SCRATCH separate the generic updater logic from the application

21 files changed, 767 insertions, 794 deletions

diff --git a/logic/BaseProcess.cpp b/logic/BaseProcess.cpp
index eb1bbfdc..b0509d46 100644
--- a/logic/BaseProcess.cpp
+++ b/logic/BaseProcess.cpp
@@ -139,6 +139,12 @@ void BaseProcess::setWorkdir(QString path)
 	m_prepostlaunchprocess.setWorkingDirectory(mcDir.absolutePath());
 }
 
+void BaseProcess::printHeader()
+{
+	emit log(m_header);
+}
+
+
 void BaseProcess::logOutput(const QStringList &lines, MessageLevel::Enum defaultLevel,
 								 bool guessLevel, bool censor)
 {
diff --git a/logic/BaseProcess.h b/logic/BaseProcess.h
index ff8b9ed3..75bf0217 100644
--- a/logic/BaseProcess.h
+++ b/logic/BaseProcess.h
@@ -54,6 +54,12 @@ public: /* methods */
 		return m_instance;
 	}
 
+	/// Set the text printed on top of the log
+	void setHeader(QString header)
+	{
+		m_header = header;
+	}
+
 	void setWorkdir(QString path);
 
 	void killProcess();
@@ -79,6 +85,8 @@ protected: /* methods */
 	bool waitForPrePost();
 	QString substituteVariables(const QString &cmd) const;
 
+	void printHeader();
+
 	virtual QMap<QString, QString> getVariables() const = 0;
 	virtual QString censorPrivateInfo(QString in) = 0;
 	virtual MessageLevel::Enum guessLevel(const QString &message, MessageLevel::Enum defaultLevel) = 0;
@@ -130,4 +138,5 @@ protected:
 	QString m_out_leftover;
 	QProcess m_prepostlaunchprocess;
 	bool killed = false;
+	QString m_header;
 };
diff --git a/logic/forge/ForgeMirrors.cpp b/logic/forge/ForgeMirrors.cpp
index 06abb88f..e922fcc3 100644
--- a/logic/forge/ForgeMirrors.cpp
+++ b/logic/forge/ForgeMirrors.cpp
@@ -21,7 +21,7 @@ void ForgeMirrors::start()
 	auto worker = ENV.qnam();
 	QNetworkReply *rep = worker->get(request);
 
-	m_reply = std::shared_ptr<QNetworkReply>(rep);
+	m_reply.reset(rep);
 	connect(rep, SIGNAL(downloadProgress(qint64, qint64)),
 			SLOT(downloadProgress(qint64, qint64)));
 	connect(rep, SIGNAL(finished()), SLOT(downloadFinished()));
diff --git a/logic/forge/ForgeXzDownload.cpp b/logic/forge/ForgeXzDownload.cpp
index ac2c4b1f..65b20959 100644
--- a/logic/forge/ForgeXzDownload.cpp
+++ b/logic/forge/ForgeXzDownload.cpp
@@ -70,7 +70,7 @@ void ForgeXzDownload::start()
 	auto worker = ENV.qnam();
 	QNetworkReply *rep = worker->get(request);
 
-	m_reply = std::shared_ptr<QNetworkReply>(rep);
+	m_reply.reset(rep);
 	connect(rep, SIGNAL(downloadProgress(qint64, qint64)),
 			SLOT(downloadProgress(qint64, qint64)));
 	connect(rep, SIGNAL(finished()), SLOT(downloadFinished()));
diff --git a/logic/minecraft/MinecraftProcess.cpp b/logic/minecraft/MinecraftProcess.cpp
index e8682a50..75287856 100644
--- a/logic/minecraft/MinecraftProcess.cpp
+++ b/logic/minecraft/MinecraftProcess.cpp
@@ -14,8 +14,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#include "BuildConfig.h"
-
 #include "logic/minecraft/MinecraftProcess.h"
 #include "logic/BaseInstance.h"
 
@@ -158,7 +156,7 @@ QStringList MinecraftProcess::javaArguments() const
 
 void MinecraftProcess::arm()
 {
-	emit log("MultiMC version: " + BuildConfig.printableVersionString() + "\n\n");
+	printHeader();
 	emit log("Minecraft folder is:\n" + workingDirectory() + "\n\n");
 
 	if (!preLaunch())
diff --git a/logic/net/ByteArrayDownload.cpp b/logic/net/ByteArrayDownload.cpp
index 9f71f911..7a41ee28 100644
--- a/logic/net/ByteArrayDownload.cpp
+++ b/logic/net/ByteArrayDownload.cpp
@@ -31,7 +31,7 @@ void ByteArrayDownload::start()
 	auto worker = ENV.qnam();
 	QNetworkReply *rep = worker->get(request);
 
-	m_reply = std::shared_ptr<QNetworkReply>(rep);
+	m_reply.reset(rep);
 	connect(rep, SIGNAL(downloadProgress(qint64, qint64)),
 			SLOT(downloadProgress(qint64, qint64)));
 	connect(rep, SIGNAL(finished()), SLOT(downloadFinished()));
diff --git a/logic/net/CacheDownload.cpp b/logic/net/CacheDownload.cpp
index 6ddfc55f..0bbe75c3 100644
--- a/logic/net/CacheDownload.cpp
+++ b/logic/net/CacheDownload.cpp
@@ -77,7 +77,7 @@ void CacheDownload::start()
 	auto worker = ENV.qnam();
 	QNetworkReply *rep = worker->get(request);
 
-	m_reply = std::shared_ptr<QNetworkReply>(rep);
+	m_reply.reset(rep);
 	connect(rep, SIGNAL(downloadProgress(qint64, qint64)),
 			SLOT(downloadProgress(qint64, qint64)));
 	connect(rep, SIGNAL(finished()), SLOT(downloadFinished()));
diff --git a/logic/net/MD5EtagDownload.cpp b/logic/net/MD5EtagDownload.cpp
index 6e1d0cfc..03752ea8 100644
--- a/logic/net/MD5EtagDownload.cpp
+++ b/logic/net/MD5EtagDownload.cpp
@@ -86,7 +86,7 @@ void MD5EtagDownload::start()
 	auto worker = ENV.qnam();
 	QNetworkReply *rep = worker->get(request);
 
-	m_reply = std::shared_ptr<QNetworkReply>(rep);
+	m_reply.reset(rep);
 	connect(rep, SIGNAL(downloadProgress(qint64, qint64)),
 			SLOT(downloadProgress(qint64, qint64)));
 	connect(rep, SIGNAL(finished()), SLOT(downloadFinished()));
diff --git a/logic/net/NetAction.h b/logic/net/NetAction.h
index 81cb1bdb..b306bdfe 100644
--- a/logic/net/NetAction.h
+++ b/logic/net/NetAction.h
@@ -19,6 +19,7 @@
 #include <QUrl>
 #include <memory>
 #include <QNetworkReply>
+#include <logic/QObjectPtr.h>
 
 enum JobStatus
 {
@@ -58,7 +59,7 @@ public:
 
 public:
 	/// the network reply
-	std::shared_ptr<QNetworkReply> m_reply;
+	QObjectPtr<QNetworkReply> m_reply;
 
 	/// the content of the content-type header
 	QString m_content_type;
diff --git a/logic/net/NetJob.cpp b/logic/net/NetJob.cpp
index e10afbc8..5a50b876 100644
--- a/logic/net/NetJob.cpp
+++ b/logic/net/NetJob.cpp
@@ -29,7 +29,7 @@ void NetJob::partSucceeded(int index)
 
 	m_doing.remove(index);
 	m_done.insert(index);
-	disconnect(downloads[index].get(), 0, this, 0);
+	downloads[index].get()->disconnect(this);
 	startMoreParts();
 }
 
