<?php
// vim: foldmethod=marker

/* Generic exception class
 */
if (!class_exists('OAuthExceptionChat')) {
	class OAuthExceptionChat extends Exception {
  		// pass
	}
}

if (!class_exists('OAuthConsumerChat')) {
	class OAuthConsumerChat {
  		public $key;
  		public $secret;

  		function __construct($key, $secret, $callback_url=NULL) {
    		$this->key = $key;
    		$this->secret = $secret;
    		$this->callback_url = $callback_url;
  		}

  		function __toString() {
    		return "OAuthConsumer[key=$this->key,secret=$this->secret]";
  		}
	}
}

if (!class_exists('OAuthTokenChat')) {
	class OAuthTokenChat {
  		// access tokens and request tokens
  		public $key;
  		public $secret;

  		/**
   		* key = the token
   		* secret = the token secret
   		*/
  		function __construct($key, $secret) {
    		$this->key = $key;
    		$this->secret = $secret;
  		}

  		/**
   		* generates the basic string serialization of a token that a server
   		* would respond to request_token and access_token calls with
   		*/
  		function to_string() {
    		return "oauth_token=" .
           		OAuthUtilChat::urlencode_rfc3986($this->key) .
           		"&oauth_token_secret=" .
           		OAuthUtilChat::urlencode_rfc3986($this->secret);
  		}

  		function __toString() {
    		return $this->to_string();
  		}
	}
}

/**
 * A class for implementing a Signature Method
 * See section 9 ("Signing Requests") in the spec
 */
if (!class_exists('OAuthSignatureMethodChat')) {
	abstract class OAuthSignatureMethodChat {
  		/**
   		* Needs to return the name of the Signature Method (ie HMAC-SHA1)
   		* @return string
   		*/
  		abstract public function get_name();

  		/**
   		* Build up the signature
   		* NOTE: The output of this function MUST NOT be urlencoded.
   		* the encoding is handled in OAuthRequest when the final
   		* request is serialized
   		* @param OAuthRequest $request
   		* @param OAuthConsumer $consumer
   		* @param OAuthToken $token
   		* @return string
   		*/
  		abstract public function build_signature($request, $consumer, $token);

  		/**
   		* Verifies that a given signature is correct
   		* @param OAuthRequest $request
   		* @param OAuthConsumer $consumer
   		* @param OAuthToken $token
   		* @param string $signature
   		* @return bool
   		*/
  		public function check_signature($request, $consumer, $token, $signature) {
    		$built = $this->build_signature($request, $consumer, $token);
    		return $built == $signature;
  		}
	}
}

/**
	* The HMAC-SHA1 signature method uses the HMAC-SHA1 signature algorithm as defined in [RFC2104]
	* where the Signature Base String is the text and the key is the concatenated values (each first
	* encoded per Parameter Encoding) of the Consumer Secret and Token Secret, separated by an '&'
	* character (ASCII code 38) even if empty.
	*   - Chapter 9.2 ("HMAC-SHA1")
	*/
if (!class_exists('OAuthSignatureMethodChat_HMAC_SHA1')) {
	class OAuthSignatureMethodChat_HMAC_SHA1 extends OAuthSignatureMethodChat {
 		function get_name() {
   			return "HMAC-SHA1";
 		}

  		public function build_signature($request, $consumer, $token) {
    		$base_string = $request->get_signature_base_string();
    		$request->base_string = $base_string;

    		$key_parts = array(
      			$consumer->secret,
      			($token) ? $token->secret : ""
    		);

    		$key_parts = OAuthUtilChat::urlencode_rfc3986($key_parts);
    		$key = implode('&', $key_parts);

    		return base64_encode(hash_hmac('sha1', $base_string, $key, true));
  		}
	}
}

/**
 * The PLAINTEXT method does not provide any security protection and SHOULD only be used
 * over a secure channel such as HTTPS. It does not use the Signature Base String.
 *   - Chapter 9.4 ("PLAINTEXT")
 */
if (!class_exists('OAuthSignatureMethodChat_PLAINTEXT')) {
	class OAuthSignatureMethodChat_PLAINTEXT extends OAuthSignatureMethodChat {
  		public function get_name() {
    		return "PLAINTEXT";
  		}

