Pumpkin-O-Meter

pumpkin.js

/**
 * Pumpkin-o-meter
 *
 * @package pumpkin
 * @author Andrew Sliwinski <andrew@diy.org>
 */

/**
 * Dependencies
 */
var request = require('request'),
    argv    = require('optimist')
                .usage('Usage: $0 -apikey [string] -domain [string] -i [seconds]')
                .demand(['apikey','domain'])
                .default('i', 0.5)
                .argv;

/**
 * Phidget
 */
var phidget = require('phidget');
var servo   = new phidget.servo();

function servoToPosition(deg, callback) {
    servo.attach(function (err) {
        servo.setEngaged(0, true, function (err) {
            servo.setPosition(0, deg, function (err) {
                servo.close(callback);
            });
        });
    });
}

function checkChartbeat (callback) {
    request({
        method: 'get',
        uri:    'http://api.chartbeat.com/live/quickstats/v3/',
        qs:     {
            apikey: argv.apikey,
            host:   argv.domain
        },
        json:   {}
    }, function (err, response, body) {
        if (err) return callback(err);
        try {
            callback(null, body.visit.avg);    
        } catch (e) {
            callback(e);
        }
    });
}

function translate (value, leftMin, leftMax, rightMin, rightMax) {
    leftSpan    = leftMax - leftMin;
    rightSpan   = rightMax - rightMin;
    valueScaled = (value - leftMin) / leftSpan;

    return rightMin + (valueScaled * rightSpan);
}

// ----------------------------
// ----------------------------

setInterval(function () {
    checkChartbeat(function (err, metric) {
        if (err) {
            console.log('Dashboard: ' + err);
        } else {
            var position = translate(metric, 0, 100, 65, 150);
            servoToPosition(position, function (err) {
                console.log('Visitor Average: %d | Position: %d', metric, position);
            });
        }
    });
}, argv.i * 60000);