Set up a callback system for the browser link.

This should somewhat simulate asynchronous method calling.

add-on/background.js

@@ -9,12 +9,5 @@ Listen for messages from the app.
 */
 port.onMessage.addListener((response) => {
   console.log("Received: " + response);
+  port.postMessage("pong");
 });
-
-/*
-On a click on the browser action, send the app a message.
-*/
-browser.browserAction.onClicked.addListener(() => {
-  console.log("Sending:  ping");
-  port.postMessage("ping");
-});

addonInter/src/main/java/edu/regis/universeplayer/addon/BrowserLink.java

@@ -0,0 +1,475 @@
+/*
+ * Copyright (c) 2021 William Hubbard. All Rights Reserved.
+ */
+
+package edu.regis.universeplayer.addon;
+
+import com.google.gson.*;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedInputStream;
+import java.io.BufferedOutputStream;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.charset.StandardCharsets;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+/**
+ * The browser link serves as a communication between this process and the
+ * browser. It automatically converts information as needed as it passes it to
+ * and from the browser process.
+ *
+ * @author William Hubbard
+ * @version 0.1
+ */
+public class BrowserLink implements Runnable
+{
+    private static Logger logger = LoggerFactory.getLogger(BrowserLink.class);
+    public static final Gson gson = new Gson();
+    
+    private BufferedInputStream browserIn;
+    private BufferedOutputStream browserOut;
+    
+    private final Object readLock = new Object();
+    
+    /**
+     * This queue serves as a cache for objects we need to send.
+     */
+    private final LinkedList<MessagePacket> sendQueue = new LinkedList<>();
+    
+    private boolean running;
+    
+    @Override
+    public void run()
+    {
+        MessagePacket packet;
+        this.running = true;
+        try
+        {
+            browserIn = new BufferedInputStream(System.in);
+            browserOut = new BufferedOutputStream(System.out);
+            
+            while (this.running)
+            {
+                /*
+                 * Sends all messages
+                 */
+                synchronized (this.sendQueue)
+                {
+                    packet = this.sendQueue.poll();
+                }
+                if (packet != null)
+                {
+                    try
+                    {
+                        this.browserOut.write(packet.message[0]);
+                        this.browserOut.write(packet.message[1]);
+                        this.browserOut.flush();
+                        
+                        /*
+                         * Wait for a response from the browser.
+                         */
+                        byte[][] returnMessage = this.readMessage();
+                        packet.returnMessage = returnMessage;
+                        if (returnMessage == null)
+                        {
+                            logger.info("Browser connection closed.");
+                            this.running = false;
+                        }
+                        synchronized (this.readLock)
+                        {
+                            logger.trace("Received message, notifying futures.");
+                            this.readLock.notifyAll();
+                        }
+                    }
+                    catch (IOException e)
+                    {
+                        logger.error("Could not send message " + new String(packet.message[1], StandardCharsets.UTF_8), e);
+                    }
+                }
+            }
+        }
+        finally
+        {
+            /*
+             * Release locks
+             */
+            synchronized (this.sendQueue)
+            {
+                while (this.sendQueue.size() > 0)
+                {
+                    packet = this.sendQueue.poll();
+                    packet.returnMessage = null;
+                }
+            }
+            synchronized (this.readLock)
+            {
+                this.readLock.notifyAll();
+            }
+            try
+            {
+                browserIn.close();
+            }
+            catch (IOException e1)
+            {
+                logger.error("Could not close browser input", e1);
+            }
+            finally
+            {
+                try
+                {
+                    browserOut.close();
+                }
+                catch (IOException e1)
+                {
+                    logger.error("Could not close browser output", e1);
+                }
+            }
+        }
+    }
+    
+    /**
+     * Reads a message from the browser input.
+     *
+     * @return - A new message packet from the browser, or null if it has been closed.
+     * @throws IOException - Should a read error occur.
+     */
+    private byte[][] readMessage() throws IOException
+    {
+        ByteBuffer headerReader;
+        int rawLength, messageLength;
+        byte[] header = new byte[4];
+        byte[] message;
+        
+        rawLength = browserIn.read(header);
+        
+        /*
+         * A value of 0 or -1 indicates that there are no more messages, and
+         * that the channel has been closed.
+         */
