4 files changed, 385 insertions, 184 deletions

diff --git a/logic/updater/DownloadUpdateTask.cpp b/logic/updater/DownloadUpdateTask.cpp
index d9aab826..6e0a92f0 100644
--- a/logic/updater/DownloadUpdateTask.cpp
+++ b/logic/updater/DownloadUpdateTask.cpp
@@ -26,9 +26,8 @@
 
 #include <QDomDocument>
 
-
-DownloadUpdateTask::DownloadUpdateTask(QString repoUrl, int versionId, QObject* parent) :
-	Task(parent)
+DownloadUpdateTask::DownloadUpdateTask(QString repoUrl, int versionId, QObject *parent)
+	: Task(parent)
 {
 	m_cVersionId = MMC->version().build;
 
@@ -45,68 +44,69 @@ void DownloadUpdateTask::executeTask()
 	findCurrentVersionInfo();
 }
 
-void DownloadUpdateTask::findCurrentVersionInfo()
+void DownloadUpdateTask::processChannels()
 {
-	setStatus(tr("Finding information about the current version."));
-
 	auto checker = MMC->updateChecker();
 
-	// 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.
-	auto processFunc = [this, &checker] () -> void
+	// Now, check the channel list again.
+	if (!checker->hasChannels())
 	{
-		// Now, check the channel list again.
-		if (checker->hasChannels())
-		{ 
-			// We still couldn't load the channel list. Give up. Call loadVersionInfo and return.
-			QLOG_INFO() << "Reloading the channel list didn't work. Giving up.";
-			loadVersionInfo();
-			return;
-		}
+		// We still couldn't load the channel list. Give up. Call loadVersionInfo and return.
+		QLOG_INFO() << "Reloading the channel list didn't work. Giving up.";
+		loadVersionInfo();
+		return;
+	}
 
-		QList<UpdateChecker::ChannelListEntry> channels = checker->getChannelList();
-		QString channelId = MMC->version().channel;
+	QList<UpdateChecker::ChannelListEntry> channels = checker->getChannelList();
+	QString channelId = MMC->version().channel;
 
-		// Search through the channel list for a channel with the correct ID.
-		for (auto channel : channels)
+	// Search through the channel list for a channel with the correct ID.
+	for (auto channel : channels)
+	{
+		if (channel.id == channelId)
 		{
-			if (channel.id == channelId)
-			{
-				QLOG_INFO() << "Found matching channel.";
-				m_cRepoUrl = channel.url;
-				break;
-			}
+			QLOG_INFO() << "Found matching channel.";
+			m_cRepoUrl = fixPathForTests(channel.url);
+			break;
 		}
+	}
 
-		// Now that we've done that, load version info.
-		loadVersionInfo();
-	};
+	// 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())
+	if (!checker->hasChannels())
 	{
 		// Load the channel list and wait for it to finish loading.
 		QLOG_INFO() << "No channel list entries found. Will try reloading it.";
 
-		QObject::connect(checker.get(), &UpdateChecker::channelListLoaded, processFunc);
+		QObject::connect(checker.get(), &UpdateChecker::channelListLoaded, this,
+						 &DownloadUpdateTask::processChannels);
 		checker->updateChanList();
 	}
 	else
 	{
-		processFunc();
+		processChannels();
 	}
 }
 
 void DownloadUpdateTask::loadVersionInfo()
 {
-	setStatus(tr("Loading version information."));
+	setStatus(tr("Loading version information..."));
 
 	// Create the net job for loading version info.
-	NetJob* netJob = new NetJob("Version Info");
-	
+	NetJob *netJob = new NetJob("Version Info");
+
 	// Find the index URL.
 	QUrl newIndexUrl = QUrl(m_nRepoUrl).resolved(QString::number(m_nVersionId) + ".json");
-	
+	QLOG_DEBUG() << 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));
 
@@ -115,10 +115,12 @@ void DownloadUpdateTask::loadVersionInfo()
 	{
 		QUrl cIndexUrl = QUrl(m_cRepoUrl).resolved(QString::number(m_cVersionId) + ".json");
 		netJob->addNetAction(ByteArrayDownload::make(cIndexUrl));
+		QLOG_DEBUG() << 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::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!
@@ -136,7 +138,8 @@ void DownloadUpdateTask::vinfoDownloadFinished()
 
