Merge pull request #83 from m-chrzan/remik

Use new modular architecture when implementing the RMI API

14 files changed, 366 insertions, 55 deletions

diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/Agent.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/Agent.java
index 392e0a1..70da4af 100644
--- a/src/main/java/pl/edu/mimuw/cloudatlas/agent/Agent.java
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/Agent.java
@@ -1,22 +1,46 @@
 package pl.edu.mimuw.cloudatlas.agent;
 
+import java.rmi.registry.LocateRegistry;
+import java.rmi.registry.Registry;
+import java.rmi.server.UnicastRemoteObject;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.Map;
 
+import pl.edu.mimuw.cloudatlas.agent.NewApiImplementation;
+import pl.edu.mimuw.cloudatlas.agent.messages.UpdateAttributesMessage;
 import pl.edu.mimuw.cloudatlas.agent.modules.Module;
 import pl.edu.mimuw.cloudatlas.agent.modules.ModuleType;
 import pl.edu.mimuw.cloudatlas.agent.modules.Qurnik;
-import pl.edu.mimuw.cloudatlas.agent.modules.RMI;
+import pl.edu.mimuw.cloudatlas.agent.modules.Remik;
 import pl.edu.mimuw.cloudatlas.agent.modules.Stanik;
 import pl.edu.mimuw.cloudatlas.agent.modules.TimerScheduler;
+import pl.edu.mimuw.cloudatlas.api.Api;
+import pl.edu.mimuw.cloudatlas.interpreter.Main;
+import pl.edu.mimuw.cloudatlas.model.PathName;
+import pl.edu.mimuw.cloudatlas.model.ZMI;
 
 public class Agent {
+    private static EventBus eventBus;
+
+    public static void runRegistry() {
+        try {
+            NewApiImplementation api = new NewApiImplementation(eventBus);
+            Api apiStub =
+                    (Api) UnicastRemoteObject.exportObject(api, 0);
+            Registry registry = LocateRegistry.getRegistry();
+            registry.rebind("Api", apiStub);
+            System.out.println("Agent: api bound");
+        } catch (Exception e) {
+            System.err.println("Agent registry initialization exception:");
+            e.printStackTrace();
+        }
+    }
 
     public static HashMap<ModuleType, Module> initializeModules() {
         HashMap<ModuleType, Module> modules = new HashMap<ModuleType, Module>();
         modules.put(ModuleType.TIMER_SCHEDULER, new TimerScheduler(ModuleType.TIMER_SCHEDULER));
-        modules.put(ModuleType.RMI, new RMI(ModuleType.RMI));
+        modules.put(ModuleType.RMI, new Remik());
         modules.put(ModuleType.STATE, new Stanik());
         modules.put(ModuleType.QUERY, new Qurnik());
         // TODO add modules as we implement them
@@ -61,15 +85,39 @@ public class Agent {
         HashMap<ModuleType, Executor> executors = initializeExecutors(modules);
         ArrayList<Thread> executorThreads = initializeExecutorThreads(executors);
 
-        Thread eventBusThread = new Thread(new EventBus(executors));
+        eventBus = new EventBus(executors);
+        Thread eventBusThread = new Thread(eventBus);
         System.out.println("Initializing event bus");
         eventBusThread.start();
+    }
 
-        System.out.println("Closing executors");
-        closeExecutors(executorThreads);
+    private static void initZones() {
+        try {
+            ZMI root = Main.createTestHierarchy2();
+            addZoneAndChildren(root, new PathName(""));
+            System.out.println("Initialized with test hierarchy");
+        } catch (Exception e) {
+            System.out.println("ERROR: failed to create test hierarchy");
+        }
+    }
+
+    private static void addZoneAndChildren(ZMI zmi, PathName pathName) {
+        try {
+            System.out.println("trying to add " + pathName.toString());
+            UpdateAttributesMessage message = new UpdateAttributesMessage("", 0, pathName.toString(), zmi.getAttributes());
+            System.out.println("added it!");
+            eventBus.addMessage(message);
+            for (ZMI son : zmi.getSons()) {
+                addZoneAndChildren(son, pathName.levelDown(son.getAttributes().getOrNull("name").toString()));
+            }
+        } catch (Exception e) {
+            System.out.println("ERROR: failed to add zone");
+        }
     }
 
     public static void main(String[] args) {
         runModulesAsThreads();
+        runRegistry();
+        initZones();
     }
 }
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/EventBus.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/EventBus.java
index 5b09253..a6d3b2d 100644
--- a/src/main/java/pl/edu/mimuw/cloudatlas/agent/EventBus.java
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/EventBus.java
@@ -20,6 +20,10 @@ public class EventBus implements Runnable {
         }
     }
 