@@ -46,7 +46,7 @@ void NetJob::partFailed(int index)
 		slot.failures++;
 		m_todo.enqueue(index);
 	}
-	disconnect(downloads[index].get(), 0, this, 0);
+	downloads[index].get()->disconnect(this);
 	startMoreParts();
 }
 
diff --git a/logic/net/NetJob.h b/logic/net/NetJob.h
index 0d8b7fbd..708afa79 100644
--- a/logic/net/NetJob.h
+++ b/logic/net/NetJob.h
@@ -108,6 +108,7 @@ private:
 		qint64 current_progress = 0;
 		qint64 total_progress = 1;
 		int failures = 0;
+		bool connected = false;
 	};
 	QString m_job_name;
 	QList<NetActionPtr> downloads;
diff --git a/logic/screenshots/ImgurAlbumCreation.cpp b/logic/screenshots/ImgurAlbumCreation.cpp
index 45db75cf..f7cc2971 100644
--- a/logic/screenshots/ImgurAlbumCreation.cpp
+++ b/logic/screenshots/ImgurAlbumCreation.cpp
@@ -36,7 +36,7 @@ void ImgurAlbumCreation::start()
 	auto worker = ENV.qnam();
 	QNetworkReply *rep = worker->post(request, data);
 
-	m_reply = std::shared_ptr<QNetworkReply>(rep);
+	m_reply.reset(rep);
 	connect(rep, &QNetworkReply::uploadProgress, this, &ImgurAlbumCreation::downloadProgress);
 	connect(rep, &QNetworkReply::finished, this, &ImgurAlbumCreation::downloadFinished);
 	connect(rep, SIGNAL(error(QNetworkReply::NetworkError)),
diff --git a/logic/screenshots/ImgurUpload.cpp b/logic/screenshots/ImgurUpload.cpp
index 1d490436..4ae37dfa 100644
--- a/logic/screenshots/ImgurUpload.cpp
+++ b/logic/screenshots/ImgurUpload.cpp
@@ -51,7 +51,7 @@ void ImgurUpload::start()
 	auto worker = ENV.qnam();
 	QNetworkReply *rep = worker->post(request, multipart);
 
