index.js

var util = require('util');
var request = require('request');
var events = require('events');
var cheerio = require('cheerio');
var URI = require('uri-js');
var _ = require('lodash');

var debug;

if (/\bmetainspector\b/.test(process.env.NODE_DEBUG)) {
  debug = function() {
    console.error('METAINSPECTOR %s', util.format.apply(util, arguments));
  };
} else {
  debug = function() {};
}

function withDefaultScheme(url) {
	return URI.parse(url).scheme ? url : "http://" + url;
}

var MetaInspector = function(url, options) {
	this.url = URI.normalize(withDefaultScheme(url));

	this.parsedUrl = URI.parse(this.url);
	this.scheme = this.parsedUrl.scheme;
	this.host = this.parsedUrl.host;
	this.rootUrl = this.scheme + "://" + this.host;

	this.options = options || {};
	//default to a sane limit, since for meta-inspector usually 5 redirects should do a job
	//more over beyond this there could be an issue with event emitter loop detection with new nodejs version
	//which prevents error event from getting fired
	this.options.maxRedirects = this.options.maxRedirects || 5;

	//some urls are timing out after one minute, hence need to specify a reasonable default timeout
	this.options.timeout = this.options.timeout || 20000; //Timeout in ms

	this.options.strictSSL = !!this.options.strictSSL;

	this.options.headers = this.options.headers || { 'User-Agent' : 'MetaInspector/1.0' };
};

//MetaInspector.prototype = new events.EventEmitter();
// MetaInspector.prototype.__proto__ = events.EventEmitter.prototype;
util.inherits(MetaInspector, events.EventEmitter);

module.exports = MetaInspector;

MetaInspector.prototype.getTitle = function() {
	debug("Parsing page title");

	if(!this.title)
	{
		this.title = this.parsedDocument('head > title').text();
	}

	return this;
};

MetaInspector.prototype.getOgTitle = function() {
	debug("Parsing page Open Graph title");

	if(!this.ogTitle)
	{
		this.ogTitle = this.parsedDocument("meta[property='og:title']").attr("content");
	}

	return this;
};

MetaInspector.prototype.getOgDescription = function() {
	debug("Parsing page Open Graph description");

	if(this.ogDescription === undefined)
	{
		this.ogDescription = this.parsedDocument("meta[property='og:description']").attr("content");
	}

	return this;
};

MetaInspector.prototype.getOgType = function() {
	debug("Parsing page's Open Graph Type");

	if(this.ogType === undefined)
	{
		this.ogType = this.parsedDocument("meta[property='og:type']").attr("content");
	}

	return this;
};

MetaInspector.prototype.getOgUpdatedTime = function()
{
	debug("Parsing page's Open Graph Updated Time");

	if(this.ogUpdatedTime === undefined)
	{
		this.ogUpdatedTime = this.parsedDocument("meta[property='og:updated_time']").attr("content");

		return this;
	}
};

MetaInspector.prototype.getOgLocale = function() {
	debug("Parsing page's Open Graph Locale");

	if(this.ogLocale === undefined)
	{
		this.ogLocale = this.parsedDocument("meta[property='og:locale']").attr("content");
	}

	return this;
};

MetaInspector.prototype.getLinks = function() {
	debug("Parsing page links");

	var _this = this;

	if(!this.links)
	{
		this.links = this.parsedDocument('a').map(function(i ,elem) {
			return _this.parsedDocument(this).attr('href');
		});
	}

	return this;
};

MetaInspector.prototype.getMetaDescription = function() {
	debug("Parsing page description based on meta elements");

	if(!this.description)
	{
		this.description = this.parsedDocument("meta[name='description']").attr("content");
	}

	return this;
};

MetaInspector.prototype.getSecondaryDescription = function() {
	debug("Parsing page secondary description");
	var _this = this;

	if(!this.description) {
		var minimumPLength = 120;

		this.parsedDocument("p").each(function(i, elem) {
			if(_this.description) {
				return;
			}

			var text = _this.parsedDocument(this).text();

