Mechanism to add Port annotation via netcfg

- intended to be used for driver to support ONOS-5895

Change-Id: Iddcf6f1b99273e8f8670b5f64fc9831e5f4ce3cd
diff --git a/core/net/src/main/java/org/onosproject/net/device/impl/PortAnnotationOperator.java b/core/net/src/main/java/org/onosproject/net/device/impl/PortAnnotationOperator.java
new file mode 100644
index 0000000..3041a07
--- /dev/null
+++ b/core/net/src/main/java/org/onosproject/net/device/impl/PortAnnotationOperator.java
@@ -0,0 +1,77 @@
+/*
+ * Copyright 2017-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.net.device.impl;
+
+import java.util.Map;
+
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.DefaultAnnotations;
+import org.onosproject.net.DefaultAnnotations.Builder;
+import org.onosproject.net.config.NetworkConfigService;
+import org.onosproject.net.config.PortConfigOperator;
+import org.onosproject.net.config.basics.PortAnnotationConfig;
+import org.onosproject.net.device.DefaultPortDescription;
+import org.onosproject.net.device.PortDescription;
+
+/**
+ * Implementations of {@link PortConfigOperator} to weave
+ * annotations added via {@link PortAnnotationConfig}.
+ */
+public class PortAnnotationOperator implements PortConfigOperator {
+
+    private NetworkConfigService networkConfigService;
+
+    /**
+     * Creates {@link PortAnnotationOperator} instance.
+     */
+    public PortAnnotationOperator() {
+    }
+
+    PortAnnotationOperator(NetworkConfigService networkConfigService) {
+        bindService(networkConfigService);
+    }
+
+    @Override
+    public void bindService(NetworkConfigService networkConfigService) {
+        this.networkConfigService = networkConfigService;
+    }
+
+    private PortAnnotationConfig lookupConfig(ConnectPoint cp) {
+        if (networkConfigService == null) {
+            return null;
+        }
+        return networkConfigService.getConfig(cp, PortAnnotationConfig.class);
+    }
+
+    @Override
+    public PortDescription combine(ConnectPoint cp, PortDescription descr) {
+        PortAnnotationConfig cfg = lookupConfig(cp);
+        if (cfg == null) {
+            return descr;
+        }
+        Map<String, String> annotations = cfg.annotations();
+        if (annotations.isEmpty()) {
+            return descr;
+        }
+
+        Builder builder = DefaultAnnotations.builder();
+        builder.putAll(descr.annotations());
+        builder.putAll(annotations);
+
+        return DefaultPortDescription.copyReplacingAnnotation(descr, builder.build());
+    }
+
+}