LSP: separate communication interface and client logic

Change-Id: I7d35fa634287b5f858c4a87aa10f99bf18d1ad07
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

10 files changed, 333 insertions, 179 deletions

diff --git a/src/libs/languageserverprotocol/basemessage.cpp b/src/libs/languageserverprotocol/basemessage.cpp
index 65fc12e449..1ee17e3eee 100644
--- a/src/libs/languageserverprotocol/basemessage.cpp
+++ b/src/libs/languageserverprotocol/basemessage.cpp
@@ -176,7 +176,7 @@ bool BaseMessage::isValid() const
     return contentLength >= 0;
 }
 
-QByteArray BaseMessage::toData()
+QByteArray BaseMessage::toData() const
 {
     return header() + content;
 }
diff --git a/src/libs/languageserverprotocol/basemessage.h b/src/libs/languageserverprotocol/basemessage.h
index 9c35ece1b0..ba8238291a 100644
--- a/src/libs/languageserverprotocol/basemessage.h
+++ b/src/libs/languageserverprotocol/basemessage.h
@@ -55,7 +55,7 @@ public:
 
     bool isComplete() const;
     bool isValid() const;
-    QByteArray toData();
+    QByteArray toData() const;
 
     QByteArray mimeType;
     QByteArray content;
diff --git a/src/plugins/languageclient/baseclient.cpp b/src/plugins/languageclient/baseclient.cpp
index 2852fa1b43..8c5572f51f 100644
--- a/src/plugins/languageclient/baseclient.cpp
+++ b/src/plugins/languageclient/baseclient.cpp
@@ -25,8 +25,9 @@
 
 #include "baseclient.h"
 
+#include "languageclientinterface.h"
 #include "languageclientmanager.h"
-#include "languageclient/languageclientutils.h"
+#include "languageclientutils.h"
 
 #include <coreplugin/icore.h>
 #include <coreplugin/idocument.h>
@@ -60,22 +61,23 @@ using namespace Utils;
 namespace LanguageClient {
 
 static Q_LOGGING_CATEGORY(LOGLSPCLIENT, "qtc.languageclient.client", QtWarningMsg);
-static Q_LOGGING_CATEGORY(LOGLSPCLIENTV, "qtc.languageclient.messages", QtWarningMsg);
-static Q_LOGGING_CATEGORY(LOGLSPCLIENTPARSE, "qtc.languageclient.parse", QtWarningMsg);
 
-BaseClient::BaseClient()
+BaseClient::BaseClient(BaseClientInterface *clientInterface)
     : m_id(Core::Id::fromString(QUuid::createUuid().toString()))
     , m_completionProvider(this)
+    , m_clientInterface(clientInterface)
 {
-    m_buffer.open(QIODevice::ReadWrite | QIODevice::Append);
     m_contentHandler.insert(JsonRpcMessageHandler::jsonRpcMimeType(),
                             &JsonRpcMessageHandler::parseContent);
+    QTC_ASSERT(clientInterface, return);
+    connect(clientInterface, &BaseClientInterface::messageReceived, this, &BaseClient::handleMessage);
+    connect(clientInterface, &BaseClientInterface::error, this, &BaseClient::setError);
+    connect(clientInterface, &BaseClientInterface::finished, this, &BaseClient::finished);
 }
 
 BaseClient::~BaseClient()
 {
     using namespace TextEditor;
-    m_buffer.close();
     // FIXME: instead of replacing the completion provider in the text document store the
     // completion provider as a prioritised list in the text document
     for (TextDocument *document : m_resetCompletionProvider)
@@ -91,6 +93,7 @@ BaseClient::~BaseClient()
 void BaseClient::initialize()
 {
     using namespace ProjectExplorer;
+    QTC_ASSERT(m_clientInterface, return);
     QTC_ASSERT(m_state == Uninitialized, return);
     qCDebug(LOGLSPCLIENT) << "initializing language server " << m_displayName;
     auto initRequest = new InitializeRequest();
@@ -108,7 +111,7 @@ void BaseClient::initialize()
     });
     // directly send data otherwise the state check would fail;
     initRequest->registerResponseHandler(&m_responseHandlers);
-    sendData(initRequest->toBaseMessage().toData());
+    m_clientInterface->sendMessage(initRequest->toBaseMessage());
     m_state = InitializeRequested;
 }
 
