Add helper classes for exporting dbus properties

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

@@ -0,0 +1,46 @@
+package org.asamk.signal.dbus;
+
+import org.asamk.Signal;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.function.Consumer;
+import java.util.function.Supplier;
+
+public class DbusInterfacePropertiesHandler {
+
+    private final String interfaceName;
+    private final List<DbusProperty<?>> properties;
+
+    public DbusInterfacePropertiesHandler(
+            final String interfaceName, final List<DbusProperty<?>> properties
+    ) {
+        this.interfaceName = interfaceName;
+        this.properties = properties;
+    }
+
+    public String getInterfaceName() {
+        return interfaceName;
+    }
+
+    @SuppressWarnings("unchecked")
+    private <T> DbusProperty<T> findProperty(String propertyName) {
+        final var property = properties.stream().filter(p -> p.getName().equals(propertyName)).findFirst();
+        if (property.isEmpty()) {
+            throw new Signal.Error.Failure("Property not found");
+        }
+        return (DbusProperty<T>) property.get();
+    }
+
+    <T> Consumer<T> getSetter(String propertyName) {
+        return this.<T>findProperty(propertyName).getSetter();
+    }
+
+    <T> Supplier<T> getGetter(String propertyName) {
+        return this.<T>findProperty(propertyName).getGetter();
+    }
+
+    Collection<DbusProperty<?>> getProperties() {
+        return 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())));
+    }
+}

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

@@ -0,0 +1,35 @@
+package org.asamk.signal.dbus;
+
+import java.util.function.Consumer;
+import java.util.function.Supplier;
+
+public class DbusProperty<T> {
+
+    private final String name;
+    private final Supplier<T> getter;
+    private final Consumer<T> setter;
+
+    public DbusProperty(final String name, final Supplier<T> getter, final Consumer<T> setter) {
+        this.name = name;
+        this.getter = getter;
+        this.setter = setter;
+    }
+
+    public DbusProperty(final String name, final Supplier<T> getter) {
+        this.name = name;
+        this.getter = getter;
+        this.setter = null;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public Consumer<T> getSetter() {
+        return setter;
+    }
+
+    public Supplier<T> getGetter() {
+        return getter;
+    }
+}