+        if (rawLength <= 0)
+        {
+            logger.info("The browser channel has been closed.");
+            return null;
+        }
+        
+        headerReader = ByteBuffer.wrap(header, 0, rawLength);
+        /*
+         * The browser outputs in whatever the native endian order,
+         * which may not be what Java does.
+         */
+        headerReader.order(ByteOrder.nativeOrder());
+        messageLength = headerReader.getInt();
+        logger.debug("Receiving message of {} length", messageLength);
+        message = new byte[messageLength];
+        browserIn.read(message);
+        logger.debug("Unpacking message {} (length {})", new String(message, StandardCharsets.UTF_8), messageLength);
+        return new byte[][] {header, message};
+    }
+    
+    /**
+     * Sends an object to the browser.
+     *
+     * @param message - The object to send.
+     * @return A future for the response from the browser.
+     */
+    public Future<Object> sendObject(Object message)
+    {
+        String messageJson;
+        byte[] messageData;
+        ByteBuffer header;
+        byte[][] packet;
+        Future<Object> future;
+        MessagePacket packetEntry;
+        
+        logger.debug("Sending message {}", message);
+        
+        messageJson = gson.toJson(message);
+        messageData = messageJson.getBytes(StandardCharsets.UTF_8);
+        header = ByteBuffer.allocate(4);
+        /*
+         * The browser outputs in whatever the native endian order is,
+         * which may not be what Java does.
+         */
+        header.order(ByteOrder.nativeOrder());
+        header.putInt(messageData.length);
+        logger.debug("Writing message {} {}", header.array(), messageJson);
+        
+        packetEntry = new MessagePacket(new byte[][] {header.array(), messageData});
+        
+        future = new Future<>()
+        {
+            private boolean canceled = false;
+            
+            @Override
+            public boolean cancel(boolean mayInterruptIfRunning)
+            {
+                synchronized (sendQueue)
+                {
+                    if (sendQueue.remove(packetEntry))
+                    {
+                        canceled = true;
+                        if (mayInterruptIfRunning)
+                        {
+                            logger.trace("Canceling future, notifying self futures.");
+                            synchronized (readLock)
+                            {
+                                readLock.notifyAll();
+                            }
+                        }
+                        else
+                        {
+                            logger.trace("Canceling future.");
+                        }
+                        return true;
+                    }
+                    else
+                    {
+                        return false;
+                    }
+                }
+            }
+            
+            @Override
+            public boolean isCancelled()
+            {
+                return this.canceled;
+            }
+            
+            @Override
+            public boolean isDone()
+            {
+                return packetEntry.returnMessage != null;
+            }
+            
+            @Override
+            public Object get() throws InterruptedException, ExecutionException
+            {
+                logger.trace("Future waiting for message");
+                synchronized (readLock)
+                {
+                    while (!this.canceled && packetEntry.returnMessage == null)
+                    {
+                        readLock.wait();
+                    }
+                }
+                if (packetEntry.returnMessage == null)
+                {
+                    throw new InterruptedException();
+                }
+                logger.trace("Future has received message");
+                try
+                {
+                    return getMessage(packetEntry.returnMessage[1]);
+                }
+                catch (IOException e)
+                {
+                    throw new ExecutionException(e);
+                }
+            }
+            
+            @Override
+            public Object get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException
+            {
+                logger.trace("Future waiting for message");
+                synchronized (readLock)
+                {
+                    while (!this.canceled && packetEntry.returnMessage == null)
+                    {
+                        readLock.wait(unit.toMillis(timeout));
+                    }
+                }
+                if (packetEntry.returnMessage == null)
+                {
+                    throw new InterruptedException();
+                }
+                logger.trace("Future has received message");
+                try
+                {
+                    return getMessage(packetEntry.returnMessage[1]);
+                }
+                catch (IOException e)
+                {
+                    throw new ExecutionException(e);
+                }
+            }
+        };
+        
+        packetEntry.returnValue = future;
+        
+        synchronized (this.sendQueue)
