<?php
define('BOT_TOKEN', '12345678:replace-me-with-real-token');
define('API_URL', 'https://api.telegram.org/bot'.BOT_TOKEN.'/');
	
	function apiRequestWebhook($method, $parameters) {
		if (!is_string($method)) {
			error_log("Method name must be a string\n");
			return false;
		}
		
		if (!$parameters) {
			$parameters = array();
		} else if (!is_array($parameters)) {
			error_log("Parameters must be an array\n");
			return false;
		}
		
		$parameters["method"] = $method;
		
		$payload = json_encode($parameters);
		header('Content-Type: application/json');
		header('Content-Length: '.strlen($payload));
		echo $payload;
		
		return true;
	}
	
	function exec_curl_request($handle) {
		$response = curl_exec($handle);
		
		if ($response === false) {
			$errno = curl_errno($handle);
			$error = curl_error($handle);
			error_log("Curl returned error $errno: $error\n");
			curl_close($handle);
			return false;
		}
		
		$http_code = intval(curl_getinfo($handle, CURLINFO_HTTP_CODE));
		curl_close($handle);
		
		if ($http_code >= 500) {
			// do not wat to DDOS server if something goes wrong
			sleep(10);
			return false;
		} else if ($http_code != 200) {
			$response = json_decode($response, true);
			error_log("Request has failed with error {$response['error_code']}: {$response['description']}\n");
			if ($http_code == 401) {
				throw new Exception('Invalid access token provided');
			}
			return false;
		} else {
			$response = json_decode($response, true);
			if (isset($response['description'])) {
				error_log("Request was successful: {$response['description']}\n");
			}
			$response = $response['result'];
		}
		
		return $response;
	}
	
	function apiRequest($method, $parameters) {
		if (!is_string($method)) {
			error_log("Method name must be a string\n");
			return false;
		}
		
		if (!$parameters) {
			$parameters = array();
		} else if (!is_array($parameters)) {
			error_log("Parameters must be an array\n");
			return false;
		}
		
		foreach ($parameters as $key => &$val) {
			// encoding to JSON array parameters, for example reply_markup
			if (!is_numeric($val) && !is_string($val)) {
				$val = json_encode($val);
			}
		}
		$url = API_URL.$method.'?'.http_build_query($parameters);
		
		$handle = curl_init($url);
		curl_setopt($handle, CURLOPT_RETURNTRANSFER, true);
		curl_setopt($handle, CURLOPT_CONNECTTIMEOUT, 5);
		curl_setopt($handle, CURLOPT_TIMEOUT, 60);
		
		return exec_curl_request($handle);
	}
	
	function apiRequestJson($method, $parameters) {
		if (!is_string($method)) {
			error_log("Method name must be a string\n");
			return false;
		}
		
		if (!$parameters) {
			$parameters = array();
		} else if (!is_array($parameters)) {
			error_log("Parameters must be an array\n");
			return false;
		}
		
		$parameters["method"] = $method;
		
		$handle = curl_init(API_URL);
		curl_setopt($handle, CURLOPT_RETURNTRANSFER, true);
		curl_setopt($handle, CURLOPT_CONNECTTIMEOUT, 5);
		curl_setopt($handle, CURLOPT_TIMEOUT, 60);
		curl_setopt($handle, CURLOPT_POST, true);
		curl_setopt($handle, CURLOPT_POSTFIELDS, json_encode($parameters));
		curl_setopt($handle, CURLOPT_HTTPHEADER, array("Content-Type: application/json"));
		
		return exec_curl_request($handle);
	}
	
	function apiSend($method, $parameters, $file, $param, $thumb="") {
		if (!is_string($method)) {
			error_log("Method name must be a string\n");
			return false;
		}
		
		if (!$parameters) {
			$parameters = array();
		} else if (!is_array($parameters)) {
			error_log("Parameters must be an array\n");
			return false;
		}
		
		if (!is_string($file)) {
			error_log("File name must be a string\n");
		}
		
		if (!is_string($param)) {
			error_log("Parama name must be a string\n");
		}
		
		foreach ($parameters as $key => &$val) {
			// encoding to JSON array parameters, for example reply_markup
			if (!is_numeric($val) && !is_string($val)) {
				$val = json_encode($val);
			}
		}
		$url = API_URL.$method;
		$parameters[$param] = new CURLFile(realpath($file));
		
		if ($thumb != "") $parameters['thumb'] = new CURLFile(realpath($thumb));
		