+    // Allows for testing with a mock EventBus
+    protected EventBus() {
+    }
+
     EventBus(HashMap<ModuleType, Executor> executors) {
         this.executors = executors;
         setEventBusReference();
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/NewApiImplementation.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/NewApiImplementation.java
new file mode 100644
index 0000000..def1d72
--- /dev/null
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/NewApiImplementation.java
@@ -0,0 +1,143 @@
+package pl.edu.mimuw.cloudatlas.agent;
+
+import java.io.PrintStream;
+
+import java.rmi.RemoteException;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.List;
+import java.util.AbstractMap.SimpleImmutableEntry;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+import java.util.regex.Pattern;
+import java.util.regex.Matcher;
+
+import pl.edu.mimuw.cloudatlas.agent.messages.RequestStateMessage;
+import pl.edu.mimuw.cloudatlas.agent.messages.ResponseMessage;
+import pl.edu.mimuw.cloudatlas.agent.messages.SetAttributeMessage;
+import pl.edu.mimuw.cloudatlas.agent.messages.StateMessage;
+import pl.edu.mimuw.cloudatlas.agent.messages.UpdateQueriesMessage;
+import pl.edu.mimuw.cloudatlas.interpreter.Interpreter;
+import pl.edu.mimuw.cloudatlas.interpreter.InterpreterException;
+import pl.edu.mimuw.cloudatlas.interpreter.Main;
+import pl.edu.mimuw.cloudatlas.interpreter.QueryResult;
+import pl.edu.mimuw.cloudatlas.model.Attribute;
+import pl.edu.mimuw.cloudatlas.model.AttributesMap;
+import pl.edu.mimuw.cloudatlas.model.PathName;
+import pl.edu.mimuw.cloudatlas.model.ValueContact;
+import pl.edu.mimuw.cloudatlas.model.Value;
+import pl.edu.mimuw.cloudatlas.model.ValueNull;
+import pl.edu.mimuw.cloudatlas.model.ValueQuery;
+import pl.edu.mimuw.cloudatlas.model.ValueSet;
+import pl.edu.mimuw.cloudatlas.model.ValueTime;
+import pl.edu.mimuw.cloudatlas.model.Type;
+import pl.edu.mimuw.cloudatlas.model.TypePrimitive;
+import pl.edu.mimuw.cloudatlas.model.ZMI;
+import pl.edu.mimuw.cloudatlas.api.Api;
+
+public class NewApiImplementation implements Api {
+    private EventBus eventBus;
+
+    public NewApiImplementation(EventBus eventBus) {
+        this.eventBus = eventBus;
+    }
+
+    public Set<String> getZoneSet() throws RemoteException {
+        CompletableFuture<ResponseMessage> responseFuture = new CompletableFuture();
+        RequestStateMessage message = new RequestStateMessage("", 0, responseFuture);
+        try {
+            eventBus.addMessage(message);
+            ResponseMessage response = responseFuture.get();
+
+            if (response.getType() == ResponseMessage.Type.STATE) {
+                StateMessage stateMessage = (StateMessage) response;
+                Set<String> zones = new HashSet<String>();
+                collectZoneNames(stateMessage.getZMI(), zones);
+                return zones;
+            } else {
+                System.out.println("ERROR: getZoneSet didn't receive a StateMessage");
+                throw new Exception("Failed to retrieve zone set");
+            }
+        } catch (Exception e) {
+            System.out.println("ERROR: exception caught in getZoneSet");
+            throw new RemoteException(e.getMessage());
+        }
+    }
+
+    private void collectZoneNames(ZMI zone, Set<String> names) {
+        names.add(zone.getPathName().toString());
+        for (ZMI son : zone.getSons()) {
+            collectZoneNames(son, names);
+        }
+    }
+
+    public AttributesMap getZoneAttributeValues(String zoneName) throws RemoteException {
+        CompletableFuture<ResponseMessage> responseFuture = new CompletableFuture();
