NOISSUE refactor *Download into more, smaller pieces

* Download is now Download.
* Download uses Sink subclasses to process various events.
* Validators can be used to further customize the Sink behaviour.

51 files changed, 823 insertions, 764 deletions

diff --git a/api/dead/src/handlers/WebResourceHandler.cpp b/api/dead/src/handlers/WebResourceHandler.cpp
index 757b870a..e4fd74fa 100644
--- a/api/dead/src/handlers/WebResourceHandler.cpp
+++ b/api/dead/src/handlers/WebResourceHandler.cpp
@@ -1,6 +1,6 @@
 #include "WebResourceHandler.h"
 
-#include "net/CacheDownload.h"
+#include "net/Download.h"
 #include "net/HttpMetaCache.h"
 #include "net/NetJob.h"
 #include "FileSystem.h"
@@ -27,7 +27,7 @@ WebResourceHandler::WebResourceHandler(const QString &url)
 	else
 	{
 		NetJob *job = new NetJob("Icon download");
-		job->addNetAction(CacheDownload::make(QUrl(url), entry));
+		job->addNetAction(Download::make(QUrl(url), entry));
 		connect(job, &NetJob::succeeded, this, &WebResourceHandler::succeeded);
 		connect(job, &NetJob::failed, this, [job, this]() {setFailure(job->failReason());});
 		connect(job, &NetJob::progress, this, &WebResourceHandler::progress);
diff --git a/api/logic/CMakeLists.txt b/api/logic/CMakeLists.txt
index 2a73566d..1048e091 100644
--- a/api/logic/CMakeLists.txt
+++ b/api/logic/CMakeLists.txt
@@ -82,21 +82,25 @@ set(PATHMATCHER_SOURCES
 
 set(NET_SOURCES
 	# network stuffs
+	net/ByteArraySink.h
+	net/ChecksumValidator.h
+	net/Download.cpp
+	net/Download.h
+	net/FileSink.cpp
+	net/FileSink.h
+	net/HttpMetaCache.cpp
+	net/HttpMetaCache.h
+	net/MetaCacheSink.cpp
+	net/MetaCacheSink.h
 	net/NetAction.h
-	net/MD5EtagDownload.h
-	net/MD5EtagDownload.cpp
-	net/ByteArrayDownload.h
-	net/ByteArrayDownload.cpp
-	net/CacheDownload.h
-	net/CacheDownload.cpp
-	net/NetJob.h
 	net/NetJob.cpp
-	net/HttpMetaCache.h
-	net/HttpMetaCache.cpp
-	net/PasteUpload.h
+	net/NetJob.h
 	net/PasteUpload.cpp
-	net/URLConstants.h
+	net/PasteUpload.h
+	net/Sink.h
 	net/URLConstants.cpp
+	net/URLConstants.h
+	net/Validator.h
 )
 
 # Game launch logic
diff --git a/api/logic/minecraft/AssetsUtils.cpp b/api/logic/minecraft/AssetsUtils.cpp
index 7a525abe..bb630528 100644
--- a/api/logic/minecraft/AssetsUtils.cpp
+++ b/api/logic/minecraft/AssetsUtils.cpp
@@ -25,7 +25,9 @@
 
 #include "AssetsUtils.h"
 #include "FileSystem.h"
-#include "net/MD5EtagDownload.h"
+#include "net/Download.h"
+#include "net/ChecksumValidator.h"
+
 
 namespace AssetsUtils
 {
@@ -191,7 +193,12 @@ NetActionPtr AssetObject::getDownloadAction()
 	QFileInfo objectFile(getLocalPath());
 	if ((!objectFile.isFile()) || (objectFile.size() != size))
 	{
-		auto objectDL = MD5EtagDownload::make(getUrl(), objectFile.filePath());
+		auto objectDL = Net::Download::makeFile(getUrl(), objectFile.filePath());
+		if(hash.size())
+		{
+			auto rawHash = QByteArray::fromHex(hash.toLatin1());
+			objectDL->addValidator(new Net::ChecksumValidator(QCryptographicHash::Sha1, rawHash));
+		}
 		objectDL->m_total_progress = size;
 		return objectDL;
 	}
diff --git a/api/logic/minecraft/Library.cpp b/api/logic/minecraft/Library.cpp
index 922db84e..584c7ac5 100644
--- a/api/logic/minecraft/Library.cpp
+++ b/api/logic/minecraft/Library.cpp
@@ -1,5 +1,6 @@
 #include "Library.h"
-#include <net/CacheDownload.h>
+#include <net/Download.h>
+#include <net/ChecksumValidator.h>
 #include <minecraft/forge/ForgeXzDownload.h>
 #include <Env.h>
 #include <FileSystem.h>
@@ -74,7 +75,7 @@ QList<NetActionPtr> Library::getDownloads(OpSys system, HttpMetaCache * cache, Q
 	bool isLocal = (hint() == "local");
 	bool isForge = (hint() == "forge-pack-xz");
 
-	auto add_download = [&](QString storage, QString dl)
+	auto add_download = [&](QString storage, QString url, QString sha1 = QString())
 	{
 		auto entry = cache->resolveEntry("libraries", storage);
 		if (!entry->isStale())
@@ -95,7 +96,16 @@ QList<NetActionPtr> Library::getDownloads(OpSys system, HttpMetaCache * cache, Q
 		}
 		else
 		{
-			out.append(CacheDownload::make(dl, entry));
+			if(sha1.size())
+			{
+				auto rawSha1 = QByteArray::fromHex(sha1.toLatin1());
+				auto dl = Net::Download::makeCached(url, entry);
+				dl->addValidator(new Net::ChecksumValidator(QCryptographicHash::Sha1, rawSha1));
+				out.append(dl);
+			}
+
+			else
+				out.append(Net::Download::makeCached(url, entry));
 		}
 		return true;
 	};
@@ -105,7 +115,7 @@ QList<NetActionPtr> Library::getDownloads(OpSys system, HttpMetaCache * cache, Q
 		if(m_mojangDownloads->artifact)
 		{
 			auto artifact = m_mojangDownloads->artifact;
-			add_download(artifact->path, artifact->url);
+			add_download(artifact->path, artifact->url, artifact->sha1);
 		}
 		if(m_nativeClassifiers.contains(system))
 		{
@@ -118,17 +128,17 @@ QList<NetActionPtr> Library::getDownloads(OpSys system, HttpMetaCache * cache, Q
 				nat64Classifier.replace("${arch}", "64");
 				auto nat32info = m_mojangDownloads->getDownloadInfo(nat32Classifier);
 				if(nat32info)
-					add_download(nat32info->path, nat32info->url);
+					add_download(nat32info->path, nat32info->url, nat32info->sha1);
 				auto nat64info = m_mojangDownloads->getDownloadInfo(nat64Classifier);
 				if(nat64info)
-					add_download(nat64info->path, nat64info->url);
+					add_download(nat64info->path, nat64info->url, nat64info->sha1);
 			}
 			else
 			{
 				auto info = m_mojangDownloads->getDownloadInfo(nativeClassifier);
 				if(info)
 				{
-					add_download(info->path, info->url);
+					add_download(info->path, info->url, info->sha1);
 				}
 			}
 		}
diff --git a/api/logic/minecraft/MinecraftVersionList.cpp b/api/logic/minecraft/MinecraftVersionList.cpp
index a5cc3a39..4e4eafbc 100644
--- a/api/logic/minecraft/MinecraftVersionList.cpp
+++ b/api/logic/minecraft/MinecraftVersionList.cpp
@@ -68,6 +68,7 @@ slots:
 
 protected:
 	NetJobPtr specificVersionDownloadJob;
+	QByteArray versionIndexData;
 	std::shared_ptr<MinecraftVersion> updatedVersion;
 	MinecraftVersionList *m_list;
 };
@@ -410,7 +411,7 @@ MCVListVersionUpdateTask::MCVListVersionUpdateTask(MinecraftVersionList *vlist,
 void MCVListVersionUpdateTask::executeTask()
 {
 	auto job = new NetJob("Version index");
-	job->addNetAction(ByteArrayDownload::make(QUrl(updatedVersion->getUrl())));
+	job->addNetAction(Net::Download::makeByteArray(QUrl(updatedVersion->getUrl()), &versionIndexData));
 	specificVersionDownloadJob.reset(job);
 	connect(specificVersionDownloadJob.get(), SIGNAL(succeeded()), SLOT(json_downloaded()));
 	connect(specificVersionDownloadJob.get(), SIGNAL(failed(QString)), SIGNAL(failed(QString)));
@@ -420,12 +421,11 @@ void MCVListVersionUpdateTask::executeTask()
 
 void MCVListVersionUpdateTask::json_downloaded()
 {
-	NetActionPtr DlJob = specificVersionDownloadJob->first();
-	auto data = std::dynamic_pointer_cast<ByteArrayDownload>(DlJob)->m_data;
 	specificVersionDownloadJob.reset();
 
 	QJsonParseError jsonError;
-	QJsonDocument jsonDoc = QJsonDocument::fromJson(data, &jsonError);
+	QJsonDocument jsonDoc = QJsonDocument::fromJson(versionIndexData, &jsonError);
+	versionIndexData.clear();
 
 	if (jsonError.error != QJsonParseError::NoError)
 	{
diff --git a/api/logic/minecraft/forge/ForgeInstaller.cpp b/api/logic/minecraft/forge/ForgeInstaller.cpp
index 353328ab..4d004bf5 100644
--- a/api/logic/minecraft/forge/ForgeInstaller.cpp
+++ b/api/logic/minecraft/forge/ForgeInstaller.cpp
@@ -397,7 +397,7 @@ protected:
 		if (entry->isStale())
 		{
 			NetJob *fjob = new NetJob("Forge download");
-			fjob->addNetAction(CacheDownload::make(forgeVersion->url(), entry));
+			fjob->addNetAction(Net::Download::makeCached(forgeVersion->url(), entry));
 			connect(fjob, &NetJob::progress, this, &Task::setProgress);
 			connect(fjob, &NetJob::status, this, &Task::setStatus);
 			connect(fjob, &NetJob::failed, [this](QString reason)
diff --git a/api/logic/minecraft/forge/ForgeVersionList.cpp b/api/logic/minecraft/forge/ForgeVersionList.cpp
index de185e5f..fe024780 100644
--- a/api/logic/minecraft/forge/ForgeVersionList.cpp
+++ b/api/logic/minecraft/forge/ForgeVersionList.cpp
@@ -131,10 +131,8 @@ void ForgeListLoadTask::executeTask()
 	forgeListEntry->setStale(true);
 	gradleForgeListEntry->setStale(true);
 
-	job->addNetAction(listDownload = CacheDownload::make(QUrl(URLConstants::FORGE_LEGACY_URL),
-														 forgeListEntry));
-	job->addNetAction(gradleListDownload = CacheDownload::make(
-						  QUrl(URLConstants::FORGE_GRADLE_URL), gradleForgeListEntry));
+	job->addNetAction(listDownload = Net::Download::makeCached(QUrl(URLConstants::FORGE_LEGACY_URL),forgeListEntry));
+	job->addNetAction(gradleListDownload = Net::Download::makeCached(QUrl(URLConstants::FORGE_GRADLE_URL), gradleForgeListEntry));
 
 	connect(listDownload.get(), SIGNAL(failed(int)), SLOT(listFailed()));
 	connect(gradleListDownload.get(), SIGNAL(failed(int)), SLOT(gradleListFailed()));
@@ -154,15 +152,14 @@ bool ForgeListLoadTask::parseForgeList(QList<BaseVersionPtr> &out)
 {
 	QByteArray data;
 	{
-		auto dlJob = listDownload;
-		auto filename = std::dynamic_pointer_cast<CacheDownload>(dlJob)->getTargetFilepath();
+		auto filename = listDownload->getTargetFilepath();
 		QFile listFile(filename);
 		if (!listFile.open(QIODevice::ReadOnly))
 		{
 			return false;
 		}
 		data = listFile.readAll();
-		dlJob.reset();
+		listDownload.reset();
 	}
 
