A bot for App.net that monitors its PMs and replies with a link to a "I'm feeling lucky" search for the text.

bot.php

<?php
/**
 * A bot for App.net that monitors its PMs and replies with a link to a 
 * "I'm feeling lucky" search for the text.
 *
 * @author Simon Welsh (@simon_w)
 * @license WTFPL Version 2 (http://www.wtfpl.net/txt/copying/)
 */

require_once dirname(__FILE__) . '/AppDotNet.php';

// We're going to the user token from dev-lite, so don't need client id/secret set
// since they're not used anywhere else.
$adn = new AppDotNet(null, null);
$adn->includeResponseEnvelope();

$adn->setAccessToken('TOKEN');

while(true) {
	// This makes a request to:
	// https://alpha-api.app.net/stream/0/channels?channel_types=net.app.core.pm&include_marker=1&include_read=0&count=200
	// Which gets all the PM channels we're subscribed to that have unread messages up to 200 channels in total.
	// We also include each channel's stream marker.
	$channels = $adn->getUserSubscriptions(array(
		'channel_types' => 'net.app.core.pm',
		'include_marker' => true,
		'include_read' => false,
		'count' => 200
	));
	handleRateLimit();

	if($channels['data']) {
		foreach($channels['data'] as $channel) {
			// Process channel
			$marker = $channel['marker'];
			$channel_id = $channel['id'];

			// We're only going to want the messages we haven't seen yet. The stream marker tells us
			// which messages we haven't seen yet.
			$last_read_id = null;
			if(isset($marker['last_read_id'])) {
				$last_read_id = $marker['last_read_id'];
			}

			// This makes a request to:
			// https://alpha-api.app.net/stream/0/channels/$channel_id/messages?since_id=$last_read_id&count=5
			$messages = $adn->getMessages($channel_id, array(
				'since_id' => $last_read_id,
				'count' => 5,
			));
			handleRateLimit();

			if($messages['data']) {

				// We store the maximum ID of any message we create so we can update the stream marker
				$max_new_id = 0;

				foreach($messages['data'] as $message) {
					// Process message
					$text = $message['text'];
					// We're going to make the text a link entity, so we should remove #s and @s
					// as a link entity can't contain hashtags or mentions.
					$body = preg_replace('/[#@](\w+)/', '$1', $text);
					$url = 'http://www.google.com/search?hl=en&btnI=I%27m+Feeling+Lucky&pws=0&q=' . rawurlencode($text);

					// We get the multibyte length of the string, as it's UTF8 rather than ASCII.
					// The link entity is going to be the entire text that was given to us
					$entity = array(
						'pos' => 0,
						'len' => mb_strlen($body),
						'url' => $url,
					);

					// Create a new message with our sanitised body and link entity.
					// This is converted to a JSON object and POSTed to:
					// https://alpha-api.app.net/stream/0/channel/$channel_id/messages
					$newMessage = array(
						'text' => $body,
						'entities' => array(
							'links' => array($entity)
						)
					);

					$createdMessage = $adn->createMessage($channel_id, $newMessage);
					handleRateLimit();

					// As it's new, the ID of this message is always going to be greater than the current one
					$max_new_id = $createdMessage['data']['id'];
				}

				if($max_new_id) {
					// We update the stream marker for the channel, which we requested earlier, to be at least
					// the id of the last message we created. This is converted to a JSON object and POSTed to:
					// https://alpha-api.app.net/stream/0/posts/marker
					$adn->updateStreamMarker(array(
						'name' => $marker['name'],
						'id' => $max_new_id,
					));
					handleRateLimit();
				}
			}
		}
	}

	// Sleep for 30 seconds so as to not hammer the API.
	sleep(30);
}

function handleRateLimit() {
	global $adn;
	if($adn->getRateLimitRemaining() == 0) {
		sleep($adn->getRateLimitReset());
	}
}