Bitstamp vs. Ripple spreads listener

arb.js

var ripple = require("ripple-lib");
var Pusher = require("pusher-client");

var west = {
	host: "s-west.ripple.com",
	port: 443,
	secure: true
};
var east = {
	host: "s-east.ripple.com",
	port: 443,
	secure: true
};
var options = {
	fee_cushion: 1.5,
	servers: [
		east,
		west
	],
	trusted: false
};
var remote = new ripple.Remote(options);

var native = new Pusher("de504dc5763aeef9ff52");

function start()
{
	remote.on("ledger_closed", update);
}

function update()
{
	var base = {
		currency: "USD",
		issuer: "rvYAfWj5gh67oV6fW32ZzP3Aw4Eubs59B"
	};
	var counter = {
		currency: "BTC",
		issuer: "rvYAfWj5gh67oV6fW32ZzP3Aw4Eubs59B"
	};
	var bid = {
		gets: base,
		pays: counter
	};
	var ask = {
		gets: counter,
		pays: base
	};

	remote.request_book_offers(bid, showbid);
	remote.request_book_offers(ask, showask);
}

function gettime()
{
	var date = new Date();

	return date.getTime().toFixed(0);
}

function showrip(error, response, type)
{
	var time = gettime();
	var offer, src, dst, price;

	if (error)
		return;

	offer = response.offers.shift();
	src = offer.TakerPays.value;
	dst = offer.TakerGets.value;
	offer = ("Ask" == type ? src / dst : dst / src);
	offer = offer.toFixed(2);
	console.log(time, type, offer, "Ripple");
}

function showbid(error, response)
{
	showrip(error, response, "Bid");
}

function showask(error, response)
{
	showrip(error, response, "Ask");
}

function showtop(data)
{
	var time = gettime();
	var bid = data.bids.shift().shift();
	var ask = data.asks.shift().shift();

	console.log(time, "Bid", bid, "Bitstamp");
	console.log(time, "Ask", ask, "Bitstamp");
}

function finish()
{
	process.exit();
}

setTimeout(finish, 3e5);
remote.connect(start);
native.subscribe("order_book").bind("data", showtop);

Makefile

PUSHER = node_modules/pusher-client/package.json
RIPPLE = node_modules/ripple-lib/package.json

all: $(PUSHER) $(RIPPLE)
	node arb | tee -a top.log

$(PUSHER):
	npm install pusher-client

$(RIPPLE):
	npm install ripple-lib

loop:
	-while true; do \
		$(MAKE); \
		sleep 1; \
	done

daemon: stop
	nohup $(MAKE) loop >/dev/null & echo $$! >daemon.pid
	sleep 1

stop:
	-if [ -f daemon.pid ]; then \
		kill "`cat daemon.pid`"; \
		rm -f daemon.pid; \
	fi

clean: stop
	-rm -fr node_modules *.log