+        RequestStateMessage message = new RequestStateMessage("", 0, responseFuture);
+        try {
+            eventBus.addMessage(message);
+            ResponseMessage response = responseFuture.get();
+
+            if (response.getType() == ResponseMessage.Type.STATE) {
+                StateMessage stateMessage = (StateMessage) response;
+                return stateMessage.getZMI().findDescendant(zoneName).getAttributes();
+            } else {
+                System.out.println("ERROR: getZoneSet didn't receive a StateMessage");
+                throw new Exception("Failed to retrieve zone set");
+            }
+        } catch (Exception e) {
+            System.out.println("ERROR: exception caught in getZoneSet");
+            throw new RemoteException(e.getMessage());
+        }
+    }
+
+    public void installQuery(String name, String queryCode) throws RemoteException {
+        Pattern queryNamePattern = Pattern.compile("&[a-zA-Z][\\w_]*");
+        Matcher matcher = queryNamePattern.matcher(name);
+        if (!matcher.matches()) {
+            throw new RemoteException("Invalid query identifier");
+        }
+        try {
+            ValueQuery query = new ValueQuery(queryCode);
+            Attribute attributeName = new Attribute(name);
+            ValueTime timestamp = new ValueTime(System.currentTimeMillis());
+            Map<Attribute, Entry<ValueQuery, ValueTime>> queries = new HashMap();
+            queries.put(attributeName, new SimpleImmutableEntry(query, timestamp));
+            UpdateQueriesMessage message = new UpdateQueriesMessage("", 0, queries);
+            eventBus.addMessage(message);
+        } catch (Exception e) {
+            throw new RemoteException("Failed to install query", e);
+        }
+    }
+
+    public void uninstallQuery(String queryName) throws RemoteException {
+        try {
+            Attribute attributeName = new Attribute(queryName);
+            ValueTime timestamp = new ValueTime(System.currentTimeMillis());
+            Map<Attribute, Entry<ValueQuery, ValueTime>> queries = new HashMap();
+            queries.put(attributeName, new SimpleImmutableEntry(null, timestamp));
+            UpdateQueriesMessage message = new UpdateQueriesMessage("", 0, queries);
+            eventBus.addMessage(message);
+        } catch (Exception e) {
+            System.out.println("ERROR: failed to remove query");
+            throw new RemoteException("Failed to uninstall query", e);
+        }
+    }
+
+    public void setAttributeValue(String zoneName, String attributeName, Value value) throws RemoteException {
+        try {
+            SetAttributeMessage message = new SetAttributeMessage("", 0, zoneName, new Attribute(attributeName), value, new ValueTime(System.currentTimeMillis()));
+            eventBus.addMessage(message);
+        } catch (Exception e) {
+            System.out.println("ERROR: failed to set attribute");
+            throw new RemoteException("Failed to set attribute", e);
+        }
+    }
+
+    public void setFallbackContacts(Set<ValueContact> contacts) throws RemoteException {
+        // this.contacts = contacts;
+    }
+}
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/RMIMessage.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/RemikMessage.java
index a8e3afb..b0300cb 100644
--- a/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/RMIMessage.java
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/RemikMessage.java
@@ -3,9 +3,20 @@ package pl.edu.mimuw.cloudatlas.agent.messages;
 import pl.edu.mimuw.cloudatlas.agent.modules.Module;
 import pl.edu.mimuw.cloudatlas.agent.modules.ModuleType;
 
