QString Document::documentRevision()
{
    std::string result;
    std::string filtered;
    QString txasm;
    QString bcguid;
    QString bcfilehash;
    QString bcattrhash;

    QString revOk    = "<h2 style=\"color:green\">" + tr("Revision successful") + "</h2>";
    QString revHint  = "<h2 style=\"color:green\">" + tr("Revision with notes") + "</h2>";
    QString revNoConf= "<h2 style=\"color:red\">"   + tr("Revision is not possible yet") + "</h2>";
    QString revError = "<h2 style=\"color:red\">"   + tr("Revision failed") + "</h2>";

    if (txid.isEmpty())
        return revError + "<p>" + tr("No Transaction stored.") + "</p>";
    
    if (filehash != getFileHash(filename))
        return revError + "<p>" 
            + tr("The current file does not match the locally saved hash. This file has been modified.") + "</p>";

    try {
        // 1. get transaction
        // RPC: Post('{"jsonrpc": "1.0", "id":"DMSExposed", "method": "getrawtransaction", "params": ["%1",true] }',
        RPCConsole::RPCExecuteCommandLine(result, "getrawtransaction " + txid.toStdString() + " true", &filtered);

        QJsonDocument jdoc = QJsonDocument::fromJson(QByteArray::fromStdString(result));
        QJsonObject jobj = jdoc.object();

        int confirmations = jobj.value("confirmations").toInt();
        QDateTime time = QDateTime::fromTime_t(jobj.value("time").toInt());
        QDateTime blocktime = QDateTime::fromTime_t(jobj.value("blocktime").toInt());
        int height = jobj.value("height").toInt();
        QString blockhash = jobj.value("blockhash").toString();

        bool found = false;
        QJsonArray jary = jobj.value("vout").toArray();
        BOOST_FOREACH (const QJsonValue & jarval, jary) {
            QJsonObject jvout = jarval.toObject();
            // {"value": 0.00000000,"valueSat": 0,"n": 1,"scriptPubKey": {"asm": "OP_RETURN 48616c6c6f2057656c74","hex": "6a0a48616c6c6f2057656c74","type": "nulldata"}}
            jvout = jvout.value("scriptPubKey").toObject();
            if (jvout.value("type").toString() == "nulldata") {
                txasm = jvout.value("asm").toString();
                if (txasm.toUpper().startsWith("OP_RETURN 444D2400010002")) {
                    txasm.remove(0, 10);
                    bcguid = txasm.mid(14, 32).toUpper();
                    bcfilehash = txasm.mid(46, 32).toUpper();
                    bcattrhash = txasm.mid(78, 32).toUpper();
                    found = true;
                    break;
                }
            }
        }
        if (!found)
            return revError + "<p>" + tr("Transaction not found.") + "</p>";

        // compare document with data from blockchain
        QString revlog = "";
        QString deviation  = tr("current value \"%1\" differs from value \"%2\" stored in blockchain.");
        QString accordance = tr("matches the blockchain value.");

        if (confirmations < minConfirms) {
            revlog.append(revNoConf);
            revlog.append("<p>" + tr("There are not enough blockchain confirmations available for revision. Please wait a while.") + "</p>");
        }
        else if (compressGuid(guid) == bcguid && attrhash == bcattrhash && filehash == bcfilehash)
            revlog.append(revOk);
        else if (filehash == bcfilehash)
            revlog.append(revHint);
        else
            revlog.append(revError);

        revlog.append("<p>");
        if (compressGuid(guid) == bcguid)
            revlog.append(QString("<b>%1</b>: <span style=\"color:green\">%2</span><br>").arg(trGUID, accordance));
        else
            revlog.append(QString("<b>%1</b>: <span style=\"color:red\">%2</span><br>")
                         .arg(trGUID, deviation.arg(compressGuid(guid), bcguid)));
        if (attrhash == bcattrhash)
            revlog.append(QString("<b>%1</b>: <span style=\"color:green\">%2</span><br>").arg(trAttrHash, accordance));
        else
            revlog.append(QString("<b>%1</b>: <span style=\"color:red\">%2</span><br>")
                         .arg(trAttrHash, deviation.arg(compressGuid(guid), bcguid)));
        if (filehash == bcfilehash) {
            revlog.append(QString("<b>%1</b>: <span style=\"color:green\">%2</span>").arg(trFileHash, accordance));
            if (confirmations >= minConfirms)
                revlog.append("</p><p>" + tr("The blockchain confirms that %1this document file%2 exists at least since %3 and has not been modified.")
                                            .arg("<a href=\"open\">", "</a>", GUIUtil::dateTimeStr(blocktime)));
        }
        else
            revlog.append(QString("<b>%1</b>: <span style=\"color:red\">%2</span>")
                         .arg(trFileHash, deviation.arg(compressGuid(guid), bcguid)));

        revlog.append("</p><p><b>" + tr("Blockchain confirmations") 
            + "</b>: " + QString::number(confirmations) 
            + ((confirmations < minConfirms) ? ("/" + QString::number(minConfirms)) : "") + "</p>");

        return revlog;

    } catch (const std::exception& e) {
        return revError + "<p>" + QString::fromStdString(e.what()) + "</p>";
    } catch (...) {
        return  revError + "<p>" + tr("Unknown error.") + "</p>";
    }
}