Implementing net config subsystem and revising its interfaces.

Added a few basic configs for device, host and links.

Added initial REST API.

Added CLI.

Tests remain to be added.

Change-Id: Ic7bba4b5ad7d553c51d69f6459b3bff146970323
diff --git a/cli/src/main/java/org/onosproject/cli/cfg/NetworkConfigCommand.java b/cli/src/main/java/org/onosproject/cli/cfg/NetworkConfigCommand.java
new file mode 100644
index 0000000..9d2e36f
--- /dev/null
+++ b/cli/src/main/java/org/onosproject/cli/cfg/NetworkConfigCommand.java
@@ -0,0 +1,109 @@
+/*
+ * Copyright 2015 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.cli.cfg;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import org.apache.karaf.shell.commands.Argument;
+import org.apache.karaf.shell.commands.Command;
+import org.onosproject.cli.AbstractShellCommand;
+import org.onosproject.incubator.net.config.Config;
+import org.onosproject.incubator.net.config.NetworkConfigService;
+import org.onosproject.incubator.net.config.SubjectFactory;
+
+import static com.google.common.base.Strings.isNullOrEmpty;
+
+/**
+ * Manages network configuration.
+ */
+@Command(scope = "onos", name = "netcfg",
+        description = "Manages network configuration")
+public class NetworkConfigCommand extends AbstractShellCommand {
+
+    @Argument(index = 0, name = "subjectKey", description = "Subject key",
+            required = false, multiValued = false)
+    String subjectKey = null;
+
+    @Argument(index = 1, name = "subject", description = "Subject",
+            required = false, multiValued = false)
+    String subject = null;
+
+    @Argument(index = 2, name = "configKey", description = "Config key",
+            required = false, multiValued = false)
+    String configKey = null;
+
+    private final ObjectMapper mapper = new ObjectMapper();
+    private NetworkConfigService service;
+
+    @Override
+    protected void execute() {
+        service = get(NetworkConfigService.class);
+        ObjectNode root = new ObjectMapper().createObjectNode();
+        if (isNullOrEmpty(subjectKey)) {
+            addAll(root);
+        } else {
+            SubjectFactory subjectFactory = service.getSubjectFactory(subjectKey);
+            if (isNullOrEmpty(subject)) {
+                addSubjectClass(root, subjectFactory);
+            } else {
+                Object s = subjectFactory.createSubject(subject);
+                if (isNullOrEmpty(configKey)) {
+                    addSubject(root, s);
+                } else {
+                    addSubjectConfig(root, getConfig(s, configKey));
+                }
+            }
+        }
+        print("%s", root.toString());
+    }
+
+    @SuppressWarnings("unchecked")
+    private void addAll(ObjectNode root) {
+        service.getSubjectClasses()
+                .forEach(sc -> {
+                    SubjectFactory sf = service.getSubjectFactory((Class) sc);
+                    addSubjectClass(newObject(root, sf.subjectKey()), sf);
+                });
+    }
+
+    @SuppressWarnings("unchecked")
+    private void addSubjectClass(ObjectNode root, SubjectFactory sf) {
+        service.getSubjects(sf.subjectClass())
+                .forEach(s -> addSubject(newObject(root, s.toString()), s));
+    }
+
+    private void addSubject(ObjectNode root, Object s) {
+        service.getConfigs(s)
+                .forEach(c -> addSubjectConfig(newObject(root, c.key()), getConfig(s, c.key())));
+    }
+
+    private void addSubjectConfig(ObjectNode root, Config config) {
+        if (config != null) {
+            root.set(config.key(), config.node());
+        }
+    }
+
+    private Config getConfig(Object s, String ck) {
+        Class<? extends Config> configClass = service.getConfigClass(ck);
+        return configClass != null ? service.getConfig(s, configClass) : null;
+    }
+
+    private ObjectNode newObject(ObjectNode parent, String key) {
+        ObjectNode node = mapper.createObjectNode();
+        parent.set(key, node);
+        return node;
+    }
+}