 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.
+	// 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();
@@ -150,61 +153,73 @@ void DownloadUpdateTask::vinfoDownloadFailed()
 
 void DownloadUpdateTask::parseDownloadedVersionInfo()
 {
-	setStatus(tr("Reading file lists."));
-
-	parseVersionInfo(NEW_VERSION, &m_nVersionFileList);
+	setStatus(tr("Reading file list for new version..."));
+	QLOG_DEBUG() << "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 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)
 	{
-		parseVersionInfo(CURRENT_VERSION, &m_cVersionFileList);
+		setStatus(tr("Reading file list for current version..."));
+		QLOG_DEBUG() << "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.
+	// Now that we're done loading version info, we can move on to the next step. Process file
+	// lists and download files.
 	processFileLists();
 }
 
-void DownloadUpdateTask::parseVersionInfo(VersionInfoFileEnum vfile, VersionFileList* list)
+bool DownloadUpdateTask::parseVersionInfo(const QByteArray &data, VersionFileList *list,
+										  QString *error)
 {
-	if (vfile == CURRENT_VERSION)  setStatus(tr("Reading file list for current version."));
-	else if (vfile == NEW_VERSION) setStatus(tr("Reading file list for new version."));
-
-	QLOG_DEBUG() << "Reading file list for" << (vfile == NEW_VERSION ? "new" : "current") << "version.";
-	
-	QByteArray data;
-	{
-		ByteArrayDownloadPtr dl = std::dynamic_pointer_cast<ByteArrayDownload>(
-				vfile == NEW_VERSION ? m_vinfoNetJob->first() : m_vinfoNetJob->operator[](1));
-		data = dl->m_data;
-	}
-
 	QJsonParseError jsonError;
 	QJsonDocument jsonDoc = QJsonDocument::fromJson(data, &jsonError);
 	if (jsonError.error != QJsonParseError::NoError)
 	{
-		QLOG_ERROR() << "Failed to parse version info JSON:" << jsonError.errorString() << "at" << jsonError.offset;
-		return;
+		*error = QString("Failed to parse version info JSON: %1 at %2")
+					 .arg(jsonError.errorString())
+					 .arg(jsonError.offset);
+		QLOG_ERROR() << error;
+		return false;
 	}
 
 	QJsonObject json = jsonDoc.object();
 
+	QLOG_DEBUG() << data;
 	QLOG_DEBUG() << "Loading version info from JSON.";
 	QJsonArray filesArray = json.value("Files").toArray();
 	for (QJsonValue fileValue : filesArray)
 	{
 		QJsonObject fileObj = fileValue.toObject();
 
-		VersionFileEntry file{
-			fileObj.value("Path").toString(),
-			fileObj.value("Perms").toVariant().toInt(),
-			FileSourceList(),
-			fileObj.value("MD5").toString(),
-		};
+		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(), };
 		QLOG_DEBUG() << "File" << file.path << "with perms" << file.mode;
-		
+
 		QJsonArray sourceArray = fileObj.value("Sources").toArray();
 		for (QJsonValue val : sourceArray)
 		{
@@ -213,11 +228,14 @@ void DownloadUpdateTask::parseVersionInfo(VersionInfoFileEnum vfile, VersionFile
 			QString type = sourceObj.value("SourceType").toString();
 			if (type == "http")
 			{
-				file.sources.append(FileSource("http", sourceObj.value("Url").toString()));
+				file.sources.append(
+					FileSource("http", fixPathForTests(sourceObj.value("Url").toString())));
 			}
 			else if (type == "httpc")
 			{
-				file.sources.append(FileSource("httpc", sourceObj.value("Url").toString(), sourceObj.value("CompressionType").toString()));
+				file.sources.append(
+					FileSource("httpc", fixPathForTests(sourceObj.value("Url").toString()),
+							   sourceObj.value("CompressionType").toString()));
 			}
 			else
 			{
@@ -229,90 +247,185 @@ void DownloadUpdateTask::parseVersionInfo(VersionInfoFileEnum vfile, VersionFile
 