  		/**
   		* oauth_signature is set to the concatenated encoded values of the Consumer Secret and
   		* Token Secret, separated by a '&' character (ASCII code 38), even if either secret is
   		* empty. The result MUST be encoded again.
   		*   - Chapter 9.4.1 ("Generating Signatures")
   		*
   		* Please note that the second encoding MUST NOT happen in the SignatureMethod, as
   		* OAuthRequest handles this!
   		*/
  		public function build_signature($request, $consumer, $token) {
    		$key_parts = array(
      			$consumer->secret,
      			($token) ? $token->secret : ""
    		);

    		$key_parts = OAuthUtilChat::urlencode_rfc3986($key_parts);
    		$key = implode('&', $key_parts);
    		$request->base_string = $key;

    		return $key;
  		}
	}
}

/**
 * The RSA-SHA1 signature method uses the RSASSA-PKCS1-v1_5 signature algorithm as defined in
 * [RFC3447] section 8.2 (more simply known as PKCS#1), using SHA-1 as the hash function for
 * EMSA-PKCS1-v1_5. It is assumed that the Consumer has provided its RSA public key in a
 * verified way to the Service Provider, in a manner which is beyond the scope of this
 * specification.
 *   - Chapter 9.3 ("RSA-SHA1")
 */
if (!class_exists('OAuthSignatureMethodChat_RSA_SHA1')) {
	abstract class OAuthSignatureMethodChat_RSA_SHA1 extends OAuthSignatureMethodChat {
  		public function get_name() {
    		return "RSA-SHA1";
  		}

  		// Up to the SP to implement this lookup of keys. Possible ideas are:
  		// (1) do a lookup in a table of trusted certs keyed off of consumer
  		// (2) fetch via http using a url provided by the requester
  		// (3) some sort of specific discovery code based on request
  		//
  		// Either way should return a string representation of the certificate
  		protected abstract function fetch_public_cert(&$request);

  		// Up to the SP to implement this lookup of keys. Possible ideas are:
  		// (1) do a lookup in a table of trusted certs keyed off of consumer
  		//
  		// Either way should return a string representation of the certificate
  		protected abstract function fetch_private_cert(&$request);

  		public function build_signature($request, $consumer, $token) {
    		$base_string = $request->get_signature_base_string();
    		$request->base_string = $base_string;

    		// Fetch the private key cert based on the request
    		$cert = $this->fetch_private_cert($request);

    		// Pull the private key ID from the certificate
    		$privatekeyid = openssl_get_privatekey($cert);

    		// Sign using the key
    		$ok = openssl_sign($base_string, $signature, $privatekeyid);

    		// Release the key resource
    		openssl_free_key($privatekeyid);

    		return base64_encode($signature);
  		}

  		public function check_signature($request, $consumer, $token, $signature) {
    		$decoded_sig = base64_decode($signature);

    		$base_string = $request->get_signature_base_string();

    		// Fetch the public key cert based on the request
    		$cert = $this->fetch_public_cert($request);

    		// Pull the public key ID from the certificate
    		$publickeyid = openssl_get_publickey($cert);

    		// Check the computed signature against the one passed in the query
    		$ok = openssl_verify($base_string, $decoded_sig, $publickeyid);

    		// Release the key resource
    		openssl_free_key($publickeyid);

    		return $ok == 1;
  		}
	}
}

if (!class_exists('OAuthRequestChat')) {
	class OAuthRequestChat {
  		private $parameters;
  		private $http_method;
  		private $http_url;
  		// for debug purposes
  		public $base_string;
  		public static $version = '1.0';
  		public static $POST_INPUT = 'php://input';

  		function __construct($http_method, $http_url, $parameters=NULL) {
    		@$parameters or $parameters = array();
    		$parameters = array_merge( OAuthUtilChat::parse_parameters(parse_url($http_url, PHP_URL_QUERY)), $parameters);
    		$this->parameters = $parameters;
    		$this->http_method = $http_method;
    		$this->http_url = $http_url;
  		}


