/**
* PayPal IPN Listener
*
* A class to listen for and handle Instant Payment Notifications (IPN) from
* the PayPal server.
*
* https://github.com/Quixotix/PHP-PayPal-IPN
*
* @package    PHP-PayPal-IPN
* @author     Micah Carrick
* @copyright  (c) 2011 - Micah Carrick
* @version    2.0.5
* @license    http://opensource.org/licenses/gpl-license.php
*
* This library is originally licensed under GPL v3, but I received
* permission from the author to use it under GPL v2.
*/
class ipn_handler
{
    /**
     *  If true, the recommended cURL PHP library is used to send the post back
     *  to PayPal. If flase then fsockopen() is used. Default true.
     *
     *  @var boolean
     */
    public $use_curl = true;

    /**
     *  If true, explicitly sets cURL to use SSL version 3. Use this if cURL
     *  is compiled with GnuTLS SSL.
     *
     *  @var boolean
     */
    public $force_ssl_v3 = true;

    /**
     *  If true, cURL will use the CURLOPT_FOLLOWLOCATION to follow any
     *  "Location: ..." headers in the response.
     *
     *  @var boolean
     */
    public $follow_location = false;

    /**
     *  If true, an SSL secure connection (port 443) is used for the post back
     *  as recommended by PayPal. If false, a standard HTTP (port 80) connection
     *  is used. Default true.
     *
     *  @var boolean
     */
    public $use_ssl = true;

    /**
     *  If true, the paypal sandbox URI www.sandbox.paypal.com is used for the
     *  post back. If false, the live URI www.paypal.com is used. Default false.
     *
     *  @var boolean
     */
    public $use_sandbox = false;

    /**
     *  The amount of time, in seconds, to wait for the PayPal server to respond
     *  before timing out. Default 30 seconds.
     *
     *  @var int
     */
    public $timeout = 60;

    private $post_data = array();
    private $post_uri = '';
    private $response_status = '';
    private $response = '';

    const PAYPAL_HOST = 'www.paypal.com';
    const SANDBOX_HOST = 'www.sandbox.paypal.com';

    /**
     *  Post Back Using cURL
     *
     *  Sends the post back to PayPal using the cURL library. Called by
     *  the processIpn() method if the use_curl property is true. Throws an
     *  exception if the post fails. Populates the response, response_status,
     *  and post_uri properties on success.
     *
     *  @param  string  The post data as a URL encoded string
     */
    protected function curlPost($encoded_data)
    {
        global $user;

        if ($this->use_ssl)
        {
            $uri = 'https://' . $this->getPaypalHost() . '/cgi-bin/webscr';
            $this->post_uri = $uri;
        }
        else
        {
            $uri = 'http://' . $this->getPaypalHost() . '/cgi-bin/webscr';
            $this->post_uri = $uri;
        }

        $ch = curl_init();

        curl_setopt($ch, CURLOPT_URL, $uri);
        curl_setopt($ch, CURLOPT_POST, true);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $encoded_data);
        curl_setopt($ch, CURLOPT_FOLLOWLOCATION, $this->follow_location);
        curl_setopt($ch, CURLOPT_TIMEOUT, $this->timeout);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_HEADER, true);

        if ($this->force_ssl_v3)
        {
            curl_setopt($ch, CURLOPT_SSLVERSION, 3);
        }

        $this->response = curl_exec($ch);
        $this->response_status = strval(curl_getinfo($ch, CURLINFO_HTTP_CODE));

        if ($this->response === false || $this->response_status == '0')
        {
            $errno = curl_errno($ch);
            $errstr = curl_error($ch);
            throw new Exception($user->lang['CURL_ERROR'] . "[$errno] $errstr");
        }
    }

    /**
     *  Post Back Using fsockopen()
     *
     *  Sends the post back to PayPal using the fsockopen() function. Called by
     *  the processIpn() method if the use_curl property is false. Throws an
     *  exception if the post fails. Populates the response, response_status,
     *  and post_uri properties on success.
     *
     *  @param  string  The post data as a URL encoded string
     */
    protected function fsockPost($encoded_data)
    {
        global $user;

        if ($this->use_ssl)
        {
            $uri = 'ssl://' . $this->getPaypalHost();
            $port = '443';
            $this->post_uri = $uri . '/cgi-bin/webscr';
        }
        else
        {
            $uri = $this->getPaypalHost(); // no "http://" in call to fsockopen()
            $port = '80';
            $this->post_uri = 'http://' . $uri . '/cgi-bin/webscr';
        }

        $fp = fsockopen($uri, $port, $errno, $errstr, $this->timeout);

        if (!$fp)
        {
            // fsockopen error
            throw new Exception($user->lang['FSOCKOPEN_ERROR'] . "[$errno] $errstr");
        }