-public class RMIMessage extends AgentMessage {
-    public RMIMessage(String messageId, long timestamp) {
+public abstract class RemikMessage extends AgentMessage {
+    public enum Type {
+        REQUEST_STATE
+    }
+
+    private Type type;
+
+    public RemikMessage(String messageId, long timestamp, Type type) {
         super(messageId, ModuleType.RMI, timestamp);
+        this.type = type;
+    }
+
+    public Type getType() {
+        return type;
     }
 
     public void callMe(Module module) throws InterruptedException, Module.InvalidMessageType {
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/RequestStateMessage.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/RequestStateMessage.java
new file mode 100644
index 0000000..698aac7
--- /dev/null
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/RequestStateMessage.java
@@ -0,0 +1,16 @@
+package pl.edu.mimuw.cloudatlas.agent.messages;
+
+import java.util.concurrent.CompletableFuture;
+
+public class RequestStateMessage extends RemikMessage {
+    CompletableFuture<ResponseMessage> responseFuture;
+
+    public RequestStateMessage(String messageId, long timestamp, CompletableFuture<ResponseMessage> responseFuture) {
+        super(messageId, timestamp, Type.REQUEST_STATE);
+        this.responseFuture = responseFuture;
+    }
+
+    public CompletableFuture<ResponseMessage> getFuture() {
+        return responseFuture;
+    }
+}
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/SetAttributeMessage.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/SetAttributeMessage.java
new file mode 100644
index 0000000..4888484
--- /dev/null
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/SetAttributeMessage.java
@@ -0,0 +1,37 @@
+package pl.edu.mimuw.cloudatlas.agent.messages;
+
+import pl.edu.mimuw.cloudatlas.agent.modules.ModuleType;
+import pl.edu.mimuw.cloudatlas.model.Attribute;
+import pl.edu.mimuw.cloudatlas.model.Value;
+import pl.edu.mimuw.cloudatlas.model.ValueTime;
+
+public class SetAttributeMessage extends StanikMessage {
+    private String pathName;
+    private Attribute attribute;
+    private Value value;
+    private ValueTime updateTimestamp;
+
+    public SetAttributeMessage(String messageId, long timestamp, String pathName, Attribute attribute, Value value, ValueTime updateTimestamp) {
+        super(messageId, timestamp, Type.SET_ATTRIBUTE);
+        this.pathName = pathName;
+        this.attribute = attribute;
+        this.value = value;
+        this.updateTimestamp = updateTimestamp;
+    }
+
+    public String getPathName() {
+        return pathName;
+    }
+
+    public Attribute getAttribute() {
+        return attribute;
+    }
+
+    public Value getValue() {
+        return value;
+    }
+
+    public ValueTime getUpdateTimestamp() {
+        return updateTimestamp;
+    }
+}
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/StanikMessage.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/StanikMessage.java
index d86de4a..844f31c 100644
--- a/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/StanikMessage.java
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/StanikMessage.java
@@ -7,6 +7,7 @@ public abstract class StanikMessage extends AgentMessage {
     public enum Type {
         GET_STATE,
         REMOVE_ZMI,
+        SET_ATTRIBUTE,
         UPDATE_ATTRIBUTES,
         UPDATE_QUERIES
     }
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Module.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Module.java
index ba5e1d1..0a934cb 100644
--- a/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Module.java
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Module.java
@@ -4,8 +4,8 @@ import pl.edu.mimuw.cloudatlas.agent.Executor;
 import pl.edu.mimuw.cloudatlas.agent.messages.AgentMessage;
 import pl.edu.mimuw.cloudatlas.agent.messages.TimerSchedulerMessage;
 import pl.edu.mimuw.cloudatlas.agent.messages.QurnikMessage;
+import pl.edu.mimuw.cloudatlas.agent.messages.RemikMessage;
 import pl.edu.mimuw.cloudatlas.agent.messages.ResponseMessage;
-import pl.edu.mimuw.cloudatlas.agent.messages.RMIMessage;
 import pl.edu.mimuw.cloudatlas.agent.messages.StanikMessage;
 
 /*
@@ -37,8 +37,8 @@ public abstract class Module {
         throw new InvalidMessageType("Got a QurnikMessage in module " + moduleType.toString());
     }
 
-    public void handleTyped(RMIMessage message) throws InterruptedException, InvalidMessageType {
-        throw new InvalidMessageType("Got an RMIMessage in module " + moduleType.toString());
+    public void handleTyped(RemikMessage message) throws InterruptedException, InvalidMessageType {
+        throw new InvalidMessageType("Got a RemikMessage in module " + moduleType.toString());
     }
 
     public void handleTyped(StanikMessage message) throws InterruptedException, InvalidMessageType {
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Qurnik.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Qurnik.java
index 9b7268a..1ab8a16 100644
--- a/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Qurnik.java
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Qurnik.java
@@ -80,13 +80,15 @@ public class Qurnik extends Module {
             Interpreter interpreter = new Interpreter(zmi);
             AttributesMap newAttributes = new AttributesMap();
             for (ValueQuery query : queries) {
-                try {
-                    List<QueryResult> result = interpreter.interpretProgram(query.getQuery());
-                    for(QueryResult r : result) {
-                        newAttributes.addOrChange(r.getName(), r.getValue());
+                if (query != null) {
+                    try {
+                        List<QueryResult> result = interpreter.interpretProgram(query.getQuery());
+                        for(QueryResult r : result) {
+                            newAttributes.addOrChange(r.getName(), r.getValue());
+                        }
+                    } catch(InterpreterException exception) {
+                        System.out.println("ERROR: thrown while running interpreter: " + exception.getMessage());
                     }
-                } catch(InterpreterException exception) {
-                    System.out.println("ERROR: thrown while running interpreter: " + exception.getMessage());
                 }
             }
 