  		/**
   		* attempt to build up a request from what was passed to the server
   		*/
  		public static function from_request($http_method=NULL, $http_url=NULL, $parameters=NULL) {
    		$scheme = (!isset($_SERVER['HTTPS']) || $_SERVER['HTTPS'] != "on")
              	? 'http'
              	: 'https';
    		@$http_url or $http_url = $scheme .
                              '://' . $_SERVER['HTTP_HOST'] .
                              ':' .
                              $_SERVER['SERVER_PORT'] .
                              $_SERVER['REQUEST_URI'];

			@$http_method or $http_method = $_SERVER['REQUEST_METHOD'];

    		// We weren't handed any parameters, so let's find the ones relevant to
    		// this request.
    		// If you run XML-RPC or similar you should use this to provide your own
    		// parsed parameter-list
    		if (!$parameters) {
      			// Find request headers
      			$request_headers = OAuthUtilChat::get_headers();

      			// Parse the query-string to find GET parameters
      			$parameters = OAuthUtilChat::parse_parameters($_SERVER['QUERY_STRING']);

      			// It's a POST request of the proper content-type, so parse POST
      			// parameters and add those overriding any duplicates from GET
      			if ($http_method == "POST" && @strstr($request_headers["Content-Type"], "application/x-www-form-urlencoded")) {
        			$post_data = OAuthUtilChat::parse_parameters(file_get_contents(self::$POST_INPUT));
        			$parameters = array_merge($parameters, $post_data);
      			}

      			// We have a Authorization-header with OAuth data. Parse the header
      			// and add those overriding any duplicates from GET or POST
      			if (@substr($request_headers['Authorization'], 0, 6) == "OAuth ") {
        			$header_parameters = OAuthUtilChat::split_header($request_headers['Authorization']);
        			$parameters = array_merge($parameters, $header_parameters);
      			}

    		}

    		return new OAuthRequestChat($http_method, $http_url, $parameters);
  		}


  		/**
   		* pretty much a helper function to set up the request
   		*/
  		public static function from_consumer_and_token($consumer, $token, $http_method, $http_url, $parameters=NULL) {
    		@$parameters or $parameters = array();
    		$defaults = array("oauth_version" => OAuthRequestChat::$version,
                      "oauth_nonce" => OAuthRequestChat::generate_nonce(),
                      "oauth_timestamp" => OAuthRequestChat::generate_timestamp(),
                      "oauth_consumer_key" => $consumer->key);
    		if ($token)
      			$defaults['oauth_token'] = $token->key;

    		$parameters = array_merge($defaults, $parameters);

    		return new OAuthRequestChat($http_method, $http_url, $parameters);
  		}

  		public function set_parameter($name, $value, $allow_duplicates = true) {
    		if ($allow_duplicates && isset($this->parameters[$name])) {
      			// We have already added parameter(s) with this name, so add to the list
      			if (is_scalar($this->parameters[$name])) {
        			// This is the first duplicate, so transform scalar (string)
        			// into an array so we can add the duplicates
        			$this->parameters[$name] = array($this->parameters[$name]);
      			}

      			$this->parameters[$name][] = $value;
    		} else {
      			$this->parameters[$name] = $value;
    		}
  		}

  		public function get_parameter($name) {
    		return isset($this->parameters[$name]) ? $this->parameters[$name] : null;
  		}

  		public function get_parameters() {
    		return $this->parameters;
  		}

  		public function unset_parameter($name) {
    		unset($this->parameters[$name]);
  		}

  		/**
   		* The request parameters, sorted and concatenated into a normalized string.
   		* @return string
   		*/
  		public function get_signable_parameters() {
    		// Grab all parameters
    		$params = $this->parameters;