 	QJsonParseError jsonError;
@@ -266,15 +263,14 @@ bool ForgeListLoadTask::parseForgeGradleList(QList<BaseVersionPtr> &out)
 	QMap<int, std::shared_ptr<ForgeVersion>> lookup;
 	QByteArray data;
 	{
-		auto dlJob = gradleListDownload;
-		auto filename = std::dynamic_pointer_cast<CacheDownload>(dlJob)->getTargetFilepath();
+		auto filename = gradleListDownload->getTargetFilepath();
 		QFile listFile(filename);
 		if (!listFile.open(QIODevice::ReadOnly))
 		{
 			return false;
 		}
 		data = listFile.readAll();
-		dlJob.reset();
+		gradleListDownload.reset();
 	}
 
 	QJsonParseError jsonError;
diff --git a/api/logic/minecraft/forge/ForgeVersionList.h b/api/logic/minecraft/forge/ForgeVersionList.h
index 62c08b2a..7b30bbb4 100644
--- a/api/logic/minecraft/forge/ForgeVersionList.h
+++ b/api/logic/minecraft/forge/ForgeVersionList.h
@@ -81,8 +81,8 @@ protected:
 	NetJobPtr listJob;
 	ForgeVersionList *m_list;
 
-	CacheDownloadPtr listDownload;
-	CacheDownloadPtr gradleListDownload;
+	Net::Download::Ptr listDownload;
+	Net::Download::Ptr gradleListDownload;
 
 private:
 	bool parseForgeList(QList<BaseVersionPtr> &out);
diff --git a/api/logic/minecraft/legacy/LegacyUpdate.cpp b/api/logic/minecraft/legacy/LegacyUpdate.cpp
index 6539b2d3..a0d1933f 100644
--- a/api/logic/minecraft/legacy/LegacyUpdate.cpp
+++ b/api/logic/minecraft/legacy/LegacyUpdate.cpp
@@ -114,7 +114,7 @@ void LegacyUpdate::fmllibsStart()
 		auto entry = metacache->resolveEntry("fmllibs", lib.filename);
 		QString urlString = lib.ours ? URLConstants::FMLLIBS_OUR_BASE_URL + lib.filename
 									 : URLConstants::FMLLIBS_FORGE_BASE_URL + lib.filename;
-		dljob->addNetAction(CacheDownload::make(QUrl(urlString), entry));
+		dljob->addNetAction(Net::Download::makeCached(QUrl(urlString), entry));
 	}
 
 	connect(dljob, &NetJob::succeeded, this, &LegacyUpdate::fmllibsFinished);
@@ -372,7 +372,7 @@ void LegacyUpdate::jarStart()
 
 	auto metacache = ENV.metacache();
 	auto entry = metacache->resolveEntry("versions", URLConstants::getJarPath(version_id));
-	dljob->addNetAction(CacheDownload::make(QUrl(URLConstants::getLegacyJarUrl(version_id)), entry));
+	dljob->addNetAction(Net::Download::makeCached(QUrl(URLConstants::getLegacyJarUrl(version_id)), entry));
 	connect(dljob, SIGNAL(succeeded()), SLOT(jarFinished()));
 	connect(dljob, SIGNAL(failed(QString)), SLOT(jarFailed(QString)));
 	connect(dljob, SIGNAL(progress(qint64, qint64)), SIGNAL(progress(qint64, qint64)));
diff --git a/api/logic/minecraft/liteloader/LiteLoaderVersionList.cpp b/api/logic/minecraft/liteloader/LiteLoaderVersionList.cpp
index b0c9736a..f8bf095f 100644
--- a/api/logic/minecraft/liteloader/LiteLoaderVersionList.cpp
+++ b/api/logic/minecraft/liteloader/LiteLoaderVersionList.cpp
@@ -146,8 +146,7 @@ void LLListLoadTask::executeTask()
 	// verify by poking the server.
 	liteloaderEntry->setStale(true);
 
-	job->addNetAction(listDownload = CacheDownload::make(QUrl(URLConstants::LITELOADER_URL),
-														 liteloaderEntry));
+	job->addNetAction(listDownload = Net::Download::makeCached(QUrl(URLConstants::LITELOADER_URL), liteloaderEntry));
 
 	connect(listDownload.get(), SIGNAL(failed(int)), SLOT(listFailed()));
 
@@ -167,8 +166,7 @@ void LLListLoadTask::listDownloaded()
 {
 	QByteArray data;
 	{
-		auto dlJob = listDownload;
-		auto filename = std::dynamic_pointer_cast<CacheDownload>(dlJob)->getTargetFilepath();
+		auto filename = listDownload->getTargetFilepath();
 		QFile listFile(filename);
 		if (!listFile.open(QIODevice::ReadOnly))
 		{
@@ -177,7 +175,7 @@ void LLListLoadTask::listDownloaded()
 		}
 		data = listFile.readAll();
 		listFile.close();
-		dlJob.reset();
+		listDownload.reset();
 	}
 
 	QJsonParseError jsonError;
diff --git a/api/logic/minecraft/liteloader/LiteLoaderVersionList.h b/api/logic/minecraft/liteloader/LiteLoaderVersionList.h
index 1dba4b6a..ae8bee92 100644
--- a/api/logic/minecraft/liteloader/LiteLoaderVersionList.h
+++ b/api/logic/minecraft/liteloader/LiteLoaderVersionList.h
@@ -112,7 +112,7 @@ slots:
 
 protected:
 	NetJobPtr listJob;
-	CacheDownloadPtr listDownload;
+	Net::Download::Ptr listDownload;
 	LiteLoaderVersionList *m_list;
 };
 
diff --git a/api/logic/minecraft/onesix/OneSixUpdate.cpp b/api/logic/minecraft/onesix/OneSixUpdate.cpp
index 1c2cd196..d3cd197d 100644
--- a/api/logic/minecraft/onesix/OneSixUpdate.cpp
+++ b/api/logic/minecraft/onesix/OneSixUpdate.cpp
@@ -31,6 +31,7 @@
 #include "minecraft/MinecraftProfile.h"
 #include "minecraft/Library.h"
 #include "net/URLConstants.h"
+#include "net/ChecksumValidator.h"
 #include "minecraft/AssetsUtils.h"
 #include "Exception.h"
 #include "MMCZip.h"
@@ -96,7 +97,13 @@ void OneSixUpdate::assetIndexStart()
 	auto metacache = ENV.metacache();
 	auto entry = metacache->resolveEntry("asset_indexes", localPath);
 	entry->setStale(true);
-	job->addNetAction(CacheDownload::make(indexUrl, entry));
+	auto hexSha1 = assets->sha1.toLatin1();
+	qDebug() << "Asset index SHA1:" << hexSha1;
+	auto dl = Net::Download::makeCached(indexUrl, entry);
+	auto rawSha1 = QByteArray::fromHex(assets->sha1.toLatin1());
+	dl->addValidator(new Net::ChecksumValidator(QCryptographicHash::Sha1, rawSha1));
+	job->addNetAction(dl);
+
 	jarlibDownloadJob.reset(job);
 
 	connect(jarlibDownloadJob.get(), SIGNAL(succeeded()), SLOT(assetIndexFinished()));
@@ -180,7 +187,7 @@ void OneSixUpdate::jarlibStart()
 
 		auto metacache = ENV.metacache();
 		auto entry = metacache->resolveEntry("versions", localPath);
-		job->addNetAction(CacheDownload::make(QUrl(urlstr), entry));
+		job->addNetAction(Net::Download::makeCached(QUrl(urlstr), entry));
 		jarlibDownloadJob.reset(job);
 	}
 
@@ -293,7 +300,7 @@ void OneSixUpdate::fmllibsStart()
 		auto entry = metacache->resolveEntry("fmllibs", lib.filename);
 		QString urlString = lib.ours ? URLConstants::FMLLIBS_OUR_BASE_URL + lib.filename
 									 : URLConstants::FMLLIBS_FORGE_BASE_URL + lib.filename;
-		dljob->addNetAction(CacheDownload::make(QUrl(urlString), entry));
+		dljob->addNetAction(Net::Download::makeCached(QUrl(urlString), entry));
 	}
 
