graf

graf

Run a bunch of async and sync functions in some kind of order.

Example

var graf = require('graf')
var crypto = require('crypto')

function a(x, y) { return x + y }
function add() {
	return Array.prototype.slice.call(arguments).reduce(a)
}

function m(x, y) { return x * y }
function multiply() {
	return Array.prototype.slice.call(arguments).reduce(m)
}

var g = graf(
	{
		input: ['a', 'b', 'x'],
		nodes: {
			sum: {
				input: ['a', 'b'],
				syncFn: add
			},
			multiply: {
				input: ['sum', 'sum', 'randomInt'],
				syncFn: multiply
			},
			randomBytes: {
				input: ['x'],
				fn: crypto.randomBytes
			},
			randomInt: {
				input: ['randomBytes'],
				syncFn: function (bytes) {
					return bytes.readUInt8(0)
				}
			},
			foo: {
				input: ['sum', 'randomInt'],
				syncFn: function (sum, int) {
					console.log("sum: %d int: %d", sum, int)
				}
			}
		},
		output: 'multiply'
	}
)

g(3, 2, 1, console.log)

Obviously not ready for prime time

API

graf(spec)

Given a spec, defined below, returns a function that will asynchronously execute the spec and return the result or error to a callback function.

spec

A graf is defined by an object called a spec. The spec defines the input, nodes, and output of the graf.

input

The input attribute defines the arguments for the graf function. The array maps argument indices to argument names, just like a normal function signature. These arguments can be used as input to the nodes of the graf. For example:

var spec = {
	input: ['x', 'y', 'z']
}

var g = graf(spec)

g(1, 2, 3)

// x = 1
// y = 2
// z = 3

nodes

The nodes define the functions to call and their relationships to one another. Each node has a name and a fn or syncFn function, and optionally input and after attributes.

• input: node names whose values will be passed to fn or syncFn
• after: node names that must complete before this node, but that do not provide input
• fn: an async function that accepts a callback(err, ...)
• syncFn: a synchronous function

The input and after attributes define the order of execution. Each node will wait until all of it's input and after nodes have completed before executing.

Any node that returns an error will prevent any unstarted nodes from executing and the graf callback to return the error.

var spec = {
	input: ['r', 'b'],
	nodes: {
		red: {
			input: ['r'],
			fn: computeRed
		},
		blue: {
			input: ['red', 'b'],
			fn: computeBlue
		},
		green: {
			after: ['blue'],
			fn: computeGreen
		}
	}
}

/*
Red will run first, followed by blue, then green.

Green has no input, so it could have run at the same time
as red if it didn't have an "after" set. "after" is useful
for manually ordering execution.
*/

output

The output attribute defines which node will be used as the result of the graf function and returned to the callback.

var spec = {
	nodes: {
		red: {
			fn: function (cb) { cb(null, "red") }
		},
		blue: {
			input: ['red'],
			syncFn: function (red) { return "hello " + red }
		}
	},
	output: 'blue'
}

var g = graf(spec)

g(console.log)

// null "hello red"

license

BSD