@@ -190,12 +193,13 @@ void BaseClient::openDocument(Core::IDocument *document)
 
 void BaseClient::sendContent(const IContent &content)
 {
+    QTC_ASSERT(m_clientInterface, return);
     QTC_ASSERT(m_state == Initialized, return);
     content.registerResponseHandler(&m_responseHandlers);
     QString error;
     if (!QTC_GUARD(content.isValid(&error)))
         Core::MessageManager::write(error);
-    sendData(content.toBaseMessage().toData());
+    m_clientInterface->sendMessage(content.toBaseMessage());
 }
 
 void BaseClient::sendContent(const DocumentUri &uri, const IContent &content)
@@ -652,6 +656,11 @@ bool BaseClient::needsRestart(const BaseSettings *settings) const
             || m_languagFilter.filePattern != settings->m_languageFilter.filePattern;
 }
 
+bool BaseClient::start()
+{
+    return m_clientInterface->start();
+}
+
 bool BaseClient::reset()
 {
     if (!m_restartsLeft)
@@ -659,9 +668,7 @@ bool BaseClient::reset()
     --m_restartsLeft;
     m_state = Uninitialized;
     m_responseHandlers.clear();
-    m_buffer.close();
-    m_buffer.setData(nullptr);
-    m_buffer.open(QIODevice::ReadWrite | QIODevice::Append);
+    m_clientInterface->resetBuffer();
     m_openedDocument.clear();
     m_serverCapabilities = ServerCapabilities();
     m_dynamicCapabilities.reset();
@@ -674,6 +681,24 @@ void BaseClient::setError(const QString &message)
     m_state = Error;
 }
 
+void BaseClient::handleMessage(const BaseMessage &message)
+{
+    if (auto handler = m_contentHandler[message.mimeType]) {
+        QString parseError;
+        handler(message.content, message.codec, parseError,
+                [this](MessageId id, const QByteArray &content, QTextCodec *codec){
+                    this->handleResponse(id, content, codec);
+                },
+                [this](const QString &method, MessageId id, const IContent *content){
+                    this->handleMethod(method, id, content);
+                });
+        if (!parseError.isEmpty())
+            log(parseError);
+    } else {
+        log(tr("Cannot handle content of type: %1").arg(QLatin1String(message.mimeType)));
+    }
+}
+
 void BaseClient::log(const QString &message, Core::MessageManager::PrintToOutputPaneFlag flag)
 {
     Core::MessageManager::write(QString("LanguageClient %1: %2").arg(name(), message), flag);
@@ -841,6 +866,7 @@ void BaseClient::intializeCallback(const InitializeRequest::Response &initRespon
 void BaseClient::shutDownCallback(const ShutdownRequest::Response &shutdownResponse)
 {
     QTC_ASSERT(m_state == ShutdownRequested, return);
+    QTC_ASSERT(m_clientInterface, return);
     optional<ShutdownRequest::Response::Error> errorValue = shutdownResponse.error();
     if (errorValue.has_value()) {
         ShutdownRequest::Response::Error error = errorValue.value();
@@ -848,7 +874,7 @@ void BaseClient::shutDownCallback(const ShutdownRequest::Response &shutdownRespo
         return;
     }
     // directly send data otherwise the state check would fail;
-    sendData(ExitNotification().toBaseMessage().toData());
+    m_clientInterface->sendMessage(ExitNotification().toBaseMessage());
     qCDebug(LOGLSPCLIENT) << "language server " << m_displayName << " shutdown";
     m_state = Shutdown;
 }
@@ -872,118 +898,4 @@ bool BaseClient::sendWorkspceFolderChanges() const
     return false;
 }
 