 	connect(dljob, SIGNAL(succeeded()), SLOT(fmllibsFinished()));
diff --git a/api/logic/net/ByteArrayDownload.cpp b/api/logic/net/ByteArrayDownload.cpp
deleted file mode 100644
index 21990eeb..00000000
--- a/api/logic/net/ByteArrayDownload.cpp
+++ /dev/null
@@ -1,105 +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 "ByteArrayDownload.h"
-#include "Env.h"
-#include <QDebug>
-
-ByteArrayDownload::ByteArrayDownload(QUrl url) : NetAction()
-{
-	m_url = url;
-	m_status = Job_NotStarted;
-}
-
-void ByteArrayDownload::start()
-{
-	qDebug() << "Downloading " << m_url.toString();
-	QNetworkRequest request(m_url);
-	request.setHeader(QNetworkRequest::UserAgentHeader, "MultiMC/5.0 (Uncached)");
-	auto worker = ENV.qnam();
-	QNetworkReply *rep = worker->get(request);
-
-	m_reply.reset(rep);
-	connect(rep, SIGNAL(downloadProgress(qint64, qint64)),
-			SLOT(downloadProgress(qint64, qint64)));
-	connect(rep, SIGNAL(finished()), SLOT(downloadFinished()));
-	connect(rep, SIGNAL(error(QNetworkReply::NetworkError)),
-			SLOT(downloadError(QNetworkReply::NetworkError)));
-	connect(rep, SIGNAL(readyRead()), SLOT(downloadReadyRead()));
-}
-
-void ByteArrayDownload::downloadProgress(qint64 bytesReceived, qint64 bytesTotal)
-{
-	m_total_progress = bytesTotal;
-	m_progress = bytesReceived;
-	emit netActionProgress(m_index_within_job, bytesReceived, bytesTotal);
-}
-
-void ByteArrayDownload::downloadError(QNetworkReply::NetworkError error)
-{
-	// error happened during download.
-	qCritical() << "Error getting URL:" << m_url.toString().toLocal8Bit()
-				 << "Network error: " << error;
-	m_status = Job_Failed;
-	m_errorString = m_reply->errorString();
-}
-
-void ByteArrayDownload::downloadFinished()
-{
-	QVariant redirect = m_reply->header(QNetworkRequest::LocationHeader);
-	QString redirectURL;
-	if(redirect.isValid())
-	{
-		redirectURL = redirect.toString();
-	}
-	// FIXME: This is a hack for https://bugreports.qt-project.org/browse/QTBUG-41061
-	else if(m_reply->hasRawHeader("Location"))
-	{
-		auto data = m_reply->rawHeader("Location");
-		if(data.size() > 2 && data[0] == '/' && data[1] == '/')
-			redirectURL = m_reply->url().scheme() + ":" + data;
-	}
-	if (!redirectURL.isEmpty())
-	{
-		m_url = QUrl(redirect.toString());
-		qDebug() << "Following redirect to " << m_url.toString();
-		start();
-		return;
-	}
-
-	// if the download succeeded
-	if (m_status != Job_Failed)
-	{
-		// nothing went wrong...
-		m_status = Job_Finished;
-		m_data = m_reply->readAll();
-		m_content_type = m_reply->header(QNetworkRequest::ContentTypeHeader).toString();
-		m_reply.reset();
-		emit succeeded(m_index_within_job);
-		return;
-	}
-	// else the download failed
-	else
-	{
-		m_reply.reset();
-		emit failed(m_index_within_job);
-		return;
-	}
-}
-
-void ByteArrayDownload::downloadReadyRead()
-{
-	// ~_~
-}
diff --git a/api/logic/net/ByteArrayDownload.h b/api/logic/net/ByteArrayDownload.h
deleted file mode 100644
index e2fc2911..00000000
--- a/api/logic/net/ByteArrayDownload.h
+++ /dev/null
@@ -1,48 +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 "NetAction.h"
-
-#include "multimc_logic_export.h"
-
-typedef std::shared_ptr<class ByteArrayDownload> ByteArrayDownloadPtr;
-class MULTIMC_LOGIC_EXPORT ByteArrayDownload : public NetAction
-{
-	Q_OBJECT
-public:
-	ByteArrayDownload(QUrl url);
-	static ByteArrayDownloadPtr make(QUrl url)
-	{
-		return ByteArrayDownloadPtr(new ByteArrayDownload(url));
-	}
-    virtual ~ByteArrayDownload() {};
-public:
-	/// if not saving to file, downloaded data is placed here
-	QByteArray m_data;
-
-	QString m_errorString;
-
-public
-slots:
-	virtual void start();
-
-protected
-slots:
-	void downloadProgress(qint64 bytesReceived, qint64 bytesTotal);
-	void downloadError(QNetworkReply::NetworkError error);
-	void downloadFinished();
-	void downloadReadyRead();
-};
diff --git a/api/logic/net/ByteArraySink.h b/api/logic/net/ByteArraySink.h
new file mode 100644
index 00000000..3deef1ed
--- /dev/null
+++ b/api/logic/net/ByteArraySink.h
@@ -0,0 +1,57 @@
+#pragma once
+
+#include "Sink.h"
+
+namespace Net {
+/*
+ * Sink object for downloads that uses an external QByteArray it doesn't own as a target.
+ */
+class ByteArraySink : public Sink
+{
+public:
+	ByteArraySink(QByteArray *output)
+		:m_output(output)
+	{
+		// nil
+	};
+
+	virtual ~ByteArraySink()
+	{
+		// nil
+	}
+
+public:
+	JobStatus init(QNetworkRequest & request) override
+	{
+		m_output->clear();
+		if(initAllValidators(request))
+			return Job_InProgress;
+		return Job_Failed;
+	};
+
+	JobStatus write(QByteArray & data) override
+	{
+		m_output->append(data);
+		if(writeAllValidators(data))
+			return Job_InProgress;
+		return Job_Failed;
+	}
+
+	JobStatus abort() override
+	{
+		m_output->clear();
+		failAllValidators();
+		return Job_Failed;
+	}
+
+	JobStatus finalize(QNetworkReply &reply) override
+	{
+		if(finalizeAllValidators(reply))
+			return Job_Finished;
+		return Job_Failed;
+	}
+
+private:
+	QByteArray * m_output;
+};
+}
diff --git a/api/logic/net/CacheDownload.cpp b/api/logic/net/CacheDownload.cpp
deleted file mode 100644
index 1ac55180..00000000
--- a/api/logic/net/CacheDownload.cpp
+++ /dev/null
@@ -1,192 +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 "CacheDownload.h"
-
-#include <QCryptographicHash>
-#include <QFileInfo>
-#include <QDateTime>
-#include <QDebug>
-#include "Env.h"
-#include <FileSystem.h>
-
-CacheDownload::CacheDownload(QUrl url, MetaEntryPtr entry)
-	: NetAction(), md5sum(QCryptographicHash::Md5)
-{
-	m_url = url;
-	m_entry = entry;
-	m_target_path = entry->getFullPath();
-	m_status = Job_NotStarted;
-}
-
-void CacheDownload::start()
-{
-	m_status = Job_InProgress;
-	if (!m_entry->isStale())
-	{
-		m_status = Job_Finished;
-		emit succeeded(m_index_within_job);
-		return;
-	}
-	// create a new save file
-	m_output_file.reset(new QSaveFile(m_target_path));
-
-	// if there already is a file and md5 checking is in effect and it can be opened
-	if (!FS::ensureFilePathExists(m_target_path))
-	{
-		qCritical() << "Could not create folder for " + m_target_path;
-		m_status = Job_Failed;
-		emit failed(m_index_within_job);
-		return;
-	}
-	if (!m_output_file->open(QIODevice::WriteOnly))
-	{
-		qCritical() << "Could not open " + m_target_path + " for writing";
-		m_status = Job_Failed;
-		emit failed(m_index_within_job);
-		return;
-	}
-	qDebug() << "Downloading " << m_url.toString();
-	QNetworkRequest request(m_url);
-
-	// check file consistency first.
-	QFile current(m_target_path);
-	if(current.exists() && current.size() != 0)
-	{
-		if (m_entry->getRemoteChangedTimestamp().size())
-			request.setRawHeader(QString("If-Modified-Since").toLatin1(),
-								m_entry->getRemoteChangedTimestamp().toLatin1());
-		if (m_entry->getETag().size())
-			request.setRawHeader(QString("If-None-Match").toLatin1(), m_entry->getETag().toLatin1());
-	}
-
-	request.setHeader(QNetworkRequest::UserAgentHeader, "MultiMC/5.0 (Cached)");
-
-	auto worker = ENV.qnam();
-	QNetworkReply *rep = worker->get(request);
-
-	m_reply.reset(rep);
-	connect(rep, SIGNAL(downloadProgress(qint64, qint64)),
-			SLOT(downloadProgress(qint64, qint64)));
-	connect(rep, SIGNAL(finished()), SLOT(downloadFinished()));
-	connect(rep, SIGNAL(error(QNetworkReply::NetworkError)),
-			SLOT(downloadError(QNetworkReply::NetworkError)));
-	connect(rep, SIGNAL(readyRead()), SLOT(downloadReadyRead()));
-}
-
-void CacheDownload::downloadProgress(qint64 bytesReceived, qint64 bytesTotal)
-{
-	m_total_progress = bytesTotal;
-	m_progress = bytesReceived;
-	emit netActionProgress(m_index_within_job, bytesReceived, bytesTotal);
-}
-
-void CacheDownload::downloadError(QNetworkReply::NetworkError error)
-{
-	// error happened during download.
-	qCritical() << "Failed " << m_url.toString() << " with reason " << error;
-	m_status = Job_Failed;
-}
-void CacheDownload::downloadFinished()
-{
-	QVariant redirect = m_reply->header(QNetworkRequest::LocationHeader);
-	QString redirectURL;
-	if(redirect.isValid())
-	{
-		redirectURL = redirect.toString();
-	}
-	// FIXME: This is a hack for https://bugreports.qt-project.org/browse/QTBUG-41061
-	else if(m_reply->hasRawHeader("Location"))
-	{
-		auto data = m_reply->rawHeader("Location");
-		if(data.size() > 2 && data[0] == '/' && data[1] == '/')
-			redirectURL = m_reply->url().scheme() + ":" + data;
-	}
-	if (!redirectURL.isEmpty())
-	{
-		m_url = QUrl(redirect.toString());
-		qDebug() << "Following redirect to " << m_url.toString();
-		start();
-		return;
-	}
-
-	// if the download succeeded
-	if (m_status == Job_Failed)
-	{
-		m_output_file->cancelWriting();
-		m_reply.reset();
-		emit failed(m_index_within_job);
-		return;
-	}
-
-	// if we wrote any data to the save file, we try to commit the data to the real file.
-	if (wroteAnyData)
-	{
-		// nothing went wrong...
-		if (m_output_file->commit())
-		{
-			m_status = Job_Finished;
-			m_entry->setMD5Sum(md5sum.result().toHex().constData());
-		}
-		else
-		{
-			qCritical() << "Failed to commit changes to " << m_target_path;
-			m_output_file->cancelWriting();
-			m_reply.reset();
-			m_status = Job_Failed;
-			emit failed(m_index_within_job);
-			return;
-		}
-	}
-	else
-	{
-		m_status = Job_Finished;
-	}
-
-	// then get rid of the save file
-	m_output_file.reset();
-
-	QFileInfo output_file_info(m_target_path);
-
-	m_entry->setETag(m_reply->rawHeader("ETag").constData());
-	if (m_reply->hasRawHeader("Last-Modified"))
-	{
-		m_entry->setRemoteChangedTimestamp(m_reply->rawHeader("Last-Modified").constData());
-	}
-	m_entry->setLocalChangedTimestamp(output_file_info.lastModified().toUTC().toMSecsSinceEpoch());
-	m_entry->setStale(false);
-	ENV.metacache()->updateEntry(m_entry);
-
-	m_reply.reset();
-	emit succeeded(m_index_within_job);
-	return;
-}
-
-void CacheDownload::downloadReadyRead()
-{
-	QByteArray ba = m_reply->readAll();
-	md5sum.addData(ba);
-	if (m_output_file->write(ba) != ba.size())
-	{
-		qCritical() << "Failed writing into " + m_target_path;
-		m_status = Job_Failed;
-		m_output_file->cancelWriting();
-		m_output_file.reset();
-		emit failed(m_index_within_job);
-		wroteAnyData = false;
-		return;
-	}
-	wroteAnyData = true;
-}
diff --git a/api/logic/net/ChecksumValidator.h b/api/logic/net/ChecksumValidator.h
new file mode 100644
index 00000000..3cd25bc3
--- /dev/null
+++ b/api/logic/net/ChecksumValidator.h
@@ -0,0 +1,57 @@
+#pragma once
+
+#include "Validator.h"
+#include <QCryptographicHash>
+#include <memory>
+#include <QFile>
+
+namespace Net {
+class ChecksumValidator: public Validator
+{
+public: /* con/des */
+	ChecksumValidator(QCryptographicHash::Algorithm algorithm, QByteArray expected = QByteArray())
+		:m_checksum(algorithm), m_expected(expected)
+	{
+	};
+	virtual ~ChecksumValidator() {};
+
+public: /* methods */
+	bool init(QNetworkRequest &) override
+	{
+		m_checksum.reset();
+		return true;
+	}
+	bool write(QByteArray & data) override
+	{
+		m_checksum.addData(data);
+		this->data.append(data);
+		return true;
+	}
+	bool abort() override
+	{
+		return true;
+	}
+	bool validate(QNetworkReply &) override
+	{
+		if(m_expected.size() && m_expected != hash())
+		{
+			qWarning() << "Checksum mismatch, download is bad.";
+			return false;
+		}
+		return true;
+	}
+	QByteArray hash()
+	{
+		return m_checksum.result();
+	}
+	void setExpected(QByteArray expected)
+	{
+		m_expected = expected;
+	}
+
+private: /* data */
+	QByteArray data;
+	QCryptographicHash m_checksum;
+	QByteArray m_expected;
+};
+}
\ No newline at end of file
diff --git a/api/logic/net/Download.cpp b/api/logic/net/Download.cpp
new file mode 100644
index 00000000..70fe7608
--- /dev/null
+++ b/api/logic/net/Download.cpp
@@ -0,0 +1,199 @@
+/* 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 "Download.h"
+
+#include <QFileInfo>
+#include <QDateTime>
+#include <QDebug>
+#include "Env.h"
+#include <FileSystem.h>
+#include "ChecksumValidator.h"
+#include "MetaCacheSink.h"
+#include "ByteArraySink.h"
+
+namespace Net {
+
+Download::Download():NetAction()
+{
+	m_status = Job_NotStarted;
+}
+
+Download::Ptr Download::makeCached(QUrl url, MetaEntryPtr entry)
+{
+	Download * dl = new Download();
+	dl->m_url = url;
+	auto md5Node = new ChecksumValidator(QCryptographicHash::Md5);
+	auto cachedNode = new MetaCacheSink(entry, md5Node);
+	dl->m_sink.reset(cachedNode);
+	dl->m_target_path = entry->getFullPath();
+	return std::shared_ptr<Download>(dl);
+}
+
+Download::Ptr Download::makeByteArray(QUrl url, QByteArray *output)
+{
+	Download * dl = new Download();
+	dl->m_url = url;
+	dl->m_sink.reset(new ByteArraySink(output));
+	return std::shared_ptr<Download>(dl);
+}
+
+Download::Ptr Download::makeFile(QUrl url, QString path)
+{
+	Download * dl = new Download();
+	dl->m_url = url;
+	dl->m_sink.reset(new FileSink(path));
+	return std::shared_ptr<Download>(dl);
+}
+
+void Download::addValidator(Validator * v)
+{
+	m_sink->addValidator(v);
+}
+
+void Download::start()
+{
+	QNetworkRequest request(m_url);
+	m_status = m_sink->init(request);
+	switch(m_status)
+	{
+		case Job_Finished:
+			emit succeeded(m_index_within_job);
+			qDebug() << "Download cache hit " << m_url.toString();
+			return;
+		case Job_InProgress:
+			qDebug() << "Downloading " << m_url.toString();
+			break;
+		case Job_NotStarted:
+		case Job_Failed:
+			emit failed(m_index_within_job);
+			return;
+	}
+
+	request.setHeader(QNetworkRequest::UserAgentHeader, "MultiMC/5.0");
+
+	auto worker = ENV.qnam();
+	QNetworkReply *rep = worker->get(request);
+
+	m_reply.reset(rep);
+	connect(rep, SIGNAL(downloadProgress(qint64, qint64)), SLOT(downloadProgress(qint64, qint64)));
+	connect(rep, SIGNAL(finished()), SLOT(downloadFinished()));
+	connect(rep, SIGNAL(error(QNetworkReply::NetworkError)), SLOT(downloadError(QNetworkReply::NetworkError)));
+	connect(rep, SIGNAL(readyRead()), SLOT(downloadReadyRead()));
+}
+
+void Download::downloadProgress(qint64 bytesReceived, qint64 bytesTotal)
+{
+	m_total_progress = bytesTotal;
+	m_progress = bytesReceived;
+	emit netActionProgress(m_index_within_job, bytesReceived, bytesTotal);
+}
+
+void Download::downloadError(QNetworkReply::NetworkError error)
+{
+	// error happened during download.
+	qCritical() << "Failed " << m_url.toString() << " with reason " << error;
+	m_status = Job_Failed;
+}
+
+bool Download::handleRedirect()
+{
+	QVariant redirect = m_reply->header(QNetworkRequest::LocationHeader);
+	QString redirectURL;
+	if(redirect.isValid())
+	{
+		redirectURL = redirect.toString();
+	}
+	// FIXME: This is a hack for https://bugreports.qt-project.org/browse/QTBUG-41061
+	else if(m_reply->hasRawHeader("Location"))
+	{
+		auto data = m_reply->rawHeader("Location");
+		if(data.size() > 2 && data[0] == '/' && data[1] == '/')
+		{
+			redirectURL = m_reply->url().scheme() + ":" + data;
+		}
+	}
+	if (!redirectURL.isEmpty())
+	{
+		m_url = QUrl(redirect.toString());
+		qDebug() << "Following redirect to " << m_url.toString();
+		start();
+		return true;
+	}
+	return false;
+}
+
+
+void Download::downloadFinished()
+{
+	// handle HTTP redirection first
+	if(handleRedirect())
+	{
+		qDebug() << "Download redirected:" << m_url.toString();
+		return;
+	}
+
+	// if the download failed before this point ...
+	if (m_status == Job_Failed)
+	{
+		qDebug() << "Download failed in previous step:" << m_url.toString();
+		m_sink->abort();
+		m_reply.reset();
+		emit failed(m_index_within_job);
+		return;
+	}
+
+	// make sure we got all the remaining data, if any
+	auto data = m_reply->readAll();
+	if(data.size())
+	{
+		qDebug() << "Writing extra" << data.size() << "bytes to" << m_target_path;
+		m_status = m_sink->write(data);
+	}
+
+	// otherwise, finalize the whole graph
+	m_status = m_sink->finalize(*m_reply.get());
+	if (m_status != Job_Finished)
+	{
+		qDebug() << "Download failed to finalize:" << m_url.toString();
+		m_sink->abort();
+		m_reply.reset();
+		emit failed(m_index_within_job);
+		return;
+	}
+	m_reply.reset();
+	qDebug() << "Download succeeded:" << m_url.toString();
+	emit succeeded(m_index_within_job);
+}
+
+void Download::downloadReadyRead()
+{
+	if(m_status == Job_InProgress)
+	{
+		auto data = m_reply->readAll();
+		m_status = m_sink->write(data);
+		if(m_status == Job_Failed)
+		{
+			qCritical() << "Failed to process response chunk for " << m_target_path;
+		}
+		// qDebug() << "Download" << m_url.toString() << "gained" << data.size() << "bytes";
+	}
+	else
+	{
+		qCritical() << "Cannot write to " << m_target_path << ", illegal status" << m_status;
+	}
+}
+
+}
diff --git a/api/logic/net/CacheDownload.h b/api/logic/net/Download.h
index d83b2a0f..8e38dfc9 100644
--- a/api/logic/net/CacheDownload.h
+++ b/api/logic/net/Download.h
@@ -17,47 +17,50 @@
 