+        {
+            sendQueue.add(packetEntry);
+        }
+        
+        return future;
+    }
+    
+    /**
+     * Queries for the next message from the browser.
+     *
+     * @return The received message
+     * @throws IOException - If there is an error when reading the next object,
+     *                     or if the browser connection is closed.
+     */
+    private Object getMessage(byte[] messageData) throws IOException
+    {
+        JsonElement message = gson.fromJson(new String(messageData, StandardCharsets.UTF_8), JsonElement.class);
+        return getMessage(message);
+    }
+    
+    /**
+     * Translates a JSON element into a Java object
+     *
+     * @param message - The message to translate.
+     * @return A java object, whether it be a primitive wrapper or an actual
+     * object.
+     * @throws IOException - Thrown if we cannot determine what type of JSON
+     *                     element was provided.
+     */
+    private Object getMessage(JsonElement message) throws IOException
+    {
+        if (message.isJsonPrimitive())
+        {
+            return getPrimitiveMessage((JsonPrimitive) message);
+        }
+        else if (message.isJsonObject())
+        {
+            return getObjectMessage((JsonObject) message);
+        }
+        else if (message.isJsonArray())
+        {
+            return getArrayMessage((JsonArray) message);
+        }
+        else if (message.isJsonNull())
+        {
+            return null;
+        }
+        else
+        {
+            throw new IOException("Unknown JSON element " + message.getClass());
+        }
+    }
+    
+    /**
+     * Translates a JSON primitive element into a Java object.
+     *
+     * @param message - The message to translate.
+     * @return A java object, whether it be a {@link Number} object, a
+     * {@link Boolean} object, or a {@link String} object.
+     * @throws IOException - Thrown if we cannot determine what type of JSON
+     *                     element was provided.
+     */
+    private Object getPrimitiveMessage(JsonPrimitive message) throws IOException
+    {
+        if (message.isBoolean())
+        {
+            return message.getAsBoolean();
+        }
+        else if (message.isNumber())
+        {
+            return message.getAsNumber();
+        }
+        else if (message.isString())
+        {
+            return message.getAsString();
+        }
+        else
+        {
+            throw new IOException("Unknown JSON element " + message.getClass());
+        }
+    }
+    
+    /**
+     * Translates a JSON object element into a Java object.
+     *
+     * @param message - The message to translate.
+     * @return A java object, or a {@link HashMap} containing objects if we
+     * cannot parse it.
+     */
+    private Object getObjectMessage(JsonObject message)
+    {
+        HashMap<String, Object> type;
+        Class<?> clazz = null;
+        if (message.has("type"))
+        {
+            try
+            {
+                clazz = Class.forName(message.getAsJsonPrimitive("type").getAsString());
+            }
+            catch (ClassNotFoundException | ClassCastException e)
+            {
+                logger.error("Illegal class type " + message.get("type"), e);
+            }
+        }
+        
+        if (clazz != null)
+        {
+            return gson.fromJson(message, clazz);
+        }
+        else
+        {
+            /*
+             * If all else fails, just return a standard hashmap. That should work.
+             */
+            type = new HashMap<>();
+            message.entrySet().forEach(entry -> {
+                try
+                {
+                    type.put(entry.getKey(), getMessage(entry.getValue()));
+                }
+                catch (IOException e)
+                {
+                    logger.error("Could not parse message entry " + entry.getKey() + " (" + entry.getValue() + ")", e);
+                }
+            });
+            return type;
+        }
+    }
+    
+    /**
+     * Translates a JSON array element into a Java array.
+     *
+     * @param message - The message to translate.
+     * @return A java array. It may contain a variety of element types.
+     * @throws IOException - Thrown if we cannot determine what type of JSON
+     *                     element was provided.
+     */
+    private Object getArrayMessage(JsonArray message) throws IOException
+    {
+        Object[] returnValue = new Object[message.size()];
+        for (int i = 0, l = returnValue.length; i < l; i++)
+        {
+            returnValue[i] = getMessage(message.get(i));
+        }
+        return returnValue;
+    }
+    
+    /**
+     * This represents a sent message in storage.
+     */
+    private class MessagePacket
+    {
+        public final byte[][] message;
+        public byte[][] returnMessage;
+        public Future<Object> returnValue;
+        
+        public MessagePacket(byte[][] message)
+        {
+            this(message, null);
+        }
+        
+        public MessagePacket(byte[][] message, Future<Object> returnValue)
+        {
+            this.message = message;
+            this.returnValue = returnValue;
+        }
+    }
+}

