add `start()` and `pause()` to interpreter

src/index.ts

@@ -42,16 +42,33 @@ export interface Interpreter_T {
   state: string;
   context: any;
   eventQueue:Array<Event_T>;
+  subscriptions: Record<string, SubscriptionCallbackFunction_T>;
   isTransitioning: boolean;
-  subscriptions: Record<string, SubscriptionCallbackFunction_T>
+  isPaused: boolean;
 }
-export function interpret(machine:Machine_T, options:{state?:string, context:any}) : Interpreter_T{
-  let {state, context} = options;
-  if(typeof state === 'undefined'){ state = machine.states[0].name; }
-  const interpreter = {machine, state, context, eventQueue:[], isTransitioning:false, subscriptions: {}}
+
+/**
+ * Description placeholder
+ *
+ * @export
+ * @param {Machine_T} machine
+ * @param {InitialContextFunction_T} initialContextFunction - in the form of a function rather than a direct value, so as to facilitate co-initialization of peer interpreters. Otherwise, the "parent" interpreter will start, but without a reference to a running child interpreter which it might expect to exist.
+ * @param {?string} [initialStateName]
+ * @returns {Interpreter_T}
+ */
+export function Interpreter(machine:Machine_T, initialContext:any, initialStateName?:string) : Interpreter_T{
+  if(typeof initialStateName === 'undefined'){ initialStateName = machine.states[0].name; }
+  const interpreter = {machine, state: initialStateName, context:initialContext, eventQueue:[], isTransitioning:false, subscriptions: {}, isPaused: true}
   send(interpreter, ['entry', null] );
   return interpreter;
 }
+export function start(interpreter:Interpreter_T){
+  interpreter.isPaused = false;
+  processEvents(interpreter);
+}
+export function pause(interpreter:Interpreter_T){
+  interpreter.isPaused = true;
+}
 
 /**  Helper function for `send()`
  */
@@ -76,16 +93,19 @@ function getMatchingEventReactionCouplings(state : State_T, event:Event_T) : Arr
 export function send(interpreter : Interpreter_T, event:Event_T){
   interpreter.eventQueue.push(event);
   if(interpreter.isTransitioning === false){
-    interpreter.isTransitioning = true;
-    while(interpreter.eventQueue.length > 0){
-      processNextEvent(interpreter);
-    }
-    interpreter.isTransitioning = false;
-    // only run subscriptions here, once the machine's state has settled:
-    Object.values(interpreter.subscriptions).forEach((subscriptionCallbackFunction)=>{ subscriptionCallbackFunction(interpreter); });
+    processEvents(interpreter);
   }
 }
 export const enqueue = send;
+function processEvents(interpreter:Interpreter_T){
+  interpreter.isTransitioning = true;
+  while(interpreter.eventQueue.length > 0 && interpreter.isPaused===false){
+    processNextEvent(interpreter);
+  }
+  interpreter.isTransitioning = false;
+  // only run subscriptions here, once the machine's state has settled:
+  Object.values(interpreter.subscriptions).forEach((subscriptionCallbackFunction)=>{ subscriptionCallbackFunction(interpreter); });
+}
 function processNextEvent(interpreter:Interpreter_T){
   const nextEvent = interpreter.eventQueue.shift();
   if(typeof nextEvent !== 'undefined'){
@@ -135,7 +155,7 @@ let subscriptionId : number = 0;
 export function subscribe(interpreter:Interpreter_T, callback:SubscriptionCallbackFunction_T){
   subscriptionId++;
   interpreter.subscriptions[subscriptionId.toString()] = callback;
-  return subscriptionId;
+  return subscriptionId.toString();
 }
 export function unsubscribe(interpreter:Interpreter_T, subscriptionId:string){
   delete interpreter.subscriptions[subscriptionId.toString()];