 #include "NetAction.h"
 #include "HttpMetaCache.h"
-#include <QCryptographicHash>
-#include <QSaveFile>
+#include "Validator.h"
+#include "Sink.h"
 
 #include "multimc_logic_export.h"
-
-typedef std::shared_ptr<class CacheDownload> CacheDownloadPtr;
-class MULTIMC_LOGIC_EXPORT CacheDownload : public NetAction
+namespace Net {
+class MULTIMC_LOGIC_EXPORT Download : public NetAction
 {
 	Q_OBJECT
-private:
-	MetaEntryPtr m_entry;
-	/// if saving to file, use the one specified in this string
-	QString m_target_path;
-
-	/// this is the output file, if any
-	std::unique_ptr<QSaveFile> m_output_file;
 
-	/// the hash-as-you-download
-	QCryptographicHash md5sum;
-
-	bool wroteAnyData = false;
+public: /* types */
+	typedef std::shared_ptr<class Download> Ptr;
 
+protected: /* con/des */
+	explicit Download();
 public:
-	explicit CacheDownload(QUrl url, MetaEntryPtr entry);
-	static CacheDownloadPtr make(QUrl url, MetaEntryPtr entry)
-	{
-		return CacheDownloadPtr(new CacheDownload(url, entry));
-	}
-	virtual ~CacheDownload(){};
+	virtual ~Download(){};
+	static Download::Ptr makeCached(QUrl url, MetaEntryPtr entry);
+	static Download::Ptr makeByteArray(QUrl url, QByteArray *output);
+	static Download::Ptr makeFile(QUrl url, QString path);
+
+public: /* methods */
+	// FIXME: remove this
 	QString getTargetFilepath()
 	{
 		return m_target_path;
 	}
-protected
-slots:
+	// FIXME: remove this
+	void addValidator(Validator * v);
+
+private: /* methods */
+	bool handleRedirect();
+
+protected slots:
 	virtual void downloadProgress(qint64 bytesReceived, qint64 bytesTotal);
 	virtual void downloadError(QNetworkReply::NetworkError error);
 	virtual void downloadFinished();
 	virtual void downloadReadyRead();
 
