Merged topic subscription search and publish into single MessagePublisher method

First step on implementing H2 storage

Minor, fixed not imported class

Cleaned MessageStore interface to avoid duplication of methods used in couple. Switched from guid + message to move messages

Separated ISubscriptionsStore from ISessionStore

Implemented H2 queue

broker/src/test/java/io/moquette/persistence/MessageStoreTCK.java

@@ -0,0 +1,92 @@
+package io.moquette.persistence;
+
+import io.moquette.spi.*;
+import io.moquette.spi.IMessagesStore.StoredMessage;
+import io.moquette.spi.ISubscriptionsStore.ClientTopicCouple;
+import io.moquette.spi.impl.subscriptions.Subscription;
+import io.moquette.spi.impl.subscriptions.Topic;
+import io.netty.buffer.ByteBuf;
+import io.netty.handler.codec.mqtt.MqttQoS;
+import org.junit.Test;
+
+import java.util.List;
+
+import static io.moquette.spi.impl.subscriptions.Topic.asTopic;
+import static io.netty.handler.codec.mqtt.MqttQoS.AT_MOST_ONCE;
+import static io.netty.handler.codec.mqtt.MqttQoS.EXACTLY_ONCE;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+/**
+ * Defines all test that an implementation of a IMessageStore should satisfy.
+ * */
+public abstract class MessageStoreTCK {
+
+    public static final String TEST_CLIENT = "TestClient";
+    protected ISessionsStore sessionsStore;
+    protected IMessagesStore messagesStore;
+
+    @Test
+    public void testDropMessagesInSessionDoesntCleanAnyRetainedStoredMessages() {
+        final ClientSession session = sessionsStore.createNewSession(TEST_CLIENT, true);
+        StoredMessage publishToStore = new StoredMessage("Hello".getBytes(), EXACTLY_ONCE, "/topic");
+        publishToStore.setClientID(TEST_CLIENT);
+        publishToStore.setRetained(true);
+        messagesStore.storeRetained(new Topic("/topic"), publishToStore);
+
+        // Exercise
+        session.cleanSession();
+
+        // Verify the message store for session is empty.
+        StoredMessage storedPublish = messagesStore.searchMatching(new IMatchingCondition() {
+
+            @Override
+            public boolean match(Topic key) {
+                return key.match(new Topic("/topic"));
+            }
+        }).iterator().next();
+        assertNotNull("The stored retained message must be present after client's session drop", storedPublish);
+    }
+
+    @Test
+    public void testStoreRetained() {
+        StoredMessage msgStored = new StoredMessage("Hello".getBytes(), MqttQoS.AT_LEAST_ONCE, "/topic");
+        msgStored.setClientID(TEST_CLIENT);
+
+        messagesStore.storeRetained(asTopic("/topic"), msgStored);
+
+        //Verify the message is in the store
+        StoredMessage msgRetrieved = messagesStore.searchMatching(new IMatchingCondition() {
+
+            @Override
+            public boolean match(Topic key) {
+                return key.match(new Topic("/topic"));
+            }
+        }).iterator().next();
+
+        final ByteBuf payload = msgRetrieved.getPayload();
+        byte[] content = new byte[payload.readableBytes()];
+        payload.readBytes(content);
+        assertEquals("Hello", new String(content));
+    }
+
+    @Test
+    public void givenSubscriptionAlreadyStoredIsOverwrittenByAnotherWithSameTopic() {
+        ClientSession session1 = sessionsStore.createNewSession("SESSION_ID_1", true);
+
+        // Subscribe on /topic with QOSType.MOST_ONE
+        Subscription oldSubscription = new Subscription(session1.clientID, new Topic("/topic"), AT_MOST_ONCE);
+        session1.subscribe(oldSubscription);
+
+        // Subscribe on /topic again that overrides the previous subscription.
+        Subscription overridingSubscription = new Subscription(session1.clientID, new Topic("/topic"), EXACTLY_ONCE);
+        session1.subscribe(overridingSubscription);
+
+        // Verify
+        final ISubscriptionsStore subscriptionsStore = sessionsStore.subscriptionStore();
+        List<ClientTopicCouple> subscriptions = subscriptionsStore.listAllSubscriptions();
+        assertEquals(1, subscriptions.size());
+        Subscription sub = subscriptionsStore.getSubscription(subscriptions.get(0));
+        assertEquals(overridingSubscription.getRequestedQos(), sub.getRequestedQos());
+    }
+}