grph v1.0.2

grph.dev

Graph programming. Create node.js or browser apps by connecting graph nodes. Use standard nodes or easily create your own.

This repo is work in progress, but feel free to check it out and contact me for questions or requests!

The Node essentials

Any node's output plug can be connected to any node's input plug. The signal propagated through the graph is mainly a single number, but can also carry other types of data.

The signal data is computed by one of the internal processors. The signal data can optionally be filtered through a standard or user-defined filter function before passed on to, and stored in, the output plug.

Each input can trigger a processor on a pulse (any signal), rise (signal value increase, e.g. 0->1), fall (signal value decrease) or change.

input plugs                              output plugs
     .----------------------------------------.
     |                  Node                  |
     |                                        |
    [0]--{trigger}--[processor0]------------[data]
     |                        '-------------[data]
     |                                        |
    [a]--{trigger}--[processor1]--<filter>--[data]
    [b]--{trigger}---'                        |
     |                                        |
     '----------------------------------------'

A useless example

The following example is quite useless, but the important part this far is how the nodes work; definitions, configuration, connections, processing and signal propagation. More useful nodes are coming.

My personal use-case is to create a modular app running on a raspberry pi to smartify my home, but the architecture is very open and one could easily create its own custom nodes and use it for anything, really.

const grph = require('grph');

grph.Logger.setLevel(grph.Logger.INFO);

// Create nodes
const request = new grph.HttpNode(app, { // <= express app
  route: '/api/:plug/:value',
  plugs: {
    name:'calc-square',
    hasResponseInput: true // create an input for the response
  }  
});
const delay = new grph.DelayNode(2.5); // seconds
const split = new grph.SplitNode(2); // two outputs
const print = new grph.PrintNode(); // just print to console

// Connect nodes
//      .---------.    .-------.      .-------.    .-------.
//  .-->| request |--->| split |----->| delay |--->| print |
//  |   '---------'    |       |---.  '-------'    '-------'
//  |                  '-------'   |
//  |                              |
//  '--------------< x² filter >---'


request.output('calc-square').connectTo(split.input());
split.output(0).connectTo(delay.input());
split.output(1).setFilter(value => value*value).connectTo(request.input());
delay.output().connectTo(print.input());

Test it with something like curl localhost:8080/api/calc-square/3 (depending on your server setup). It should respond with {value:9} immediately and then print the request value to the console after a 2.5 second delay.

How to run the attached example

node -r dotenv/config test.js

Make sure to create your own .env file in the module root with contents:

HTTP_LISTEN_PORT=8080
HTTP_LISTEN_ADDR=localhost

Then run curl localhost:8080/api/v1/set-pulse-duration/6 or curl localhost:8080/api/v1/multiply-2/123.

More to come..

so be sure to check back later!