-void BaseClient::parseData(const QByteArray &data)
-{
-    const qint64 preWritePosition = m_buffer.pos();
-    qCDebug(LOGLSPCLIENTPARSE) << "parse buffer pos: " << preWritePosition;
-    qCDebug(LOGLSPCLIENTPARSE) << "  data: " << data;
-    if (!m_buffer.atEnd())
-        m_buffer.seek(preWritePosition + m_buffer.bytesAvailable());
-    m_buffer.write(data);
-    m_buffer.seek(preWritePosition);
-    while (!m_buffer.atEnd()) {
-        QString parseError;
-        BaseMessage::parse(&m_buffer, parseError, m_currentMessage);
-        qCDebug(LOGLSPCLIENTPARSE) << "  complete: " << m_currentMessage.isComplete();
-        qCDebug(LOGLSPCLIENTPARSE) << "  length: " << m_currentMessage.contentLength;
-        qCDebug(LOGLSPCLIENTPARSE) << "  content: " << m_currentMessage.content;
-        if (!parseError.isEmpty())
-            log(parseError);
-        if (!m_currentMessage.isComplete())
-            break;
-        if (auto handler = m_contentHandler[m_currentMessage.mimeType]){
-            QString parseError;
-            handler(m_currentMessage.content, m_currentMessage.codec, parseError,
-                    [this](MessageId id, const QByteArray &content, QTextCodec *codec){
-                this->handleResponse(id, content, codec);
-            },
-                    [this](const QString &method, MessageId id, const IContent *content){
-                this->handleMethod(method, id, content);
-            });
-            if (!parseError.isEmpty())
-                log(parseError);
-        } else {
-            log(tr("Cannot handle content of type: %1").arg(QLatin1String(m_currentMessage.mimeType)));
-        }
-        m_currentMessage = BaseMessage();
-    }
-    if (m_buffer.atEnd()) {
-        m_buffer.close();
-        m_buffer.setData(nullptr);
-        m_buffer.open(QIODevice::ReadWrite | QIODevice::Append);
-    }
-}
-
-StdIOClient::StdIOClient(const QString &executable, const QString &arguments)
-    : m_executable(executable)
-    , m_arguments(arguments)
-{
-    connect(&m_process, &QProcess::readyReadStandardError,
-            this, &StdIOClient::readError);
-    connect(&m_process, &QProcess::readyReadStandardOutput,
-            this, &StdIOClient::readOutput);
-    connect(&m_process, static_cast<void(QProcess::*)(int, QProcess::ExitStatus)>(&QProcess::finished),
-            this, &StdIOClient::onProcessFinished);
-
-    m_process.setArguments(Utils::QtcProcess::splitArgs(m_arguments));
-    m_process.setProgram(m_executable);
-}
-
-StdIOClient::~StdIOClient()
-{
-    Utils::SynchronousProcess::stopProcess(m_process);
-}
-
-bool StdIOClient::needsRestart(const StdIOSettings *settings)
-{
-    return m_executable != settings->m_executable || m_arguments != settings->m_arguments;
-}
-
-bool StdIOClient::start()
-{
-    m_process.start();
-    if (!m_process.waitForStarted() || m_process.state() != QProcess::Running) {
-        setError(m_process.errorString());
-        return false;
-    }
-    return true;
-}
-
-void StdIOClient::setWorkingDirectory(const QString &workingDirectory)
-{
-    m_process.setWorkingDirectory(workingDirectory);
-}
-
-void StdIOClient::sendData(const QByteArray &data)
-{
-    if (m_process.state() != QProcess::Running) {
-        log(tr("Cannot send data to unstarted server %1").arg(m_process.program()));
-        return;
-    }
-    qCDebug(LOGLSPCLIENTV) << "StdIOClient send data:";
-    qCDebug(LOGLSPCLIENTV).noquote() << data;
-    m_process.write(data);
-}
-
-void StdIOClient::onProcessFinished(int exitCode, QProcess::ExitStatus exitStatus)
-{
-    if (exitStatus == QProcess::CrashExit)
-        setError(tr("Crashed with exit code %1: %2").arg(exitCode, m_process.error()));
-    emit finished();
-}
-
-void StdIOClient::readError()
-{
-    qCDebug(LOGLSPCLIENTV) << "StdIOClient std err:\n";
-    qCDebug(LOGLSPCLIENTV).noquote() << m_process.readAllStandardError();
-}
-
-void StdIOClient::readOutput()
-{
-    const QByteArray &out = m_process.readAllStandardOutput();
-    qDebug(LOGLSPCLIENTV) << "StdIOClient std out:\n";
-    qDebug(LOGLSPCLIENTV).noquote() << out;
-    parseData(out);
-}
-
 } // namespace LanguageClient
diff --git a/src/plugins/languageclient/baseclient.h b/src/plugins/languageclient/baseclient.h
index 318d9ce67f..3487d97e8b 100644
--- a/src/plugins/languageclient/baseclient.h
+++ b/src/plugins/languageclient/baseclient.h
@@ -56,12 +56,14 @@ namespace TextEditor
 
 namespace LanguageClient {
 
+class BaseClientInterface;
+
 class BaseClient : public QObject
 {
     Q_OBJECT
 
 public:
-    BaseClient();
+    explicit BaseClient(BaseClientInterface *clientInterface); // takes ownership
      ~BaseClient() override;
 