-	m_reply = std::shared_ptr<QNetworkReply>(rep);
+	m_reply.reset(rep);
 	connect(rep, &QNetworkReply::uploadProgress, this, &ImgurUpload::downloadProgress);
 	connect(rep, &QNetworkReply::finished, this, &ImgurUpload::downloadFinished);
 	connect(rep, SIGNAL(error(QNetworkReply::NetworkError)),
diff --git a/logic/updater/DownloadTask.cpp b/logic/updater/DownloadTask.cpp
new file mode 100644
index 00000000..badbc0d0
--- /dev/null
+++ b/logic/updater/DownloadTask.cpp
@@ -0,0 +1,179 @@
+/* Copyright 2013-2014 MultiMC Contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "DownloadTask.h"
+
+#include "logic/updater/UpdateChecker.h"
+#include "GoUpdate.h"
+#include "logic/net/NetJob.h"
+#include "pathutils.h"
+
+#include <QFile>
+#include <QTemporaryDir>
+#include <QCryptographicHash>
+
+namespace GoUpdate
+{
+
+DownloadTask::DownloadTask(Status status, QObject *parent)
+	: Task(parent)
+{
+	m_status = status;
+
+	m_updateFilesDir.setAutoRemove(false);
+}
+
+void DownloadTask::setUseLocalUpdater(bool useLocal)
+{
+	m_keepLocalUpdater = useLocal;
+}
+
+void DownloadTask::executeTask()
+{
+	loadVersionInfo();
+}
+
+void DownloadTask::loadVersionInfo()
+{
+	setStatus(tr("Loading version information..."));
+
+	m_currentVersionFileListDownload.reset();
+	m_newVersionFileListDownload.reset();
+
+	NetJob *netJob = new NetJob("Version Info");
+
+	// Find the index URL.
+	QUrl newIndexUrl = QUrl(m_status.newRepoUrl).resolved(QString::number(m_status.newVersionId) + ".json");
+	qDebug() << m_status.newRepoUrl << " turns into " << newIndexUrl;
+
+	netJob->addNetAction(m_newVersionFileListDownload = ByteArrayDownload::make(newIndexUrl));
+
+	// If we have a current version URL, get that one too.
+	if (!m_status.currentRepoUrl.isEmpty())
+	{
+		QUrl cIndexUrl = QUrl(m_status.currentRepoUrl).resolved(QString::number(m_status.currentVersionId) + ".json");
+		netJob->addNetAction(m_currentVersionFileListDownload = ByteArrayDownload::make(cIndexUrl));
+		qDebug() << m_status.currentRepoUrl << " turns into " << cIndexUrl;
+	}
+
+	// connect signals and start the job
+	connect(netJob, &NetJob::succeeded, this, &DownloadTask::processDownloadedVersionInfo);
+	connect(netJob, &NetJob::failed, this, &DownloadTask::vinfoDownloadFailed);
+	m_vinfoNetJob.reset(netJob);
+	netJob->start();
+}
+
+void DownloadTask::vinfoDownloadFailed()
+{
+	// Something failed. We really need the second download (current version info), so parse
+	// downloads anyways as long as the first one succeeded.
+	if (m_newVersionFileListDownload->m_status != Job_Failed)
+	{
+		processDownloadedVersionInfo();
+		return;
+	}
+
+	// TODO: Give a more detailed error message.
+	qCritical() << "Failed to download version info files.";
+	emitFailed(tr("Failed to download version info files."));
+}
+
+void DownloadTask::processDownloadedVersionInfo()
+{
+	VersionFileList m_currentVersionFileList;
+	VersionFileList m_newVersionFileList;
+	OperationList operationList;
+
+	setStatus(tr("Reading file list for new version..."));
+	qDebug() << "Reading file list for new version...";
+	QString error;
+	if (!parseVersionInfo(m_newVersionFileListDownload->m_data, m_newVersionFileList, error))
+	{
+		qCritical() << error;
+		emitFailed(error);
+		return;
+	}
+
+	// if we have the current version info, use it.
+	if (m_currentVersionFileListDownload && m_currentVersionFileListDownload->m_status != Job_Failed)
+	{
+		setStatus(tr("Reading file list for current version..."));
+		qDebug() << "Reading file list for current version...";
+		// if this fails, it's not a complete loss.
+		QString error;
+		if(!parseVersionInfo( m_currentVersionFileListDownload->m_data, m_currentVersionFileList, error))
+		{
+			qDebug() << error << "This is not a fatal error.";
+		}
+	}
+
+	// We don't need this any more.
+	m_currentVersionFileListDownload.reset();
+	m_newVersionFileListDownload.reset();
+	m_vinfoNetJob.reset();
+
+	setStatus(tr("Processing file lists - figuring out how to install the update..."));
+
+	// make a new netjob for the actual update files
+	NetJobPtr netJob (new NetJob("Update Files"));
+
+	// fill netJob and operationList
+	if (!processFileLists(m_currentVersionFileList, m_newVersionFileList, m_status.rootPath, m_updateFilesDir.path(), netJob, operationList, m_keepLocalUpdater))
+	{
+		emitFailed(tr("Failed to process update lists..."));
+		return;
+	}
+
+	// write the instruction file for the file swapper
+	if(!writeInstallScript(operationList, PathCombine(m_updateFilesDir.path(), "file_list.xml")))
+	{
+		emitFailed(tr("Failed to write update script file."));
+		return;
+	}
+
+	// Now start the download.
+	QObject::connect(netJob.get(), &NetJob::succeeded, this, &DownloadTask::fileDownloadFinished);
+	QObject::connect(netJob.get(), &NetJob::progress, this, &DownloadTask::fileDownloadProgressChanged);
+	QObject::connect(netJob.get(), &NetJob::failed, this, &DownloadTask::fileDownloadFailed);
+
+	setStatus(tr("Downloading %1 update files.").arg(QString::number(netJob->size())));
+	qDebug() << "Begin downloading update files to" << m_updateFilesDir.path();
+	m_filesNetJob = netJob;
+	m_filesNetJob->start();
+}
+
+void DownloadTask::fileDownloadFinished()
+{
+	emitSucceeded();
+}
+
+void DownloadTask::fileDownloadFailed()
+{
+	// TODO: Give more info about the failure.
+	qCritical() << "Failed to download update files.";
+	emitFailed(tr("Failed to download update files."));
+}
+
+void DownloadTask::fileDownloadProgressChanged(qint64 current, qint64 total)
+{
+	setProgress((int)(((float)current / (float)total) * 100));
+}
+
+QString DownloadTask::updateFilesDir()
+{
+	return m_updateFilesDir.path();
+}
+
+}
\ No newline at end of file
diff --git a/logic/updater/DownloadTask.h b/logic/updater/DownloadTask.h
new file mode 100644
index 00000000..2b8c6299
--- /dev/null
+++ b/logic/updater/DownloadTask.h
@@ -0,0 +1,85 @@
+/* Copyright 2013-2014 MultiMC Contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include "logic/tasks/Task.h"
+#include "logic/net/NetJob.h"
+#include "GoUpdate.h"
+
+namespace GoUpdate
+{
+/*!
+ * The DownloadTask is a task that takes a given version ID and repository URL,
+ * downloads that version's files from the repository, and prepares to install them.
+ */
+class DownloadTask : public Task
+{
+	Q_OBJECT
+
+public:
+	explicit DownloadTask(Status status, QObject* parent = 0);
+
+	/// Get the directory that will contain the update files.
+	QString updateFilesDir();
+
+	/// set updater download behavior
+	void setUseLocalUpdater(bool useLocal);
+
+protected:
+	//! Entry point for tasks.
+	virtual void executeTask() override;
+
+	/*!
+	 * Downloads the version info files from the repository.
+	 * The files for both the current build, and the build that we're updating to need to be downloaded.
+	 * If the current version's info file can't be found, MultiMC will not delete files that
+	 * were removed between versions. It will still replace files that have changed, however.
+	 * Note that although the repository URL for the current version is not given to the update task,
+	 * the task will attempt to look it up in the UpdateChecker's channel list.
+	 * If an error occurs here, the function will call emitFailed and return false.
+	 */
+	void loadVersionInfo();
+
+	NetJobPtr m_vinfoNetJob;
+	ByteArrayDownloadPtr m_currentVersionFileListDownload;
+	ByteArrayDownloadPtr m_newVersionFileListDownload;
+
+	NetJobPtr m_filesNetJob;
+
+	Status m_status;
+
+	bool m_keepLocalUpdater;
+
+	/*!
+	 * Temporary directory to store update files in.
+	 * This will be set to not auto delete. Task will fail if this fails to be created.
+	 */
+	QTemporaryDir m_updateFilesDir;
+
+protected slots:
+	/*!
+	 * This function is called when version information is finished downloading
+	 * and at least the new file list download succeeded
+	 */
+	void processDownloadedVersionInfo();
+	void vinfoDownloadFailed();
+
+	void fileDownloadFinished();
+	void fileDownloadFailed();
+	void fileDownloadProgressChanged(qint64 current, qint64 total);
+};
+
+}
\ No newline at end of file
diff --git a/logic/updater/DownloadUpdateTask.cpp b/logic/updater/DownloadUpdateTask.cpp
deleted file mode 100644
index 228d26d2..00000000
--- a/logic/updater/DownloadUpdateTask.cpp
+++ /dev/null
@@ -1,549 +0,0 @@
-/* Copyright 2013-2015 MultiMC Contributors
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include "DownloadUpdateTask.h"
-
-#include "MultiMC.h"
-#include "logic/Env.h"
-#include "BuildConfig.h"
-
-#include "logic/updater/UpdateChecker.h"
-#include "logic/net/NetJob.h"
-#include "pathutils.h"
-
-#include <QFile>
-#include <QTemporaryDir>
-#include <QCryptographicHash>
-
-#include <QDomDocument>
-
-DownloadUpdateTask::DownloadUpdateTask(QString rootPath, QString repoUrl, int versionId, QObject *parent)
-	: Task(parent)
-{
-	m_cVersionId = BuildConfig.VERSION_BUILD;
-	m_rootPath = rootPath;
-
-	m_nRepoUrl = repoUrl;
-	m_nVersionId = versionId;
-
-	m_updateFilesDir.setAutoRemove(false);
-}
-
-void DownloadUpdateTask::executeTask()
-{
-	// GO!
-	// This will call the next step when it's done.
-	findCurrentVersionInfo();
-}
-
-void DownloadUpdateTask::processChannels()
-{
-	auto checker = MMC->updateChecker();
-
-	// Now, check the channel list again.
-	if (!checker->hasChannels())
-	{
-		// We still couldn't load the channel list. Give up. Call loadVersionInfo and return.
-		qDebug() << "Reloading the channel list didn't work. Giving up.";
-		loadVersionInfo();
-		return;
-	}
-
-	QList<UpdateChecker::ChannelListEntry> channels = checker->getChannelList();
-	QString channelId = BuildConfig.VERSION_CHANNEL;
-
-	m_cRepoUrl.clear();
-	// Search through the channel list for a channel with the correct ID.
-	for (auto channel : channels)
-	{
-		if (channel.id == channelId)
-		{
-			qDebug() << "Found matching channel.";
-			m_cRepoUrl = channel.url;
-			break;
-		}
-	}
-
-	// Now that we've done that, load version info.
-	loadVersionInfo();
-}
-
-void DownloadUpdateTask::findCurrentVersionInfo()
-{
-	setStatus(tr("Finding information about the current version..."));
-
-	auto checker = MMC->updateChecker();
-
-	if (!checker->hasChannels())
-	{
-		// Load the channel list and wait for it to finish loading.
-		qDebug() << "No channel list entries found. Will try reloading it.";
-
-		QObject::connect(checker.get(), &UpdateChecker::channelListLoaded, this,
-						 &DownloadUpdateTask::processChannels);
-		checker->updateChanList(false);
-	}
-	else
-	{
-		processChannels();
-	}
-}
-
-void DownloadUpdateTask::loadVersionInfo()
-{
-	setStatus(tr("Loading version information..."));
-
-	// Create the net job for loading version info.
-	NetJob *netJob = new NetJob("Version Info");
-
-	// Find the index URL.
-	QUrl newIndexUrl = QUrl(m_nRepoUrl).resolved(QString::number(m_nVersionId) + ".json");
-	qDebug() << m_nRepoUrl << " turns into " << newIndexUrl;
-
-	// Add a net action to download the version info for the version we're updating to.
-	netJob->addNetAction(ByteArrayDownload::make(newIndexUrl));
-
-	// If we have a current version URL, get that one too.
