# /wire-rust — Wire a New Rust Command to TypeScript Use this skill when adding a new editing command that starts in Rust and needs to be callable from the TypeScript app layer. Follow the 5 touchpoints below in order. ## Touchpoints ### 1. Rust Core — `crates/shift-core/src/edit_session.rs` Add the method to `EditSession`. This is where the actual mutation logic lives. ```rust pub fn my_command(&mut self, ...) -> Result, String> { // mutation logic } ``` Return types: - `Vec` — affected point IDs (for commands that return them) - `Result, String>` — fallible with affected IDs - `()` — no return value needed - `Result<(), String>` — fallible, no return value ### 2. NAPI Binding — `crates/shift-node/src/font_engine.rs` Add a `#[napi]` method using one of the 4 command helpers: | Helper | Use when | | -------------------- | -------------------------------------- | | `command` | Returns `Vec`, infallible | | `command_simple` | Returns `()`, infallible | | `command_try` | Returns `Result, String>` | | `command_try_simple` | Returns `Result<(), String>` | ```rust #[napi] pub fn my_command(&mut self, arg: String) -> Result { let parsed = parse_or_err!(arg, MyType, "my type"); self.command_try(|s| s.my_command(parsed).map(|id| vec![id])) } ``` Parse string arguments BEFORE the closure (parse_or_err! returns early on failure). Run `cargo test --package shift-node && cargo clippy && cargo fmt` to verify. ### 3. FontEngineAPI Interface — `apps/desktop/src/shared/bridge/FontEngineAPI.ts` Add the method signature to the `FontEngineAPI` interface. This is the bridge contract. ```typescript myCommand(arg: string): string; ``` All command methods return `string` (JSON). The preload auto-forwards automatically — no changes needed there. ### 4. EditingManager — `apps/desktop/src/renderer/src/engine/editing.ts` Add a one-liner using `#dispatch` or `#dispatchVoid`: ```typescript // Returns affected point IDs myCommand(arg: SomeType): PointId[] { return this.#dispatch(this.#engine.raw.myCommand(arg)); } // Void command myCommand(arg: SomeType): void { this.#dispatchVoid(this.#engine.raw.myCommand(arg)); } ``` `#dispatch` and `#dispatchVoid` handle: session check, JSON parse, error throw, glyph emit. ### 5. MockFontEngine — `apps/desktop/src/renderer/src/engine/mock.ts` Add mock implementation. Use the helpers: ```typescript myCommand(arg: string): string { if (!this.#snapshot) return this.#makeResult(false, [], "No active edit session"); const contour = this.#findContour(arg); if (!contour) return this.#makeResult(false, [], `Contour ${arg} not found`); // mock logic return this.#makeResult(true, []); } ``` Available helpers: - `#withSession(fn)` — throws if no session, calls fn with snapshot - `#findContour(id)` — returns MockContour or undefined - `#findPoint(id)` — returns `{ contour, point, index }` or null - `#makeResult(success, affectedPointIds, error?)` — builds CommandResult JSON ## Zero-Maintenance Layers These layers require NO changes when adding new commands: - **Preload** (`apps/desktop/src/preload/preload.ts`) — auto-forwards all FontEngineAPI methods via `buildFontEngineAPI()` - **FontEngine** (`apps/desktop/src/renderer/src/engine/FontEngine.ts`) — exposes `raw` getter; command methods live in EditingManager ## Verification Checklist ```bash cargo test --package shift-node && cargo clippy && cargo fmt pnpm build:native && pnpm typecheck && pnpm test && pnpm lint:check ```

/wire-rust — Wire a New Rust Command to TypeScript

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