feat: workflow middleware system

[himself65]

Middleware

withStore

const workflow = withStore(
  () => ({
    pendingTasks: new Set<Promise<unknown>>(),
  }),
  createWorkflow(),
);

workflow.handle([startEvent], () => {
  workflow.getStore().pendingTasks.add(
    new Promise((resolve) => {
      setTimeout(() => {
        resolve();
      }, 100);
    }),
  );
});

const { getStore } = workflow.createContext();

withDirectedGraph

make first parameter of handler to be sendEvent and its type safe and runtime safe when you create a workflow with directedGraph.

// before:
workflow.handle([startEvent], (start) => {});
// after:
workflow.handle([startEvent], (sendEvent, start) => {});

const startEvent = workflowEvent<void, "start">();
const disallowedEvent = workflowEvent<void, "disallowed">({
  debugLabel: "disallowed",
});
const parseEvent = workflowEvent<string, "parse">();
const stopEvent = workflowEvent<number, "stop">();
const workflow = directedGraph(createWorkflow(), [
  [[startEvent], [stopEvent]],
  [[startEvent], [parseEvent]],
]);

workflow.handle([startEvent], (sendEvent, start) => {
  sendEvent(
    disallowedEvent.with(), // <-- ❌ Type Check Failed, Runtime Error
  );
  sendEvent(parseEvent.with("")); // <-- ✅
  sendEvent(stopEvent.with(1)); // <-- ✅
});