Added checks for bitstream file extension (#61)

Previously, using a file extension other than `.LPC` or `.BIN` would
result in the GUI depositing an empty file. This commit adds checks
for the extension. The program will now warn the user if the requested
extension is unsupported, and it will default to `.LPC` in that case

Author: tornupnegatives

src/ui/gui/MainWindow.cpp

@@ -204,11 +204,24 @@ void MainWindow::onSaveBitstream() {
         "ASCII Bitstream (*.lpc);;" \
         "Binary Bitstream (*.bin)");
 
-    if (filepath.isNull()) {
+    if (filepath.isNull() || filepath.isEmpty()) {
         qDebug() << "Save bitstream canceled";
         return;
     }
 
+    // Default to ASCII if requested file extension is invalid
+    QFileInfo fi(filepath);
+    QString ext = fi.suffix().toLower();
+
+    if (ext != "bin" && ext != "lpc") {
+        QMessageBox::warning(
+            this,
+            "Invalid Extension",
+            "The file must use .bin or .lpc.\nDefaulting to .lpc."
+        );
+    }
+
+    filepath = fi.path() + "/" + fi.completeBaseName() + ".lpc";
     exportBitstream(filepath.toStdString());
 }
 
@@ -569,6 +582,8 @@ void MainWindow::exportBitstream(const std::string& path) {
         binOut.write(
             reinterpret_cast<char*>(bin.data()),
             static_cast<int>(bin.size()));
+    } else {
+        qDebug() << "Unrecognized extension for file" << filepath;
     }
 }