Copy policy-endpoints from drools-pdp to common

Issue-ID: POLICY-967
Change-Id: I374c155ee102c3e157c60d0a22d7191544abb76a
Signed-off-by: mmis <michael.morris@ericsson.com>

1 files changed, 229 insertions, 0 deletions

diff --git a/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/bus/internal/TopicBase.java b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/bus/internal/TopicBase.java
new file mode 100644
index 00000000..ed15ddf7
--- /dev/null
+++ b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/bus/internal/TopicBase.java
@@ -0,0 +1,229 @@
+/*
+ * ============LICENSE_START=======================================================
+ * policy-endpoints
+ * ================================================================================
+ * Copyright (C) 2017-2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * 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.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.endpoints.event.comm.bus.internal;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.commons.collections4.queue.CircularFifoQueue;
+import org.onap.policy.common.endpoints.event.comm.Topic;
+import org.onap.policy.common.endpoints.event.comm.TopicListener;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public abstract class TopicBase implements Topic {
+
+    /**
+     * logger
+     */
+    private static Logger logger = LoggerFactory.getLogger(TopicBase.class);
+
+    /**
+     * list of servers
+     */
+    protected List<String> servers;
+
+    /**
+     * Topic
+     */
+    protected String topic;
+
+    /**
+     * event cache
+     */
+    protected CircularFifoQueue<String> recentEvents = new CircularFifoQueue<>(10);
+
+    /**
+     * Am I running? reflects invocation of start()/stop() !locked & start() => alive stop() =>
+     * !alive
+     */
+    protected volatile boolean alive = false;
+
+    /**
+     * Am I locked? reflects invocation of lock()/unlock() operations locked => !alive (but not in
+     * the other direction necessarily) locked => !offer, !run, !start, !stop (but this last one is
+     * obvious since locked => !alive)
+     */
+    protected volatile boolean locked = false;
+
+    /**
+     * All my subscribers for new message notifications
+     */
+    protected final ArrayList<TopicListener> topicListeners = new ArrayList<>();
+
+    /**
+     * Instantiates a new Topic Base
+     * 
+     * @param servers list of servers
+     * @param topic topic name
+     * 
+     * @return a Topic Base
+     * @throws IllegalArgumentException if invalid parameters are present
+     */
+    public TopicBase(List<String> servers, String topic) {
+
+        if (servers == null || servers.isEmpty()) {
+            throw new IllegalArgumentException("Server(s) must be provided");
+        }
+
+        if (topic == null || topic.isEmpty()) {
+            throw new IllegalArgumentException("A Topic must be provided");
+        }
+
+        this.servers = servers;
+        this.topic = topic;
+    }
+
+    @Override
+    public void register(TopicListener topicListener) {
+
+        logger.info("{}: registering {}", this, topicListener);
+
+        synchronized (this) {
+            if (topicListener == null) {
+                throw new IllegalArgumentException("TopicListener must be provided");
+            }
+
+            for (TopicListener listener : this.topicListeners) {
+                if (listener == topicListener) {
+                    return;
+                }
+            }
+
+            this.topicListeners.add(topicListener);
+        }
+    }
+
+    @Override
+    public void unregister(TopicListener topicListener) {
+
+        logger.info("{}: unregistering {}", this, topicListener);
+
+        synchronized (this) {
+            if (topicListener == null) {
+                throw new IllegalArgumentException("TopicListener must be provided");
+            }
+
+            this.topicListeners.remove(topicListener);
+        }
+    }
+
+    /**
+     * broadcast event to all listeners
+     * 
+     * @param message the event
+     * @return true if all notifications are performed with no error, false otherwise
+     */
+    protected boolean broadcast(String message) {
+        List<TopicListener> snapshotListeners = this.snapshotTopicListeners();
+
+        boolean success = true;
+        for (TopicListener topicListener : snapshotListeners) {
+            try {
+                topicListener.onTopicEvent(this.getTopicCommInfrastructure(), this.topic, message);
+            } catch (Exception e) {
+                logger.warn("{}: notification error @ {} because of {}", this, topicListener, e.getMessage(), e);
+                success = false;
+            }
+        }
+        return success;
+    }
+
+    /**
+     * take a snapshot of current topic listeners
+     * 
+     * @return the topic listeners
+     */
+    protected synchronized List<TopicListener> snapshotTopicListeners() {
+        @SuppressWarnings("unchecked")
+        List<TopicListener> listeners = (List<TopicListener>) topicListeners.clone();
+        return listeners;
+    }
+
+    @Override
+    public boolean lock() {
+
+        logger.info("{}: locking", this);
+
+        synchronized (this) {
+            if (this.locked) {
+                return true;
+            }
+
+            this.locked = true;
+        }
+
+        return this.stop();
+    }
+
+    @Override
+    public boolean unlock() {
+        logger.info("{}: unlocking", this);
+
+        synchronized (this) {
+            if (!this.locked) {
+                return true;
+            }
+
+            this.locked = false;
+        }
+
+        try {
+            return this.start();
+        } catch (Exception e) {
+            logger.warn("{}: cannot after unlocking because of {}", this, e.getMessage(), e);
+            return false;
+        }
+    }
+
+    @Override
+    public boolean isLocked() {
+        return this.locked;
+    }
+
+    @Override
+    public String getTopic() {
+        return topic;
+    }
+
+    @Override
+    public boolean isAlive() {
+        return this.alive;
+    }
+
+    @Override
+    public List<String> getServers() {
+        return servers;
+    }
+
+    @Override
+    public synchronized String[] getRecentEvents() {
+        String[] events = new String[recentEvents.size()];
+        return recentEvents.toArray(events);
+    }
+
+
+    @Override
+    public String toString() {
+        return "TopicBase [servers=" + servers + ", topic=" + topic + ", #recentEvents=" + recentEvents.size()
+                + ", locked=" + locked + ", #topicListeners=" + topicListeners.size() + "]";
+    }
+}