 		list->append(file);
 	}
+
+	return true;
 }
 
 void DownloadUpdateTask::processFileLists()
 {
-	setStatus(tr("Processing file lists. Figuring out how to install the update."));
+	// 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())));
+	QLOG_DEBUG() << "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 
+	// 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 : m_cVersionFileList)
+	for (VersionFileEntry entry : currentVersion)
 	{
+		QFileInfo toDelete(entry.path);
+		if (!toDelete.exists())
+		{
+			QLOG_ERROR() << "Expected file " << toDelete.absoluteFilePath()
+						 << " doesn't exist!";
+			QLOG_ERROR() << "CWD: " << QDir::currentPath();
+		}
 		bool keep = false;
-		for (VersionFileEntry newEntry : m_nVersionFileList)
+
+		//
+		for (VersionFileEntry newEntry : newVersion)
 		{
 			if (newEntry.path == entry.path)
 			{
-				QLOG_DEBUG() << "Not deleting" << entry.path << "because it is still present in the new version.";
+				QLOG_DEBUG() << "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)
-			m_operationList.append(UpdateOperation::DeleteOp(entry.path));
+		if (!keep)
+		{
+			QFileInfo toDelete(entry.path);
+			if (toDelete.exists())
+				ops.append(UpdateOperation::DeleteOp(entry.path));
+		}
 	}
 
-	// Create a network job for downloading files.
-	NetJob* netJob = new NetJob("Update Files");
-
 	// Next, check each file in MultiMC's folder and see if we need to update them.
-	for (VersionFileEntry entry : m_nVersionFileList)
+	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.
+		// 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;
 		QFile entryFile(entry.path);
-		if (entryFile.open(QFile::ReadOnly))
+		QFileInfo entryInfo(entry.path);
+
+		bool needs_upgrade = false;
+		if (!entryFile.exists())
 		{
-			QCryptographicHash hash(QCryptographicHash::Md5);
-			hash.addData(entryFile.readAll());
-			fileMD5 = hash.result().toHex();
+			needs_upgrade = true;
+		}
+		else
+		{
+			bool pass = true;
+			if (!entryInfo.isReadable())
+			{
+				QLOG_ERROR() << "File " << entry.path << " is not readable.";
+				pass = false;
+			}
+			if (!entryInfo.isWritable())
+			{
+				QLOG_ERROR() << "File " << entry.path << " is not writable.";
+				pass = false;
+			}
+			if (!entryFile.open(QFile::ReadOnly))
+			{
+				QLOG_ERROR() << "File " << entry.path << " cannot be opened for reading.";
+				pass = false;
+			}
+			if (!pass)
+			{
+				QLOG_ERROR() << "CWD: " << QDir::currentPath();
+				ops.clear();
+				return false;
+			}
 		}
 
-		if (!entryFile.exists() || fileMD5.isEmpty() || fileMD5 != entry.md5)
+		QCryptographicHash hash(QCryptographicHash::Md5);
+		auto foo = entryFile.readAll();
+
+		hash.addData(foo);
+		fileMD5 = hash.result().toHex();
+		if ((fileMD5 != entry.md5))
 		{
-			QLOG_DEBUG() << "Found file" << entry.path << "that needs updating.";
+			QLOG_DEBUG() << "MD5Sum does not match!";
+			QLOG_DEBUG() << "Expected:'" << entry.md5 << "'";
+			QLOG_DEBUG() << "Got:     '" << fileMD5 << "'";
+			needs_upgrade = true;
+		}
+
+		// skip file. it doesn't need an upgrade.
+		if (!needs_upgrade)
+		{
+			QLOG_DEBUG() << "File" << entry.path << " does not need updating.";
+			continue;
+		}
 
-			// 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)
+		// yep. this file actually needs an upgrade. PROCEED.
+		QLOG_DEBUG() << "Found file" << entry.path << " 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")
 			{
-				if (source.type == "http")
-				{
-					QLOG_DEBUG() << "Will download" << entry.path << "from" << source.url;
+				QLOG_DEBUG() << "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("/", "_"));
+				// 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("/", "_"));
 
