Add concept of configurable WebUI URL base path

This provides the underlying support for having a configurable base path. Future commit(s) will expose this functionality to users.

src/base/preferences.cpp

@@ -1026,6 +1026,19 @@ void Preferences::setWebUITrustedReverseProxiesList(const QString &addr)
     setValue(u"Preferences/WebUI/TrustedReverseProxiesList"_s, addr);
 }
 
+QString Preferences::getWebUIBasePath() const
+{
+    return value(u"Preferences/WebUI/BasePath"_s, u"/"_s);
+}
+
+void Preferences::setWebUIBasePath(const QString &path)
+{
+    if (path == getWebUIBasePath())
+        return;
+
+    setValue(u"Preferences/WebUI/BasePath"_s, path);
+}
+
 bool Preferences::isDynDNSEnabled() const
 {
     return value(u"Preferences/DynDNS/Enabled"_s, false);

src/base/preferences.h

@@ -237,6 +237,8 @@ public:
     void setWebUIReverseProxySupportEnabled(bool enabled);
     QString getWebUITrustedReverseProxiesList() const;
     void setWebUITrustedReverseProxiesList(const QString &addr);
+    QString getWebUIBasePath() const;
+    void setWebUIBasePath(const QString &path);
 
     // Dynamic DNS
     bool isDynDNSEnabled() const;

src/webui/webapplication.cpp

@@ -495,6 +495,13 @@ void WebApplication::configure()
     }
 
     m_isReverseProxySupportEnabled = pref->isWebUIReverseProxySupportEnabled();
+    const QString newBasePath = m_isReverseProxySupportEnabled ? pref->getWebUIBasePath() : u"/"_s;
+    if (m_basePath != newBasePath)
+    {
+        m_cachedFiles.clear();
+        m_basePath = newBasePath;
+    }
+
     if (m_isReverseProxySupportEnabled)
     {
         const QStringList proxyList = pref->getWebUITrustedReverseProxiesList().split(u';', Qt::SkipEmptyParts);
@@ -576,20 +583,25 @@ void WebApplication::sendFile(const Path &path)
 
     QByteArray data = readResult.value();
     const QMimeType mimeType = QMimeDatabase().mimeTypeForFileNameAndData(path.data(), data);
-    const bool isTranslatable = !m_isAltUIUsed && mimeType.inherits(u"text/plain"_s);
+    const bool isTextFile = mimeType.inherits(u"text/plain"_s);
-
+    if (isTextFile)
-    if (isTranslatable)
     {
         auto dataStr = QString::fromUtf8(data);
+        dataStr.replace(u"${BASE_PATH}"_s, m_basePath);
+
+        const bool isTranslatable = !m_isAltUIUsed;
+        if (isTranslatable)
+        {
             // Translate the file
             translateDocument(dataStr);
 
             // Add the language options
             if (path == (m_rootFolder / Path(PRIVATE_FOLDER) / Path(u"views/preferences.html"_s)))
                 dataStr.replace(u"${LANGUAGE_OPTIONS}"_s, createLanguagesOptionsHtml());
+        }
 
         data = dataStr.toUtf8();
-        m_cachedFiles[path] = {data, mimeType.name(), lastModified}; // caching translated file
+        m_cachedFiles[path] = {data, mimeType.name(), lastModified};
     }
 
     print(data, mimeType.name());

src/webui/webapplication.h

@@ -225,6 +225,7 @@ private:
     };
     bool m_isAltUIUsed = false;
     Path m_rootFolder;
+    QString m_basePath;
 
     struct CachedFile
     {