-	if (!m_cRepoUrl.isEmpty())
-	{
-		QUrl cIndexUrl = QUrl(m_cRepoUrl).resolved(QString::number(m_cVersionId) + ".json");
-		netJob->addNetAction(ByteArrayDownload::make(cIndexUrl));
-		qDebug() << m_cRepoUrl << " turns into " << cIndexUrl;
-	}
-
-	// Connect slots so we know when it's done.
-	QObject::connect(netJob, &NetJob::succeeded, this,
-					 &DownloadUpdateTask::vinfoDownloadFinished);
-	QObject::connect(netJob, &NetJob::failed, this, &DownloadUpdateTask::vinfoDownloadFailed);
-
-	// Store the NetJob in a class member. We don't want to lose it!
-	m_vinfoNetJob.reset(netJob);
-
-	// Finally, we start the network job and the thread's event loop to wait for it to finish.
-	netJob->start();
-}
-
-void DownloadUpdateTask::vinfoDownloadFinished()
-{
-	// Both downloads succeeded. OK. Parse stuff.
-	parseDownloadedVersionInfo();
-}
-
-void DownloadUpdateTask::vinfoDownloadFailed()
-{
-	// Something failed. We really need the second download (current version info), so parse
-	// downloads anyways as long as the first one succeeded.
-	if (m_vinfoNetJob->first()->m_status != Job_Failed)
-	{
-		parseDownloadedVersionInfo();
-		return;
-	}
-
-	// TODO: Give a more detailed error message.
-	qCritical() << "Failed to download version info files.";
-	emitFailed(tr("Failed to download version info files."));
-}
-
-void DownloadUpdateTask::parseDownloadedVersionInfo()
-{
-	setStatus(tr("Reading file list for new version..."));
-	qDebug() << "Reading file list for new version...";
-	QString error;
-	if (!parseVersionInfo(
-			 std::dynamic_pointer_cast<ByteArrayDownload>(m_vinfoNetJob->first())->m_data,
-			 &m_nVersionFileList, &error))
-	{
-		emitFailed(error);
-		return;
-	}
-
-	// If there is a second entry in the network job's list, load it as the current version's
-	// info.
-	if (m_vinfoNetJob->size() >= 2 && m_vinfoNetJob->operator[](1)->m_status != Job_Failed)
-	{
-		setStatus(tr("Reading file list for current version..."));
-		qDebug() << "Reading file list for current version...";
-		QString error;
-		parseVersionInfo(
-			std::dynamic_pointer_cast<ByteArrayDownload>(m_vinfoNetJob->operator[](1))->m_data,
-			&m_cVersionFileList, &error);
-	}
-
-	// We don't need this any more.
-	m_vinfoNetJob.reset();
-
-	// Now that we're done loading version info, we can move on to the next step. Process file
-	// lists and download files.
-	processFileLists();
-}
-
-bool DownloadUpdateTask::parseVersionInfo(const QByteArray &data, VersionFileList *list,
-										  QString *error)
-{
-	QJsonParseError jsonError;
-	QJsonDocument jsonDoc = QJsonDocument::fromJson(data, &jsonError);
-	if (jsonError.error != QJsonParseError::NoError)
-	{
-		*error = QString("Failed to parse version info JSON: %1 at %2")
-					 .arg(jsonError.errorString())
-					 .arg(jsonError.offset);
-		qCritical() << error;
-		return false;
-	}
-
-	QJsonObject json = jsonDoc.object();
-
-	qDebug() << data;
-	qDebug() << "Loading version info from JSON.";
-	QJsonArray filesArray = json.value("Files").toArray();
-	for (QJsonValue fileValue : filesArray)
-	{
-		QJsonObject fileObj = fileValue.toObject();
-
-		QString file_path = fileObj.value("Path").toString();
-#ifdef Q_OS_MAC
-		// On OSX, the paths for the updater need to be fixed.
-		// basically, anything that isn't in the .app folder is ignored.
-		// everything else is changed so the code that processes the files actually finds
-		// them and puts the replacements in the right spots.
-		if (!fixPathForOSX(file_path))
-			continue;
-#endif
-		VersionFileEntry file{file_path,		fileObj.value("Perms").toVariant().toInt(),
-							  FileSourceList(), fileObj.value("MD5").toString(), };
-		qDebug() << "File" << file.path << "with perms" << file.mode;
-
-		QJsonArray sourceArray = fileObj.value("Sources").toArray();
-		for (QJsonValue val : sourceArray)
-		{
-			QJsonObject sourceObj = val.toObject();
-
-			QString type = sourceObj.value("SourceType").toString();
-			if (type == "http")
-			{
-				file.sources.append(
-					FileSource("http", sourceObj.value("Url").toString()));
-			}
-			else if (type == "httpc")
-			{
-				file.sources.append(
-					FileSource("httpc", sourceObj.value("Url").toString(),
-							   sourceObj.value("CompressionType").toString()));
-			}
-			else
-			{
-				qWarning() << "Unknown source type" << type << "ignored.";
-			}
-		}
-
-		qDebug() << "Loaded info for" << file.path;
-
-		list->append(file);
-	}
-
-	return true;
-}
-
-void DownloadUpdateTask::processFileLists()
-{
-	// Create a network job for downloading files.
-	NetJob *netJob = new NetJob("Update Files");
-
-	if (!processFileLists(netJob, m_cVersionFileList, m_nVersionFileList, m_operationList))
-	{
-		emitFailed(tr("Failed to process update lists..."));
-		return;
-	}
-
-	// Add listeners to wait for the downloads to finish.
-	QObject::connect(netJob, &NetJob::succeeded, this,
-					 &DownloadUpdateTask::fileDownloadFinished);
-	QObject::connect(netJob, &NetJob::progress, this,
-					 &DownloadUpdateTask::fileDownloadProgressChanged);
-	QObject::connect(netJob, &NetJob::failed, this, &DownloadUpdateTask::fileDownloadFailed);
-
-	// Now start the download.
-	setStatus(tr("Downloading %1 update files.").arg(QString::number(netJob->size())));
-	qDebug() << "Begin downloading update files to" << m_updateFilesDir.path();
-	m_filesNetJob.reset(netJob);
-	netJob->start();
-
-	writeInstallScript(m_operationList, PathCombine(m_updateFilesDir.path(), "file_list.xml"));
-}
-
-bool
-DownloadUpdateTask::processFileLists(NetJob *job,
-									 const DownloadUpdateTask::VersionFileList &currentVersion,
-									 const DownloadUpdateTask::VersionFileList &newVersion,
-									 DownloadUpdateTask::UpdateOperationList &ops)
-{
-	setStatus(tr("Processing file lists - figuring out how to install the update..."));
-
-	// First, if we've loaded the current version's file list, we need to iterate through it and
-	// delete anything in the current one version's list that isn't in the new version's list.
-	for (VersionFileEntry entry : currentVersion)
-	{
-		QFileInfo toDelete(PathCombine(m_rootPath, entry.path));
-		if (!toDelete.exists())
-		{
-			qCritical() << "Expected file " << toDelete.absoluteFilePath()
-						 << " doesn't exist!";
-		}
-		bool keep = false;
-
-		//
-		for (VersionFileEntry newEntry : newVersion)
-		{
-			if (newEntry.path == entry.path)
-			{
-				qDebug() << "Not deleting" << entry.path
-							 << "because it is still present in the new version.";
-				keep = true;
-				break;
-			}
-		}
-
-		// If the loop reaches the end and we didn't find a match, delete the file.
-		if (!keep)
-		{
-			if (toDelete.exists())
-				ops.append(UpdateOperation::DeleteOp(entry.path));
-		}
-	}
-
-	// Next, check each file in MultiMC's folder and see if we need to update them.
-	for (VersionFileEntry entry : newVersion)
-	{
-		// TODO: Let's not MD5sum a ton of files on the GUI thread. We should probably find a
-		// way to do this in the background.
-		QString fileMD5;
-		QString realEntryPath = PathCombine(m_rootPath, entry.path);
-		QFile entryFile(realEntryPath);
-		QFileInfo entryInfo(realEntryPath);
-
-		bool needs_upgrade = false;
-		if (!entryFile.exists())
-		{
-			needs_upgrade = true;
-		}
-		else
-		{
-			bool pass = true;
-			if (!entryInfo.isReadable())
-			{
-				qCritical() << "File " << realEntryPath << " is not readable.";
-				pass = false;
-			}
-			if (!entryInfo.isWritable())
-			{
-				qCritical() << "File " << realEntryPath << " is not writable.";
-				pass = false;
-			}
-			if (!entryFile.open(QFile::ReadOnly))
-			{
-				qCritical() << "File " << realEntryPath << " cannot be opened for reading.";
-				pass = false;
-			}
-			if (!pass)
-			{
-				ops.clear();
-				return false;
-			}
-		}
-
-		if(!needs_upgrade)
-		{
-			QCryptographicHash hash(QCryptographicHash::Md5);
-			auto foo = entryFile.readAll();
-
-			hash.addData(foo);
-			fileMD5 = hash.result().toHex();
-			if ((fileMD5 != entry.md5))
-			{
-				qDebug() << "MD5Sum does not match!";
-				qDebug() << "Expected:'" << entry.md5 << "'";
-				qDebug() << "Got:     '" << fileMD5 << "'";
-				needs_upgrade = true;
-			}
-		}
-
-		// skip file. it doesn't need an upgrade.
-		if (!needs_upgrade)
-		{
-			qDebug() << "File" << realEntryPath << " does not need updating.";
-			continue;
-		}
-
-		// yep. this file actually needs an upgrade. PROCEED.
-		qDebug() << "Found file" << realEntryPath << " that needs updating.";
-
-		// if it's the updater we want to treat it separately
-		bool isUpdater = entry.path.endsWith("updater") || entry.path.endsWith("updater.exe");
-
-		// Go through the sources list and find one to use.
-		// TODO: Make a NetAction that takes a source list and tries each of them until one
-		// works. For now, we'll just use the first http one.
-		for (FileSource source : entry.sources)
-		{
-			if (source.type == "http")
-			{
-				qDebug() << "Will download" << entry.path << "from" << source.url;
-
-				// Download it to updatedir/<filepath>-<md5> where filepath is the file's
-				// path with slashes replaced by underscores.
-				QString dlPath =
-					PathCombine(m_updateFilesDir.path(), QString(entry.path).replace("/", "_"));
-
-				if (isUpdater)
-				{
-					if(BuildConfig.UPDATER_FORCE_LOCAL)
-					{
-						qDebug() << "Skipping updater download and using local version.";
-					}
-					else
-					{
-						auto cache_entry = ENV.metacache()->resolveEntry("root", entry.path);
-						qDebug() << "Updater will be in " << cache_entry->getFullPath();
-						// force check.
-						cache_entry->stale = true;
-
-						auto download = CacheDownload::make(QUrl(source.url), cache_entry);
-						job->addNetAction(download);
-					}
-				}
-				else
-				{
-					// We need to download the file to the updatefiles folder and add a task
-					// to copy it to its install path.
-					auto download = MD5EtagDownload::make(source.url, dlPath);
-					download->m_expected_md5 = entry.md5;
-					job->addNetAction(download);
-					ops.append(UpdateOperation::CopyOp(dlPath, entry.path, entry.mode));
-				}
-			}
-		}
-	}
-	return true;
-}
-
-bool DownloadUpdateTask::writeInstallScript(UpdateOperationList &opsList, QString scriptFile)
-{
-	// Build the base structure of the XML document.
-	QDomDocument doc;
-
-	QDomElement root = doc.createElement("update");
-	root.setAttribute("version", "3");
-	doc.appendChild(root);
-
-	QDomElement installFiles = doc.createElement("install");
-	root.appendChild(installFiles);
-
-	QDomElement removeFiles = doc.createElement("uninstall");
-	root.appendChild(removeFiles);
-
-	// Write the operation list to the XML document.
-	for (UpdateOperation op : opsList)
-	{
-		QDomElement file = doc.createElement("file");
-
-		switch (op.type)
-		{
-		case UpdateOperation::OP_COPY:
-		{
-			// Install the file.
-			QDomElement name = doc.createElement("source");
-			QDomElement path = doc.createElement("dest");
-			QDomElement mode = doc.createElement("mode");
-			name.appendChild(doc.createTextNode(op.file));