-					// We need to download the file to the updatefiles folder and add a task to copy it to its install path.
+				if (isUpdater)
+				{
+					auto cache_entry = MMC->metacache()->resolveEntry("root", entry.path);
+					QLOG_DEBUG() << "Updater will be in " << cache_entry->getFullPath();
+					if(cache_entry->stale)
+					{
+						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_check_md5 = true;
 					download->m_expected_md5 = entry.md5;
-					netJob->addNetAction(download);
-
-					// Now add a copy operation to our operations list to install the file.
-					m_operationList.append(UpdateOperation::CopyOp(dlPath, entry.path, entry.mode));
+					job->addNetAction(download);
+					ops.append(UpdateOperation::CopyOp(dlPath, entry.path, entry.mode));
 				}
 			}
 		}
 	}
-
-	// 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())));
-	QLOG_DEBUG() << "Begin downloading update files to" << m_updateFilesDir.path();
-	m_filesNetJob.reset(netJob);
-	netJob->start();
-
-	writeInstallScript(m_operationList, PathCombine(m_updateFilesDir.path(), "file_list.xml"));
+	return true;
 }
 
-void DownloadUpdateTask::writeInstallScript(UpdateOperationList& opsList, QString scriptFile)
+bool DownloadUpdateTask::writeInstallScript(UpdateOperationList &opsList, QString scriptFile)
 {
 	// Build the base structure of the XML document.
 	QDomDocument doc;
@@ -334,36 +447,38 @@ void DownloadUpdateTask::writeInstallScript(UpdateOperationList& opsList, QStrin
 
 		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);
-				QLOG_DEBUG() << "Will install file" << op.file;
-				}
-				break;
+		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);
+			QLOG_DEBUG() << "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);
-				QLOG_DEBUG() << "Will remove file" << op.file;
-				}
-				break;
+		case UpdateOperation::OP_DELETE:
+		{
+			// Delete the file.
+			file.appendChild(doc.createTextNode(op.file));
+			removeFiles.appendChild(file);
+			QLOG_DEBUG() << "Will remove file" << op.file;
+		}
+		break;
 
-			default:
-				QLOG_WARN() << "Can't write update operation of type" << op.type << "to file. Not implemented.";
-				continue;
+		default:
+			QLOG_WARN() << "Can't write update operation of type" << op.type
+						<< "to file. Not implemented.";
+			continue;
 		}
 	}
 
@@ -377,6 +492,36 @@ void DownloadUpdateTask::writeInstallScript(UpdateOperationList& opsList, QStrin
 	else
 	{
 		emitFailed(tr("Failed to write update script file."));
+		return false;
+	}
+
+	return true;
+}
+
+QString DownloadUpdateTask::fixPathForTests(const QString &path)
+{
+	if (path.startsWith("$PWD"))
+	{
+		QString foo = path;
+		foo.replace("$PWD", qApp->applicationDirPath());
+		return QUrl::fromLocalFile(foo).toString(QUrl::FullyEncoded);
+	}
+	return path;
+}
+
+bool DownloadUpdateTask::fixPathForOSX(QString &path)
+{
+	if (path.startsWith("MultiMC.app/"))
+	{
+		// remove the prefix and add a new, more appropriate one.
+		path.remove(0, 12);
+		path = QString("../../") + path;
+		return true;
+	}
+	else
+	{
+		QLOG_ERROR() << "Update path not within .app: " << path;
+		return false;
 	}
 }
 
@@ -394,11 +539,10 @@ void DownloadUpdateTask::fileDownloadFailed()
 
 void DownloadUpdateTask::fileDownloadProgressChanged(qint64 current, qint64 total)
 {
-	setProgress((int)(((float)current / (float)total)*100));
+	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
index f5b23d12..b1d14846 100644
--- a/logic/updater/DownloadUpdateTask.h
+++ b/logic/updater/DownloadUpdateTask.h
@@ -34,7 +34,8 @@ public:
 	 */
 	QString updateFilesDir();
 	
-protected:
+public:
+
 	// TODO: We should probably put these data structures into a separate header...
 
