“Taken at face value, You3b is an absolutely horrible idea. ”
- downloadsquad.com

“If your Youtube addiction has you seeking out more and more videos, constantly, non-stop, perhaps you’d be satisfied once and for all with You3B.”
-killerstartups.com

/**
*	Represents one Craigslist page.
*	Can either be a page of results or a single listing page.
*/
class Craigslist extends PlacemarkSource {

private $url;

private $type;

const url_pattern = "/craigslist/i";

private $regexes = array(
/**
*	This should match the URL of any single Craigslist listing page.
*	They will look like
*	http://montreal.craigslist.org/sub/298262212.html
*	http://newyork.craigslist.org/brk/sys/299139631.html
*/
'single_listing_url' => "/craigslist.[a-z]{2,3}/(.+).html/i",

/**
*	This should match the URL of any page with multiple Craigslist pages
*	These pages may look like :
*	http://newyork.craigslist.org/search/bik/brk?query=&minAsk=min&maxAsk=200&hasPic=1
*	OR
*	http://montreal.craigslist.org/sub/
*	http://newyork.craigslist.org/que/bik/
*	BUT NOT
*	http://montreal.craigslist.org/sub/298262212.html
*	http://newyork.craigslist.org/brk/sys/299139631.html
*/
'multiple_listing_page_url' => "/craigslist.[a-z]{2,3}/i",

/**
*	This should match the URL of any Craigslist listing feed.
*	These pages should looke like:
*	http://philadelphia.craigslist.org/apa/index.rss
*	http://philadelphia.craigslist.org/search/apa?query=&minAsk=&maxAsk=200&bedrooms=&addTwo=purrr&addThree=wooof&hasPic=1&format=rss
*/
'feed_url' => "/craigslist.[a-z]{2,3}/(.+)(index.|format=)?(rss)/i",

/**
*	This Regex should match 1) URLs of listing pages 2) Titles of listings
*/
'get_listings' => "/<p>(.*?)<a href="(.*?)">(.*?)</a><font size="-1"> ((.*?))</font>(.*?)?</p>/i",

/**
*	In the pages of most Craigslist listings, the city that you are exploring is in a link at the top.
*	<a href="http://philadelphia.craigslist.org">philadelphia craigslist</a>
*	or
*	<a href="/"> new york craigslist</a>
*/
'city_in_title' => "/<a href="(.+)?">(.*?) craigslist</a>/i"
);

/*
*	The constructor for a Craigslist listing.
*	Most times, if you are parsing an entire page of listings, you will know the city
*	for every posting and the title along with the url before you construct them.  So if you
*	provide them, the constructor will go faster.
*/
function Craigslist($_url, $limit=null) {

$this->url = $_url;
$this->limit = $limit;

// First we will figure out what kind of page we are dealing with.
if(preg_match($this->regexes['single_listing_url'], $this->url)) {

$this->type = "single"; // an actual listing page.

} else if(preg_match($this->regexes['feed_url'], $this->url)) {

$this->type = "feed";	// A feed of listings

} else if(preg_match($this->regexes['multiple_listing_page_url'], $this->url)) {

$this->type = "multiple";  //  a search results or browse page

}
}

/**
*	Takes a relative URL from the current page and turns it into a full URL.
*/
function unrelativize($relative_url) {
$u = parse_url($this->url);
if(substr($relative_url, 0, 1) == '/') {
return "http://".$u['host'].$relative_url;
} else {
return "http://".$u['host'].dirname($u['path']).$relative_url;
}
}

/*
function parsePlacemarks() {
foreach($this->placemarks as $p) {
$p->parse();
}
}
*/

function getPlacemarks() {

switch($this->type) {

// It is a single listing, so just parse the current page.
case 'single':
$this->placemarks[] = new CraigsListing($this->url);
break;

// If if is a page of many listings, get all of the URLs.
case 'multiple':
$content = HttpClient::quickGet($this->url);

// The city appears in a link at the top.
preg_match($this->regexes['city_in_title'], $content, $matches);
$city = $matches[2];

//assert('$city!=null');

preg_match_all($this->regexes['get_listings'], $content, $matches);
$listing_urls = $matches[2];
$titles = $matches[3];
$locations = $matches[4];

foreach(array_keys($listing_urls) as $i) {
$listing_urls[$i] = $this->unrelativize($listing_urls[$i]);
}

if(count($listing_urls) == 0) {
trigger_error("Earthify couldn't find any listings on the page you provided.");
}