     BaseClient(const BaseClient &) = delete;
@@ -124,8 +126,8 @@ public:
 
     bool needsRestart(const BaseSettings *) const;
 
-    virtual bool start() { return true; }
-    virtual bool reset();
+    bool start();
+    bool reset();
 
     void log(const QString &message,
              Core::MessageManager::PrintToOutputPaneFlag flag = Core::MessageManager::NoModeSwitch);
@@ -143,8 +145,7 @@ signals:
 
 protected:
     void setError(const QString &message);
-    virtual void sendData(const QByteArray &data) = 0;
-    void parseData(const QByteArray &data);
+    void handleMessage(const LanguageServerProtocol::BaseMessage &message);
 
 private:
     void handleResponse(const LanguageServerProtocol::MessageId &id, const QByteArray &content,
@@ -168,7 +169,6 @@ private:
     State m_state = Uninitialized;
     QHash<LanguageServerProtocol::MessageId, LanguageServerProtocol::ResponseHandler> m_responseHandlers;
     QHash<QByteArray, ContentHandler> m_contentHandler;
-    QBuffer m_buffer;
     QString m_displayName;
     LanguageFilter m_languagFilter;
     QList<Utils::FileName> m_openedDocument;
@@ -177,41 +177,9 @@ private:
     DynamicCapabilities m_dynamicCapabilities;
     LanguageClientCompletionAssistProvider m_completionProvider;
     QSet<TextEditor::TextDocument *> m_resetCompletionProvider;
-    LanguageServerProtocol::BaseMessage m_currentMessage;
     QHash<LanguageServerProtocol::DocumentUri, LanguageServerProtocol::MessageId> m_highlightRequests;
     int m_restartsLeft = 5;
-};
-
-class StdIOClient : public BaseClient
-{
-    Q_OBJECT
-public:
-    StdIOClient(const QString &executable, const QString &arguments);
-    ~StdIOClient() override;
-
-    StdIOClient() = delete;
-    StdIOClient(const StdIOClient &) = delete;
-    StdIOClient(StdIOClient &&) = delete;
-    StdIOClient &operator=(const StdIOClient &) = delete;
-    StdIOClient &operator=(StdIOClient &&) = delete;
-
-    bool needsRestart(const StdIOSettings *settings);
-
-    bool start() override;
-
-    void setWorkingDirectory(const QString &workingDirectory);
-
-protected:
-    void sendData(const QByteArray &data) final;
-    QProcess m_process;
-
-private:
-    void readError();
-    void readOutput();
-    void onProcessFinished(int exitCode, QProcess::ExitStatus exitStatus);
-
-    const QString m_executable;
-    const QString m_arguments;
+    QScopedPointer<BaseClientInterface> m_clientInterface;
 };
 