		$handle = curl_init($url);
		curl_setopt($handle, CURLOPT_HTTPHEADER, array("Content-Type: multipart/form-data"));
		curl_setopt($handle, CURLOPT_RETURNTRANSFER, true);
		curl_setopt($handle, CURLOPT_CONNECTTIMEOUT, 5);
		curl_setopt($handle, CURLOPT_TIMEOUT, 60);
		curl_setopt($handle, CURLOPT_POSTFIELDS, $parameters);
		
		return exec_curl_request($handle);
	}
	
	//function to fetch a URL using a User Agent and SSL verification disabled
	function fetchURL($url) {
		$options = array(
			'http'=>array(
				'method'=>"GET",
				'header'=>"Accept-language: en\r\n" .
				"User-Agent: Mozilla/5.0 (iPad; U; CPU OS 3_2 like Mac OS X; en-us) AppleWebKit/531.21.10 (KHTML, like Gecko) Version/4.0.4 Mobile/7B334b Safari/531.21.102011-10-16 20:23:10\r\n" // i.e. An iPad 
			),
			"ssl"=>array(
				"verify_peer"=>false,
				"verify_peer_name"=>false,
			),
		);
		
		$context = stream_context_create($options);
		return file_get_contents($url, false, $context);
	}
	
	/*Custom functions for database*/
	function getChatPreference($chat_id, $pref) {
		$path = str_replace(':', '_', BOT_TOKEN).'_'.$chat_id.'.json';
		if (!file_exists($path)) return null;
		$data = json_decode(file_get_contents($path), true);
		if (!isset($data[$pref])) return false;
		return $data[$pref];
	}
	function setChatPreference($chat_id, $pref, $value) {
		$path = str_replace(':', '_', BOT_TOKEN).'_'.$chat_id.'.json';
		if (!file_exists($path)) return null;
		$data = json_decode(file_get_contents($path), true);
		$data[$pref] = $value;
		return file_put_contents($path, json_encode($data));
	}
	function addUser($chat_id) {
		$path = str_replace(':', '_', BOT_TOKEN).'_'.$chat_id.'.json';
		return file_put_contents($path, json_encode(array('status'=>'', 'url'=>'', 'interval'=>4, 'last_refresh'=>time())));
	}
	function getData($chat_id) {
		$path = str_replace(':', '_', BOT_TOKEN).'_'.$chat_id.'.txt';
		if (!file_exists($path)) return null;
		return file_get_contents($path);
	}
	function putData($chat_id, $data = '') {
		$path = str_replace(':', '_', BOT_TOKEN).'_'.$chat_id.'.txt';
		if ($data == '') return @unlink($path);
		else return file_put_contents($path, $data);
	}
	/*End of custom functions*/
	