-			path.appendChild(doc.createTextNode(op.dest));
-			// We need to add a 0 at the beginning here, because Qt doesn't convert to octal
-			// correctly.
-			mode.appendChild(doc.createTextNode("0" + QString::number(op.mode, 8)));
-			file.appendChild(name);
-			file.appendChild(path);
-			file.appendChild(mode);
-			installFiles.appendChild(file);
-			qDebug() << "Will install file " << op.file << " to " << op.dest;
-		}
-		break;
-
-		case UpdateOperation::OP_DELETE:
-		{
-			// Delete the file.
-			file.appendChild(doc.createTextNode(op.file));
-			removeFiles.appendChild(file);
-			qDebug() << "Will remove file" << op.file;
-		}
-		break;
-
-		default:
-			qWarning() << "Can't write update operation of type" << op.type
-						<< "to file. Not implemented.";
-			continue;
-		}
-	}
-
-	// Write the XML document to the file.
-	QFile outFile(scriptFile);
-
-	if (outFile.open(QIODevice::WriteOnly))
-	{
-		outFile.write(doc.toByteArray());
-	}
-	else
-	{
-		emitFailed(tr("Failed to write update script file."));
-		return false;
-	}
-
-	return true;
-}
-
-bool DownloadUpdateTask::fixPathForOSX(QString &path)
-{
-	if (path.startsWith("MultiMC.app/"))
-	{
-		// remove the prefix and add a new, more appropriate one.
-		path.remove(0, 12);
-		return true;
-	}
-	else
-	{
-		qCritical() << "Update path not within .app: " << path;
-		return false;
-	}
-}
-
-void DownloadUpdateTask::fileDownloadFinished()
-{
-	emitSucceeded();
-}
-
-void DownloadUpdateTask::fileDownloadFailed()
-{
-	// TODO: Give more info about the failure.
-	qCritical() << "Failed to download update files.";
-	emitFailed(tr("Failed to download update files."));
-}
-
-void DownloadUpdateTask::fileDownloadProgressChanged(qint64 current, qint64 total)
-{
-	setProgress((int)(((float)current / (float)total) * 100));
-}
-
-QString DownloadUpdateTask::updateFilesDir()
-{
-	return m_updateFilesDir.path();
-}
diff --git a/logic/updater/DownloadUpdateTask.h b/logic/updater/DownloadUpdateTask.h
deleted file mode 100644
index 9a994687..00000000
--- a/logic/updater/DownloadUpdateTask.h
+++ /dev/null
@@ -1,220 +0,0 @@
-/* Copyright 2013-2015 MultiMC Contributors
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#pragma once
-
-#include "logic/tasks/Task.h"
-#include "logic/net/NetJob.h"
-
-/*!
- * The DownloadUpdateTask is a task that takes a given version ID and repository URL,
- * downloads that version's files from the repository, and prepares to install them.
- */
-class DownloadUpdateTask : public Task
-{
-	Q_OBJECT
-
-public:
-	explicit DownloadUpdateTask(QString rootPath, QString repoUrl, int versionId, QObject* parent=0);
-
-	/*!
-	 * Gets the directory that contains the update files.
-	 */
-	QString updateFilesDir();
-
-public:
-
-	// TODO: We should probably put these data structures into a separate header...
-
-	/*!
-	 * Struct that describes an entry in a VersionFileEntry's `Sources` list.
-	 */
-	struct FileSource
-	{
-		FileSource(QString type, QString url, QString compression="")
-		{
-			this->type = type;
-			this->url = url;
-			this->compressionType = compression;
-		}
-
-		QString type;
-		QString url;
-		QString compressionType;
-	};
-	typedef QList<FileSource> FileSourceList;
-
-	/*!
-	 * Structure that describes an entry in a GoUpdate version's `Files` list.
-	 */
-	struct VersionFileEntry
-	{
-		QString path;
-		int mode;
-		FileSourceList sources;
-		QString md5;
-	};
-	typedef QList<VersionFileEntry> VersionFileList;
-
-	/*!
-	 * Structure that describes an operation to perform when installing updates.
-	 */
-	struct UpdateOperation
-	{
-		static UpdateOperation CopyOp(QString fsource, QString fdest, int fmode=0644) { return UpdateOperation{OP_COPY, fsource, fdest, fmode}; }
-		static UpdateOperation MoveOp(QString fsource, QString fdest, int fmode=0644) { return UpdateOperation{OP_MOVE, fsource, fdest, fmode}; }
-		static UpdateOperation DeleteOp(QString file) { return UpdateOperation{OP_DELETE, file, "", 0644}; }
-		static UpdateOperation ChmodOp(QString file, int fmode) { return UpdateOperation{OP_CHMOD, file, "", fmode}; }
-
-		//! Specifies the type of operation that this is.
-		enum Type
-		{
-			OP_COPY,
-			OP_DELETE,
-			OP_MOVE,
-			OP_CHMOD,
-		} type;
-
-		//! The file to operate on. If this is a DELETE or CHMOD operation, this is the file that will be modified.
-		QString file;
-
-		//! The destination file. If this is a DELETE or CHMOD operation, this field will be ignored.
-		QString dest;
-
-		//! The mode to change the source file to. Ignored if this isn't a CHMOD operation.
-		int mode;
-
-		// Yeah yeah, polymorphism blah blah inheritance, blah blah object oriented. I'm lazy, OK?
-	};
-	typedef QList<UpdateOperation> UpdateOperationList;
-
-protected:
-	friend class DownloadUpdateTaskTest;
-
-
-	/*!
-	 * Used for arguments to parseVersionInfo and friends to specify which version info file to parse.
-	 */
-	enum VersionInfoFileEnum { NEW_VERSION, CURRENT_VERSION };
-
-
-	//! Entry point for tasks.
-	virtual void executeTask();
-
-	/*!
-	 * Attempts to find the version ID and repository URL for the current version.
-	 * The function will look up the repository URL in the UpdateChecker's channel list.
-	 * If the repository URL can't be found, this function will return false.
-	 */
-	virtual void findCurrentVersionInfo();
-
-	/*!
-	 * This runs after we've tried loading the channel list.
-	 * If the channel list doesn't need to be loaded, this will be called immediately.
-	 * If the channel list does need to be loaded, this will be called when it's done.
-	 */
-	void processChannels();
-
-	/*!
-	 * Downloads the version info files from the repository.
-	 * The files for both the current build, and the build that we're updating to need to be downloaded.
-	 * If the current version's info file can't be found, MultiMC will not delete files that
-	 * were removed between versions. It will still replace files that have changed, however.
-	 * Note that although the repository URL for the current version is not given to the update task,
-	 * the task will attempt to look it up in the UpdateChecker's channel list.
-	 * If an error occurs here, the function will call emitFailed and return false.
-	 */
-	virtual void loadVersionInfo();
-
-	/*!
-	 * This function is called when version information is finished downloading.
-	 * This handles parsing the JSON downloaded by the version info network job and then calls processFileLists.
-	 * Note that this function will sometimes be called even if the version info download emits failed. If
-	 * we couldn't download the current version's info file, we can still update. This will be called even if the
-	 * current version's info file fails to download, as long as the new version's info file succeeded.
-	 */
-	virtual void parseDownloadedVersionInfo();
-
-	/*!
-	 * Loads the file list from the given version info JSON object into the given list.
-	 */
-	virtual bool parseVersionInfo(const QByteArray &data, VersionFileList* list, QString *error);
-
-	/*!
-	 * Takes a list of file entries for the current version's files and the new version's files
-	 * and populates the downloadList and operationList with information about how to download and install the update.
-	 */
-	virtual bool processFileLists(NetJob *job, const VersionFileList &currentVersion, const VersionFileList &newVersion, UpdateOperationList &ops);
-
-	/*!
-	 * Calls \see processFileLists to populate the \see m_operationList and a NetJob, and then executes
-	 * the NetJob to fetch all needed files
-	 */
-	virtual void processFileLists();
-
-	/*!
-	 * Takes the operations list and writes an install script for the updater to the update files directory.
-	 */
-	virtual bool writeInstallScript(UpdateOperationList& opsList, QString scriptFile);
-
-	UpdateOperationList m_operationList;
-
-	VersionFileList m_nVersionFileList;
-	VersionFileList m_cVersionFileList;
-
-	//! Network job for downloading version info files.
-	NetJobPtr m_vinfoNetJob;
-
-	//! Network job for downloading update files.
-	NetJobPtr m_filesNetJob;
-
-	// Version ID and repo URL for the new version.
-	int m_nVersionId;
-	QString m_nRepoUrl;
-
-	// Version ID and repo URL for the currently installed version.
-	int m_cVersionId;
-	QString m_cRepoUrl;
-
-	// path to the root of the application
-	QString m_rootPath;
-
-	/*!
-	 * Temporary directory to store update files in.
-	 * This will be set to not auto delete. Task will fail if this fails to be created.
-	 */
-	QTemporaryDir m_updateFilesDir;
-
-	/*!
-	 * Filters paths
-	 * This fixes destination paths for OSX.
-	 * The updater runs in MultiMC.app/Contents/MacOs by default
-	 * The destination paths are such as this: MultiMC.app/blah/blah
-	 *
-	 * Therefore we chop off the 'MultiMC.app' prefix
-	 *
-	 * Returns false if the path couldn't be fixed (is invalid)
-	 */
-	static bool fixPathForOSX(QString &path);
-
-protected slots:
-	void vinfoDownloadFinished();
-	void vinfoDownloadFailed();
-
-	void fileDownloadFinished();
-	void fileDownloadFailed();
-	void fileDownloadProgressChanged(qint64 current, qint64 total);
-};
-
diff --git a/logic/updater/GoUpdate.cpp b/logic/updater/GoUpdate.cpp
new file mode 100644
index 00000000..84dc164c
--- /dev/null
+++ b/logic/updater/GoUpdate.cpp
@@ -0,0 +1,315 @@
+#include "GoUpdate.h"
+#include <pathutils.h>
+#include <QDebug>
+#include <QDomDocument>
+#include <QFile>
+#include <logic/Env.h>
+
+namespace GoUpdate
+{
+
+bool parseVersionInfo(const QByteArray &data, VersionFileList &list, QString &error)
+{
+	QJsonParseError jsonError;
+	QJsonDocument jsonDoc = QJsonDocument::fromJson(data, &jsonError);
+	if (jsonError.error != QJsonParseError::NoError)
+	{
+		error = QString("Failed to parse version info JSON: %1 at %2")
+					.arg(jsonError.errorString())
+					.arg(jsonError.offset);
+		qCritical() << error;
+		return false;
+	}
+
+	QJsonObject json = jsonDoc.object();
+
+	qDebug() << data;
+	qDebug() << "Loading version info from JSON.";
+	QJsonArray filesArray = json.value("Files").toArray();
+	for (QJsonValue fileValue : filesArray)
+	{
+		QJsonObject fileObj = fileValue.toObject();
+
+		QString file_path = fileObj.value("Path").toString();
+#ifdef Q_OS_MAC
+		// On OSX, the paths for the updater need to be fixed.
+		// basically, anything that isn't in the .app folder is ignored.
+		// everything else is changed so the code that processes the files actually finds
+		// them and puts the replacements in the right spots.
+		if (!fixPathForOSX(file_path))
+			continue;
+#endif
+		VersionFileEntry file{file_path,		fileObj.value("Perms").toVariant().toInt(),
+							  FileSourceList(), fileObj.value("MD5").toString(), };
+		qDebug() << "File" << file.path << "with perms" << file.mode;
+
+		QJsonArray sourceArray = fileObj.value("Sources").toArray();
+		for (QJsonValue val : sourceArray)
+		{
+			QJsonObject sourceObj = val.toObject();
+
+			QString type = sourceObj.value("SourceType").toString();
+			if (type == "http")
+			{
+				file.sources.append(FileSource("http", sourceObj.value("Url").toString()));
+			}
+			else
+			{
