Make QmlDebug protocol more robust

The protocol so far was client->server only. That is, there was no
sane way for a client to check whether a plugin on the server (service)
was available or not. E.g. calling Client::setEnabled(true) 'succeeded',
without a check whether there is actually a service to talk to.

The new protocol replaces this shortcoming by a service discovery
mechanism: Both client & service announce their available plugins at
handshake time, and later on if there are changes. The status is
reflected in Client::status() and Service::Status() , which are either

  NotConnected - no network connection, or not registered properly
  Unavailable - TCP/IP connection works, but no plugin with the same
name on the other side
  Enabled - You can connect to plugin on other side

The status changes happen automatically (no setEnabled() anymore).

Furthermore a version ID was added to the handshake, so that we can
extend the protocol further in the future :)

1 files changed, 99 insertions, 27 deletions

diff --git a/src/declarative/debugger/qdeclarativedebugservice.cpp b/src/declarative/debugger/qdeclarativedebugservice.cpp
index 1f2bf4f..0fbc1e3 100644
--- a/src/declarative/debugger/qdeclarativedebugservice.cpp
+++ b/src/declarative/debugger/qdeclarativedebugservice.cpp
@@ -54,6 +54,30 @@
 
 QT_BEGIN_NAMESPACE
 
+/*
+  QDeclarativeDebug Protocol (Version 1):
+
+  handshake:
+    1. Client sends
+         "QDeclarativeDebugServer" 0 version pluginNames
+       version: an int representing the highest protocol version the client knows
+       pluginNames: plugins available on client side
+    2. Server sends
+         "QDeclarativeDebugClient" 0 version pluginNames
+       version: an int representing the highest protocol version the client & server know
+       pluginNames: plugins available on server side. plugins both in the client and server message are enabled.
+  client plugin advertisement
+    1. Client sends
+         "QDeclarativeDebugServer" 1 pluginNames
+  server plugin advertisement
+    1. Server sends
+         "QDeclarativeDebugClient" 1 pluginNames
+  plugin communication:
+       Everything send with a header different to "QDeclarativeDebugServer" is sent to the appropriate plugin.
+  */
+
+const int protocolVersion = 1;
+
 class QDeclarativeDebugServerPrivate;
 class QDeclarativeDebugServer : public QObject
 {
@@ -82,11 +106,13 @@ class QDeclarativeDebugServerPrivate : public QObjectPrivate
 public:
     QDeclarativeDebugServerPrivate();
 
+    void advertisePlugins();
+
     int port;
     QTcpSocket *connection;
     QPacketProtocol *protocol;
     QHash<QString, QDeclarativeDebugService *> plugins;
-    QStringList enabledPlugins;
+    QStringList clientPlugins;
     QTcpServer *tcpServer;
     bool gotHello;
 };
@@ -106,6 +132,18 @@ QDeclarativeDebugServerPrivate::QDeclarativeDebugServerPrivate()
 {
 }
 
+void QDeclarativeDebugServerPrivate::advertisePlugins()
+{
+    if (!connection
+            || connection->state() != QTcpSocket::ConnectedState
+            || !gotHello)
+        return;
+
+    QPacket pack;
+    pack << QString(QLatin1String("QDeclarativeDebugClient")) << 1 << plugins.keys();
+    protocol->send(pack);
+}
+
 void QDeclarativeDebugServer::listen()
 {
     Q_D(QDeclarativeDebugServer);
@@ -202,9 +240,13 @@ void QDeclarativeDebugServer::readyRead()
 
