refactor: replace xstate with a simple built-in state machine (#7460)

Author: AlCalzone

.github/dependabot.yml

@@ -18,8 +18,6 @@ updates:
       # so only apply patch and minor updates automatically
       - dependency-name: '@types/node'
         update-types: ['version-update:semver-major']
-      # xstate usually requires manual intervention
-      - dependency-name: 'xstate'
 
   - package-ecosystem: github-actions
     directory: '/'

packages/cc/src/cc/TransportServiceCC.ts

@@ -15,15 +15,10 @@ import type {
 } from "@zwave-js/host/safe";
 import { Bytes } from "@zwave-js/shared/safe";
 import { buffer2hex } from "@zwave-js/shared/safe";
-import {
-	type CCRaw,
-	type CCResponseRole,
-	CommandClass,
-} from "../lib/CommandClass.js";
+import { type CCRaw, CommandClass } from "../lib/CommandClass.js";
 import {
 	CCCommand,
 	commandClass,
-	expectedCCResponse,
 	implementedVersion,
 } from "../lib/CommandClassDecorators.js";
 import { TransportServiceCommand } from "../lib/_Types.js";
@@ -81,7 +76,7 @@ export function isTransportServiceEncapsulation(
 }
 
 @CCCommand(TransportServiceCommand.FirstSegment)
-// @expectedCCResponse(TransportServiceCCReport)
+// Handling expected responses is done by the RX state machine
 export class TransportServiceCCFirstSegment extends TransportServiceCC {
 	public constructor(
 		options: WithAddress<TransportServiceCCFirstSegmentOptions>,
@@ -227,7 +222,7 @@ export interface TransportServiceCCSubsequentSegmentOptions
 }
 
 @CCCommand(TransportServiceCommand.SubsequentSegment)
-// @expectedCCResponse(TransportServiceCCReport)
+// Handling expected responses is done by the RX state machine
 export class TransportServiceCCSubsequentSegment extends TransportServiceCC {
 	public constructor(
 		options: WithAddress<TransportServiceCCSubsequentSegmentOptions>,
@@ -465,23 +460,8 @@ export interface TransportServiceCCSegmentRequestOptions {
 	datagramOffset: number;
 }
 
-function testResponseForSegmentRequest(
-	sent: TransportServiceCCSegmentRequest,
-	received: TransportServiceCC,
-): CCResponseRole {
-	return (
-		(sent.datagramOffset === 0
-			&& received instanceof TransportServiceCCFirstSegment
-			&& received.sessionId === sent.sessionId)
-		|| (sent.datagramOffset > 0
-			&& received instanceof TransportServiceCCSubsequentSegment
-			&& sent.datagramOffset === received.datagramOffset
-			&& received.sessionId === sent.sessionId)
-	);
-}
-
 @CCCommand(TransportServiceCommand.SegmentRequest)
-@expectedCCResponse(TransportServiceCC, testResponseForSegmentRequest)
+// Handling expected responses is done by the RX state machine
 export class TransportServiceCCSegmentRequest extends TransportServiceCC {
 	public constructor(
 		options: WithAddress<TransportServiceCCSegmentRequestOptions>,

packages/core/src/fsm/FSM.ts

@@ -0,0 +1,88 @@
+export interface StateMachineTransition<
+	State extends StateMachineState,
+	Effect = undefined,
+> {
+	effect?: Effect;
+	newState: State;
+}
+
+export interface StateMachineState {
+	value: number | string;
+	done?: boolean;
+}
+
+export interface StateMachineInput {
+	value: number | string;
+}
+
+export type StateMachineTransitionMap<
+	State extends StateMachineState,
+	Input extends StateMachineInput,
+	Effect = undefined,
+> = (
+	state: State,
+) => (
+	input: Input,
+) => StateMachineTransition<State, Effect | undefined> | undefined;
+
+export type InferStateMachineTransitions<
+	T extends StateMachine<any, any, any>,
+> = T extends StateMachine<infer S, infer I, infer E>
+	? StateMachineTransitionMap<S, I, E | undefined>
+	: never;
+
+export class StateMachine<
+	State extends StateMachineState,
+	Input extends StateMachineInput,
+	Effect = undefined,
+> {
+	public constructor(
+		initialState: State,
+		transitions: StateMachineTransitionMap<
+			State,
+			Input,
+			Effect | undefined
+		>,
+	) {
+		this._initial = this._state = initialState;
+		this.transitions = transitions;
+	}
+
+	protected transitions: StateMachineTransitionMap<
+		State,
+		Input,
+		Effect | undefined
+	>;
+
+	/** Restarts the machine from the initial state */
+	public restart(): void {
+		this._state = this._initial;
+	}
+
+	/** Determines the next transition to take */
+	public next(
+		input: Input,
+	): StateMachineTransition<State, Effect | undefined> | undefined {
+		if (this._state.done) return;
+		return this.transitions(this._state)(input);
+	}
+
+	/** Transitions the machine to the next state. This does not execute effects */
+	public transition(next?: State): void {
+		// Allow some convenience by passing the transition's next state directly
+		if (next == undefined) return;
+		this._state = next;
+	}
+
+	private _initial: State;
+	private _state: State;
+	/** Returns the current state of the state machine */
+	public get state(): State {
+		return this._state;
+	}
+
+	/** Returns whether this state machine is done */
+	public get done(): boolean {
+		return !!this._state.done;
+	}
+}

packages/core/src/index.ts

@@ -3,6 +3,7 @@ export * from "./crypto/index.node.js";
 export * from "./definitions/index.js";
 export * from "./dsk/index.js";
 export * from "./error/ZWaveError.js";
+export * from "./fsm/FSM.js";
 export * from "./log/Controller.js";
 export * from "./log/shared.js";
 export * from "./log/shared_safe.js";

packages/zwave-js/package.json

@@ -118,8 +118,7 @@
     "semver": "^7.6.3",
     "serialport": "^12.0.0",
     "source-map-support": "^0.5.21",
-    "winston": "^3.15.0",
-    "xstate": "4.38.3"
+    "winston": "^3.15.0"
   },
   "devDependencies": {
     "@alcalzone/esm2cjs": "^1.4.1",
@@ -130,7 +129,6 @@
     "@types/semver": "^7.5.8",
     "@types/sinon": "^17.0.3",
     "@types/source-map-support": "^0.5.10",
-    "@xstate/test": "^0.5.1",
     "@zwave-js/maintenance": "workspace:*",
     "@zwave-js/transformers": "workspace:*",
     "del-cli": "^6.0.0",