 } // namespace LanguageClient
diff --git a/src/plugins/languageclient/languageclient.pro b/src/plugins/languageclient/languageclient.pro
index c9c821676f..6364a78720 100644
--- a/src/plugins/languageclient/languageclient.pro
+++ b/src/plugins/languageclient/languageclient.pro
@@ -7,6 +7,7 @@ HEADERS += \
     dynamiccapabilities.h \
     languageclient_global.h \
     languageclientcodeassist.h \
+    languageclientinterface.h \
     languageclientmanager.h \
     languageclientoutline.h \
     languageclientplugin.h \
@@ -18,6 +19,7 @@ SOURCES += \
     baseclient.cpp \
     dynamiccapabilities.cpp \
     languageclientcodeassist.cpp \
+    languageclientinterface.cpp \
     languageclientmanager.cpp \
     languageclientoutline.cpp \
     languageclientplugin.cpp \
diff --git a/src/plugins/languageclient/languageclient.qbs b/src/plugins/languageclient/languageclient.qbs
index 62de6c7309..d2db93edbc 100644
--- a/src/plugins/languageclient/languageclient.qbs
+++ b/src/plugins/languageclient/languageclient.qbs
@@ -22,6 +22,8 @@ QtcPlugin {
         "languageclient_global.h",
         "languageclientcodeassist.cpp",
         "languageclientcodeassist.h",
+        "languageclientinterface.cpp",
+        "languageclientinterface.h",
         "languageclientmanager.cpp",
         "languageclientmanager.h",
         "languageclientoutline.cpp",
diff --git a/src/plugins/languageclient/languageclientinterface.cpp b/src/plugins/languageclient/languageclientinterface.cpp
new file mode 100644
index 0000000000..b67db95dde
--- /dev/null
+++ b/src/plugins/languageclient/languageclientinterface.cpp
@@ -0,0 +1,165 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#include "languageclientinterface.h"
+
+#include "languageclientsettings.h"
+
+#include <utils/qtcprocess.h>
+#include <utils/synchronousprocess.h>
+
+#include <QLoggingCategory>
+
+using namespace LanguageServerProtocol;
+
+static Q_LOGGING_CATEGORY(LOGLSPCLIENTV, "qtc.languageclient.messages", QtWarningMsg);
+static Q_LOGGING_CATEGORY(LOGLSPCLIENTPARSE, "qtc.languageclient.parse", QtWarningMsg);
+
+namespace LanguageClient {
+
+BaseClientInterface::BaseClientInterface()
+{
+    m_buffer.open(QIODevice::ReadWrite | QIODevice::Append);
+}
+
+BaseClientInterface::~BaseClientInterface()
+{
+    m_buffer.close();
+}
+
+void BaseClientInterface::sendMessage(const BaseMessage &message)
+{
+    sendData(message.toData());
+}
+
+void BaseClientInterface::resetBuffer()
+{
+    m_buffer.close();
+    m_buffer.setData(nullptr);
+    m_buffer.open(QIODevice::ReadWrite | QIODevice::Append);
+}
+
+void BaseClientInterface::parseData(const QByteArray &data)
+{
+    const qint64 preWritePosition = m_buffer.pos();
+    qCDebug(LOGLSPCLIENTPARSE) << "parse buffer pos: " << preWritePosition;
+    qCDebug(LOGLSPCLIENTPARSE) << "  data: " << data;
+    if (!m_buffer.atEnd())
+        m_buffer.seek(preWritePosition + m_buffer.bytesAvailable());
+    m_buffer.write(data);
+    m_buffer.seek(preWritePosition);
+    while (!m_buffer.atEnd()) {
+        QString parseError;
+        BaseMessage::parse(&m_buffer, parseError, m_currentMessage);
+        qCDebug(LOGLSPCLIENTPARSE) << "  complete: " << m_currentMessage.isComplete();
+        qCDebug(LOGLSPCLIENTPARSE) << "  length: " << m_currentMessage.contentLength;
+        qCDebug(LOGLSPCLIENTPARSE) << "  content: " << m_currentMessage.content;
+        if (!parseError.isEmpty())
+            emit error(parseError);
+        if (!m_currentMessage.isComplete())
+            break;
+        emit messageReceived(m_currentMessage);
+        m_currentMessage = BaseMessage();
+    }
+    if (m_buffer.atEnd()) {
+        m_buffer.close();
+        m_buffer.setData(nullptr);
+        m_buffer.open(QIODevice::ReadWrite | QIODevice::Append);
+    }
+}
+
+StdIOClientInterface::StdIOClientInterface(const QString &executable, const QString &arguments)
+    : m_executable(executable)
+    , m_arguments(arguments)
+{
+    connect(&m_process, &QProcess::readyReadStandardError,
+            this, &StdIOClientInterface::readError);
+    connect(&m_process, &QProcess::readyReadStandardOutput,
+            this, &StdIOClientInterface::readOutput);
+    connect(&m_process, QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
+            this, &StdIOClientInterface::onProcessFinished);
+
+    m_process.setArguments(Utils::QtcProcess::splitArgs(m_arguments));
