<?php

define('IPN_CERTIFICATE_PATH', __DIR__ . '/cert/cacert.pem');
class ipnlistener
{
    public $use_curl = true;

    public $force_ssl_v3 = false;

    public $follow_location = false;

    public $use_ssl = false;

    public $use_sandbox = false;

    public $timeout = 30;
    private $post_data = [];
    private $post_uri = '';
    private $response_status = '';
    private $response = '';

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

    protected function curlPost($encoded_data)
    {
        if ($this->use_ssl) {
            $uri = 'https://'.$this->getPaypalHost().'/cgi-bin/webscr';
            $this->post_uri = $uri;
        } else {
            $uri = 'https://'.$this->getPaypalHost().'/cgi-bin/webscr';
            $this->post_uri = $uri;
        }
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, true);
        curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
        curl_setopt($ch, CURLOPT_CAINFO, IPN_CERTIFICATE_PATH);
        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("cURL error: [$errno] $errstr");
        }
    }

    protected function fsockPost($encoded_data)
    {
        if ($this->use_ssl) {
            $uri = 'ssl://'.$this->getPaypalHost();
            $port = '443';
            $this->post_uri = $uri.'/cgi-bin/webscr';
        } else {
            $uri = $this->getPaypalHost();
            $port = '80';
            $this->post_uri = 'https://'.$uri.'/cgi-bin/webscr';
        }
        $fp = fsockopen($uri, $port, $errno, $errstr, $this->timeout);
        if (!$fp) {
            throw new Exception("fsockopen error: [$errno] $errstr");
        }
        $header = "POST /cgi-bin/webscr HTTP/1.1\r\n";
        $header .= 'Host: '.$this->getPaypalHost()."\r\n";
        $header .= "Content-Type: application/x-www-form-urlencoded\r\n";
        $header .= 'Content-Length: '.strlen($encoded_data)."\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)) {
                $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 self::SANDBOX_HOST;
        } else {
            return self::PAYPAL_HOST;
        }
    }

    public function getPostUri()
    {
        return $this->post_uri;
    }

    public function getResponse()
    {
        return $this->response;
    }

    public function getResponseStatus()
    {
        return $this->response_status;
    }

    public function getTextReport()
    {
        $r = '';
        for ($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 {
            $r .= " (fsockopen)\n";
        }
        for ($i = 0; $i < 80; ++$i) {
            $r .= '-';
        }
        $r .= "\n{$this->getResponse() }\n";
        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;
    }

    public function processIpn($post_data = null)
    {
        $encoded_data = 'cmd=_notify-validate';
        if ($post_data === null) {
            if (!empty($_POST)) {
                $this->post_data = $_POST;
                $encoded_data .= '&'.file_get_contents('php://input');
            } else {
                throw new Exception('No POST data found.');
            }
        } else {
            $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($this->response_status, '200') === false) {
            throw new Exception('Invalid response status: '.$this->response_status);
        }
        if (strpos($this->response, 'VERIFIED') !== false) {
            return true;
        } elseif (strpos($this->response, 'INVALID') !== false) {
            return false;
        } else {
            throw new Exception('Unexpected response from PayPal.');
        }
    }

    public function requirePostMethod()
    {
        if ($_SERVER['REQUEST_METHOD'] && $_SERVER['REQUEST_METHOD'] != 'POST') {
            header('Allow: POST', true, 405);
            throw new Exception('Invalid HTTP request method.');
        }
    }
}