google-shortlinks-endpoint.php

<?php
/*
This PHP script will function as a URL Shortening endpoint for Google Apps
Short Links.

Copyright (C) 2010 Matt Martz <matt@sivel.net> (http://sivel.net/)
This program is released under the GNU General Public License version 2
http://www.gnu.org/licenses/gpl-2.0.txt

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
version 2 as published by the Free Software Foundation.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License version 2
along with this program; if not, see <http://www.gnu.org/licenses/gpl-2.0.txt>
*/

/*
Sample requests:
	Hashed shortlink:
		http://s.example.org/google-shortlinks-endpoint.php?url=http://google.com
	Custom shortlink:
		http://s.example.org/google-shortlinks-endpoint.php?url=http://google.com&shortcut=google

Generally a request coming from something like TweetDeck will just be a hashed
shortlink request.

TweetDeck Directions:
 - Click the 'Settings' Button (the wrench icon)
 - Click 'Services'
 - Select 'Other' for the service you wish to use to shorten URLs
 - Enter the URL to google-shortlinks-endpoint.php. ex: http://example.org/google-shortlinks-endpoint.php?url=%@
 - Click 'Save settings' and enjoy!
*/

/* Modify the following 3 variables */
$hostname = 's.example.org'; # The hostname specified for use by Google Apps Short Links
$secret = 'mfkeOkdugagcavTedyupcleqokDodken'; # Your Short Links HMAC secret
$email = 'email@example.org'; # Your email address which is allowed to use the API

/* That's all, stop editing! */

/**
 * Set HTTP status header.
 *
 * Accepts an int and responds with the proper HTTP status header.
 * Code was borowed from a WordPress function of the same name to
 * make this work.
 *
 * @param int $header HTTP status code
 */
function status_header( $header ) {
	switch ( $header ) {
		case 400:
			$text = 'Bad Request';
			break;
		case 500:
			$text = 'Internal Server Error';
			break;
	}

	$protocol = $_SERVER["SERVER_PROTOCOL"];
	if ( 'HTTP/1.1' != $protocol && 'HTTP/1.0' != $protocol )
		$protocol = 'HTTP/1.0';
	header( "$protocol $header $text", true, $header );
	die();
}

// Bail if a URL was not specified
if ( ! isset( $_GET['url'] ) ) {
	status_header( 400 );
}

// Determine if a shortcut name was provied if not we are only creating a random hash
$method = isset( $_GET['shortcut'] ) ? 'get_or_create_shortlink' : 'get_or_create_hash';
$base_url = "http://$hostname/js/$method";

// Build the array of query variables
$args = array(
	'is_public' => 'true',
	'oauth_signature_method' => 'HMAC-SHA1',
	'shortcut' => isset( $_GET['shortcut'] )  ? $_GET['shortcut'] : 'shortlink',
	'timestamp' => time() . '.0',
	'url' => $_GET['url'],
	'user' => $email,
);

// Build the query string from the above array
$query = http_build_query( $args );

// Build the signature base string to be used in creating the OAuth Signature
$signature_base_string = sprintf( "GET&%s&%s", urlencode( $base_url ), urlencode( $query ) );

// Build the OAuth Signature using the above base string and our HMAC secret, using HMAC-SHA1
$signature = urlencode( base64_encode( hash_hmac( 'sha1', $signature_base_string, $secret, true ) ) );

// Build the URL with the base url, query string and auth signature
$url = "$base_url?$query&oauth_signature=$signature";

// Build the cURL request
$request = curl_init( $url );
curl_setopt( $request, CURLOPT_CONNECTTIMEOUT, 5 );
curl_setopt( $request, CURLOPT_HEADER, false );
curl_setopt( $request, CURLOPT_RETURNTRANSFER, true );
curl_setopt( $request, CURLOPT_FOLLOWLOCATION, true );
curl_setopt( $request, CURLOPT_MAXREDIRS, 5 );
curl_setopt( $request, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1 );

// Execute the cURL request
$response = curl_exec( $request );

$http_code = curl_getinfo( $request, CURLINFO_HTTP_CODE );

curl_close( $request );

header( 'Content-Type: text/plain' );

// Send the resultant URL back
if ( $http_code != 200 ) {
	status_header( 500 );
} else {
	$response_decode = json_decode( $response );
	if ( $response_decode->status != 'ok' )
		status_header( 500 );
	echo "http://$hostname/{$response_decode->shortcut}";
}