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/RMI.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/RMI.java
deleted file mode 100644
index 1a86fc7..0000000
--- a/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/RMI.java
+++ /dev/null
@@ -1,37 +0,0 @@
-package pl.edu.mimuw.cloudatlas.agent.modules;
-
-import pl.edu.mimuw.cloudatlas.agent.ApiImplementation;
-import pl.edu.mimuw.cloudatlas.agent.messages.AgentMessage;
-import pl.edu.mimuw.cloudatlas.agent.messages.RMIMessage;
-import pl.edu.mimuw.cloudatlas.api.Api;
-import pl.edu.mimuw.cloudatlas.interpreter.Main;
-import pl.edu.mimuw.cloudatlas.model.ZMI;
-
-import java.rmi.registry.LocateRegistry;
-import java.rmi.registry.Registry;
-import java.rmi.server.UnicastRemoteObject;
-
-public class RMI extends Module {
-    public RMI(ModuleType moduleType) {
-        super(moduleType);
-        runRegistry();
-    }
-
-    public void runRegistry() {
-        try {
-            ZMI root = Main.createTestHierarchy2();
-            ApiImplementation api = new ApiImplementation(root);
-            Api apiStub =
-                    (Api) UnicastRemoteObject.exportObject(api, 0);
-            Registry registry = LocateRegistry.getRegistry();
-            registry.rebind("Api", apiStub);
-            System.out.println("Agent: api bound");
-        } catch (Exception e) {
-            System.err.println("Agent registry initialization exception:");
-            e.printStackTrace();
-        }
-    }
-
-    public void handleTyped(RMIMessage event) throws InterruptedException {
-    }
-}
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Remik.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Remik.java
new file mode 100644
index 0000000..9645d71
--- /dev/null
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Remik.java
@@ -0,0 +1,54 @@
+package pl.edu.mimuw.cloudatlas.agent.modules;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.HashMap;
+import java.util.Map;
+
+
+import pl.edu.mimuw.cloudatlas.agent.messages.GetStateMessage;
+import pl.edu.mimuw.cloudatlas.agent.messages.RemikMessage;
+import pl.edu.mimuw.cloudatlas.agent.messages.RequestStateMessage;
+import pl.edu.mimuw.cloudatlas.agent.messages.ResponseMessage;
+
+/*
+ * Remik is a cute little module that allows RMI functions to interface with
+ * agent's asynchronous modules.
+ */
+public class Remik extends Module {
+    private Map<Long, CompletableFuture<ResponseMessage>> awaitingRequests;
+    private long nextRequestId = 0;
+
+    public Remik() {
+        super(ModuleType.RMI);
+        awaitingRequests = new HashMap();
+    }
+
+    public void handleTyped(RemikMessage message) throws InvalidMessageType, InterruptedException {
+        switch (message.getType()) {
+            case REQUEST_STATE:
+                handleRequestState((RequestStateMessage) message);
+                break;
+            default:
+                throw new InvalidMessageType("This type of message cannot be handled by Remik");
+        }
+    }
+
+    public void handleTyped(ResponseMessage message) {
+        CompletableFuture<ResponseMessage> responseFuture = awaitingRequests.get(message.getRequestId());
+
+        if (responseFuture == null) {
+            System.out.println("ERROR: Remik got response for nonexistent/finished request");
+        } else {
+            responseFuture.complete(message);
+        }
+    }
+
+    private void handleRequestState(RequestStateMessage message) throws InterruptedException {
+        awaitingRequests.put(nextRequestId, message.getFuture());
+
+        GetStateMessage getStateMessage = new GetStateMessage("", 0, ModuleType.RMI, nextRequestId);
+        nextRequestId++;
+
+        sendMessage(getStateMessage);
+    }
+}
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Stanik.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Stanik.java
index b030901..3e5b790 100644
--- a/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Stanik.java
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Stanik.java
@@ -6,6 +6,7 @@ import java.util.Map.Entry;
 import pl.edu.mimuw.cloudatlas.agent.messages.AgentMessage;
 import pl.edu.mimuw.cloudatlas.agent.messages.GetStateMessage;
 import pl.edu.mimuw.cloudatlas.agent.messages.RemoveZMIMessage;
+import pl.edu.mimuw.cloudatlas.agent.messages.SetAttributeMessage;
 import pl.edu.mimuw.cloudatlas.agent.messages.StateMessage;
 import pl.edu.mimuw.cloudatlas.agent.messages.StanikMessage;
 import pl.edu.mimuw.cloudatlas.agent.messages.UpdateAttributesMessage;
@@ -49,6 +50,9 @@ public class Stanik extends Module {
             case REMOVE_ZMI:
                 handleRemoveZMI((RemoveZMIMessage) message);
                 break;
+            case SET_ATTRIBUTE:
+                handleSetAttribte((SetAttributeMessage) message);
+                break;
             case UPDATE_ATTRIBUTES:
                 handleUpdateAttributes((UpdateAttributesMessage) message);
                 break;
@@ -85,6 +89,27 @@ public class Stanik extends Module {
         }
     }
 
