feat(commands): type command payload dispatch

commands/dispatcher.test.ts

@@ -7,7 +7,7 @@ import { viewportPanCommand } from "./viewport";
 describe("command dispatcher", () => {
   test("throws for unknown commands", () => {
     const store = createAppStore(createInitialAppState("Test"), createCommandRegistry([]));
-    expect(() => store.dispatch("missing", undefined)).toThrow("Unknown command: missing");
+    expect(() => store.dispatch("missing" as never, undefined as never)).toThrow("Unknown command: missing");
   });
 
   test("dispatch applies command result to store", () => {

commands/dispatcher.ts

@@ -1,8 +1,9 @@
 import type { AppState } from "@editor/state";
 import type { CommandContext } from "./command";
+import type { CommandId, CommandPayloads } from "./payloads";
 import type { CommandRegistry } from "./registry";
 
-export type Dispatch = <TPayload>(commandId: string, payload: TPayload) => AppState;
+export type Dispatch = <TCommandId extends CommandId>(commandId: TCommandId, payload: CommandPayloads[TCommandId]) => AppState;
 
 export type CommandDispatcher = {
   dispatch: Dispatch;

commands/index.ts

@@ -1,5 +1,6 @@
 export type { Command, CommandContext } from "./command";
 export type { CommandDispatcher, Dispatch } from "./dispatcher";
+export type { CommandId, CommandPayloads } from "./payloads";
 export { createCommandDispatcher } from "./dispatcher";
 export type { CommandRegistry } from "./registry";
 export { createCommandRegistry } from "./registry";

commands/payloads.ts

@@ -0,0 +1,16 @@
+import type {
+  ViewportPanPayload,
+  ViewportSetSizePayload,
+  ViewportSetZoomPayload,
+  ViewportZoomAroundPointPayload,
+} from "./viewport";
+
+export type CommandPayloads = {
+  "viewport.pan": ViewportPanPayload;
+  "viewport.setZoom": ViewportSetZoomPayload;
+  "viewport.zoomAroundPoint": ViewportZoomAroundPointPayload;
+  "viewport.setSize": ViewportSetSizePayload;
+  "viewport.reset": void;
+};
+
+export type CommandId = keyof CommandPayloads;