    		// Remove oauth_signature if present
    		// Ref: Spec: 9.1.1 ("The oauth_signature parameter MUST be excluded.")
    		if (isset($params['oauth_signature'])) {
      			unset($params['oauth_signature']);
    		}

    		return OAuthUtilChat::build_http_query($params);
  		}

  		/**
   		* Returns the base string of this request
   		*
   		* The base string defined as the method, the url
   		* and the parameters (normalized), each urlencoded
   		* and the concated with &.
   		*/
  		public function get_signature_base_string() {
    		$parts = array(
      			$this->get_normalized_http_method(),
      			$this->get_normalized_http_url(),
      			$this->get_signable_parameters()
    		);

    		$parts = OAuthUtilChat::urlencode_rfc3986($parts);

    		return implode('&', $parts);
  		}

  		/**
   		* just uppercases the http method
   		*/
  		public function get_normalized_http_method() {
    		return strtoupper($this->http_method);
  		}

  		/**
   		* parses the url and rebuilds it to be
   		* scheme://host/path
   		*/
  		public function get_normalized_http_url() {
    		$parts = parse_url($this->http_url);

    		$port = @$parts['port'];
    		$scheme = $parts['scheme'];
    		$host = $parts['host'];
    		$path = @$parts['path'];

    		$port or $port = ($scheme == 'https') ? '443' : '80';

    		if (($scheme == 'https' && $port != '443')
        		|| ($scheme == 'http' && $port != '80')) {
      				$host = "$host:$port";
    		}
    		return "$scheme://$host$path";
  		}

  		/**
   		* builds a url usable for a GET request
   		*/
  		public function to_url() {
    		$post_data = $this->to_postdata();
    		$out = $this->get_normalized_http_url();
    		if ($post_data) {
      			$out .= '?'.$post_data;
    		}
    		return $out;
  		}

  		/**
   		* builds the data one would send in a POST request
   		*/
  		public function to_postdata() {
    		return OAuthUtilChat::build_http_query($this->parameters);
  		}

  		/**
   		* builds the Authorization: header
   		*/
  		public function to_header($realm=null) {
    		$first = true;
			if($realm) {
      			$out = 'Authorization: OAuth realm="' . OAuthUtilChat::urlencode_rfc3986($realm) . '"';
      			$first = false;
    		} else
      			$out = 'Authorization: OAuth';

    		$total = array();
    		foreach ($this->parameters as $k => $v) {
      			if (substr($k, 0, 5) != "oauth") continue;
      			if (is_array($v)) {
        			throw new OAuthExceptionChat('Arrays not supported in headers');
      			}
      			$out .= ($first) ? ' ' : ',';
      			$out .= OAuthUtilChat::urlencode_rfc3986($k) .
              		'="' .
              		OAuthUtilChat::urlencode_rfc3986($v) .
              		'"';
      			$first = false;
    		}
    		return $out;
  		}

  		public function __toString() {
    		return $this->to_url();
  		}


  		public function sign_request($signature_method, $consumer, $token) {
    		$this->set_parameter("oauth_signature_method", $signature_method->get_name(), false);
    		$signature = $this->build_signature($signature_method, $consumer, $token);
    		$this->set_parameter("oauth_signature", $signature, false);
  		}

  		public function build_signature($signature_method, $consumer, $token) {
    		$signature = $signature_method->build_signature($this, $consumer, $token);
    		return $signature;
  		}

  		/**
   		* util function: current timestamp
   		*/
  		private static function generate_timestamp() {
    		return time();
  		}

  		/**
   		* util function: current nonce
   		*/
  		private static function generate_nonce() {
    		$mt = microtime();
    		$rand = mt_rand();

    		return md5($mt . $rand); // md5s look nicer than numbers
  		}
	}
}

if (!class_exists('OAuthServerChat')) {
	class OAuthServerChat {
  		protected $timestamp_threshold = 300; // in seconds, five minutes
  		protected $version = '1.0';             // hi blaine
  		protected $signature_methods = array();

  		protected $data_store;

  		function __construct($data_store) {
    		$this->data_store = $data_store;
  		}

  		public function add_signature_method($signature_method) {
    		$this->signature_methods[$signature_method->get_name()] =
      			$signature_method;
  		}

