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node-easy-flow

Simple and easy to use Finite State Machine (FSM) for Node.js (similar to EasyFlow for Java).

This library greatly simplifies development of asynchronous event-driven applications.

Thanks to its convenient hierarchical transition builder, logic of complex applications remains clear and application itself manageable.

Usecase for node-easy-flow is somehow similar to async.series() or async.waterfall() (see here), only node-easy-flow is more suitable for handling complex, non-linear logic.

Install

Install locally

npm install node-easy-flow

Quick start

FSM is defined with node-easy-flow through combination of transitions and handlers

var EasyFlow = require('node-easy-flow/lib/easy-flow-v1');

var flow = EasyFlow.create(function (from, on, to, finish, trigger, whenEnter) {
    // states
    var SHOWING_WELCOME = 'SHOWING_WELCOME',
        WAITING_FOR_PIN = 'WAITING_FOR_PIN',
        CHECKING_PIN = 'CHECKING_PIN',
        SHOWING_MAIN_MENU = 'SHOWING_MAIN_MENU',
        SHOWING_BALANCE = 'SHOWING_BALANCE',
        ...

    // events
    var cardPresent = 'cardPresent',
        pinProvided = 'pinProvided',
        pinValid = 'pinValid',
        cancel = 'cancel',
        menuShowBalance = 'menuShowBalance',
        ...

    // transition definitions
    from(SHOWING_WELCOME,
        on(cardPresent, to(WAITING_FOR_PIN,
            on(pinProvided, to(CHECKING_PIN,
                on(pinValid, to(SHOWING_MAIN_MENU,
                    on(menuShowBalance, to(SHOWING_BALANCE,
                        on(cancel, to(SHOWING_MAIN_MENU))
                    )),
                    ...
                ))
                ...
            ))
            ...
        ))
        ...
    );

    // handler definitions
    whenEnter(SHOWING_WELCOME, function (context) {
        console.log('\n\n*** Welcome ***\n');
        context.invalidPinCounter = 0;
        rl.question('Select your option and press [Enter]...\n 1 Insert card\n 2 Terminate ATM\n', function (option) {
            trigger(option == 1 ? cardPresent : switchOff, context);
        });
    });

    whenEnter(WAITING_FOR_PIN, function (context) {
        console.log('\n\n*** Waiting for PIN ***\n');
        rl.question('Please enter your PIN and press [Enter] or just press [Enter] to cancel (current PIN is 1234)...\n', function (pin) {
            if (pin.length === 4) {
                context.pin = pin;
                trigger(pinProvided, context);
            } else {
                trigger(cancel, context);
            }
        });
    });
    ...
});

Then it can be started using context object

flow.start({ balance: 1000 });

See full example here

See also

EasyFlow for Java

License

ISC License (ISC)

Copyright (c) 2015, Andrey Chausenko andrey.chausenko@gmail.com

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.