+    /*
+     * Always adds the new attribute.
+     * The zone must already exist.
+     * The zone's timestamp will be the maximum of its current timestamp or the
+     * timestamp provided with the new value.
+     */
+    public void handleSetAttribte(SetAttributeMessage message) {
+        try {
+            ZMI zmi = hierarchy.findDescendant(new PathName(message.getPathName()));
+            ValueTime updateTimestamp = message.getUpdateTimestamp();
+            ValueTime currentTimestamp = (ValueTime) zmi.getAttributes().getOrNull("timestamp");
+            if (ValueUtils.valueLower(currentTimestamp, updateTimestamp)) {
+                zmi.getAttributes().addOrChange("timestamp", updateTimestamp);
+            }
+
+            zmi.getAttributes().addOrChange(message.getAttribute(), message.getValue());
+        } catch (ZMI.NoSuchZoneException e) {
+            System.out.println("DEBUG: trying to set attribute in zone that doesn't exist");
+        }
+    }
+
     public void handleUpdateAttributes(UpdateAttributesMessage message) {
         try {
             validateUpdateAttributesMessage(message);
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/interpreter/Main.java b/src/main/java/pl/edu/mimuw/cloudatlas/interpreter/Main.java
index f91f25e..1e0bb4f 100644
--- a/src/main/java/pl/edu/mimuw/cloudatlas/interpreter/Main.java
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/interpreter/Main.java
@@ -277,16 +277,19 @@ public class Main {
         ZMI root = new ZMI();
         root.getAttributes().add("level", new ValueInt(0l));
         root.getAttributes().add("name", new ValueString(null));
+        root.getAttributes().add("timestamp", new ValueTime(10l));
 
         ZMI uw = new ZMI(root);
         root.addSon(uw);
         uw.getAttributes().add("level", new ValueInt(1l));
         uw.getAttributes().add("name", new ValueString("uw"));
+        uw.getAttributes().add("timestamp", new ValueTime(10l));
 
         ZMI pjwstk = new ZMI(root);
         root.addSon(pjwstk);
         pjwstk.getAttributes().add("level", new ValueInt(1l));
         pjwstk.getAttributes().add("name", new ValueString("pjwstk"));
+        pjwstk.getAttributes().add("timestamp", new ValueTime(10l));
 
         ZMI violet07 = new ZMI(uw);
         uw.addSon(violet07);
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/model/ZMI.java b/src/main/java/pl/edu/mimuw/cloudatlas/model/ZMI.java
index 54fbf43..cda0296 100644
--- a/src/main/java/pl/edu/mimuw/cloudatlas/model/ZMI.java
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/model/ZMI.java
@@ -219,8 +219,12 @@ public class ZMI implements Cloneable, Serializable {
      * @return a <code>PathName</code> object representing this zone
      */
     public PathName getPathName() {
-        String name = ((ValueString)getAttributes().get("name")).getValue();
-        return getFather() == null? PathName.ROOT : getFather().getPathName().levelDown(name);
+        if (getFather() == null) {
+            return PathName.ROOT;
+        } else {
+            String name = ((ValueString)getAttributes().get("name")).getValue();
+            return getFather().getPathName().levelDown(name);
+        }
     }
 
     public static ZMI deserialize(InputStream in) {