  		// high level functions

  		/**
   		* process a request_token request
   		* returns the request token on success
   		*/
  		public function fetch_request_token(&$request) {
    		$this->get_version($request);

    		$consumer = $this->get_consumer($request);

    		// no token required for the initial token request
    		$token = NULL;

    		$this->check_signature($request, $consumer, $token);

    		// Rev A change
    		$callback = $request->get_parameter('oauth_callback');
    		$new_token = $this->data_store->new_request_token($consumer, $callback);

    		return $new_token;
  		}

  		/**
   		* process an access_token request
   		* returns the access token on success
   		*/
  		public function fetch_access_token(&$request) {
    		$this->get_version($request);

    		$consumer = $this->get_consumer($request);

    		// requires authorized request token
    		$token = $this->get_token($request, $consumer, "request");

    		$this->check_signature($request, $consumer, $token);

    		// Rev A change
    		$verifier = $request->get_parameter('oauth_verifier');
    		$new_token = $this->data_store->new_access_token($token, $consumer, $verifier);

    		return $new_token;
  		}

  		/**
   		* verify an api call, checks all the parameters
   		*/
  		public function verify_request(&$request) {
    		$this->get_version($request);
    		$consumer = $this->get_consumer($request);
    		$token = $this->get_token($request, $consumer, "access");
    		$this->check_signature($request, $consumer, $token);
    		return array($consumer, $token);
  		}

  		// Internals from here
  		/**
   		* version 1
   		*/
  		private function get_version(&$request) {
    		$version = $request->get_parameter("oauth_version");
    		if (!$version) {
      			// Service Providers MUST assume the protocol version to be 1.0 if this parameter is not present.
      			// Chapter 7.0 ("Accessing Protected Ressources")
      			$version = '1.0';
    		}
    		if ($version !== $this->version) {
      			throw new OAuthExceptionChat("OAuth version '$version' not supported");
    		}
    		return $version;
  		}

  		/**
   		* figure out the signature with some defaults
   		*/
  		private function get_signature_method(&$request) {
    		$signature_method = @$request->get_parameter("oauth_signature_method");

    		if (!$signature_method) {
      			// According to chapter 7 ("Accessing Protected Ressources") the signature-method
      			// parameter is required, and we can't just fallback to PLAINTEXT
      			throw new OAuthExceptionChat('No signature method parameter. This parameter is required');
    		}

    		if (!in_array($signature_method, array_keys($this->signature_methods))) {
     			throw new OAuthExceptionChat(
       				"Signature method '$signature_method' not supported " .
       				"try one of the following: " .
       				implode(", ", array_keys($this->signature_methods))
     				);
    		}
    		return $this->signature_methods[$signature_method];
  		}

  		/**
   		* try to find the consumer for the provided request's consumer key
   		*/
  		private function get_consumer(&$request) {
    		$consumer_key = @$request->get_parameter("oauth_consumer_key");
    		if (!$consumer_key) {
      			throw new OAuthExceptionChat("Invalid consumer key");
    		}

    		$consumer = $this->data_store->lookup_consumer($consumer_key);
    		if (!$consumer) {
      			throw new OAuthExceptionChat("Invalid consumer");
    		}

    		return $consumer;
  		}

  		/**
   		* try to find the token for the provided request's token key
   		*/
  		private function get_token(&$request, $consumer, $token_type="access") {
    		$token_field = @$request->get_parameter('oauth_token');
			$token = $this->data_store->lookup_token($consumer, $token_type, $token_field);
    		if (!$token) {
      			throw new OAuthExceptionChat("Invalid $token_type token: $token_field");
    		}
    		return $token;
  		}

  		/**
   		* all-in-one function to check the signature on a request
   		* should guess the signature method appropriately
   		*/
  		private function check_signature(&$request, $consumer, $token) {
    		// this should probably be in a different method
    		$timestamp = @$request->get_parameter('oauth_timestamp');
    		$nonce = @$request->get_parameter('oauth_nonce');