// Loop through all of the matches and make placemarks from them.
$max = isset($this->limit)
? min(count($listing_urls), $this->limit)
: count($listing_urls);

for($i=0; $i<$max; $i++) {
// Check to make sure the link exists first
if(HttpClient::url_exists($listing_urls[$i])) {
$listing = new CraigsListing($listing_urls[$i]);
$listing->setTitle($titles[$i]);
$listing->setCity($city);
$this->placemarks[] = $listing;
} else {
trigger_error("{$listing_urls[$i]} returned a 200 or 302 status, which means that it doesn't exist.", E_USER_WARNING);
}
}
break;

// If this is the RSS feed from a particular kind Craigslist page, just parse the RSS
case 'feed':
$content = HttpClient::quickGet($this->url);

$xml = new SimpleXMLElement($content);

// The city name appears in the channel title.
preg_match("/<title>craigslist | (.*?) in (.+)</title>/", $content, $matches);
$city = $matches[2];

//assert('$city!=null');

// Loop through all of the matches and make placemarks from them.
$max = isset($this->limit)
? min(count($xml->item), $this->limit)
: count($xml->item);

for($i=0; $i<$max; $i++) {

$link =  (string)$xml->item[$i]->link;

// Check to make sure the URL exists first.
if(HttpClient::url_exists($link)) {
$listing = new CraigsListing($link);
$listing->title = (string)$xml->item[$i]->title;
$listing->city = $city;
$this->placemarks[] = $listing;
} else {
trigger_error("{$listing_urls[$i]} returned a 200 or 302 status, which means that it doesn't exist.", E_USER_WARNING);
}
}
break;
}

return $this->placemarks;
} // end getPlacemarks()
}

/**************************
*
*	Serializer.php
*	Turns an array of Placemark objects into an Earthify KML script.
*
*	Written by Jeff Crouse at Eyebeam
*	February 8, 2007
*
***************************/
class KMLSerializer {

public static function serialize($placemarks) {

// Create the XML document and the root tag (kml)
$dom = new DomDocument('1.0', 'utf-8');
$root = $dom->createElement("kml");
$dom->appendChild($root);

// Create the Document tag
$doc = $dom->createElement("Document");
$root->appendChild($doc);

// Add a Earthify tag to the document tag.
$doc->appendChild($dom->createElement("name", "Earthify"));

// Make two folders within the document.  One for locatable items, one for lost ones
$found = $dom->createElement('Folder');
$found->appendChild($dom->createElement("name", "Earthifyable Listings"));
$doc->appendChild($found);

$lost = $dom->createElement('Folder');
$lost->appendChild($dom->createElement("name", "Un-Earthifyable Listings"));
$lost->appendChild($dom->createElement("description", "Items whose coordinates could not be geocoded."));
$doc->appendChild($lost);

// Loop through all of the listings and add them to the document.
foreach($placemarks as $placemark) {
if($placemark instanceof Placemark) {

// Make the placemark tag in which all of this shit will go.
$placemark_dom = $dom->createElement("Placemark");
$placemark_dom->setAttribute("id", $placemark->getId());

// Make the name tag for the Placemark
$name = $dom->createElement("name", htmlspecialchars($placemark->getTitle()));
$placemark_dom->appendChild($name);

// Make the description tag for the placemark.
$description = $dom->createElement("description");
$cdata = $dom->createCDATASection($placemark->description());
$description->appendChild( $cdata );
$placemark_dom->appendChild($description);

// If we can't find any coordinates, add this item to the "lost" folder.
if($placemark->getCoords()) {
// Make the Point element for the placemark
$point = $dom->createElement("Point");
$coords = $dom->createElement("coordinates", $placemark->getCoords());
$point->appendChild($coords);
$placemark_dom->appendChild($point);

// Add the placemark to the "Found" folder
$found->appendChild($placemark_dom);
} else {
$lost->appendChild($placemark_dom);

}
} else {
trigger_error("KMLSerializer received something that wasn't a Placemark.", E_WARNING);
}
}

return $dom->saveXML();
}

This document is the written portion of my MS defense at Georgia Tech. It is a survey of artworks that use live information sources, and a study of how emerging web technologies can encourage this type of art. Finally, it proposes Switchboard, my library for real-time art, and discusses the design and implementation of it.