 	/*!
@@ -53,7 +54,6 @@ protected:
 		QString url;
 		QString compressionType;
 	};
-
 	typedef QList<FileSource> FileSourceList;
 
 	/*!
@@ -66,10 +66,8 @@ protected:
 		FileSourceList sources;
 		QString md5;
 	};
-
 	typedef QList<VersionFileEntry> VersionFileList;
 
-
 	/*!
 	 * Structure that describes an operation to perform when installing updates.
 	 */
@@ -100,9 +98,12 @@ protected:
 
 		// 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.
 	 */
@@ -120,6 +121,13 @@ protected:
 	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 
@@ -142,20 +150,25 @@ protected:
 	/*!
 	 * Loads the file list from the given version info JSON object into the given list.
 	 */
-	virtual void parseVersionInfo(VersionInfoFileEnum vfile, VersionFileList* 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 void writeInstallScript(UpdateOperationList& opsList, QString scriptFile);
+	virtual bool writeInstallScript(UpdateOperationList& opsList, QString scriptFile);
 
-	VersionFileList m_downloadList;
 	UpdateOperationList m_operationList;
 
 	VersionFileList m_nVersionFileList;
@@ -181,6 +194,26 @@ protected:
 	 */
 	QTemporaryDir m_updateFilesDir;
 
+	/*!
+	 * Filters paths
+	 * Path of the format $PWD/path, it is converted to a file:///$PWD/ URL
+	 */
+	static QString fixPathForTests(const QString &path);
+
+	/*!
+	 * 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 and prepend ../..
+	 * 
+	 * Returns false if the path couldn't be fixed (is invalid)
+	 * 
+	 * Has no effect on systems that aren't OSX
+	 */
+	static bool fixPathForOSX(QString &path);
+
 protected slots:
 	void vinfoDownloadFinished();
 	void vinfoDownloadFailed();
diff --git a/logic/updater/UpdateChecker.cpp b/logic/updater/UpdateChecker.cpp
index 5ff1898e..d0795c0d 100644
--- a/logic/updater/UpdateChecker.cpp
+++ b/logic/updater/UpdateChecker.cpp
@@ -44,17 +44,19 @@ QList<UpdateChecker::ChannelListEntry> UpdateChecker::getChannelList() const
 
 bool UpdateChecker::hasChannels() const
 {
-	return m_channels.isEmpty();
+	return !m_channels.isEmpty();
 }
 
-void UpdateChecker::checkForUpdate()
+void UpdateChecker::checkForUpdate(bool notifyNoUpdate)
 {
 	QLOG_DEBUG() << "Checking for updates.";
 
-	// If the channel list hasn't loaded yet, load it and defer checking for updates until later.
+	// If the channel list hasn't loaded yet, load it and defer checking for updates until
+	// later.
 	if (!m_chanListLoaded)
 	{
-		QLOG_DEBUG() << "Channel list isn't loaded yet. Loading channel list and deferring update check.";
+		QLOG_DEBUG() << "Channel list isn't loaded yet. Loading channel list and deferring "
+						"update check.";
 		m_checkUpdateWaiting = true;
 		updateChanList();
 		return;
@@ -72,7 +74,8 @@ void UpdateChecker::checkForUpdate()
 	// TODO: Allow user to select channels. For now, we'll just use the current channel.
 	QString updateChannel = m_currentChannel;
 
-	// Find the desired channel within the channel list and get its repo URL. If if cannot be found, error.
+	// Find the desired channel within the channel list and get its repo URL. If if cannot be
+	// found, error.
 	m_repoUrl = "";
 	for (ChannelListEntry entry : m_channels)
 	{
@@ -91,20 +94,22 @@ void UpdateChecker::checkForUpdate()
 
 	auto job = new NetJob("GoUpdate Repository Index");
 	job->addNetAction(ByteArrayDownload::make(indexUrl));
-	connect(job, SIGNAL(succeeded()), SLOT(updateCheckFinished()));
+	connect(job, &NetJob::succeeded, [this, notifyNoUpdate]()
+	{ updateCheckFinished(notifyNoUpdate); });
 	connect(job, SIGNAL(failed()), SLOT(updateCheckFailed()));
 	indexJob.reset(job);
 	job->start();
 }
 
-void UpdateChecker::updateCheckFinished()
+void UpdateChecker::updateCheckFinished(bool notifyNoUpdate)
 {
 	QLOG_DEBUG() << "Finished downloading repo index. Checking for new versions.";
 