    		$this->check_timestamp($timestamp);
    		$this->check_nonce($consumer, $token, $nonce, $timestamp);

    		$signature_method = $this->get_signature_method($request);

    		$signature = $request->get_parameter('oauth_signature');
    		$valid_sig = $signature_method->check_signature($request, $consumer, $token, $signature);

    		if (!$valid_sig) {
      			throw new OAuthExceptionChat("Invalid signature");
    		}
  		}

  		/**
   		* check that the timestamp is new enough
   		*/
  		private function check_timestamp($timestamp) {
    		if( ! $timestamp )
      			throw new OAuthExceptionChat('Missing timestamp parameter. The parameter is required');

    		// verify that timestamp is recentish
    		$now = time();
    		if (abs($now - $timestamp) > $this->timestamp_threshold) {
      			throw new OAuthExceptionChat("Expired timestamp, yours $timestamp, ours $now");
    		}
  		}

  		/**
   		* check that the nonce is not repeated
   		*/
  		private function check_nonce($consumer, $token, $nonce, $timestamp) {
    		if( ! $nonce )
      			throw new OAuthExceptionChat(
        	'Missing nonce parameter. The parameter is required'
      		);

    		// verify that the nonce is uniqueish
    		$found = $this->data_store->lookup_nonce(
      		$consumer,
      		$token,
      		$nonce,
      		$timestamp
    		);
    		if ($found) {
      			throw new OAuthExceptionChat("Nonce already used: $nonce");
    		}
  		}
	}
}

if (!class_exists('OAuthDataStore')) {
	class OAuthDataStore {
  		function lookup_consumer($consumer_key) {
    		// implement me
  		}

  		function lookup_token($consumer, $token_type, $token) {
    		// implement me
  		}

  		function lookup_nonce($consumer, $token, $nonce, $timestamp) {
    		// implement me
  		}

  		function new_request_token($consumer, $callback = null) {
    		// return a new token attached to this consumer
  		}

  		function new_access_token($token, $consumer, $verifier = null) {
    		// return a new access token attached to this consumer
    		// for the user associated with this token if the request token
    		// is authorized
    		// should also invalidate the request token
  		}
	}
}

if (!class_exists('OAuthUtilChat')) {
	class OAuthUtilChat {
  		public static function urlencode_rfc3986($input) {
  			if (is_array($input)) {
    			return array_map(array('OAuthUtilChat', 'urlencode_rfc3986'), $input);
  			} else if (is_scalar($input)) {
    			return str_replace('+', ' ', str_replace('%7E', '~', rawurlencode($input)));
  			} else {
    			return '';
  			}
		}


  		// This decode function isn't taking into consideration the above
  		// modifications to the encoding process. However, this method doesn't
  		// seem to be used anywhere so leaving it as is.
  		public static function urldecode_rfc3986($string) {
    		return urldecode($string);
  		}

  		// Utility function for turning the Authorization: header into
  		// parameters, has to do some unescaping
  		// Can filter out any non-oauth parameters if needed (default behaviour)
  		public static function split_header($header, $only_allow_oauth_parameters = true) {
    		$pattern = '/(([-_a-z]*)=("([^"]*)"|([^,]*)),?)/';
    		$offset = 0;
    		$params = array();

    		while (preg_match($pattern, $header, $matches, PREG_OFFSET_CAPTURE, $offset) > 0) {
      			$match = $matches[0];
      			$header_name = $matches[2][0];
      			$header_content = (isset($matches[5])) ? $matches[5][0] : $matches[4][0];
      			if (preg_match('/^oauth_/', $header_name) || !$only_allow_oauth_parameters) {
        			$params[$header_name] = OAuthUtilChat::urldecode_rfc3986($header_content);
      			}
      			$offset = $match[1] + strlen($match[0]);
    		}

    		if (isset($params['realm'])) {
      			unset($params['realm']);
    		}

    		return $params;
  		}

  		// helper to try to sort out headers for people who aren't running apache
  		public static function get_headers() {
    		if (function_exists('apache_request_headers')) {
      			// we need this to get the actual Authorization: header
      			// because apache tends to tell us it doesn't exist
      			$headers = apache_request_headers();

