I wanted to interface with GroupMe and I was hoping they have an API. Not only is there an API but they have an entire system for making Bots.

In one group I’m a part of, the members kept changing their names and it was hard to keep track who really was who.

This bot has no memory, thus when it sees someone change their name it will download all the messages ever posted then process who’s who. The group I tested this on had 2500+ messages, which takes about 5-10 seconds to process. For larger groups, and as smaller groups continue, it would be best to cache messages instead of re-lookup all past messages.

<?php

$group_id = 'YOUR_GROUP_ID_THE_BOT_IS_ASSIGNED_TO';
$token = 'YOUR_TOKEN';
$bot_id = 'YOUR_BOT_ID';

$data = json_decode(file_get_contents('php://input'));

if($data != null){
	if($data->system != true){
		exit;
	}
	if(strpos($data->text, 'changed name') === false){
		exit;
	}
	
	preg_match('/(.+?) changed name to (.+)/', $data->text, $matches);
	$new_name_change = $matches[2];
}


// download all the messages
$url_base = "https://api.groupme.com/v3/groups/".$group_id."/messages?token=".$token."&limit=100&";
$before_id = '';
$messages = array();

do {
	if($before_id != ''){
		$url = $url_base.'before_id='.$before_id;
	} else {
		$url = $url_base;
	}
	
	$response = json_decode(file_get_contents($url));
	if(empty($response)){
		// no response, no results
		break;
	}
	$response = $response->response;
	
	$count = $response->count;
	$messagesNew = $response->messages;
	$messages = array_merge($messages, $messagesNew);
	
	$before_id = end($messagesNew)->id;
} while($count > 0);

// sort only the system messages for name changes
$system = array();
$system_all = array();
foreach($messages as $message){
	if($message->system == true){
		$system_all[$message->created_at] = $message->text;
		if(strpos($message->text, 'changed name') !== false){
			$system[$message->created_at] = $message->text;
		}
	}
}

// build maps
$system = array_reverse($system);

// overrides
$overrides = array(
	// 'correct real name' => 'name when joined'
);

$map = $overrides;
foreach($system as $change){
	preg_match('/(.+?) changed name to (.+)/', $change, $matches);
	$orig = $matches[1];
	$new = $matches[2];

	if(in_array($orig, array_values($map))){
		$keys = array_keys($map, $orig);
		$key = $keys[0];
		$map[$key] = $new;
		
		if($key == $new){
			unset($map[$key]);
		}
		continue;
	}

	if(!isset($map[$orig])){
		$map[$orig] = $new;
		continue;
	}
}

if(!empty($new_name_change)){
	$keys = array_keys($map, $new_name_change);
	if(empty($keys)){
		// user changed their name back to their real name
		exit;	
	}
	$name = $keys[0];
	
	// build url
	$message = urlencode($new_name_change.'\'s real name is '.$name);
	$url = 'https://api.groupme.com/v3/bots/post?bot_id='.$bot_id.'&text='.$message;//.'&token='.$token;
	
	// send message
	$ch = curl_init();
	curl_setopt($ch, CURLOPT_URL, $url);
	curl_setopt($ch, CURLOPT_POST, true);
	curl_setopt($ch, CURLOPT_POSTFIELDS, array());
	curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
	$result = curl_exec($ch);
}

?>