-public
-slots:
+public slots:
 	virtual void start();
+
+private: /* data */
+	// FIXME: remove this, it has no business being here.
+	QString m_target_path;
+	std::unique_ptr<Sink> m_sink;
 };
+}
\ No newline at end of file
diff --git a/api/logic/net/FileSink.cpp b/api/logic/net/FileSink.cpp
new file mode 100644
index 00000000..b4c418a5
--- /dev/null
+++ b/api/logic/net/FileSink.cpp
@@ -0,0 +1,99 @@
+#include "FileSink.h"
+#include <QFile>
+#include <QFileInfo>
+#include "Env.h"
+#include "FileSystem.h"
+
+namespace Net {
+
+FileSink::FileSink(QString filename)
+	:m_filename(filename)
+{
+	// nil
+};
+
+FileSink::~FileSink()
+{
+	// nil
+};
+
+JobStatus FileSink::init(QNetworkRequest& request)
+{
+	auto result = initCache(request);
+	if(result != Job_InProgress)
+	{
+		return result;
+	}
+	// create a new save file and open it for writing
+	if (!FS::ensureFilePathExists(m_filename))
+	{
+		qCritical() << "Could not create folder for " + m_filename;
+		return Job_Failed;
+	}
+	m_output_file.reset(new QSaveFile(m_filename));
+	if (!m_output_file->open(QIODevice::WriteOnly))
+	{
+		qCritical() << "Could not open " + m_filename + " for writing";
+		return Job_Failed;
+	}
+
+	if(initAllValidators(request))
+		return Job_InProgress;
+	return Job_Failed;
+}
+
+JobStatus FileSink::initCache(QNetworkRequest &)
+{
+	return Job_InProgress;
+}
+
+JobStatus FileSink::write(QByteArray& data)
+{
+	if (!writeAllValidators(data) || m_output_file->write(data) != data.size())
+	{
+		qCritical() << "Failed writing into " + m_filename;
+		m_output_file->cancelWriting();
+		m_output_file.reset();
+		wroteAnyData = false;
+		return Job_Failed;
+	}
+	wroteAnyData = true;
+	return Job_InProgress;
+}
+
+JobStatus FileSink::abort()
+{
+	m_output_file->cancelWriting();
+	failAllValidators();
+	return Job_Failed;
+}
+
+JobStatus FileSink::finalize(QNetworkReply& reply)
+{
+	// if we wrote any data to the save file, we try to commit the data to the real file.
+	if (wroteAnyData)
+	{
+		// ask validators for data consistency
+		// we only do this for actual downloads, not 'your data is still the same' cache hits
+		if(!finalizeAllValidators(reply))
+			return Job_Failed;
+		// nothing went wrong...
+		if (!m_output_file->commit())
+		{
+			qCritical() << "Failed to commit changes to " << m_filename;
+			m_output_file->cancelWriting();
+			return Job_Failed;
+		}
+	}
+	// then get rid of the save file
+	m_output_file.reset();
+
+	return finalizeCache(reply);
+}
+
+JobStatus FileSink::finalizeCache(QNetworkReply &)
+{
+	return Job_Finished;
+}
+
+}
diff --git a/api/logic/net/FileSink.h b/api/logic/net/FileSink.h
new file mode 100644
index 00000000..7adc9c47
--- /dev/null
+++ b/api/logic/net/FileSink.h
@@ -0,0 +1,27 @@
+#pragma once
+#include "Sink.h"
+#include <QSaveFile>
+
+namespace Net {
+class FileSink : public Sink
+{
+public: /* con/des */
+	FileSink(QString filename);
+	virtual ~FileSink();
+
+public: /* methods */
+	JobStatus init(QNetworkRequest & request) override;
+	JobStatus write(QByteArray & data) override;
+	JobStatus abort() override;
+	JobStatus finalize(QNetworkReply & reply) override;
+
+protected: /* methods */
+	virtual JobStatus initCache(QNetworkRequest &);
+	virtual JobStatus finalizeCache(QNetworkReply &reply);
+
+protected: /* data */
+	QString m_filename;
+	bool wroteAnyData = false;
+	std::unique_ptr<QSaveFile> m_output_file;
+};
+}
diff --git a/api/logic/net/MD5EtagDownload.cpp b/api/logic/net/MD5EtagDownload.cpp
deleted file mode 100644
index 3b4d5dcd..00000000
--- a/api/logic/net/MD5EtagDownload.cpp
+++ /dev/null
@@ -1,155 +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 "Env.h"
-#include "MD5EtagDownload.h"
-#include <FileSystem.h>
-#include <QCryptographicHash>
-#include <QDebug>
-
-MD5EtagDownload::MD5EtagDownload(QUrl url, QString target_path) : NetAction()
-{
-	m_url = url;
-	m_target_path = target_path;
-	m_status = Job_NotStarted;
-}
-
-void MD5EtagDownload::start()
-{
-	QString filename = m_target_path;
-	m_output_file.setFileName(filename);
-	// if there already is a file and md5 checking is in effect and it can be opened
-	if (m_output_file.exists() && m_output_file.open(QIODevice::ReadOnly))
-	{
-		// get the md5 of the local file.
-		m_local_md5 =
-			QCryptographicHash::hash(m_output_file.readAll(), QCryptographicHash::Md5)
-				.toHex()
-				.constData();
-		m_output_file.close();
-		// if we are expecting some md5sum, compare it with the local one
-		if (!m_expected_md5.isEmpty())
-		{
-			// skip if they match
-			if(m_local_md5 == m_expected_md5)
-			{
-				qDebug() << "Skipping " << m_url.toString() << ": md5 match.";
-				emit succeeded(m_index_within_job);
-				return;
-			}
-		}
-		else
-		{
-			// no expected md5. we use the local md5sum as an ETag
-		}
-	}
-	if (!FS::ensureFilePathExists(filename))
-	{
-		emit failed(m_index_within_job);
-		return;
-	}
-
-	QNetworkRequest request(m_url);
-
-	qDebug() << "Downloading " << m_url.toString() << " local MD5: " << m_local_md5;
-
-	if(!m_local_md5.isEmpty())
-	{
-		request.setRawHeader(QString("If-None-Match").toLatin1(), m_local_md5.toLatin1());
-	}
-	if(!m_expected_md5.isEmpty())
-		qDebug() << "Expecting " << m_expected_md5;
-
-	request.setHeader(QNetworkRequest::UserAgentHeader, "MultiMC/5.0 (Uncached)");
-
-	// Go ahead and try to open the file.
-	// If we don't do this, empty files won't be created, which breaks the updater.
-	// Plus, this way, we don't end up starting a download for a file we can't open.
-	if (!m_output_file.open(QIODevice::WriteOnly))
-	{
-		emit failed(m_index_within_job);
-		return;
-	}
-
-	auto worker = ENV.qnam();
-	QNetworkReply *rep = worker->get(request);
-
-	m_reply.reset(rep);
-	connect(rep, SIGNAL(downloadProgress(qint64, qint64)),
-			SLOT(downloadProgress(qint64, qint64)));
-	connect(rep, SIGNAL(finished()), SLOT(downloadFinished()));
-	connect(rep, SIGNAL(error(QNetworkReply::NetworkError)),
-			SLOT(downloadError(QNetworkReply::NetworkError)));
-	connect(rep, SIGNAL(readyRead()), SLOT(downloadReadyRead()));
-}
-
-void MD5EtagDownload::downloadProgress(qint64 bytesReceived, qint64 bytesTotal)
-{
-	m_total_progress = bytesTotal;
-	m_progress = bytesReceived;
-	emit netActionProgress(m_index_within_job, bytesReceived, bytesTotal);
-}
-
-void MD5EtagDownload::downloadError(QNetworkReply::NetworkError error)
-{
-	qCritical() << "Error" << error << ":" << m_reply->errorString() << "while downloading"
-				 << m_reply->url();
-	m_status = Job_Failed;
-}
-
-void MD5EtagDownload::downloadFinished()
-{
-	// if the download succeeded
-	if (m_status != Job_Failed)
-	{
-		// nothing went wrong...
-		m_status = Job_Finished;
-		m_output_file.close();
-
-		// FIXME: compare with the real written data md5sum
-		// this is just an ETag
-		qDebug() << "Finished " << m_url.toString() << " got " << m_reply->rawHeader("ETag").constData();
-
-		m_reply.reset();
-		emit succeeded(m_index_within_job);
-		return;
-	}
-	// else the download failed
-	else
-	{
-		m_output_file.close();
-		m_output_file.remove();
-		m_reply.reset();
-		emit failed(m_index_within_job);
-		return;
-	}
-}
-
-void MD5EtagDownload::downloadReadyRead()
-{
-	if (!m_output_file.isOpen())
-	{
-		if (!m_output_file.open(QIODevice::WriteOnly))
-		{
-			/*
-			* Can't open the file... the job failed
-			*/
-			m_reply->abort();
-			emit failed(m_index_within_job);
-			return;
-		}
-	}
-	m_output_file.write(m_reply->readAll());
-}
diff --git a/api/logic/net/MD5EtagDownload.h b/api/logic/net/MD5EtagDownload.h
deleted file mode 100644
index cd1cb550..00000000
--- a/api/logic/net/MD5EtagDownload.h
+++ /dev/null
@@ -1,52 +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 "NetAction.h"
-#include <QFile>
-
-typedef std::shared_ptr<class MD5EtagDownload> Md5EtagDownloadPtr;
-class MD5EtagDownload : public NetAction
-{
-	Q_OBJECT
-public:
-	/// the expected md5 checksum. Only set from outside
-	QString m_expected_md5;
-	/// the md5 checksum of a file that already exists.
-	QString m_local_md5;
-	/// if saving to file, use the one specified in this string
-	QString m_target_path;
-	/// this is the output file, if any
-	QFile m_output_file;
-
-public:
-	explicit MD5EtagDownload(QUrl url, QString target_path);
-	static Md5EtagDownloadPtr make(QUrl url, QString target_path)
-	{
-		return Md5EtagDownloadPtr(new MD5EtagDownload(url, target_path));
-	}
-	virtual ~MD5EtagDownload(){};
-protected
-slots:
-	virtual void downloadProgress(qint64 bytesReceived, qint64 bytesTotal);
-	virtual void downloadError(QNetworkReply::NetworkError error);
-	virtual void downloadFinished();
-	virtual void downloadReadyRead();
-
-public
-slots:
-	virtual void start();
-};
diff --git a/api/logic/net/MetaCacheSink.cpp b/api/logic/net/MetaCacheSink.cpp
new file mode 100644
index 00000000..539b4bb3
--- /dev/null
+++ b/api/logic/net/MetaCacheSink.cpp
@@ -0,0 +1,59 @@
+#include "MetaCacheSink.h"
+#include <QFile>
+#include <QFileInfo>
+#include "Env.h"
+#include "FileSystem.h"
+
+namespace Net {
+
+MetaCacheSink::MetaCacheSink(MetaEntryPtr entry, ChecksumValidator * md5sum)
+	:Net::FileSink(entry->getFullPath()), m_entry(entry), m_md5Node(md5sum)
+{
+	addValidator(md5sum);
+};
+
+MetaCacheSink::~MetaCacheSink()
+{
+	// nil
+};
+
+JobStatus MetaCacheSink::initCache(QNetworkRequest& request)
+{
+	if (!m_entry->isStale())
+	{
+		return Job_Finished;
+	}
+	// check if file exists, if it does, use its information for the request
+	QFile current(m_filename);
+	if(current.exists() && current.size() != 0)
+	{
+		if (m_entry->getRemoteChangedTimestamp().size())
+		{
+			request.setRawHeader(QString("If-Modified-Since").toLatin1(), m_entry->getRemoteChangedTimestamp().toLatin1());
+		}
+		if (m_entry->getETag().size())
+		{
+			request.setRawHeader(QString("If-None-Match").toLatin1(), m_entry->getETag().toLatin1());
+		}
+	}
+	return Job_InProgress;
+}
+
+JobStatus MetaCacheSink::finalizeCache(QNetworkReply & reply)
+{
+	QFileInfo output_file_info(m_filename);
+	if(wroteAnyData)
+	{
+		m_entry->setMD5Sum(m_md5Node->hash().toHex().constData());
+	}
+	m_entry->setETag(reply.rawHeader("ETag").constData());
+	if (reply.hasRawHeader("Last-Modified"))
+	{
+		m_entry->setRemoteChangedTimestamp(reply.rawHeader("Last-Modified").constData());
+	}
+	m_entry->setLocalChangedTimestamp(output_file_info.lastModified().toUTC().toMSecsSinceEpoch());
+	m_entry->setStale(false);
+	ENV.metacache()->updateEntry(m_entry);
+	return Job_Finished;
+}
+}
diff --git a/api/logic/net/MetaCacheSink.h b/api/logic/net/MetaCacheSink.h
new file mode 100644
index 00000000..98e9bba1
--- /dev/null
+++ b/api/logic/net/MetaCacheSink.h
@@ -0,0 +1,21 @@
+#pragma once
+#include "FileSink.h"
+#include "ChecksumValidator.h"
+#include "net/HttpMetaCache.h"
+
+namespace Net {
+class MetaCacheSink : public FileSink
+{
+public: /* con/des */
+	MetaCacheSink(MetaEntryPtr entry, ChecksumValidator * md5sum);
+	virtual ~MetaCacheSink();
+
+protected: /* methods */
+	JobStatus initCache(QNetworkRequest & request) override;
+	JobStatus finalizeCache(QNetworkReply & reply) override;
+
+private: /* data */
+	MetaEntryPtr m_entry;
+	ChecksumValidator * m_md5Node;
+};
+}
diff --git a/api/logic/net/NetAction.h b/api/logic/net/NetAction.h
index 3c395605..2b3f1b7b 100644
--- a/api/logic/net/NetAction.h
+++ b/api/logic/net/NetAction.h
@@ -59,9 +59,6 @@ public:
 	/// the network reply
 	unique_qobject_ptr<QNetworkReply> m_reply;
 
-	/// the content of the content-type header
-	QString m_content_type;
-
 	/// source URL
 	QUrl m_url;
 
diff --git a/api/logic/net/NetJob.cpp b/api/logic/net/NetJob.cpp
index 76c61c35..ca86242a 100644
--- a/api/logic/net/NetJob.cpp
+++ b/api/logic/net/NetJob.cpp
@@ -14,9 +14,7 @@
  */
 
 #include "NetJob.h"
-#include "MD5EtagDownload.h"
-#include "ByteArrayDownload.h"
-#include "CacheDownload.h"
+#include "Download.h"
 