addonInter/src/main/java/edu/regis/universeplayer/addon/Main.java

@@ -4,181 +4,32 @@
 
 package edu.regis.universeplayer.addon;
 
-import com.google.gson.Gson;
-import com.google.gson.JsonElement;
-import com.google.gson.JsonObject;
-import com.google.gson.JsonPrimitive;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.io.BufferedInputStream;
+import java.util.LinkedList;
-import java.io.BufferedOutputStream;
+import java.util.concurrent.ExecutionException;
-import java.io.DataOutputStream;
+import java.util.concurrent.Future;
-import java.io.IOException;
-import java.nio.ByteBuffer;
-import java.nio.ByteOrder;
-import java.nio.charset.StandardCharsets;
 
 public class Main
 {
     private static Logger logger = LoggerFactory.getLogger(Main.class);
     
-    private static final Gson gson = new Gson();
+    public static void main(String[] args) throws ExecutionException, InterruptedException
-    
-    private static BufferedInputStream browserIn;
-    private static BufferedOutputStream browserOut;
-    
-    public static void main(String[] args)
     {
-        boolean running = true;
+        LinkedList<Future<Object>> requests = new LinkedList<>();
-        int rawLength, messageLength;
+        BrowserLink link = new BrowserLink();
-        byte[] header = new byte[4];
+        Thread linkThread = new Thread(link);
-        byte[] message;
+        linkThread.start();
-        JsonElement messageJson;
+        logger.info("Sending message");
-        JsonPrimitive jsonPrimative;
+        for (int i = 0, l = 20; i < l; i++)
-        JsonObject jsonObject;
-        ByteBuffer headerReader;
-        
-        System.err.printf("Working from directory %s\n", System.getProperty("user.dir"));
-        if (ByteOrder.nativeOrder().equals(ByteOrder.BIG_ENDIAN))
         {
-            logger.info("Incoming messages will be Big-endian");
+            Future<Object> future = link.sendObject("ping");
+            requests.add(future);
         }
-        else
+        while (requests.size() > 0)
         {
-            logger.info("Incoming messages will be Little-endian");
+            logger.info("Message received: {}", requests.poll().get());
-        }
-        try
-        {
-            browserIn = new BufferedInputStream(System.in);
-            browserOut = new BufferedOutputStream(System.out);
-            while (running)
-            {
-                try
-                {
-                    rawLength = browserIn.read(header);
-                    
-                    if (rawLength <= 0)
-                    {
-                        running = false;
-                        break;
-                    }
-                    
-                    headerReader = ByteBuffer.wrap(header, 0, rawLength);
-                    /*
-                     * The browser outputs in whatever the native endian order,
-                     * which may not be what Java does.
-                     */
-                    headerReader.order(ByteOrder.nativeOrder());
-                    messageLength = headerReader.getInt();
-                    logger.debug("Receiving message of {} length", messageLength);
-                    message = new byte[messageLength];
-                    browserIn.read(message);
-                    logger.debug("Unpacking message {} (length {})", new String(message, "UTF-8"), messageLength);
-                    
-                    messageJson = gson.fromJson(new String(message, StandardCharsets.UTF_8), JsonElement.class);
-                    logger.debug("Reading JSON element {} (type: {})", messageJson, messageJson.getClass());
-                    
-                    if (messageJson.isJsonPrimitive())
-                    {
-                        jsonPrimative = ((JsonPrimitive) messageJson);
-                        if (jsonPrimative.isBoolean())
-                        {
-                            handleMessage(jsonPrimative.getAsBoolean());
-                        }
-                        else if (jsonPrimative.isNumber())
-                        {
-                            handleMessage(jsonPrimative.getAsNumber());
-                        }
-                        else if (jsonPrimative.isString())
-                        {
-                            handleMessage(jsonPrimative.getAsString());
-                        }
-                    }
-                    else if (messageJson.isJsonObject())
-                    {
-                        jsonObject = ((JsonObject) messageJson);
-                        // TODO - Parse the object into Java objects
-                    }
-                }
-                catch (IOException e)
-                {
-                    logger.error("Could not create input stream", e);
-                    // Forward it to the browser via STDERR
-                    e.printStackTrace();
-                }
-            }
-        }
-        finally
-        {
-            try
-            {
-                browserIn.close();
-            }
-            catch (IOException e1)
-            {
-                logger.error("Could not close browser input", e1);
-            }
-            try
-            {
-                browserOut.close();
-            }
-            catch (IOException e1)
-            {
-                logger.error("Could not close browser output", e1);
-            }
-        }
-    }
-    
-    /**
-     * A callback for when a message is sent from the browser
-     *
-     * @param message - The message sent.
-     */
-    private static void handleMessage(Object message)
-    {
-        if (message instanceof String)
-        {
-            if (message.equals("ping"))
-            {
-                sendMessage("pong");
-            }
-        }
-    }
-    
-    /**
-     * A callback for when a message is sent from the browser
-     *
-     * @param message - The message sent.
-     */
-    public static void sendMessage(Object message)
-    {
-        String messageJson;
-        byte[] messageData;
-        ByteBuffer headerWriter;
-        
-        logger.debug("Sending message {}", message);
-        
-        messageJson = gson.toJson(message);
-        messageData = messageJson.getBytes(StandardCharsets.UTF_8);
-        headerWriter = ByteBuffer.allocate(4);
-        /*
-         * The browser outputs in whatever the native endian order,
-         * which may not be what Java does.
-         */
-        headerWriter.order(ByteOrder.nativeOrder());
-        headerWriter.putInt(messageData.length);
-        logger.debug("Writing message {} {}", headerWriter.array(), messageJson);
-        try
-        {
-            browserOut.write(headerWriter.array());
-            browserOut.write(messageData);
-            browserOut.flush();
-        }
-        catch (IOException e)
-        {
-            logger.error("Could not write message", e);
-            e.printStackTrace();
         }
     }
 }

addonInter/src/main/resources/log4j2.xml

@@ -4,7 +4,7 @@
   -->
 <Configuration status="WARN">
     <Appenders>
-        <Console name="Console" target="SYSTEM_OUT">
+        <Console name="Console" target="SYSTEM_ERR">
             <PatternLayout pattern="%d%c%L %-5level - %msg%n"/>
         </Console>
         <File name="File" fileName="addonInter.log" append="false">