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ihsm

Class-based hierarchical state machines for TypeScript — states as classes, protocol as methods, actors with run-to-completion dispatch.

0 production dependencies100% runtime coverageNode 22+

Quick start​

npm install ihsm
import { InitialState, makeActor, Port, TopState } from 'ihsm';

interface DoorCtx {
  openCount: number;
}

interface DoorConfig {
  context: DoorCtx;
  notifications: { open(): void; close(): void };
}

class DoorTop extends TopState<DoorConfig> {}

@InitialState
class Closed extends DoorTop {
  open(): void {
    this.ctx.openCount += 1;
    this.hsm.transition(Open);
  }
}

class Open extends DoorTop {
  close(): void {
    this.hsm.transition(Closed);
  }
}

const door = makeActor(DoorTop, { openCount: 0 });
await door.hsm.sync();

door.notify.open();
await door.hsm.sync();

Learning path​

1 · Reference + playgrounds​

Reference — concepts, semantics, and interactive trace panels for standard examples 01–19 (plus config 00 and testing testing-01–05).

2 · Deterministic testing​

Testing — runnable DST examples first, then the full technique: TestPort, mock ports, simulated time, fault injection.