<?php

/**
 * Namespace for Valve RCON related classes and functions.
 * @package NAE\Valve\Rcon
 */
namespace NAE\Valve\Rcon;

/**
 * A Class to interact with a Valve RCON server.
 * @author "Marcel Naeve" <php@naeve.info>
 * @license MIT License (http://www.opensource.org/licenses/mit)
 */
class ValveRcon {

    /**
     * @var string IP address of the RCON server
     */
    private $ip;

    /**
     * @var int Port number of the RCON server
     */
    private $port;

    /**
     * @var string Password to authenticate with the RCON server
     */
    private $password;

    /**
     * @var int Timeout for socket operations in seconds
     */
    private $timeout;

    /**
     * @var resource Socket resource for RCON communication
     */
    private $socket;

    /**
     * @var array Error details if any occurs during communication
     */
    private $err;

    /**
     * Constructor, setting variables.
     * @param string $ip IP address of the RCON server
     * @param int $port Port number of the RCON server
     * @param string $password Password to authenticate with the RCON server
     * @param int $timeout Timeout for socket operations in seconds (default: 2 seconds)
     */
    public function __construct(string $ip, int $port, string $password, int $timeout=2) {
        $this->ip = $ip;
        $this->port = $port;
        $this->password = $password;
        $this->timeout = $timeout;
    }

    /**
     * Establishes a connection to the RCON server.
     * @return bool Connection established successfully?
     */
    private function connect() : bool {

        // prepare variables for error handling
        $errno = null;
        $errmsg = "";

        $this->socket = fsockopen(  // connect to RCON server
            "udp://{$this->ip}",
            $this->port,
            $errno,
            $errmsg,
            $this->timeout
        );

        if(!$this->socket) { // connection failed?
            $this->err = [
                "code" => $errno,
                "message" => "Socket connection failed: $errmsg"
            ];
            return false;
        }

        return true;

    }

    /**
     * Closes the connection to the RCON server
     */
    private function disconnect() : void {
        
        if ( $this->isConnected() ) {
            fclose($this->socket);
            $this->socket = NULL;
        }
       
    }

    /**
     * Checks if the connection to the RCON server is established.
     */
    private function isConnected() : bool {

        return ( get_resource_type($this->socket) !== null ); // check if socket is resource type, as it should be

    }

    /**
     * Receives data from the RCON server.
     * @return string|null Received data or null if no data is available
     */
    private function read() : ?string {
        
        if (!$this->isConnected()) {
            return null;
        }                              
        
        stream_set_timeout($this->socket, 0, $this->timeout * 100000);  // set timeout
        
        $response = '';
        while ($buffer = fread($this->socket, 4096)) {                  // loop while there's more data
            list($header, $content) = explode("\n", $buffer, 2);        // split into header and content
            $response .= $content;                                      // append content to response
        }
        
        $response = trim($response);                                    // remove whitespaces around the response
        
        if (empty($response))                                           // no data received, return null
            return null;
        
        return preg_replace("/\^./","", $response);                     // return response without prefix
           
    }

    /**
     * Writes a command to the RCON server.
     * @return bool $cmd Command writen successfully?
     */
    private function write(string $cmd) : bool {
        
        if (!$this->isConnected()) {
            return false;
        }
        
        if( false === fwrite($this->socket, str_repeat(chr(255), 4) . "rcon {$this->password} {$cmd}\n") ) {
            return false;
        }

        return true;
        
    }

    /**
     * Sends a command to the RCON server and optionally reads the response.
     * @param string $cmd Command to send to the RCON server
     * @param bool $read Should the response be read from the RCON server? (default: false)
     * @return string|null Response from the RCON server or null if no response is expected or read fails
     */
    public function sendCommand(string $cmd, bool $read=false) : ?string {

        $this->connect();
        if(!$this->write($cmd)) { // sending the command
            $this->err = [
                "code" => 0,
                "message" => "Command could not be sent"
            ];
            $this->disconnect();
            return null;
        }
        
        if (!$read) {
            $this->disconnect();
            return null;
        }
        
        if(!$res = $this->read()) { // reading the response
            $this->err = [
                "code" => 0,
                "message" => "Response could not be read"
            ];
        }
        $this->disconnect();
        
        return $res;

    }

    /**
     * Returns the last error details if any occurred during communication.
     * @return object|null Last error details or null if no error has occurred (error object contains code and message as properties)
     */
    public function getError() :?object {
        
        if($this->err === null) {
            return null; // no error has occurred, return null
        }

        return json_decode(json_encode($this->err)); // return last error as object

    }
    

}