 	QJsonParseError jsonError;
 	QByteArray data;
 	{
-		ByteArrayDownloadPtr dl = std::dynamic_pointer_cast<ByteArrayDownload>(indexJob->first());
+		ByteArrayDownloadPtr dl =
+			std::dynamic_pointer_cast<ByteArrayDownload>(indexJob->first());
 		data = dl->m_data;
 		indexJob.reset();
 	}
@@ -112,7 +117,8 @@ void UpdateChecker::updateCheckFinished()
 	QJsonDocument jsonDoc = QJsonDocument::fromJson(data, &jsonError);
 	if (jsonError.error != QJsonParseError::NoError || !jsonDoc.isObject())
 	{
-		QLOG_ERROR() << "Failed to parse GoUpdate repository index. JSON error" << jsonError.errorString() << "at offset" << jsonError.offset;
+		QLOG_ERROR() << "Failed to parse GoUpdate repository index. JSON error"
+					 << jsonError.errorString() << "at offset" << jsonError.offset;
 		return;
 	}
 
@@ -122,7 +128,8 @@ void UpdateChecker::updateCheckFinished()
 	int apiVersion = object.value("ApiVersion").toVariant().toInt(&success);
 	if (apiVersion != API_VERSION || !success)
 	{
-		QLOG_ERROR() << "Failed to check for updates. API version mismatch. We're using" << API_VERSION << "server has" << apiVersion;
+		QLOG_ERROR() << "Failed to check for updates. API version mismatch. We're using"
+					 << API_VERSION << "server has" << apiVersion;
 		return;
 	}
 
@@ -132,19 +139,27 @@ void UpdateChecker::updateCheckFinished()
 	for (QJsonValue versionVal : versions)
 	{
 		QJsonObject version = versionVal.toObject();
-		if (newestVersion.value("Id").toVariant().toInt() < version.value("Id").toVariant().toInt())
+		if (newestVersion.value("Id").toVariant().toInt() <
+			version.value("Id").toVariant().toInt())
 		{
-			QLOG_DEBUG() << "Found newer version with ID" << version.value("Id").toVariant().toInt();
+			QLOG_DEBUG() << "Found newer version with ID"
+						 << version.value("Id").toVariant().toInt();
 			newestVersion = version;
 		}
 	}
 
-	// We've got the version with the greatest ID number. Now compare it to our current build number and update if they're different.
+	// We've got the version with the greatest ID number. Now compare it to our current build
+	// number and update if they're different.
 	int newBuildNumber = newestVersion.value("Id").toVariant().toInt();
 	if (newBuildNumber != MMC->version().build)
 	{
 		// Update!
-		emit updateAvailable(m_repoUrl, newestVersion.value("Name").toVariant().toString(), newBuildNumber);
+		emit updateAvailable(m_repoUrl, newestVersion.value("Name").toVariant().toString(),
+							 newBuildNumber);
+	}
+	else if (notifyNoUpdate)
+	{
+		emit noUpdateFound();
 	}
 
 	m_updateChecking = false;
@@ -163,12 +178,13 @@ void UpdateChecker::updateChanList()
 	if (m_channelListUrl.isEmpty())
 	{
 		QLOG_ERROR() << "Failed to update channel list. No channel list URL set."
-					 << "If you'd like to use MultiMC's update system, please pass the channel list URL to CMake at compile time.";
+					 << "If you'd like to use MultiMC's update system, please pass the channel "
+						"list URL to CMake at compile time.";
 		return;
 	}
 
