ConfigStore: Add a rename method and implement it

Signed-off-by: Samuel Holland <samuel@sholland.org>

app/src/main/java/com/wireguard/android/configStore/ConfigStore.java

@@ -42,6 +42,14 @@ public interface ConfigStore {
      */
     Config load(final String name) throws Exception;
 
+    /**
+     * Rename the configuration for the tunnel given by {@code name}.
+     *
+     * @param name        The identifier for the existing configuration in persistent storage.
+     * @param replacement The new identifier for the configuration in persistent storage.
+     */
+    void rename(String name, String replacement) throws Exception;
+
     /**
      * Save the configuration for an existing tunnel given by {@code name}.
      *

app/src/main/java/com/wireguard/android/configStore/FileConfigStore.java

@@ -69,6 +69,17 @@ public final class FileConfigStore implements ConfigStore {
         }
     }
 
+    @Override
+    public void rename(final String name, final String replacement) throws IOException {
+        Log.d(TAG, "Renaming configuration for tunnel " + name + " to " + replacement);
+        final File file = fileFor(name);
+        final File replacementFile = fileFor(replacement);
+        if (!replacementFile.createNewFile())
+            throw new IOException("Configuration for " + replacement + " already exists");
+        if (!file.renameTo(replacementFile))
+            throw new IOException("Cannot rename configuration file " + file.getName());
+    }
+
     @Override
     public Config save(final String name, final Config config) throws IOException {
         Log.d(TAG, "Saving configuration for tunnel " + name);