      			// sanitize the output of apache_request_headers because
      			// we always want the keys to be Cased-Like-This and arh()
      			// returns the headers in the same case as they are in the
      			// request
      			$out = array();
      			foreach( $headers AS $key => $value ) {
        			$key = str_replace(" ", "-", ucwords(strtolower(str_replace("-", " ", $key))));
        			$out[$key] = $value;
      			}
    		} else {
      			// otherwise we don't have apache and are just going to have to hope
      			// that $_SERVER actually contains what we need
      			$out = array();
      			if( isset($_SERVER['CONTENT_TYPE']) )
        			$out['Content-Type'] = $_SERVER['CONTENT_TYPE'];
      			if( isset($_ENV['CONTENT_TYPE']) )
        			$out['Content-Type'] = $_ENV['CONTENT_TYPE'];

      			foreach ($_SERVER as $key => $value) {
        			if (substr($key, 0, 5) == "HTTP_") {
          				// this is chaos, basically it is just there to capitalize the first
          				// letter of every word that is not an initial HTTP and strip HTTP
          				// code from przemek
          				$key = str_replace(" ", "-", ucwords(strtolower(str_replace("_", " ", substr($key, 5)))));
          				$out[$key] = $value;
        			}
      			}
    		}
    		return $out;
  		}

  		// This function takes a input like a=b&a=c&d=e and returns the parsed
  		// parameters like this
  		// array('a' => array('b','c'), 'd' => 'e')
  		public static function parse_parameters( $input ) {
    		if (!isset($input) || !$input) return array();

    		$pairs = explode('&', $input);

    		$parsed_parameters = array();
    		foreach ($pairs as $pair) {
      			$split = explode('=', $pair, 2);
      			$parameter = OAuthUtilChat::urldecode_rfc3986($split[0]);
      			$value = isset($split[1]) ? OAuthUtilChat::urldecode_rfc3986($split[1]) : '';

      			if (isset($parsed_parameters[$parameter])) {
        			// We have already recieved parameter(s) with this name, so add to the list
        			// of parameters with this name

        			if (is_scalar($parsed_parameters[$parameter])) {
          				// This is the first duplicate, so transform scalar (string) into an array
          				// so we can add the duplicates
          				$parsed_parameters[$parameter] = array($parsed_parameters[$parameter]);
        			}

        			$parsed_parameters[$parameter][] = $value;
      			} else {
        			$parsed_parameters[$parameter] = $value;
      			}
    		}
    		return $parsed_parameters;
  		}

  		public static function build_http_query($params) {
    		if (!$params) return '';

    		// Urlencode both keys and values
    		$keys = OAuthUtilChat::urlencode_rfc3986(array_keys($params));
    		$values = OAuthUtilChat::urlencode_rfc3986(array_values($params));
    		$params = array_combine($keys, $values);

    		// Parameters are sorted by name, using lexicographical byte value ordering.
    		// Ref: Spec: 9.1.1 (1)
    		uksort($params, 'strcmp');

    		$pairs = array();
    		foreach ($params as $parameter => $value) {
      			if (is_array($value)) {
        			// If two or more parameters share the same name, they are sorted by their value
        			// Ref: Spec: 9.1.1 (1)
        			natsort($value);
        			foreach ($value as $duplicate_value) {
          				$pairs[] = $parameter . '=' . $duplicate_value;
        			}
      			} else {
        			$pairs[] = $parameter . '=' . $value;
      			}
    		}
    		// For each parameter, the name is separated from the corresponding value by an '=' character (ASCII code 61)
    		// Each name-value pair is separated by an '&' character (ASCII code 38)
    		return implode('&', $pairs);
  		}
	}
}