 	m_chanListLoading = true;
-	NetJob* job = new NetJob("Update System Channel List");
+	NetJob *job = new NetJob("Update System Channel List");
 	job->addNetAction(ByteArrayDownload::make(QUrl(m_channelListUrl)));
 	QObject::connect(job, &NetJob::succeeded, this, &UpdateChecker::chanListDownloadFinished);
 	QObject::connect(job, &NetJob::failed, this, &UpdateChecker::chanListDownloadFailed);
@@ -180,7 +196,8 @@ void UpdateChecker::chanListDownloadFinished()
 {
 	QByteArray data;
 	{
-		ByteArrayDownloadPtr dl = std::dynamic_pointer_cast<ByteArrayDownload>(chanListJob->first());
+		ByteArrayDownloadPtr dl =
+			std::dynamic_pointer_cast<ByteArrayDownload>(chanListJob->first());
 		data = dl->m_data;
 		chanListJob.reset();
 	}
@@ -190,17 +207,20 @@ void UpdateChecker::chanListDownloadFinished()
 	if (jsonError.error != QJsonParseError::NoError)
 	{
 		// TODO: Report errors to the user.
-		QLOG_ERROR() << "Failed to parse channel list JSON:" << jsonError.errorString() << "at" << jsonError.offset;
+		QLOG_ERROR() << "Failed to parse channel list JSON:" << jsonError.errorString() << "at"
+					 << jsonError.offset;
 		return;
 	}
-	
+
 	QJsonObject object = jsonDoc.object();
 
 	bool success = false;
 	int formatVersion = object.value("format_version").toVariant().toInt(&success);
 	if (formatVersion != CHANLIST_FORMAT || !success)
 	{
-		QLOG_ERROR() << "Failed to check for updates. Channel list format version mismatch. We're using" << CHANLIST_FORMAT << "server has" << formatVersion;
+		QLOG_ERROR()
+			<< "Failed to check for updates. Channel list format version mismatch. We're using"
+			<< CHANLIST_FORMAT << "server has" << formatVersion;
 		return;
 	}
 
@@ -210,12 +230,10 @@ void UpdateChecker::chanListDownloadFinished()
 	for (QJsonValue chanVal : channelArray)
 	{
 		QJsonObject channelObj = chanVal.toObject();
-		ChannelListEntry entry{
-				channelObj.value("id").toVariant().toString(),
-				channelObj.value("name").toVariant().toString(),
-				channelObj.value("description").toVariant().toString(),
-				channelObj.value("url").toVariant().toString()
-			};
+		ChannelListEntry entry{channelObj.value("id").toVariant().toString(),
+							   channelObj.value("name").toVariant().toString(),
+							   channelObj.value("description").toVariant().toString(),
+							   channelObj.value("url").toVariant().toString()};
 		if (entry.id.isEmpty() || entry.name.isEmpty() || entry.url.isEmpty())
 		{
 			QLOG_ERROR() << "Channel list entry with empty ID, name, or URL. Skipping.";
@@ -233,7 +251,7 @@ void UpdateChecker::chanListDownloadFinished()
 
 	// If we're waiting to check for updates, do that now.
 	if (m_checkUpdateWaiting)
-		checkForUpdate();
+		checkForUpdate(false);
 
 	emit channelListLoaded();
 }
@@ -244,4 +262,3 @@ void UpdateChecker::chanListDownloadFailed()
 	QLOG_ERROR() << "Failed to download channel list.";
 	emit channelListLoaded();
 }
-
diff --git a/logic/updater/UpdateChecker.h b/logic/updater/UpdateChecker.h
index 59fb8e47..a47e8903 100644
--- a/logic/updater/UpdateChecker.h
+++ b/logic/updater/UpdateChecker.h
@@ -25,7 +25,10 @@ class UpdateChecker : public QObject
 
 public:
 	UpdateChecker();
-	void checkForUpdate();
+	void checkForUpdate(bool notifyNoUpdate);
+
+	void setCurrentChannel(const QString &channel) { m_currentChannel = channel; }
+	void setChannelListUrl(const QString &url) { m_channelListUrl = url; }
 
 	/*!
 	 * Causes the update checker to download the channel list from the URL specified in config.h (generated by CMake).
@@ -62,14 +65,18 @@ signals:
 	//! Signal emitted when the channel list finishes loading or fails to load.
 	void channelListLoaded();
 
+	void noUpdateFound();
+
 private slots:
-	void updateCheckFinished();
+	void updateCheckFinished(bool notifyNoUpdate);
 	void updateCheckFailed();
 
 	void chanListDownloadFinished();
 	void chanListDownloadFailed();
 
 private:
+	friend class UpdateCheckerTest;
+
 	NetJobPtr indexJob;
 	NetJobPtr chanListJob;