installer: remove existing installation before installing current version

branding/templates/qtinstaller/packages/bitmaskvpn/meta/install.js

@@ -36,10 +36,17 @@ function Component() {
     // Check whether OS is supported.
     // start installer with -v to see debug output
 
+    installer.gainAdminRights();
+
     console.log("OS: " + systemInfo.productType);
     console.log("Kernel: " + systemInfo.kernelType + "/" + systemInfo.kernelVersion);
     installer.setDefaultPageVisible(QInstaller.TargetDirectory, false);
 
+    if (installer.isInstaller()) {
+        console.log("Checking for existing installation")
+        component.loaded.connect(this, Component.prototype.installerLoaded);
+    }
+
     var validOs = false;
 
     if (systemInfo.kernelType === "winnt") {
@@ -100,6 +107,26 @@ Component.prototype.createOperations = function ()
     }
 }
 
+Component.prototype.installerLoaded = function () {
+    var dir = installer.value("TargetDir")
+    var maintenancetoolPath = Dir.toNativeSeparator(dir + "/uninstall.exe")
+    if (systemInfo.productType == "macos") {
+        maintenancetoolPath = Dir.toNativeSeparator(dir + "/uninstall.app" + "/Contents/MacOS/uninstall")
+    }
+    if (installer.fileExists(dir) && installer.fileExists(maintenancetoolPath)) {
+        console.log("Found existing installation at: " + dir)
+        var result = QMessageBox.warning("uninstallprevious.critical", "Uninstall previous version", "To proceed existing installation needs to be removed. Click OK to remove existing installation.",
+            QMessageBox.Ok | QMessageBox.Cancel);
+        if (result == QMessageBox.Ok) {
+            console.log("Running uninstall using maintenance tool at: " + maintenancetoolPath)
+            installer.execute(maintenancetoolPath, ["purge", "-c"]);
+        }
+        if (result == QMessageBox.Cancel) {
+            cancelInstaller("Need to removed existing installation to proceed.");
+        }
+    }
+}
+
 function preInstallWindows() {
     console.log("Pre-installation for Windows: check for running bitmask");
     component.addOperation(
@@ -196,4 +223,4 @@ function uninstallWindows() {
         "Execute", "{0}", "powershell", "-NonInteractive", "-NoProfile", "-command",
         "Remove-LocalGroup -Name 'OpenVPN Administrator' -ErrorAction Ignore",
     );
-}
\ No newline at end of file
+}