+    m_process.setProgram(m_executable);
+}
+
+StdIOClientInterface::~StdIOClientInterface()
+{
+    Utils::SynchronousProcess::stopProcess(m_process);
+}
+
+bool StdIOClientInterface::needsRestart(const StdIOSettings *settings)
+{
+    return m_executable != settings->m_executable || m_arguments != settings->m_arguments;
+}
+
+bool StdIOClientInterface::start()
+{
+    m_process.start();
+    if (!m_process.waitForStarted() || m_process.state() != QProcess::Running) {
+        emit error(m_process.errorString());
+        return false;
+    }
+    return true;
+}
+
+void StdIOClientInterface::setWorkingDirectory(const QString &workingDirectory)
+{
+    m_process.setWorkingDirectory(workingDirectory);
+}
+
+void StdIOClientInterface::sendData(const QByteArray &data)
+{
+    if (m_process.state() != QProcess::Running) {
+        emit error(tr("Cannot send data to unstarted server %1").arg(m_process.program()));
+        return;
+    }
+    qCDebug(LOGLSPCLIENTV) << "StdIOClient send data:";
+    qCDebug(LOGLSPCLIENTV).noquote() << data;
+    m_process.write(data);
+}
+
+void StdIOClientInterface::onProcessFinished(int exitCode, QProcess::ExitStatus exitStatus)
+{
+    if (exitStatus == QProcess::CrashExit)
+        emit error(tr("Crashed with exit code %1: %2").arg(exitCode, m_process.error()));
+    emit finished();
+}
+
+void StdIOClientInterface::readError()
+{
+    qCDebug(LOGLSPCLIENTV) << "StdIOClient std err:\n";
+    qCDebug(LOGLSPCLIENTV).noquote() << m_process.readAllStandardError();
+}
+
+void StdIOClientInterface::readOutput()
+{
+    const QByteArray &out = m_process.readAllStandardOutput();
+    qCDebug(LOGLSPCLIENTV) << "StdIOClient std out:\n";
+    qCDebug(LOGLSPCLIENTV).noquote() << out;
+    parseData(out);
+}
+
+} // namespace LanguageClient
diff --git a/src/plugins/languageclient/languageclientinterface.h b/src/plugins/languageclient/languageclientinterface.h
new file mode 100644
index 0000000000..3dc2602d52
--- /dev/null
+++ b/src/plugins/languageclient/languageclientinterface.h
@@ -0,0 +1,96 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#pragma once
+
+#include <languageserverprotocol/basemessage.h>
+
+#include <QBuffer>
+#include <QProcess>
+
+namespace LanguageClient {
+
+class StdIOSettings;
+
+class BaseClientInterface : public QObject
+{
+    Q_OBJECT
+public:
+    BaseClientInterface();
+
+    virtual ~BaseClientInterface();
+
+    void sendMessage(const LanguageServerProtocol::BaseMessage &message);
+    virtual bool start() { return true; }
+
+    void resetBuffer();
+
+signals:
+    void messageReceived(LanguageServerProtocol::BaseMessage message);
+    void finished();
+    void error(const QString &message);
+
+protected:
+    virtual void sendData(const QByteArray &data) = 0;
+    void parseData(const QByteArray &data);
+
+private:
+    QBuffer m_buffer;
+    LanguageServerProtocol::BaseMessage m_currentMessage;
+};
+
+class StdIOClientInterface : public BaseClientInterface
+{
+    Q_OBJECT
+public:
+    StdIOClientInterface(const QString &executable, const QString &arguments);
+    ~StdIOClientInterface() override;
+
+    StdIOClientInterface() = delete;
+    StdIOClientInterface(const StdIOClientInterface &) = delete;
+    StdIOClientInterface(StdIOClientInterface &&) = delete;
+    StdIOClientInterface &operator=(const StdIOClientInterface &) = delete;
+    StdIOClientInterface &operator=(StdIOClientInterface &&) = delete;
+
+    bool needsRestart(const StdIOSettings *settings);
+
+    bool start() override;
+
+    void setWorkingDirectory(const QString &workingDirectory);
+
+protected:
+    void sendData(const QByteArray &data) final;
+    QProcess m_process;
+
+private:
+    void readError();
+    void readOutput();
+    void onProcessFinished(int exitCode, QProcess::ExitStatus exitStatus);
+
+    const QString m_executable;
+    const QString m_arguments;
+};
+
+} // namespace LanguageClient
diff --git a/src/plugins/languageclient/languageclientsettings.cpp b/src/plugins/languageclient/languageclientsettings.cpp
index 36ec211b85..fb30fbe0fc 100644
--- a/src/plugins/languageclient/languageclientsettings.cpp
+++ b/src/plugins/languageclient/languageclientsettings.cpp
@@ -28,6 +28,7 @@
 #include "baseclient.h"
 #include "languageclientmanager.h"
 #include "languageclient_global.h"
+#include "languageclientinterface.h"
 
