input
`modified`/`generated`/`deleted` records, and capability flags. The provider also
exports `shapeToStep(shape)` and `booleanHistoryFromStep(objectStep, toolStep,
operation)`. The latter is the cross-WASM transport: Bitbybit exports STEP text,
the native provider reads it with `STEPControl_Reader`, returns the Boolean
result again as `resultStep`, and no linear-memory pointer crosses the boundary.

The TypeScript boundary mapper is `mapNativeOcctHistoryRecords`; the reusable
`createNativeOcctStepHistoryBridge` exports Bitbybit ShapeHandles to STEP and
converts provider source names into document object IDs before calling
`captureNativeTopologyHistory`. The direct handle API remains for calls that
stay inside this single native WASM instance.