        $header = "POST /cgi-bin/webscr HTTP/1.1\r\n";
        $header .= "Content-Length: " . strlen($encoded_data) . "\r\n";
        $header .= "Content-Type: application/x-www-form-urlencoded\r\n";
        $header .= "Host: " . $this->getPaypalHost() . "\r\n";
        $header .= "Connection: close\r\n\r\n";

        fputs($fp, $header . $encoded_data . "\r\n\r\n");

        while(!feof($fp))
        {
            if (empty($this->response))
            {
                // extract HTTP status from first line
                $this->response .= $status = fgets($fp, 1024);
                $this->response_status = trim(substr($status, 9, 4));
            }
            else
            {
                $this->response .= fgets($fp, 1024);
            }
        }

        fclose($fp);
    }

    private function getPaypalHost()
    {
        if ($this->use_sandbox)
        {
            return ipn_handler::SANDBOX_HOST;
        }
        else
        {
            return ipn_handler::PAYPAL_HOST;
        }
    }

    /**
     *  Get POST URI
     *
     *  Returns the URI that was used to send the post back to PayPal. This can
     *  be useful for troubleshooting connection problems. The default URI
     *  would be "ssl://www.sandbox.paypal.com:443/cgi-bin/webscr"
     *
     *  @return string
     */
    public function getPostUri()
    {
        return $this->post_uri;
    }

    /**
     *  Get Response
     *
     *  Returns the entire response from PayPal as a string including all the
     *  HTTP headers.
     *
     *  @return string
     */
    public function getResponse()
    {
        return $this->response;
    }

    /**
     *  Get Response Status
     *
     *  Returns the HTTP response status code from PayPal. This should be "200"
     *  if the post back was successful.
     *
     *  @return string
     */
    public function getResponseStatus()
    {
        return $this->response_status;
    }

    /**
     *  Get Text Report
     *
     *  Returns a report of the IPN transaction in plain text format. This is
     *  useful in emails to order processors and system administrators. Override
     *  this method in your own class to customize the report.
     *
     *  @return string
     */
    public function getTextReport()
    {
        $r = '';

        // date and POST url
        for ($i = 0; $i < 80; $i++)
        {
            $r .= '-';
        }

        $r .= "\n[" . date('m/d/Y g:i A') . '] - ' . $this->getPostUri();
        if ($this->use_curl)
        {
            $r .= " (curl)\n";
        }
        else
        {
            $r .= " (fsockopen)\n";
        }

        // HTTP Response
        for ($i = 0; $i < 80; $i++)
        {
            $r .= '-';
        }

        $r .= "\n{$this->getResponse()}\n";

        // POST vars
        for ($i = 0; $i < 80; $i++)
        {
            $r .= '-';
        }

        $r .= "\n";

        foreach ($this->post_data as $key => $value)
        {
            $r .= str_pad($key, 25) . "$value\n";
        }

        $r .= "\n\n";

        return $r;
    }

    /**
     *  Process IPN
     *
     *  Handles the IPN post back to PayPal and parsing the response. Call this
     *  method from your IPN listener script. Returns true if the response came
     *  back as "VERIFIED", false if the response came back "INVALID", and
     *  throws an exception if there is an error.
     *
     *  @param array
     *
     *  @return boolean
     */
    public function processIpn($post_data = null)
    {
        global $user;

        $encoded_data = 'cmd=_notify-validate';

        if ($post_data === null)
        {
            // use raw POST data
            if (!empty($_POST))
            {
                $this->post_data = $_POST;
                $encoded_data .= '&' . file_get_contents('php://input');
            }
            else
            {
                throw new Exception($user->lang['NO_POST_DATA']);
            }
        }
        else
        {
            // use provided data array
            $this->post_data = $post_data;

            foreach ($this->post_data as $key => $value)
            {
                $encoded_data .= "&$key=" . urlencode($value);
            }
        }

        if ($this->use_curl)
        {
            $this->curlPost($encoded_data);
        }
        else
        {
            $this->fsockPost($encoded_data);
        }

        if (strpos($this->response_status, '200') === false)
        {
            throw new Exception($user->lang['INVALID_RESPONSE'] . $this->response_status);
        }

        if (strpos(trim($this->response), "VERIFIED") !== false)
        {
            return true;
        }
        elseif (trim(strpos($this->response), "INVALID") !== false)
        {
            return false;
        }
        else
        {
            throw new Exception($user->lang['UNEXPECTED_ERROR']);
        }
    }

    /**
     *  Require Post Method
     *
     *  Throws an exception and sets a HTTP 405 response header if the request
     *  method was not POST.
     */
    public function requirePostMethod()
    {
        global $user;

        // require POST requests
        if ($_SERVER['REQUEST_METHOD'] && $_SERVER['REQUEST_METHOD'] != 'POST')
        {
            header('Allow: POST', true, 405);
            throw new Exception($user->lang['INVALID_REQUEST_METHOD']);
        }
    }
}