mini-state-machine/dist/factory.js

A miniature state machine

import { cloneArray } from "./clone.js";
import { createEventsInterface } from "./events.js";
import { getState } from "./state.js";
import { generatePaths, getPath, transition, verifyTransitions } from "./transition.js";
/**
 * Create a state machine instance
 * @param config Configuration for the new state machine
 * @returns A state machine instance
 */
export function createStateMachine({ initial, transitions }) {
    if (!initial || initial.length <= 0) {
        throw new Error(`Invalid initial state: ${initial}`);
    }
    verifyTransitions(transitions);
    const context = {
        events: createEventsInterface(),
        paths: generatePaths(transitions),
        pending: false,
        state: initial,
        next: null,
        history: []
    };
    const sm = {
        get pending() {
            return context.pending;
        },
        get state() {
            return getState(context);
        },
        can: transition => !!getPath(context, transition),
        cannot: transition => !sm.can(transition),
        getHistory: () => cloneArray(context.history),
        is: state => sm.state === state,
        off: (event, stateOrTransition, cb) => context.events.remove(event, stateOrTransition, cb),
        on: (event, stateOrTransition, cb) => context.events.add(event, stateOrTransition, cb),
        once: (event, stateOrTransition, cb) => context.events.add(event, stateOrTransition, cb, { once: true }),
        onIdle: cb => {
            const handler = context.events.addIdle(cb);
            if (!context.pending) {
                context.events.emitIdle(cb);
            }
            return handler;
        },
        transition: action => transition(context, action)
    };
    return sm;
}