			// If we found a paragraph with more than
			if(text.length >= minimumPLength) {
				_this.description = text;
			}
		});
	}

	return this;
};

MetaInspector.prototype.getDescription = function() {
	debug("Parsing page description based on meta description or secondary description");
	this.getMetaDescription();
	this.getSecondaryDescription();

	return this;
};

MetaInspector.prototype.getKeywords = function() {
	debug("Parsing page keywords from apropriate metatag");

	if(!this.keywords) {
		var keywordsString = this.parsedDocument("meta[name='keywords']").attr("content");

		if(keywordsString) {
			this.keywords = keywordsString.split(',');
		} else {
			this.keywords = [];
		}
	}

	return this;
};

MetaInspector.prototype.getAuthor = function() {
	debug("Parsing page author from apropriate metatag");

	if(!this.author) {
		this.author = this.parsedDocument("meta[name='author']").attr("content");
	}

	return this;
};

MetaInspector.prototype.getCharset = function() {
	debug("Parsing page charset from apropriate metatag");

	if(!this.charset) {
		this.charset = this.parsedDocument("meta[charset]").attr("charset");
	}

	return this;
};

MetaInspector.prototype.getImage = function() {
	debug("Parsing page image based on the Open Graph image");

	if(!this.image) {
		var img = this.parsedDocument("meta[property='og:image']").attr("content");
		if (img) {
			this.image = this.getAbsolutePath(img);
		}
	}

	return this;
};

MetaInspector.prototype.getImages = function() {
	debug("Parsing page body images");
	var _this = this;

	if(this.images === undefined) {
		this.images = this.parsedDocument('img').map(function(i ,elem) {
			var src = _this.parsedDocument(this).attr('src');
			return _this.getAbsolutePath(src);
		});
	}

	return this;
};

MetaInspector.prototype.getFeeds = function() {
	debug("Parsing page feeds based on rss or atom feeds");

	if(!this.feeds) {
		this.feeds = this.parseFeeds("rss") || this.parseFeeds("atom");
	}

	return this;
};

MetaInspector.prototype.parseFeeds = function(format) {
	var _this = this;
	var feeds = this.parsedDocument("link[type='application/" + format + "+xml']").map(function(i ,elem) {
		return _this.parsedDocument(this).attr('href');
	});

	return feeds;
};

MetaInspector.prototype.initAllProperties = function() {
	// title of the page, as string
	this.getTitle()
			.getAuthor()
			.getCharset()
			.getKeywords()
			.getLinks()
			.getDescription()
			.getImage()
			.getImages()
			.getFeeds()
			.getOgTitle()
			.getOgDescription()
			.getOgType()
			.getOgUpdatedTime()
			.getOgLocale();
};

MetaInspector.prototype.getAbsolutePath = function(href) {
	if((/^(http:|https:)?\/\//i).test(href)) { return href; }
	if(!(/^\//).test(href)) {
		href = '/' + href;
	}

	return this.rootUrl + href;
};

MetaInspector.prototype.fetch = function() {
	var _this = this;
	var totalChunks = 0;
	var r = request(_.assign({uri : this.url, gzip: true}, this.options), function(error, response, body) {
		if(!error && response.statusCode === 200) {
			_this.document = body;
			_this.parsedDocument = cheerio.load(body);
			_this.response = response;

			_this.initAllProperties();

			_this.emit("fetch");
		}
		else{
			_this.emit("error", error);
		}
	});

	if(_this.options.limit) {
		_this.__stoppedAtLimit = false;
		r.on('data', function(chunk) {
			totalChunks += chunk.length;
			if(totalChunks > _this.options.limit) {
				if(!_this.__stoppedAtLimit) {
					_this.emit("limit");
					_this.__stoppedAtLimit = true;
				}
				r.abort();
			}
		});
	}
};