<?php
/**
 * Předpokladem je PHP verze 5.1.2 a vyšší s moduly mhash, mcrypt.
 *
 * Obsahuje pomocne funkcionality pro komunikaci s platebnim rozh-
 * ranim GoPay.
 */
class ButtonHelper{

    function iconRychloplatba(){
        return "https://www.gopay.cz/download/PT_rychloplatba.png";
    }
    function iconDaruj(){
        return "https://www.gopay.cz/download/PT_daruj.png";
    }
    function iconBuynow(){
        return "https://www.gopay.cz/download/PT_buynow.png";
    }
    function iconDonate(){
        return "https://www.gopay.cz/download/PT_donate.png";
    }
    /**
     * URL platebni brany pro platebni tlacitko
     *
     * @return URL
     */
    function buttonURL(){
        return 'https://testgw.gopay.cz/zaplatit-tlacitko';
    }


    /**
     * Sestaveni retezce pro podpis platebniho prikazu
     *
     * @param long $buyerGoId
     * @param string $productName
     * @param long $totalPriceInCents
     * @param string $variableSymbol
     * @param string $failedURL
     * @param string $successURL
     * @param string $key
     * @return retezec pro podpis
     */
    function concatPaymentCommand(
        $buyerGoId,
        $productName,
        $totalPriceInCents,
        $variableSymbol,
        $failedURL,
        $successURL,
        $key){

        return $buyerGoId."|".$productName."|".$totalPriceInCents."|".$variableSymbol."|".$failedURL."|".$successURL."|".$key;
    }


    /**
     * Sestaveni retezce pro podpis popisu platby (paymentIdentity)
     *
     * @param long $buyerGoId
     * @param long $paymentSessionId
     * @param string $variableSymbol
     * @param string $key
     * @return retezec pro podpis
     */
    function concatPaymentIdentity(
        $buyerGoId,
        $paymentSessionId,
        $variableSymbol,
        $key){
        return $buyerGoId."|".$paymentSessionId."|".$variableSymbol."|".$key;
    }

    /**
     * Sifrovani dat 3DES
     *
     * @param string $data
     * @param string $key
     * @return sifrovany obsah v HEX forme
     */
    function encrypt($data, $key){
        $td = mcrypt_module_open (MCRYPT_3DES, '', MCRYPT_MODE_ECB, '');
        $mcrypt_iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
        mcrypt_generic_init ($td, substr($key, 0, mcrypt_enc_get_key_size($td)), $mcrypt_iv);
        $encrypted_data = mcrypt_generic ($td, $data);
        mcrypt_generic_deinit ($td);
        mcrypt_module_close ($td);

        return bin2hex($encrypted_data);
    }

    /**
     * desifrovani
     *
     * @param string $data
     * @param string $key
     * @return desifrovany retezec
     */
    function decrypt($data, $key){
        $td = mcrypt_module_open (MCRYPT_3DES, '', MCRYPT_MODE_ECB, '');
        $mcrypt_iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
        mcrypt_generic_init ($td, substr($key, 0, mcrypt_enc_get_key_size($td)), $mcrypt_iv);

        $decrypted_data = mdecrypt_generic($td, ButtonHelper::convert($data));
        mcrypt_generic_deinit ($td);
        mcrypt_module_close ($td);

        return Trim($decrypted_data);

    }

    /**
     * hash SHA1 dat
     *
     * @param string $data
     * @return otisk dat SHA1
     */
    function hash($data){
        $hash = mhash(MHASH_SHA1,$data);
        return bin2hex($hash);
    }

    /**
     * konverze z HEX -> string
     *
     * @param string $hexString
     * @return konverze z HEX -> string
     */
    function convert($hexString){

        $hexLenght = strlen($hexString);
        // only hex numbers is allowed
        if ($hexLenght % 2 != 0 || preg_match("/[^\da-fA-F]/",$hexString)) return FALSE;
        $binString = "";
        for ($x = 1; $x <= $hexLenght/2; $x++)
        {
            $binString .= chr(hexdec(substr($hexString,2 * $x - 2,2)));

        }

        return $binString;

    }


    /**
     * Kontrola parametru predavanych ve zpetnem volani
     * po potvrzeni/zruseni platby
     *
     * - verifikace podpisu
     *
     *
     * @param long $returnedGoId - buyerGoId vracene v redirectu
     * @param long $returnedPaymentSessionId - paymentSessionId vracene v redirectu
     * @param string $returnedVariableSymbol - variableSymbol vracene v redirectu
     * @param string $returnedEncryptedSignature - encryptedSignature vracene v redirectu
     * @param long $buyerGoId - identifikace uzivatele
     * @param string $variableSymbol - oznaceni objednavky
     * @param string $secret - klic urceny k podepisovani komunikace
     *
     * @return true
     * @return false
     */
    function checkPaymentIdentity(
                $returnedGoId,
                $returnedPaymentSessionId,
                $returnedVariableSymbol,
                $returnedEncryptedSignature,
                $buyerGoId,
                $variableSymbol,
                $secret
                ){

