Add helper classes for exporting dbus properties

src/main/java/org/asamk/signal/dbus/DbusProperties.java

@@ -0,0 +1,66 @@
+package org.asamk.signal.dbus;
+
+import org.asamk.Signal;
+import org.freedesktop.dbus.interfaces.Properties;
+import org.freedesktop.dbus.types.Variant;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+public abstract class DbusProperties implements Properties {
+
+    private final List<DbusInterfacePropertiesHandler> handlers = new ArrayList<>();
+
+    protected void addPropertiesHandler(DbusInterfacePropertiesHandler handler) {
+        this.handlers.add(handler);
+    }
+
+    DbusInterfacePropertiesHandler getHandler(String interfaceName) {
+        final var handler = getHandlerOptional(interfaceName);
+        if (handler.isEmpty()) {
+            throw new Signal.Error.Failure("Property not found");
+        }
+        return handler.get();
+    }
+
+    private java.util.Optional<DbusInterfacePropertiesHandler> getHandlerOptional(final String interfaceName) {
+        return handlers.stream().filter(h -> h.getInterfaceName().equals(interfaceName)).findFirst();
+    }
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public <A> A Get(final String interface_name, final String property_name) {
+        final var handler = getHandler(interface_name);
+        final var getter = handler.getGetter(property_name);
+        if (getter == null) {
+            throw new Signal.Error.Failure("Property not found");
+        }
+        return (A) getter.get();
+    }
+
+    @Override
+    public <A> void Set(final String interface_name, final String property_name, final A value) {
+        final var handler = getHandler(interface_name);
+        final var setter = handler.getSetter(property_name);
+        if (setter == null) {
+            throw new Signal.Error.Failure("Property not found");
+        }
+        setter.accept(value);
+    }
+
+    @Override
+    public Map<String, Variant<?>> GetAll(final String interface_name) {
+        final var handler = getHandlerOptional(interface_name);
+        if (handler.isEmpty()) {
+            return Map.of();
+        }
+
+        return handler.get()
+                .getProperties()
+                .stream()
+                .filter(p -> p.getGetter() != null)
+                .collect(Collectors.toMap(DbusProperty::getName, p -> new Variant<>(p.getGetter().get())));
+    }
+}