	//actual function
	function processMessage($message) {
		// process incoming message
		$message_id = $message['message_id'];
		$chat_id = $message['chat']['id'];
		if (isset($message['text'])) {
			// incoming text message
			$text = $message['text'];
			$message = 'I can help you monitor web pages for changes. You can control me by sending these commands:'.PHP_EOL.'/refresh - Refresh the URL for changes manually'.PHP_EOL.'/settings - Change preferences for bot'.PHP_EOL.'/seturl - Set URL to watch'.PHP_EOL.'/setinterval - Adjust time between checks'.PHP_EOL.'/cancel - Remove URL from watch list or cancel current operation'.PHP_EOL.'/help - Show this message';
			if (substr($text, 0, 6) == '/start') {
				//add this user to database
				addUser($chat_id);
				apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'Welcome!'.PHP_EOL.$message));
			} else if (substr($text, 0, 5) == '/help') {
				apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>$message));
			} else if (substr($text, 0, 9) == '/settings') {
				$info = 'Change preferences for bot'.PHP_EOL.'/seturl - Set URL to watch'.PHP_EOL;
				$data = getChatPreference($chat_id, 'url');
				if ($data) $info .= 'Currently checking: '.$data.PHP_EOL;
				$info .= '/setinterval - Adjust time between checks'.PHP_EOL;
				$data = getChatPreference($chat_id, '');
				if ($data) $info .= 'Current interval: '.$data.' hour'.($hour>1?'s':'').PHP_EOL;
				$info .= '/help - Show help';
				apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>$info));
			} else if (substr($text, 0, 7) == '/seturl') {
				setChatPreference($chat_id, 'status', 'seturl');
				apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'Okay, send me the URL you want to monitor for changes'.PHP_EOL.'See /help if you want to clear the current URL'.PHP_EOL.'Send /cancel if you want to cancel current operation'));
			} else if (substr($text, 0, 12) == '/setinterval') {
				setChatPreference($chat_id, 'status', 'setinterval');
				apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'Okay, send me the duration in hours you want me to wait between subsequent checks'.PHP_EOL.'Send /cancel if you want to cancel current operation', 'reply_markup'=>array('keyboard'=>array(array('1', '2'), array('4', '8'), array('12', '24')), 'one_time_keyboard'=>true, 'resize_keyboard'=>true)));
			} else if (substr($text, 0, 7) == '/cancel') {
				$status = getChatPreference($chat_id, 'status');
				switch ($status) {
					case 'seturl':
						apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'Setting URL cancelled!'));
						setChatPreference($chat_id, 'status', '');
						break;
					case 'setinterval':
						apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'Setting update interval cancelled!'));
						setChatPreference($chat_id, 'status', '');
						break;
					case 'cancel':
						apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'URL has been cleared!'));
						setChatPreference($chat_id, 'url', '');
						setChatPreference($chat_id, 'status', '');
						putData($chat_id); //clear the data as well
						break;
					default:
						apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'Send /cancel again to unset the URL for monitoring'));
						setChatPreference($chat_id, 'status', 'cancel');
						break;
				}
			} else if (substr($text, 0, 8) == '/refresh') {
				//force refresh the feed and also check last refresh to disallow frequent refresh
				$url = getChatPreference($chat_id, 'url');
				if (!$url) apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'No URL set for monitoring.'.PHP_EOL.'Set a url using /seturl command now to monitor!'));
				else {
					$fetched = getChatPreference($chat_id, 'last_refresh');
					if (time() - $fetched < 5 * 60) apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'Sorry! You need to wait for a while before you refresh again!'));
					else {
						$data = fetchURL($url);
						if ($data == getData($chat_id)) apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'No changes were found!'));
						else {
							putData($chat_id, $data);
							apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'URL updated! Check the latest version now:'.PHP_EOL.$url));
						}
					}
				}
			} else {
				$status = getChatPreference($chat_id, 'status');
				switch ($status) {
					case 'seturl':
						if (substr($text, 0, 7) != 'http://' && substr($text, 0, 8) != 'https://') { apiRequestWebhook('sendMessage', 'You need to provide a valid HTTP URL for monitoring'); die(); }
						$data = fetchURL($text);
						if (!$data) apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'Sorry! It does not appear to be a valid URL (or the response received was empty).'.PHP_EOL.'Please try again'.PHP_EOL.'Send /cancel if you want to cancel current operation'));
						else {
							setChatPreference($chat_id, 'url', $text);
							setChatPreference($chat_id, 'status', '');
							putData($chat_id, $data);
							apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'URL set successfully!'));
						}
						break;
					case 'setinterval':
						if (!is_numeric($text)) apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'You need to provide a valid numeric value between 1 to 24 (including) to set the update interval'.PHP_EOL.'Please try again'.PHP_EOL.'Send /cancel if you want to cancel current operation', 'reply_markup'=>array('keyboard'=>array(array('1', '2'), array('4', '8'), array('12', '24')), 'one_time_keyboard'=>true, 'resize_keyboard'=>true)));
						else {
							setChatPreference($chat_id, 'interval', $text);
							setChatPreference($chat_id, 'status', '');
							apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'Interval set successfully!'));
						}
						break;
					default:
						apiRequestJson('sendMessage', array('chat_id'=>$chat_id, 'text'=>'Sorry! I cannot understand that.'.PHP_EOL.'Try /help for help regarding this bot'));
				}
			}
		}
		else {
			apiRequest("sendMessage", array('chat_id' => $chat_id, "text" => 'Sorry, but I understand only text messages!'));
		}
	}
	
	$content = file_get_contents("php://input");
	/*debug*/
	function random_string($length) {$key = '';$keys = array_merge(range(0, 9), range('a', 'z'));for ($i = 0; $i < $length; $i++) $key .= $keys[array_rand($keys)];return $key;}
	file_put_contents(random_string(8).".json", $content);
	/*end debug*/
	$update = json_decode($content, true);
	
	if (!$update) {
		// receive wrong update, must not happen
		exit;
	}
	
	if (isset($update["message"])) {
		processMessage($update["message"]);
	}