+				qWarning() << "Unknown source type" << type << "ignored.";
+			}
+		}
+
+		qDebug() << "Loaded info for" << file.path;
+
+		list.append(file);
+	}
+
+	return true;
+}
+
+bool processFileLists
+(
+	const VersionFileList &currentVersion,
+	const VersionFileList &newVersion,
+	const QString &rootPath,
+	const QString &tempPath,
+	NetJobPtr job,
+	OperationList &ops,
+	bool useLocalUpdater
+)
+{
+	// First, if we've loaded the current version's file list, we need to iterate through it and
+	// delete anything in the current one version's list that isn't in the new version's list.
+	for (VersionFileEntry entry : currentVersion)
+	{
+		QFileInfo toDelete(PathCombine(rootPath, entry.path));
+		if (!toDelete.exists())
+		{
+			qCritical() << "Expected file " << toDelete.absoluteFilePath()
+						 << " doesn't exist!";
+		}
+		bool keep = false;
+
+		//
+		for (VersionFileEntry newEntry : newVersion)
+		{
+			if (newEntry.path == entry.path)
+			{
+				qDebug() << "Not deleting" << entry.path
+							 << "because it is still present in the new version.";
+				keep = true;
+				break;
+			}
+		}
+
+		// If the loop reaches the end and we didn't find a match, delete the file.
+		if (!keep)
+		{
+			if (toDelete.exists())
+				ops.append(Operation::DeleteOp(entry.path));
+		}
+	}
+
+	// Next, check each file in MultiMC's folder and see if we need to update them.
+	for (VersionFileEntry entry : newVersion)
+	{
+		// TODO: Let's not MD5sum a ton of files on the GUI thread. We should probably find a
+		// way to do this in the background.
+		QString fileMD5;
+		QString realEntryPath = PathCombine(rootPath, entry.path);
+		QFile entryFile(realEntryPath);
+		QFileInfo entryInfo(realEntryPath);
+
+		bool needs_upgrade = false;
+		if (!entryFile.exists())
+		{
+			needs_upgrade = true;
+		}
+		else
+		{
+			bool pass = true;
+			if (!entryInfo.isReadable())
+			{
+				qCritical() << "File " << realEntryPath << " is not readable.";
+				pass = false;
+			}
+			if (!entryInfo.isWritable())
+			{
+				qCritical() << "File " << realEntryPath << " is not writable.";
+				pass = false;
+			}
+			if (!entryFile.open(QFile::ReadOnly))
+			{
+				qCritical() << "File " << realEntryPath << " cannot be opened for reading.";
+				pass = false;
+			}
+			if (!pass)
+			{
+				ops.clear();
+				return false;
+			}
+		}
+
+		if(!needs_upgrade)
+		{
+			QCryptographicHash hash(QCryptographicHash::Md5);
+			auto foo = entryFile.readAll();
+
+			hash.addData(foo);
+			fileMD5 = hash.result().toHex();
+			if ((fileMD5 != entry.md5))
+			{
+				qDebug() << "MD5Sum does not match!";
+				qDebug() << "Expected:'" << entry.md5 << "'";
+				qDebug() << "Got:     '" << fileMD5 << "'";
+				needs_upgrade = true;
+			}
+		}
+
+		// skip file. it doesn't need an upgrade.
+		if (!needs_upgrade)
+		{
+			qDebug() << "File" << realEntryPath << " does not need updating.";
+			continue;
+		}
+
+		// yep. this file actually needs an upgrade. PROCEED.
+		qDebug() << "Found file" << realEntryPath << " that needs updating.";
+
+		// if it's the updater we want to treat it separately
+		bool isUpdater = entry.path.endsWith("updater") || entry.path.endsWith("updater.exe");
+
+		// Go through the sources list and find one to use.
+		// TODO: Make a NetAction that takes a source list and tries each of them until one
+		// works. For now, we'll just use the first http one.
+		for (FileSource source : entry.sources)
+		{
+			if (source.type != "http")
+				continue;
+
+			qDebug() << "Will download" << entry.path << "from" << source.url;
+
+			// Download it to updatedir/<filepath>-<md5> where filepath is the file's
+			// path with slashes replaced by underscores.
+			QString dlPath = PathCombine(tempPath, QString(entry.path).replace("/", "_"));
+
+			if (isUpdater)
+			{
+				if(useLocalUpdater)
+				{
+					qDebug() << "Skipping updater download and using local version.";
+				}
+				else
+				{
+					auto cache_entry = ENV.metacache()->resolveEntry("root", entry.path);
+					qDebug() << "Updater will be in " << cache_entry->getFullPath();
+					// force check.
+					cache_entry->stale = true;
+
+					auto download = CacheDownload::make(QUrl(source.url), cache_entry);
+					job->addNetAction(download);
+				}
+			}
+			else
+			{
+				// We need to download the file to the updatefiles folder and add a task
+				// to copy it to its install path.
+				auto download = MD5EtagDownload::make(source.url, dlPath);
+				download->m_expected_md5 = entry.md5;
+				job->addNetAction(download);
+				ops.append(Operation::CopyOp(dlPath, entry.path, entry.mode));
+			}
+		}
+	}
+	return true;
+}
+
+bool fixPathForOSX(QString &path)
+{
+	if (path.startsWith("MultiMC.app/"))
+	{
+		// remove the prefix and add a new, more appropriate one.
+		path.remove(0, 12);
+		return true;
+	}
+	else
+	{
+		qCritical() << "Update path not within .app: " << path;
+		return false;
+	}
+}
+
+bool writeInstallScript(OperationList &opsList, QString scriptFile)
+{
+	// Build the base structure of the XML document.
+	QDomDocument doc;
+
+	QDomElement root = doc.createElement("update");
+	root.setAttribute("version", "3");
+	doc.appendChild(root);
+
+	QDomElement installFiles = doc.createElement("install");
+	root.appendChild(installFiles);
+
+	QDomElement removeFiles = doc.createElement("uninstall");
+	root.appendChild(removeFiles);
+
+	// Write the operation list to the XML document.
+	for (Operation op : opsList)
+	{
+		QDomElement file = doc.createElement("file");
+
+		switch (op.type)
+		{
+		case Operation::OP_COPY:
+		{
+			// Install the file.
+			QDomElement name = doc.createElement("source");
+			QDomElement path = doc.createElement("dest");
+			QDomElement mode = doc.createElement("mode");
+			name.appendChild(doc.createTextNode(op.file));
+			path.appendChild(doc.createTextNode(op.dest));
+			// We need to add a 0 at the beginning here, because Qt doesn't convert to octal
+			// correctly.
+			mode.appendChild(doc.createTextNode("0" + QString::number(op.mode, 8)));
+			file.appendChild(name);
+			file.appendChild(path);
+			file.appendChild(mode);
+			installFiles.appendChild(file);
+			qDebug() << "Will install file " << op.file << " to " << op.dest;
+		}
+		break;
+
+		case Operation::OP_DELETE:
+		{
+			// Delete the file.
+			file.appendChild(doc.createTextNode(op.file));
+			removeFiles.appendChild(file);
+			qDebug() << "Will remove file" << op.file;
+		}
+		break;
+
+		default:
+			qWarning() << "Can't write update operation of type" << op.type
+						<< "to file. Not implemented.";
+			continue;
+		}
+	}
+
+	// Write the XML document to the file.
+	QFile outFile(scriptFile);
+
+	if (outFile.open(QIODevice::WriteOnly))
+	{
+		outFile.write(doc.toByteArray());
+	}
+	else
+	{
+		return false;
+	}
+
+	return true;
+}
+
+
+}
\ No newline at end of file
diff --git a/logic/updater/GoUpdate.h b/logic/updater/GoUpdate.h
new file mode 100644
index 00000000..bea6cce7
--- /dev/null
+++ b/logic/updater/GoUpdate.h
@@ -0,0 +1,135 @@
+#pragma once
+#include <QByteArray>
+#include <logic/net/NetJob.h>
+
+namespace GoUpdate
+{
+
+/**
+ * A temporary object exchanged between updated checker and the actual update task
+ */
+struct Status
+{
+	bool updateAvailable = false;
+
+	int newVersionId = -1;
+	QString newRepoUrl;
+
+	int currentVersionId = -1;
+	QString currentRepoUrl;
+
+	// path to the root of the application
+	QString rootPath;
+};
+
+/**
+ * Struct that describes an entry in a VersionFileEntry's `Sources` list.
+ */
+struct FileSource
+{
+	FileSource(QString type, QString url, QString compression="")
+	{
+		this->type = type;
+		this->url = url;
+		this->compressionType = compression;
+	}
+
+	bool operator==(const FileSource &f2) const
+	{
+		return type == f2.type && url == f2.url && compressionType == f2.compressionType;
+	}
+
+	QString type;
+	QString url;
+	QString compressionType;
+};
+typedef QList<FileSource> FileSourceList;
+
+/**
+ * Structure that describes an entry in a GoUpdate version's `Files` list.
+ */
+struct VersionFileEntry
+{
+	QString path;
+	int mode;
+	FileSourceList sources;
+	QString md5;
+	bool operator==(const VersionFileEntry &v2) const
+	{
+		return path == v2.path && mode == v2.mode && sources == v2.sources && md5 == v2.md5;
+	}
+};
+typedef QList<VersionFileEntry> VersionFileList;
+
+/**
+ * Structure that describes an operation to perform when installing updates.
+ */
+struct Operation
+{
+	static Operation CopyOp(QString fsource, QString fdest, int fmode=0644) { return Operation{OP_COPY, fsource, fdest, fmode}; }
+	static Operation MoveOp(QString fsource, QString fdest, int fmode=0644) { return Operation{OP_MOVE, fsource, fdest, fmode}; }
+	static Operation DeleteOp(QString file) { return Operation{OP_DELETE, file, "", 0644}; }
+	static Operation ChmodOp(QString file, int fmode) { return Operation{OP_CHMOD, file, "", fmode}; }
+
+	// FIXME: for some types, some of the other fields are irrelevant!
+	bool operator==(const Operation &u2) const
+	{
+		return type == u2.type && file == u2.file && dest == u2.dest && mode == u2.mode;
+	}
+
+	//! Specifies the type of operation that this is.
+	enum Type
+	{
+		OP_COPY,
+		OP_DELETE,
+		OP_MOVE,
+		OP_CHMOD,
+	} type;
+
+	//! The file to operate on. If this is a DELETE or CHMOD operation, this is the file that will be modified.
+	QString file;
+
+	//! The destination file. If this is a DELETE or CHMOD operation, this field will be ignored.
+	QString dest;
+
+	//! The mode to change the source file to. Ignored if this isn't a CHMOD operation.
+	int mode;
+};
+typedef QList<Operation> OperationList;
+
+/**
+ * Takes the @OperationList list and writes an install script for the updater to the update files directory.
+ */
+bool writeInstallScript(OperationList& opsList, QString scriptFile);
+
+/**
+ * Loads the file list from the given version info JSON object into the given list.
+ */
+bool parseVersionInfo(const QByteArray &data, VersionFileList& list, QString &error);
+
+/*!
+ * Takes a list of file entries for the current version's files and the new version's files
+ * and populates the downloadList and operationList with information about how to download and install the update.
+ */
+bool processFileLists
+(
+	const VersionFileList &currentVersion,
+	const VersionFileList &newVersion,
+	const QString &rootPath,
+	const QString &tempPath,
+	NetJobPtr job,
+	OperationList &ops,
+	bool useLocalUpdater
+);
+
+/*!
+ * This fixes destination paths for OSX - removes 'MultiMC.app' prefix
+ * The updater runs in MultiMC.app/Contents/MacOs by default
+ * The destination paths are such as this: MultiMC.app/blah/blah
+ *
+ * @return false if the path couldn't be fixed (is invalid)
+ */
+bool fixPathForOSX(QString &path);
+
+}
+Q_DECLARE_METATYPE(GoUpdate::Status);
\ No newline at end of file
diff --git a/logic/updater/UpdateChecker.cpp b/logic/updater/UpdateChecker.cpp
index 8ac84bf1..7d214ed4 100644
--- a/logic/updater/UpdateChecker.cpp
+++ b/logic/updater/UpdateChecker.cpp
@@ -23,10 +23,12 @@
 #define API_VERSION 0
 #define CHANLIST_FORMAT 0
 