     if (!d->gotHello) {
         QPacket hello = d->protocol->read();
-        QString name; 
-        hello >> name >> d->enabledPlugins;
-        if (name != QLatin1String("QDeclarativeDebugServer")) {
+
+        QString name;
+        int op;
+        hello >> name >> op;
+
+        if (name != QLatin1String("QDeclarativeDebugServer")
+                || op != 0) {
             qWarning("QDeclarativeDebugServer: Invalid hello message");
             QObject::disconnect(d->protocol, SIGNAL(readyRead()), this, SLOT(readyRead()));
             d->protocol->deleteLater();
@@ -213,6 +255,23 @@ void QDeclarativeDebugServer::readyRead()
             d->connection = 0;
             return;
         }
+
+        int version;
+        hello >> version >> d->clientPlugins;
+
+        QHash<QString, QDeclarativeDebugService*>::Iterator iter = d->plugins.begin();
+        for (; iter != d->plugins.end(); ++iter) {
+            QDeclarativeDebugService::Status newStatus = QDeclarativeDebugService::Unavailable;
+            if (d->clientPlugins.contains(iter.key()))
+                newStatus = QDeclarativeDebugService::Enabled;
+            iter.value()->statusChanged(newStatus);
+        }
+
+        QPacket helloAnswer;
+        helloAnswer << QString(QLatin1String("QDeclarativeDebugClient")) << 0 << protocolVersion << d->plugins.keys();
+        d->protocol->send(helloAnswer);
+        d->connection->flush();
+
         d->gotHello = true;
         qWarning("QDeclarativeDebugServer: Connection established");
     }
@@ -226,32 +285,29 @@ void QDeclarativeDebugServer::readyRead()
         pack >> name;
 
         if (name == debugServer) {
-            int op = -1; QString plugin;
-            pack >> op >> plugin;
+            int op = -1;
+            pack >> op;
 
             if (op == 1) {
-                // Enable
-                if (!d->enabledPlugins.contains(plugin)) {
-                    d->enabledPlugins.append(plugin);
-                    QHash<QString, QDeclarativeDebugService *>::Iterator iter = 
-                        d->plugins.find(plugin);
-                    if (iter != d->plugins.end())
-                        (*iter)->enabledChanged(true);
-                }
-
-            } else if (op == 2) {
-                // Disable
-                if (d->enabledPlugins.contains(plugin)) {
-                    d->enabledPlugins.removeAll(plugin);
-                    QHash<QString, QDeclarativeDebugService *>::Iterator iter = 
-                        d->plugins.find(plugin);
-                    if (iter != d->plugins.end())
-                        (*iter)->enabledChanged(false);
+                // Service Discovery
+                QStringList oldClientPlugins = d->clientPlugins;
+                pack >> d->clientPlugins;
+
+                QHash<QString, QDeclarativeDebugService*>::Iterator iter = d->plugins.begin();
+                for (; iter != d->plugins.end(); ++iter) {
+                    const QString pluginName = iter.key();
+                    QDeclarativeDebugService::Status newStatus = QDeclarativeDebugService::Unavailable;
+                    if (d->clientPlugins.contains(pluginName))
+                        newStatus = QDeclarativeDebugService::Enabled;
+
+                    if (oldClientPlugins.contains(pluginName)
+                            != d->clientPlugins.contains(pluginName)) {
+                        iter.value()->statusChanged(newStatus);
+                    }
                 }
             } else {
                 qWarning("QDeclarativeDebugServer: Invalid control message %d", op);
             }
-
         } else {
             QByteArray message;
             pack >> message;
@@ -287,6 +343,16 @@ QDeclarativeDebugService::QDeclarativeDebugService(const QString &name, QObject
         d->server = 0;
     } else {
         d->server->d_func()->plugins.insert(name, this);
+        d->server->d_func()->advertisePlugins();
+    }
+}
+
+QDeclarativeDebugService::~QDeclarativeDebugService()
+{
+    Q_D(const QDeclarativeDebugService);
+    if (d->server) {
+        d->server->d_func()->plugins.remove(d->name);
+        d->server->d_func()->advertisePlugins();
     }
 }
 
@@ -296,10 +362,16 @@ QString QDeclarativeDebugService::name() const
     return d->name;
 }
 
-bool QDeclarativeDebugService::isEnabled() const
+QDeclarativeDebugService::Status QDeclarativeDebugService::status() const
 {
     Q_D(const QDeclarativeDebugService);
-    return (d->server && d->server->d_func()->enabledPlugins.contains(d->name));
+    if (!d->server
+            || !d->server->hasDebuggingClient())
+        return NotConnected;
+    if (d->server->d_func()->clientPlugins.contains(d->name))
+        return Enabled;
+
+    return Unavailable;
 }
 
 namespace {
@@ -422,7 +494,7 @@ void QDeclarativeDebugService::sendMessage(const QByteArray &message)
     d->server->d_func()->connection->flush();
 }
 
-void QDeclarativeDebugService::enabledChanged(bool)
+void QDeclarativeDebugService::statusChanged(Status)
 {
 }