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53 lines
1.7 KiB
53 lines
1.7 KiB
import assert from "./assert.js";
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import { log } from "./logging.js";
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export default class FSM {
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constructor(data, events) {
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// data is really only for logging/debugging
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this.data = data;
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this.events = events;
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this.state = "START";
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this.on_state = undefined;
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}
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onTransition(cb) {
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this.transition_cb = cb;
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}
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transition(next_state) {
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this.state = next_state;
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if(this.transition_cb) {
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this.transition_cb(this);
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}
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}
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event_names() {
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return Object.getOwnPropertyNames(Object.getPrototypeOf(this.events)).filter(k => k !== "constructor");
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}
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async do(event, ...args) {
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const evhandler = this.events[event];
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assert(evhandler !== undefined, `Invalid event ${event}. Available ones are '${this.event_names()}'.`);
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// NOTE: you have to use .call to pass in the this.events object or else this === undefined in the call
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const next_state = await evhandler.call(this.events, this.state, ...args);
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assert(next_state, `The event "${event}" returned "${next_state}" but must be a truthy true state.`);
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if(Array.isArray(next_state)) {
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assert(next_state.length == 2, `Returning an array only allows 2 elements (state, func) but you returned ${next_state}`);
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let [state, func] = next_state;
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log.debug(`FSM ${this.events.constructor.name}: (${event}) = ${this.state} -> ${state} (${args})`, "DATA:", this.data, func ? `THEN ${func.name}()` : undefined);
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this.transition(state);
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await func();
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} else {
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log.debug(`FSM ${this.events.constructor.name}: (${event}) = ${this.state} -> ${next_state} (${args})`, "DATA:", this.data);
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this.transition(next_state);
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}
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return this.state;
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}
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}
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