-UpdateChecker::UpdateChecker(QString channelListUrl, int currentBuild)
+UpdateChecker::UpdateChecker(QString channelListUrl, QString currentChannel, int currentBuild)
 {
 	m_channelListUrl = channelListUrl;
+	m_currentChannel = currentChannel;
 	m_currentBuild = currentBuild;
+
 	m_updateChecking = false;
 	m_chanListLoading = false;
 	m_checkUpdateWaiting = false;
@@ -69,24 +71,26 @@ void UpdateChecker::checkForUpdate(QString updateChannel, bool notifyNoUpdate)
 
 	// Find the desired channel within the channel list and get its repo URL. If if cannot be
 	// found, error.
-	m_repoUrl = "";
+	m_newRepoUrl = "";
 	for (ChannelListEntry entry : m_channels)
 	{
 		if (entry.id == updateChannel)
-			m_repoUrl = entry.url;
+			m_newRepoUrl = entry.url;
+		if (entry.id == m_currentChannel)
+			m_currentRepoUrl = entry.url;
 	}
 
-	qDebug() << "m_repoUrl = " << m_repoUrl;
+	qDebug() << "m_repoUrl = " << m_newRepoUrl;
 
 	// If we didn't find our channel, error.
-	if (m_repoUrl.isEmpty())
+	if (m_newRepoUrl.isEmpty())
 	{
 		qCritical() << "m_repoUrl is empty!";
 		emit updateCheckFailed();
 		return;
 	}
 