 #include <coreplugin/icore.h>
 #include <utils/algorithm.h>
@@ -399,6 +400,13 @@ bool BaseSettings::isValid() const
 
 BaseClient *BaseSettings::createClient() const
 {
+    BaseClientInterface *interface = createInterface();
+    if (QTC_GUARD(interface)) {
+        auto *client = new BaseClient(interface);
+        client->setName(m_name);
+        client->setSupportedLanguage(m_languageFilter);
+        return client;
+    }
     return nullptr;
 }
 
@@ -467,8 +475,8 @@ bool StdIOSettings::needsRestart() const
 {
     if (BaseSettings::needsRestart())
         return true;
-    if (auto stdIOClient = qobject_cast<StdIOClient *>(m_client))
-        return stdIOClient->needsRestart(this);
+    if (auto stdIOInterface = qobject_cast<StdIOClientInterface *>(m_client))
+        return stdIOInterface->needsRestart(this);
     return false;
 }
 
@@ -477,14 +485,6 @@ bool StdIOSettings::isValid() const
     return BaseSettings::isValid() && !m_executable.isEmpty();
 }
 
-BaseClient *StdIOSettings::createClient() const
-{
-    auto client = new StdIOClient(m_executable, m_arguments);
-    client->setName(m_name);
-    client->setSupportedLanguage(m_languageFilter);
-    return client;
-}
-
 QVariantMap StdIOSettings::toMap() const
 {
     QVariantMap map = BaseSettings::toMap();
@@ -500,6 +500,11 @@ void StdIOSettings::fromMap(const QVariantMap &map)
     m_arguments = map[argumentsKey].toString();
 }
 
+BaseClientInterface *StdIOSettings::createInterface() const
+{
+    return new StdIOClientInterface(m_executable, m_arguments);
+}
+
 BaseSettingsWidget::BaseSettingsWidget(const BaseSettings *settings, QWidget *parent)
     : QWidget(parent)
     , m_name(new QLineEdit(settings->m_name, this))
diff --git a/src/plugins/languageclient/languageclientsettings.h b/src/plugins/languageclient/languageclientsettings.h
index 54877412a7..1b229788a6 100644
--- a/src/plugins/languageclient/languageclientsettings.h
+++ b/src/plugins/languageclient/languageclientsettings.h
@@ -44,6 +44,7 @@ namespace LanguageClient {
 constexpr char noLanguageFilter[] = "No Filter";
 
 class BaseClient;
+class BaseClientInterface;
 
 struct LanguageFilter
 {
@@ -73,11 +74,13 @@ public:
     virtual BaseSettings *copy() const { return new BaseSettings(*this); }
     virtual bool needsRestart() const;
     virtual bool isValid() const ;
-    virtual BaseClient *createClient() const;
+    BaseClient *createClient() const;
     virtual QVariantMap toMap() const;
     virtual void fromMap(const QVariantMap &map);
 
 protected:
+    virtual BaseClientInterface *createInterface() const { return nullptr; }
+
     BaseSettings(const BaseSettings &other) = default;
     BaseSettings(BaseSettings &&other) = default;
     BaseSettings &operator=(const BaseSettings &other) = default;
@@ -105,11 +108,12 @@ public:
     BaseSettings *copy() const override { return new StdIOSettings(*this); }
     bool needsRestart() const override;
     bool isValid() const override;
-    BaseClient *createClient() const override;
     QVariantMap toMap() const override;
     void fromMap(const QVariantMap &map) override;
 
 protected:
+    BaseClientInterface *createInterface() const override;
+
     StdIOSettings(const StdIOSettings &other) = default;
     StdIOSettings(StdIOSettings &&other) = default;
     StdIOSettings &operator=(const StdIOSettings &other) = default;