 #include <QDebug>
 
diff --git a/api/logic/net/NetJob.h b/api/logic/net/NetJob.h
index 167fe176..3d16b21f 100644
--- a/api/logic/net/NetJob.h
+++ b/api/logic/net/NetJob.h
@@ -16,9 +16,7 @@
 #pragma once
 #include <QtNetwork>
 #include "NetAction.h"
-#include "ByteArrayDownload.h"
-#include "MD5EtagDownload.h"
-#include "CacheDownload.h"
+#include "Download.h"
 #include "HttpMetaCache.h"
 #include "tasks/Task.h"
 #include "QObjectPtr.h"
diff --git a/api/logic/net/Sink.h b/api/logic/net/Sink.h
new file mode 100644
index 00000000..53f2b221
--- /dev/null
+++ b/api/logic/net/Sink.h
@@ -0,0 +1,70 @@
+#pragma once
+
+#include "net/NetAction.h"
+
+#include "multimc_logic_export.h"
+#include "Validator.h"
+
+namespace Net {
+class MULTIMC_LOGIC_EXPORT Sink
+{
+public: /* con/des */
+	Sink() {};
+	virtual ~Sink() {};
+
+public: /* methods */
+	virtual JobStatus init(QNetworkRequest & request) = 0;
+	virtual JobStatus write(QByteArray & data) = 0;
+	virtual JobStatus abort() = 0;
+	virtual JobStatus finalize(QNetworkReply & reply) = 0;
+
+	void addValidator(Validator * validator)
+	{
+		if(validator)
+		{
+			validators.push_back(std::shared_ptr<Validator>(validator));
+		}
+	}
+
+protected: /* methods */
+	bool finalizeAllValidators(QNetworkReply & reply)
+	{
+		for(auto & validator: validators)
+		{
+			if(!validator->validate(reply))
+				return false;
+		}
+		return true;
+	}
+	bool failAllValidators()
+	{
+		bool success = true;
+		for(auto & validator: validators)
+		{
+			success &= validator->abort();
+		}
+		return success;
+	}
+	bool initAllValidators(QNetworkRequest & request)
+	{
+		for(auto & validator: validators)
+		{
+			if(!validator->init(request))
+				return false;
+		}
+		return true;
+	}
+	bool writeAllValidators(QByteArray & data)
+	{
+		for(auto & validator: validators)
+		{
+			if(!validator->write(data))
+				return false;
+		}
+		return true;
+	}
+
+protected: /* data */
+	std::vector<std::shared_ptr<Validator>> validators;
+};
+}
diff --git a/api/logic/net/Validator.h b/api/logic/net/Validator.h
new file mode 100644
index 00000000..a390ab28
--- /dev/null
+++ b/api/logic/net/Validator.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#include "net/NetAction.h"
+
+#include "multimc_logic_export.h"
+
+namespace Net {
+class MULTIMC_LOGIC_EXPORT Validator
+{
+public: /* con/des */
+	Validator() {};
+	virtual ~Validator() {};
+
+public: /* methods */
+	virtual bool init(QNetworkRequest & request) = 0;
+	virtual bool write(QByteArray & data) = 0;
+	virtual bool abort() = 0;
+	virtual bool validate(QNetworkReply & reply) = 0;
+};
+}
\ No newline at end of file
diff --git a/api/logic/news/NewsChecker.cpp b/api/logic/news/NewsChecker.cpp
index be4aa1d1..7cc87953 100644
--- a/api/logic/news/NewsChecker.cpp
+++ b/api/logic/news/NewsChecker.cpp
@@ -37,7 +37,7 @@ void NewsChecker::reloadNews()
 	qDebug() << "Reloading news.";
 
 	NetJob* job = new NetJob("News RSS Feed");
-	job->addNetAction(ByteArrayDownload::make(m_feedUrl));
+	job->addNetAction(Net::Download::makeByteArray(m_feedUrl, &newsData));
 	QObject::connect(job, &NetJob::succeeded, this, &NewsChecker::rssDownloadFinished);
 	QObject::connect(job, &NetJob::failed, this, &NewsChecker::rssDownloadFailed);
 	m_newsNetJob.reset(job);
@@ -49,13 +49,7 @@ void NewsChecker::rssDownloadFinished()
 	// Parse the XML file and process the RSS feed entries.
 	qDebug() << "Finished loading RSS feed.";
 
-	QByteArray data;
-	{
-		ByteArrayDownloadPtr dl = std::dynamic_pointer_cast<ByteArrayDownload>(m_newsNetJob->first());
-		data = dl->m_data;
-		m_newsNetJob.reset();
-	}
-
+	m_newsNetJob.reset();
 	QDomDocument doc;
 	{
 		// Stuff to store error info in.
@@ -64,12 +58,14 @@ void NewsChecker::rssDownloadFinished()
 		int errorCol = -1;
 
 		// Parse the XML.
-		if (!doc.setContent(data, false, &errorMsg, &errorLine, &errorCol))
+		if (!doc.setContent(newsData, false, &errorMsg, &errorLine, &errorCol))
 		{
 			QString fullErrorMsg = QString("Error parsing RSS feed XML. %s at %d:%d.").arg(errorMsg, errorLine, errorCol);
 			fail(fullErrorMsg);
+			newsData.clear();
 			return;
 		}
+		newsData.clear();
 	}
 
 	// If the parsing succeeded, read it.
diff --git a/api/logic/news/NewsChecker.h b/api/logic/news/NewsChecker.h
index b8b90728..90b2f6d1 100644
--- a/api/logic/news/NewsChecker.h
+++ b/api/logic/news/NewsChecker.h
@@ -74,7 +74,7 @@ protected slots:
 	void rssDownloadFinished();
 	void rssDownloadFailed(QString reason);
 
-protected:
+protected: /* data */
 	//! The URL for the RSS feed to fetch.
 	QString m_feedUrl;
 
@@ -87,21 +87,19 @@ protected:
 	//! True if news has been loaded.
 	bool m_loadedNews;
 
+	QByteArray newsData;
+
 	/*!
 	 * Gets the error message that was given last time the news was loaded.
 	 * If the last news load succeeded, this will be an empty string.
 	 */
 	QString m_lastLoadError;
 
+protected slots:
+	/// Emits newsLoaded() and sets m_lastLoadError to empty string.
+	void succeed();
 
-	/*!
-	 * Emits newsLoaded() and sets m_lastLoadError to empty string.
-	 */
-	void Q_SLOT succeed();
-
-	/*!
-	 * Emits newsLoadingFailed() and sets m_lastLoadError to the given message.
-	 */
-	void Q_SLOT fail(const QString& errorMsg);
+	/// Emits newsLoadingFailed() and sets m_lastLoadError to the given message.
+	void fail(const QString& errorMsg);
 };
 
diff --git a/api/logic/notifications/NotificationChecker.cpp b/api/logic/notifications/NotificationChecker.cpp
index ab2570b7..6d006c31 100644
--- a/api/logic/notifications/NotificationChecker.cpp
+++ b/api/logic/notifications/NotificationChecker.cpp
@@ -6,7 +6,7 @@
 #include <QDebug>
 
 #include "Env.h"
-#include "net/CacheDownload.h"
+#include "net/Download.h"
 
 
 NotificationChecker::NotificationChecker(QObject *parent)
@@ -55,9 +55,8 @@ void NotificationChecker::checkForNotifications()
 	m_checkJob.reset(new NetJob("Checking for notifications"));
 	auto entry = ENV.metacache()->resolveEntry("root", "notifications.json");
 	entry->setStale(true);
-	m_checkJob->addNetAction(m_download = CacheDownload::make(m_notificationsUrl, entry));
-	connect(m_download.get(), &CacheDownload::succeeded, this,
-			&NotificationChecker::downloadSucceeded);
+	m_checkJob->addNetAction(m_download = Net::Download::makeCached(m_notificationsUrl, entry));
+	connect(m_download.get(), &Net::Download::succeeded, this, &NotificationChecker::downloadSucceeded);
 	m_checkJob->start();
 }
 
diff --git a/api/logic/notifications/NotificationChecker.h b/api/logic/notifications/NotificationChecker.h
index a2d92ab9..c8e831d5 100644
--- a/api/logic/notifications/NotificationChecker.h
+++ b/api/logic/notifications/NotificationChecker.h
@@ -3,7 +3,7 @@
 #include <QObject>
 
 #include "net/NetJob.h"
-#include "net/CacheDownload.h"
+#include "net/Download.h"
 
 #include "multimc_logic_export.h"
 
@@ -55,7 +55,7 @@ private:
 	QList<NotificationEntry> m_entries;
 	QUrl m_notificationsUrl;
 	NetJobPtr m_checkJob;
-	CacheDownloadPtr m_download;
+	Net::Download::Ptr m_download;
 
 	QString m_appVersionChannel;
 	QString m_appPlatform;
diff --git a/api/logic/status/StatusChecker.cpp b/api/logic/status/StatusChecker.cpp
index 13cac037..d09c9976 100644
--- a/api/logic/status/StatusChecker.cpp
+++ b/api/logic/status/StatusChecker.cpp
@@ -43,7 +43,7 @@ void StatusChecker::reloadStatus()
 	// qDebug() << "Reloading status.";
 
 	NetJob* job = new NetJob("Status JSON");
-	job->addNetAction(ByteArrayDownload::make(URLConstants::MOJANG_STATUS_URL));
+	job->addNetAction(Net::Download::makeByteArray(URLConstants::MOJANG_STATUS_URL, &dataSink));
 	QObject::connect(job, &NetJob::succeeded, this, &StatusChecker::statusDownloadFinished);
 	QObject::connect(job, &NetJob::failed, this, &StatusChecker::statusDownloadFailed);
 	m_statusNetJob.reset(job);
@@ -55,15 +55,10 @@ void StatusChecker::statusDownloadFinished()
 {
 	qDebug() << "Finished loading status JSON.";
 	m_statusEntries.clear();
-	QByteArray data;
-	{
-		ByteArrayDownloadPtr dl = std::dynamic_pointer_cast<ByteArrayDownload>(m_statusNetJob->first());
-		data = dl->m_data;
-		m_statusNetJob.reset();
-	}
+	m_statusNetJob.reset();
 
 	QJsonParseError jsonError;
-	QJsonDocument jsonDoc = QJsonDocument::fromJson(data, &jsonError);
+	QJsonDocument jsonDoc = QJsonDocument::fromJson(dataSink, &jsonError);
 
 	if (jsonError.error != QJsonParseError::NoError)
 	{
diff --git a/api/logic/status/StatusChecker.h b/api/logic/status/StatusChecker.h
index c1a54dba..452248f4 100644
--- a/api/logic/status/StatusChecker.h
+++ b/api/logic/status/StatusChecker.h
@@ -26,35 +26,35 @@
 class MULTIMC_LOGIC_EXPORT StatusChecker : public QObject
 {
 	Q_OBJECT
-public:
+public: /* con/des */
 	StatusChecker();
 
+public: /* methods */
 	QString getLastLoadErrorMsg() const;
-
 	bool isLoadingStatus() const;
-
 	QMap<QString, QString> getStatusEntries() const;
 
-	void Q_SLOT reloadStatus();
-
-protected:
-	virtual void timerEvent(QTimerEvent *);
-
 signals:
 	void statusLoading(bool loading);
 	void statusChanged(QMap<QString, QString> newStatus);
 
+public slots:
+	void reloadStatus();
+
+protected: /* methods */
+	virtual void timerEvent(QTimerEvent *);
+
 protected slots:
 	void statusDownloadFinished();
 	void statusDownloadFailed(QString reason);
+	void succeed();
+	void fail(const QString& errorMsg);
 
