ONOS-542 Defining application subsystem interfaces & public constructs.

Change-Id: Iba0d2cb69dace5beee8a68def9918059ce755b5c
diff --git a/core/api/src/main/java/org/onosproject/core/Application.java b/core/api/src/main/java/org/onosproject/core/Application.java
new file mode 100644
index 0000000..d876a67
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/core/Application.java
@@ -0,0 +1,77 @@
+/*
+ * 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.core;
+
+import java.net.URI;
+import java.util.Optional;
+import java.util.Set;
+
+/**
+ * Abstraction of a network control/management application.
+ */
+public interface Application {
+
+    /**
+     * Returns the application name id.
+     *
+     * @return application identifier
+     */
+    ApplicationId id();
+
+    /**
+     * Returns the application version.
+     *
+     * @return application version
+     */
+    Version version();
+
+    /**
+     * Returns description of the application.
+     *
+     * @return application description text
+     */
+    String description();
+
+    /**
+     * Returns the name of the application origin, group or company.
+     *
+     * @return application origin
+     */
+    String origin();
+
+    /**
+     * Returns the permissions requested by the application.
+     *
+     * @return requested permissions
+     */
+    Set<Permission> permissions();
+
+    /**
+     * Returns the feature repository URI. Null value signifies that the
+     * application did not provide its own features repository.
+     *
+     * @return optional feature repo URL
+     */
+    Optional<URI> featuresRepo();
+
+    /**
+     * Returns the set of features comprising the application. At least one
+     * feature must be given.
+     *
+     * @return application features
+     */
+    Set<String> features();
+}
diff --git a/core/api/src/main/java/org/onosproject/core/ApplicationIdStore.java b/core/api/src/main/java/org/onosproject/core/ApplicationIdStore.java
index cef3f15..2236fc5 100644
--- a/core/api/src/main/java/org/onosproject/core/ApplicationIdStore.java
+++ b/core/api/src/main/java/org/onosproject/core/ApplicationIdStore.java
@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 package org.onosproject.core;
+// FIXME: Move to org.onosproject.app package
 
 import java.util.Set;
 
@@ -31,12 +32,21 @@
 
     /**
      * Returns an existing application id from a given id.
+     *
      * @param id the short value of the id
-     * @return an application id
+     * @return an application id; null if no such app registered
      */
     ApplicationId getAppId(Short id);
 
     /**
+     * Returns registered application id from the given name.
+     *
+     * @param name application name
+     * @return an application id; null if no such app registered
+     */
+    ApplicationId getAppId(String name);
+
+    /**
      * Registers a new application by its name, which is expected
      * to follow the reverse DNS convention, e.g.
      * {@code org.flying.circus.app}
diff --git a/core/api/src/main/java/org/onosproject/core/DefaultApplication.java b/core/api/src/main/java/org/onosproject/core/DefaultApplication.java
new file mode 100644
index 0000000..4da85a5
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/core/DefaultApplication.java
@@ -0,0 +1,136 @@
+/*
+ * 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.core;
+
+import java.net.URI;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+
+import static com.google.common.base.MoreObjects.toStringHelper;
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * Default implementation of network control/management application descriptor.
+ */
+public class DefaultApplication implements Application {
+
+    private final ApplicationId appId;
+    private final Version version;
+    private final String description;
+    private final String origin;
+    private final Set<Permission> permissions;
+    private final Optional<URI> featuresRepo;
+    private final Set<String> features;
+
+    /**
+     * Creates a new application descriptor using the supplied data.
+     *
+     * @param appId        application identifier
+     * @param version      application version
+     * @param description  application description
+     * @param origin       origin company
+     * @param permissions  requested permissions
+     * @param featuresRepo optional features repo URI
+     * @param features     application features
+     */
+    public DefaultApplication(ApplicationId appId, Version version,
+                              String description, String origin,
+                              Set<Permission> permissions,
+                              Optional<URI> featuresRepo, Set<String> features) {
+        this.appId = checkNotNull(appId, "ID cannot be null");
+        this.version = checkNotNull(version, "Version cannot be null");
+        this.description = checkNotNull(description, "Description cannot be null");
+        this.origin = checkNotNull(origin, "Origin cannot be null");
+        this.permissions = checkNotNull(permissions, "Permissions cannot be null");
+        this.featuresRepo = checkNotNull(featuresRepo, "Features repo cannot be null");
+        this.features = checkNotNull(features, "Features cannot be null");
+        checkArgument(!features.isEmpty(), "There must be at least one feature");
+    }
+
+    @Override
+    public ApplicationId id() {
+        return appId;
+    }
+
+    @Override
+    public Version version() {
+        return version;
+    }
+
+    @Override
+    public String description() {
+        return description;
+    }
+
+    @Override
+    public String origin() {
+        return origin;
+    }
+
+    @Override
+    public Set<Permission> permissions() {
+        return permissions;
+    }
+
+    @Override
+    public Optional<URI> featuresRepo() {
+        return featuresRepo;
+    }
+
+    @Override
+    public Set<String> features() {
+        return features;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(appId, version, description, origin, permissions,
+                            featuresRepo, features);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj == null || getClass() != obj.getClass()) {
+            return false;
+        }
+        final DefaultApplication other = (DefaultApplication) obj;
+        return Objects.equals(this.appId, other.appId) &&
+                Objects.equals(this.version, other.version) &&
+                Objects.equals(this.description, other.description) &&
+                Objects.equals(this.origin, other.origin) &&
+                Objects.equals(this.permissions, other.permissions) &&
+                Objects.equals(this.featuresRepo, other.featuresRepo) &&
+                Objects.equals(this.features, other.features);
+    }
+
+    @Override
+    public String toString() {
+        return toStringHelper(this)
+                .add("appId", appId)
+                .add("version", version)
+                .add("description", description)
+                .add("origin", origin)
+                .add("permissions", permissions)
+                .add("featuresRepo", featuresRepo)
+                .add("features", features)
+                .toString();
+    }
+}
diff --git a/core/api/src/main/java/org/onosproject/core/DefaultApplicationId.java b/core/api/src/main/java/org/onosproject/core/DefaultApplicationId.java
index e6f448e..3a07b2b 100644
--- a/core/api/src/main/java/org/onosproject/core/DefaultApplicationId.java
+++ b/core/api/src/main/java/org/onosproject/core/DefaultApplicationId.java
@@ -18,6 +18,7 @@
 import java.util.Objects;
 
 import static com.google.common.base.MoreObjects.toStringHelper;
+import static com.google.common.base.Preconditions.checkArgument;
 
 /**
  * Application identifier.
@@ -33,8 +34,9 @@
      * @param id   application identifier
      * @param name application name
      */
-    public DefaultApplicationId(Short id, String name) {
-        this.id = id;
+    public DefaultApplicationId(int id, String name) {
+        checkArgument(0 <= id && id <= Short.MAX_VALUE, "id is outside range");
+        this.id = (short) id;
         this.name = name;
     }
 
diff --git a/core/api/src/main/java/org/onosproject/core/Permission.java b/core/api/src/main/java/org/onosproject/core/Permission.java
new file mode 100644
index 0000000..d32d059
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/core/Permission.java
@@ -0,0 +1,23 @@
+/*
+ * 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.core;
+
+/**
+ * Representation of an application permission.
+ */
+public interface Permission {
+    // TODO: to be fleshed out
+}