Code refactor, support multiple gateways and non-SAML authentication (#9)

* Code refactor

* Update README.md

GPClient/preloginresponse.cpp

@@ -0,0 +1,97 @@
+#include "preloginresponse.h"
+
+#include <QXmlStreamReader>
+#include <QMap>
+
+QString PreloginResponse::xmlAuthMessage = "authentication-message";
+QString PreloginResponse::xmlLabelUsername = "username-label";
+QString PreloginResponse::xmlLabelPassword = "password-label";
+QString PreloginResponse::xmlSamlMethod = "saml-auth-method";
+QString PreloginResponse::xmlSamlRequest = "saml-request";
+QString PreloginResponse::xmlRegion = "region";
+
+PreloginResponse::PreloginResponse()
+{
+    add(xmlAuthMessage, "");
+    add(xmlLabelUsername, "");
+    add(xmlLabelPassword, "");
+    add(xmlSamlMethod, "");
+    add(xmlSamlRequest, "");
+    add(xmlRegion, "");
+}
+
+PreloginResponse PreloginResponse::parse(const QByteArray& xml)
+{
+    QXmlStreamReader xmlReader(xml);
+    PreloginResponse response;
+    response.setRawResponse(xml);
+
+    while (!xmlReader.atEnd()) {
+        xmlReader.readNextStartElement();
+        QString name = xmlReader.name().toString();
+        if (response.has(name)) {
+            response.add(name, xmlReader.readElementText());
+        }
+    }
+    return response;
+}
+
+const QByteArray& PreloginResponse::rawResponse() const
+{
+    return _rawResponse;
+}
+
+QString PreloginResponse::authMessage() const
+{
+    return resultMap.value(xmlAuthMessage);
+}
+
+QString PreloginResponse::labelUsername() const
+{
+    return resultMap.value(xmlLabelUsername);
+}
+
+QString PreloginResponse::labelPassword() const
+{
+    return resultMap.value(xmlLabelPassword);
+}
+
+QString PreloginResponse::samlMethod() const
+{
+    return resultMap.value(xmlSamlMethod);
+}
+
+QString PreloginResponse::samlRequest() const
+{
+    return QByteArray::fromBase64(resultMap.value(xmlSamlRequest).toUtf8());
+}
+
+QString PreloginResponse::region() const
+{
+    return resultMap.value(xmlRegion);
+}
+
+bool PreloginResponse::hasSamlAuthFields() const
+{
+    return !samlMethod().isEmpty() && !samlRequest().isEmpty();
+}
+
+bool PreloginResponse::hasNormalAuthFields() const
+{
+    return !labelUsername().isEmpty() && !labelPassword().isEmpty();
+}
+
+void PreloginResponse::setRawResponse(const QByteArray &response)
+{
+    _rawResponse = response;
+}
+
+bool PreloginResponse::has(const QString &name) const
+{
+    return resultMap.contains(name);
+}
+
+void PreloginResponse::add(const QString &name, const QString &value)
+{
+    resultMap.insert(name, value);
+}