-protected:
+protected: /* data */
 	QMap<QString, QString> m_prevEntries;
 	QMap<QString, QString> m_statusEntries;
 	NetJobPtr m_statusNetJob;
 	QString m_lastLoadError;
-
-	void Q_SLOT succeed();
-	void Q_SLOT fail(const QString& errorMsg);
+	QByteArray dataSink;
 };
 
diff --git a/api/logic/trans/TranslationDownloader.cpp b/api/logic/trans/TranslationDownloader.cpp
index ee5c1fd2..61e24c9a 100644
--- a/api/logic/trans/TranslationDownloader.cpp
+++ b/api/logic/trans/TranslationDownloader.cpp
@@ -1,6 +1,6 @@
 #include "TranslationDownloader.h"
 #include "net/NetJob.h"
-#include "net/CacheDownload.h"
+#include "net/Download.h"
 #include "net/URLConstants.h"
 #include "Env.h"
 #include <QDebug>
@@ -12,7 +12,7 @@ void TranslationDownloader::downloadTranslations()
 {
 	qDebug() << "Downloading Translations Index...";
 	m_index_job.reset(new NetJob("Translations Index"));
-	m_index_task = ByteArrayDownload::make(QUrl("http://files.multimc.org/translations/index"));
+	m_index_task = Net::Download::makeByteArray(QUrl("http://files.multimc.org/translations/index"), &m_data);
 	m_index_job->addNetAction(m_index_task);
 	connect(m_index_job.get(), &NetJob::failed, this, &TranslationDownloader::indexFailed);
 	connect(m_index_job.get(), &NetJob::succeeded, this, &TranslationDownloader::indexRecieved);
@@ -22,17 +22,15 @@ void TranslationDownloader::indexRecieved()
 {
 	qDebug() << "Got translations index!";
 	m_dl_job.reset(new NetJob("Translations"));
-	QList<QByteArray> lines = m_index_task->m_data.split('\n');
+	QList<QByteArray> lines = m_data.split('\n');
+	m_data.clear();
 	for (const auto line : lines)
 	{
 		if (!line.isEmpty())
 		{
 			MetaEntryPtr entry = ENV.metacache()->resolveEntry("translations", "mmc_" + line);
 			entry->setStale(true);
-			CacheDownloadPtr dl = CacheDownload::make(
-				QUrl(URLConstants::TRANSLATIONS_BASE_URL + line),
-				entry);
-			m_dl_job->addNetAction(dl);
+			m_dl_job->addNetAction(Net::Download::makeCached(QUrl(URLConstants::TRANSLATIONS_BASE_URL + line), entry));
 		}
 	}
 	connect(m_dl_job.get(), &NetJob::succeeded, this, &TranslationDownloader::dlGood);
diff --git a/api/logic/trans/TranslationDownloader.h b/api/logic/trans/TranslationDownloader.h
index e7893805..ad3a648d 100644
--- a/api/logic/trans/TranslationDownloader.h
+++ b/api/logic/trans/TranslationDownloader.h
@@ -6,8 +6,9 @@
 #include <QObject>
 #include <net/NetJob.h>
 #include "multimc_logic_export.h"
-
-class ByteArrayDownload;
+namespace Net{
+class Download;
+}
 class NetJob;
 
 class MULTIMC_LOGIC_EXPORT TranslationDownloader : public QObject
@@ -26,7 +27,8 @@ private slots:
 	void dlGood();
 
 private:
-	std::shared_ptr<ByteArrayDownload> m_index_task;
+	std::shared_ptr<Net::Download> m_index_task;
 	NetJobPtr m_dl_job;
 	NetJobPtr m_index_job;
+	QByteArray m_data;
 };
diff --git a/api/logic/updater/DownloadTask.cpp b/api/logic/updater/DownloadTask.cpp
index 6947e8bf..9bb31695 100644
--- a/api/logic/updater/DownloadTask.cpp
+++ b/api/logic/updater/DownloadTask.cpp
@@ -43,22 +43,19 @@ 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));
+	netJob->addNetAction(m_newVersionFileListDownload = Net::Download::makeByteArray(newIndexUrl, &newVersionFileListData));
 
 	// 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));
+		netJob->addNetAction(m_currentVersionFileListDownload = Net::Download::makeByteArray(cIndexUrl, &currentVersionFileListData));
 		qDebug() << m_status.currentRepoUrl << " turns into " << cIndexUrl;
 	}
 
@@ -92,7 +89,7 @@ void DownloadTask::processDownloadedVersionInfo()
 	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))
+	if (!parseVersionInfo(newVersionFileListData, m_newVersionFileList, error))
 	{
 		qCritical() << error;
 		emitFailed(error);
@@ -106,7 +103,7 @@ void DownloadTask::processDownloadedVersionInfo()
 		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))
+		if(!parseVersionInfo( currentVersionFileListData, m_currentVersionFileList, error))
 		{
 			qDebug() << error << "This is not a fatal error.";
 		}
diff --git a/api/logic/updater/DownloadTask.h b/api/logic/updater/DownloadTask.h
index 83b4a142..f6e1288e 100644
--- a/api/logic/updater/DownloadTask.h
+++ b/api/logic/updater/DownloadTask.h
@@ -64,8 +64,10 @@ protected:
 	void loadVersionInfo();
 
 	NetJobPtr m_vinfoNetJob;
-	ByteArrayDownloadPtr m_currentVersionFileListDownload;
-	ByteArrayDownloadPtr m_newVersionFileListDownload;
+	QByteArray currentVersionFileListData;
+	QByteArray newVersionFileListData;
+	Net::Download::Ptr m_currentVersionFileListDownload;
+	Net::Download::Ptr m_newVersionFileListDownload;
 
 	NetJobPtr m_filesNetJob;
 
diff --git a/api/logic/updater/GoUpdate.cpp b/api/logic/updater/GoUpdate.cpp
index 4e465d5c..716048a0 100644
--- a/api/logic/updater/GoUpdate.cpp
+++ b/api/logic/updater/GoUpdate.cpp
@@ -4,6 +4,9 @@
 #include <QFile>
 #include <FileSystem.h>
 
+#include "net/Download.h"
+#include "net/ChecksumValidator.h"
+
 namespace GoUpdate
 {
 
@@ -189,8 +192,9 @@ bool processFileLists
 
 			// 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;
+			auto download = Net::Download::makeFile(source.url, dlPath);
+			auto rawMd5 = QByteArray::fromHex(entry.md5.toLatin1());
+			download->addValidator(new Net::ChecksumValidator(QCryptographicHash::Md5, rawMd5));
 			job->addNetAction(download);
 			ops.append(Operation::CopyOp(dlPath, entry.path, entry.mode));
 		}
diff --git a/api/logic/updater/UpdateChecker.cpp b/api/logic/updater/UpdateChecker.cpp
index 1cdac916..7dc5823e 100644
--- a/api/logic/updater/UpdateChecker.cpp
+++ b/api/logic/updater/UpdateChecker.cpp
@@ -28,11 +28,6 @@ UpdateChecker::UpdateChecker(QString channelListUrl, QString currentChannel, int
 	m_channelListUrl = channelListUrl;
 	m_currentChannel = currentChannel;
 	m_currentBuild = currentBuild;
-
-	m_updateChecking = false;
-	m_chanListLoading = false;
-	m_checkUpdateWaiting = false;
-	m_chanListLoaded = false;
 }
 
 QList<UpdateChecker::ChannelListEntry> UpdateChecker::getChannelList() const
@@ -93,9 +88,8 @@ void UpdateChecker::checkForUpdate(QString updateChannel, bool notifyNoUpdate)
 	QUrl indexUrl = QUrl(m_newRepoUrl).resolved(QUrl("index.json"));
 
 	auto job = new NetJob("GoUpdate Repository Index");
-	job->addNetAction(ByteArrayDownload::make(indexUrl));
-	connect(job, &NetJob::succeeded, [this, notifyNoUpdate]()
-	{ updateCheckFinished(notifyNoUpdate); });
+	job->addNetAction(Net::Download::makeByteArray(indexUrl, &indexData));
+	connect(job, &NetJob::succeeded, [this, notifyNoUpdate](){ updateCheckFinished(notifyNoUpdate); });
 	connect(job, &NetJob::failed, this, &UpdateChecker::updateCheckFailed);
 	indexJob.reset(job);
 	job->start();
@@ -106,19 +100,15 @@ void UpdateChecker::updateCheckFinished(bool notifyNoUpdate)
 	qDebug() << "Finished downloading repo index. Checking for new versions.";
 
 	QJsonParseError jsonError;
-	QByteArray data;
-	{
-		ByteArrayDownloadPtr dl =
-			std::dynamic_pointer_cast<ByteArrayDownload>(indexJob->first());
-		data = dl->m_data;
-		indexJob.reset();
-	}
+	indexJob.reset();
 
-	QJsonDocument jsonDoc = QJsonDocument::fromJson(data, &jsonError);
+	QJsonDocument jsonDoc = QJsonDocument::fromJson(indexData, &jsonError);
+	indexData.clear();
 	if (jsonError.error != QJsonParseError::NoError || !jsonDoc.isObject())
 	{
 		qCritical() << "Failed to parse GoUpdate repository index. JSON error"
 					 << jsonError.errorString() << "at offset" << jsonError.offset;
+		m_updateChecking = false;
 		return;
 	}
 
@@ -130,6 +120,7 @@ void UpdateChecker::updateCheckFinished(bool notifyNoUpdate)
 	{
 		qCritical() << "Failed to check for updates. API version mismatch. We're using"
 					 << API_VERSION << "server has" << apiVersion;
+		m_updateChecking = false;
 		return;
 	}
 
@@ -165,7 +156,6 @@ void UpdateChecker::updateCheckFinished(bool notifyNoUpdate)
 	{
 		emit noUpdateFound();
 	}
-
 	m_updateChecking = false;
 }
 
@@ -178,6 +168,12 @@ void UpdateChecker::updateChanList(bool notifyNoUpdate)
 {
 	qDebug() << "Loading the channel list.";
 
+	if (m_chanListLoading)
+	{
+		qDebug() << "Ignoring channel list update request. Already grabbing channel list.";
+		return;
+	}
+
 	if (m_channelListUrl.isEmpty())
 	{
 		qCritical() << "Failed to update channel list. No channel list URL set."
@@ -188,9 +184,8 @@ void UpdateChecker::updateChanList(bool notifyNoUpdate)
 
 	m_chanListLoading = true;
 	NetJob *job = new NetJob("Update System Channel List");
-	job->addNetAction(ByteArrayDownload::make(QUrl(m_channelListUrl)));
-	connect(job, &NetJob::succeeded, [this, notifyNoUpdate]()
-	{ chanListDownloadFinished(notifyNoUpdate); });
+	job->addNetAction(Net::Download::makeByteArray(QUrl(m_channelListUrl), &chanlistData));
+	connect(job, &NetJob::succeeded, [this, notifyNoUpdate]() { chanListDownloadFinished(notifyNoUpdate); });
 	QObject::connect(job, &NetJob::failed, this, &UpdateChecker::chanListDownloadFailed);
 	chanListJob.reset(job);
 	job->start();
@@ -198,21 +193,16 @@ void UpdateChecker::updateChanList(bool notifyNoUpdate)
 
 void UpdateChecker::chanListDownloadFinished(bool notifyNoUpdate)
 {
-	QByteArray data;
-	{
-		ByteArrayDownloadPtr dl =
-			std::dynamic_pointer_cast<ByteArrayDownload>(chanListJob->first());
-		data = dl->m_data;
-		chanListJob.reset();
-	}
+	chanListJob.reset();
 