        $valid = true;
        if($returnedVariableSymbol != $variableSymbol){
            $valid = false;
            echo "PI invalid VS <br>";
        }

        if($returnedGoId != $goId){
            $valid = false;
            echo "PI invalid EID<br>";
        }

        $hashedSignature=ButtonHelper::hash(
                ButtonHelper::concatPaymentIdentity(
                    $returnedGoId,
                    $returnedPaymentSessionId,
                    $returnedVariableSymbol,
                    $secret)
            );
        $decryptedHash = ButtonHelper::decrypt($returnedEncryptedSignature, $secret);

        if($decryptedHash != $hashedSignature){
            $valid = false;
            echo "PI invalid signature <br>";
        }

        return $valid;
    }


    /**
     * Sestaveni formulare platebniho tl.
     *
     *
     * @param long $buyerGoId - identifikace uzivatele
     * @param long $totalPrice - cena objednavky v centech
     * @param string $productName - nazev zbozi
     * @param string $variableSymbol - identifikace akt. objednavky
     * @param string $successURL - URL, kam se ma prejit po uspesnem zaplaceni
     * @param string $failedURL - URL, kam se ma prejit po neuspesnem zaplaceni
     * @param string $secret - klic urceny k podepisovani komunikace
     * @param string $iconUrl - URL obrazku tlacitka
     *
     * @return HTML kod platebniho tlacitka
     */
    function createForm(
            $buyerGoId,
            $totalPrice,
            $productName,
            $variableSymbol,
            $successURL,
            $failedURL,
            $secret,
            $iconUrl
            ){

        $encryptedSignature = ButtonHelper::encrypt(
                ButtonHelper::hash(
                        ButtonHelper::concatPaymentCommand(
                        $buyerGoId,
                        $productName,
                        $totalPrice,
                        $variableSymbol,
                        $failedURL,
                        $successURL,
                        $secret)
                    ), $secret);

        $formBuffer = "";
        $formBuffer .= "<form method='post' action='" . ButtonHelper::buttonURL() . "' target='_blank'>\n";
            $formBuffer .= "<input type='hidden' name='paymentCommand.buyerGoId' value='" . $buyerGoId . "' />\n";
            $formBuffer .= "<input type='hidden' name='paymentCommand.totalPrice' value='" . $totalPrice . "' />\n";
            $formBuffer .= "<input type='hidden' name='paymentCommand.productName' value='" . $productName . "' />\n";
            $formBuffer .= "<input type='hidden' name='paymentCommand.variableSymbol' value='" . $variableSymbol . "' />\n";
            $formBuffer .= "<input type='hidden' name='paymentCommand.successURL' value='" . $successURL . "' />\n";
            $formBuffer .= "<input type='hidden' name='paymentCommand.failedURL' value='" . $failedURL . "' />\n";
            $formBuffer .= "<input type='hidden' name='paymentCommand.encryptedSignature' value='" . $encryptedSignature . "' />\n";
            $formBuffer .= "<input type='submit' name='submit' value='' style='background:url(" . $iconUrl . ") no-repeat;width:100px;height:30px;border:none;'>\n";
        $formBuffer .= "</form>\n";

        return $formBuffer;
    }

    /**
     * Sestaveni platebniho tl. jako odkazu
     *
     *
     * @param long $buyerGoId - identifikace uzivatele
     * @param long $totalPrice - cena objednavky v centech
     * @param string $productName - nazev zbozi
     * @param string $variableSymbol - identifikace akt. objednavky
     * @param string $successURL - URL, kam se ma prejit po uspesnem zaplaceni
     * @param string $failedURL - URL, kam se ma prejit po neuspesnem zaplaceni
     * @param string $secret - klic urceny k podepisovani komunikace
     * @param string $iconUrl - URL obrazku tlacitka
     *
     * @return HTML kod platebniho tlacitka
     */
    function createHref(
            $buyerGoId,
            $totalPrice,
            $productName,
            $variableSymbol,
            $successURL,
            $failedURL,
            $secret,
            $iconUrl
            ){

        $encryptedSignature = ButtonHelper::encrypt(
                ButtonHelper::hash(
                        ButtonHelper::concatPaymentCommand(
                        $buyerGoId,
                        $productName,
                        $totalPrice,
                        $variableSymbol,
                        $failedURL,
                        $successURL,
                        $secret)
                    ), $secret);

        $params = "";
        $params .= "paymentCommand.buyerGoId=" . $buyerGoId;
        $params .= "&paymentCommand.totalPrice=" . $totalPrice;
        $params .= "&paymentCommand.productName=" . urlencode($productName);
        $params .= "&paymentCommand.variableSymbol=" . urlencode($variableSymbol);
        $params .= "&paymentCommand.successURL=" . urlencode($successURL);
        $params .= "&paymentCommand.failedURL=" . urlencode($failedURL);
        $params .= "&paymentCommand.encryptedSignature=" . urlencode($encryptedSignature);

        $formBuffer = "";
        $formBuffer .= "<a target='_blank' href='" . ButtonHelper::buttonURL() . "?" . $params . "' >";
        $formBuffer .= " <img src='" . $iconUrl . "' border='0' style='border:none;'/> ";
        $formBuffer .= "</a>";

        return $formBuffer;
    }
}
?>