-	QUrl indexUrl = QUrl(m_repoUrl).resolved(QUrl("index.json"));
+	QUrl indexUrl = QUrl(m_newRepoUrl).resolved(QUrl("index.json"));
 
 	auto job = new NetJob("GoUpdate Repository Index");
 	job->addNetAction(ByteArrayDownload::make(indexUrl));
@@ -149,8 +153,13 @@ void UpdateChecker::updateCheckFinished(bool notifyNoUpdate)
 	{
 		qDebug() << "Found newer version with ID" << newBuildNumber;
 		// Update!
-		emit updateAvailable(m_repoUrl, newestVersion.value("Name").toVariant().toString(),
-							 newBuildNumber);
+		GoUpdate::Status updateStatus;
+		updateStatus.updateAvailable = true;
+		updateStatus.currentVersionId = m_currentBuild;
+		updateStatus.currentRepoUrl = m_currentRepoUrl;
+		updateStatus.newVersionId = newBuildNumber;
+		updateStatus.newRepoUrl = m_newRepoUrl;
+		emit updateAvailable(updateStatus);
 	}
 	else if (notifyNoUpdate)
 	{
diff --git a/logic/updater/UpdateChecker.h b/logic/updater/UpdateChecker.h
index 2b08680a..0eaceea0 100644
--- a/logic/updater/UpdateChecker.h
+++ b/logic/updater/UpdateChecker.h
@@ -16,6 +16,7 @@
 #pragma once
 
 #include "logic/net/NetJob.h"
+#include "GoUpdate.h"
 
 #include <QUrl>
 
@@ -24,7 +25,7 @@ class UpdateChecker : public QObject
 	Q_OBJECT
 
 public:
-	UpdateChecker(QString channelListUrl, int currentBuild);
+	UpdateChecker(QString channelListUrl, QString currentChannel, int currentBuild);
 	void checkForUpdate(QString updateChannel, bool notifyNoUpdate);
 
 	/*!
@@ -57,7 +58,7 @@ public:
 
 signals:
 	//! Signal emitted when an update is available. Passes the URL for the repo and the ID and name for the version.
-	void updateAvailable(QString repoUrl, QString versionName, int versionId);
+	void updateAvailable(GoUpdate::Status status);
 
 	//! Signal emitted when the channel list finishes loading or fails to load.
 	void channelListLoaded();
@@ -77,8 +78,6 @@ private:
 	NetJobPtr indexJob;
 	NetJobPtr chanListJob;
 
-	QString m_repoUrl;
-
 	QString m_channelListUrl;
 
 	QList<ChannelListEntry> m_channels;
@@ -110,6 +109,11 @@ private:
 	 * if m_checkUpdateWaiting, this is the last used update channel
 	 */
 	QString m_deferredUpdateChannel;
+
 	int m_currentBuild = -1;
+	QString m_currentChannel;
+	QString m_currentRepoUrl;
+
+	QString m_newRepoUrl;
 };