 	QJsonParseError jsonError;
-	QJsonDocument jsonDoc = QJsonDocument::fromJson(data, &jsonError);
+	QJsonDocument jsonDoc = QJsonDocument::fromJson(chanlistData, &jsonError);
+	chanlistData.clear();
 	if (jsonError.error != QJsonParseError::NoError)
 	{
 		// TODO: Report errors to the user.
-		qCritical() << "Failed to parse channel list JSON:" << jsonError.errorString() << "at"
-					 << jsonError.offset;
+		qCritical() << "Failed to parse channel list JSON:" << jsonError.errorString() << "at" << jsonError.offset;
+		m_chanListLoading = false;
 		return;
 	}
 
@@ -225,6 +215,7 @@ void UpdateChecker::chanListDownloadFinished(bool notifyNoUpdate)
 		qCritical()
 			<< "Failed to check for updates. Channel list format version mismatch. We're using"
 			<< CHANLIST_FORMAT << "server has" << formatVersion;
+		m_chanListLoading = false;
 		return;
 	}
 
diff --git a/api/logic/updater/UpdateChecker.h b/api/logic/updater/UpdateChecker.h
index c7fad10e..39026b62 100644
--- a/api/logic/updater/UpdateChecker.h
+++ b/api/logic/updater/UpdateChecker.h
@@ -18,8 +18,6 @@
 #include "net/NetJob.h"
 #include "GoUpdate.h"
 
-#include <QUrl>
-
 #include "multimc_logic_export.h"
 
 class MULTIMC_LOGIC_EXPORT UpdateChecker : public QObject
@@ -78,7 +76,9 @@ private:
 	friend class UpdateCheckerTest;
 
 	NetJobPtr indexJob;
+	QByteArray indexData;
 	NetJobPtr chanListJob;
+	QByteArray chanlistData;
 
 	QString m_channelListUrl;
 
@@ -88,24 +88,24 @@ private:
 	 * True while the system is checking for updates.
 	 * If checkForUpdate is called while this is true, it will be ignored.
 	 */
-	bool m_updateChecking;
+	bool m_updateChecking = false;
 
 	/*!
 	 * True if the channel list has loaded.
 	 * If this is false, trying to check for updates will call updateChanList first.
 	 */
-	bool m_chanListLoaded;
+	bool m_chanListLoaded = false;
 
 	/*!
 	 * Set to true while the channel list is currently loading.
 	 */
-	bool m_chanListLoading;
+	bool m_chanListLoading = false;
 
 	/*!
 	 * Set to true when checkForUpdate is called while the channel list isn't loaded.
 	 * When the channel list finishes loading, if this is true, the update checker will check for updates.
 	 */
-	bool m_checkUpdateWaiting;
+	bool m_checkUpdateWaiting = false;
 
 	/*!
 	 * if m_checkUpdateWaiting, this is the last used update channel
diff --git a/api/logic/wonko/tasks/BaseWonkoEntityRemoteLoadTask.cpp b/api/logic/wonko/tasks/BaseWonkoEntityRemoteLoadTask.cpp
index 727ec89d..32d2071d 100644
--- a/api/logic/wonko/tasks/BaseWonkoEntityRemoteLoadTask.cpp
+++ b/api/logic/wonko/tasks/BaseWonkoEntityRemoteLoadTask.cpp
@@ -15,7 +15,7 @@
 
 #include "BaseWonkoEntityRemoteLoadTask.h"
 
-#include "net/CacheDownload.h"
+#include "net/Download.h"
 #include "net/HttpMetaCache.h"
 #include "net/NetJob.h"
 #include "wonko/format/WonkoFormat.h"
@@ -37,7 +37,7 @@ void BaseWonkoEntityRemoteLoadTask::executeTask()
 
 	auto entry = ENV.metacache()->resolveEntry("wonko", url().toString());
 	entry->setStale(true);
-	m_dl = CacheDownload::make(url(), entry);
+	m_dl = Net::Download::makeCached(url(), entry);
 	job->addNetAction(m_dl);
 	connect(job, &NetJob::failed, this, &BaseWonkoEntityRemoteLoadTask::emitFailed);
 	connect(job, &NetJob::succeeded, this, &BaseWonkoEntityRemoteLoadTask::networkFinished);
diff --git a/api/logic/wonko/tasks/BaseWonkoEntityRemoteLoadTask.h b/api/logic/wonko/tasks/BaseWonkoEntityRemoteLoadTask.h
index 91ed6af0..d2bdd5a2 100644
--- a/api/logic/wonko/tasks/BaseWonkoEntityRemoteLoadTask.h
+++ b/api/logic/wonko/tasks/BaseWonkoEntityRemoteLoadTask.h
@@ -18,6 +18,11 @@
 #include "tasks/Task.h"
 #include <memory>
 
+namespace Net
+{
+	class Download;
+}
+
 class BaseWonkoEntity;
 class WonkoIndex;
 class WonkoVersionList;
@@ -43,7 +48,7 @@ private:
 	void executeTask() override;
 
 	BaseWonkoEntity *m_entity;
-	std::shared_ptr<class CacheDownload> m_dl;
+	std::shared_ptr<Net::Download> m_dl;
 };
 
 class WonkoIndexRemoteLoadTask : public BaseWonkoEntityRemoteLoadTask
diff --git a/application/MainWindow.cpp b/application/MainWindow.cpp
index 39a6a7e9..06d165da 100644
--- a/application/MainWindow.cpp
+++ b/application/MainWindow.cpp
@@ -59,7 +59,7 @@
 #include <SkinUtils.h>
 #include <net/URLConstants.h>
 #include <net/NetJob.h>
-#include <net/CacheDownload.h>
+#include <net/Download.h>
 #include <news/NewsChecker.h>
 #include <notifications/NotificationChecker.h>
 #include <tools/BaseProfiler.h>
@@ -519,7 +519,7 @@ MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new MainWindow
 
 	auto accounts = MMC->accounts();
 
-	QList<CacheDownloadPtr> skin_dls;
+	QList<Net::Download::Ptr> skin_dls;
 	for (int i = 0; i < accounts->count(); i++)
 	{
 		auto account = accounts->at(i);
@@ -531,7 +531,7 @@ MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new MainWindow
 		for (auto profile : account->profiles())
 		{
 			auto meta = Env::getInstance().metacache()->resolveEntry("skins", profile.id + ".png");
-			auto action = CacheDownload::make(QUrl("https://" + URLConstants::SKINS_BASE + profile.id + ".png"), meta);
+			auto action = Net::Download::makeCached(QUrl("https://" + URLConstants::SKINS_BASE + profile.id + ".png"), meta);
 			skin_dls.append(action);
 			meta->setStale(true);
 		}
@@ -1045,9 +1045,8 @@ InstancePtr MainWindow::instanceFromZipPack(QString instName, QString instGroup,
 		const QString path = url.host() + '/' + url.path();
 		auto entry = ENV.metacache()->resolveEntry("general", path);
 		entry->setStale(true);
-		CacheDownloadPtr dl = CacheDownload::make(url, entry);
 		NetJob job(tr("Modpack download"));
-		job.addNetAction(dl);
+		job.addNetAction(Net::Download::makeCached(url, entry));
 
 		// FIXME: possibly causes endless loop problems
 		ProgressDialog dlDialog(this);
diff --git a/application/dialogs/AboutDialog.cpp b/application/dialogs/AboutDialog.cpp
index fd61adde..a474cfe6 100644
--- a/application/dialogs/AboutDialog.cpp
+++ b/application/dialogs/AboutDialog.cpp
@@ -109,16 +109,16 @@ AboutDialog::~AboutDialog()
 
 void AboutDialog::loadPatronList()
 {
-	NetJob* job = new NetJob("Patreon Patron List");
-	patronListDownload = ByteArrayDownload::make(QUrl("http://files.multimc.org/patrons.txt"));
-	job->addNetAction(patronListDownload);
-	connect(job, &NetJob::succeeded, this, &AboutDialog::patronListLoaded);
-	job->start();
+	netJob.reset(new NetJob("Patreon Patron List"));
+	netJob->addNetAction(Net::Download::makeByteArray(QUrl("http://files.multimc.org/patrons.txt"), &dataSink));
+	connect(netJob.get(), &NetJob::succeeded, this, &AboutDialog::patronListLoaded);
+	netJob->start();
 }
 
 void AboutDialog::patronListLoaded()
 {
-	QString patronListStr(patronListDownload->m_data);
+	QString patronListStr(dataSink);
+	dataSink.clear();
 	QString html = getCreditsHtml(patronListStr.split("\n", QString::SkipEmptyParts));
 	ui->creditsText->setHtml(html);
 }
diff --git a/application/dialogs/AboutDialog.h b/application/dialogs/AboutDialog.h
index 1885e9c0..5b5874a5 100644
--- a/application/dialogs/AboutDialog.h
+++ b/application/dialogs/AboutDialog.h
@@ -16,8 +16,7 @@
 #pragma once
 
 #include <QDialog>
-
-#include <net/ByteArrayDownload.h>
+#include <net/NetJob.h>
 
 namespace Ui
 {
@@ -43,5 +42,6 @@ slots:
 private:
 	Ui::AboutDialog *ui;
 
-	ByteArrayDownloadPtr patronListDownload;
+	NetJobPtr netJob;
+	QByteArray dataSink;
 };
diff --git a/application/dialogs/UpdateDialog.cpp b/application/dialogs/UpdateDialog.cpp
index 31220e50..6e109bcb 100644
--- a/application/dialogs/UpdateDialog.cpp
+++ b/application/dialogs/UpdateDialog.cpp
@@ -46,8 +46,7 @@ void UpdateDialog::loadChangelog()
 		url = QString("https://api.github.com/repos/MultiMC/MultiMC5/compare/%1...%2").arg(BuildConfig.GIT_COMMIT, channel);
 		m_changelogType = CHANGELOG_COMMITS;
 	}
-	changelogDownload = ByteArrayDownload::make(QUrl(url));
-	dljob->addNetAction(changelogDownload);
+	dljob->addNetAction(Net::Download::makeByteArray(QUrl(url), &changelogData));
 	connect(dljob.get(), &NetJob::succeeded, this, &UpdateDialog::changelogLoaded);
 	connect(dljob.get(), &NetJob::failed, this, &UpdateDialog::changelogFailed);
 	dljob->start();
@@ -201,12 +200,13 @@ void UpdateDialog::changelogLoaded()
 	switch(m_changelogType)
 	{
 		case CHANGELOG_COMMITS:
-			result = reprocessCommits(changelogDownload->m_data);
+			result = reprocessCommits(changelogData);
 			break;
 		case CHANGELOG_MARKDOWN:
-			result = reprocessMarkdown(changelogDownload->m_data);
+			result = reprocessMarkdown(changelogData);
 			break;
 	}
+	changelogData.clear();
 	ui->changelogBrowser->setHtml(result);
 }
 
diff --git a/application/dialogs/UpdateDialog.h b/application/dialogs/UpdateDialog.h
index 403b78ad..f8ecf006 100644
--- a/application/dialogs/UpdateDialog.h
+++ b/application/dialogs/UpdateDialog.h
@@ -16,7 +16,6 @@
 #pragma once
 
 #include <QDialog>
-#include "net/ByteArrayDownload.h"
 #include "net/NetJob.h"
 
 namespace Ui
@@ -60,7 +59,7 @@ public slots:
 	void changelogFailed(QString reason);
 
 private:
-	ByteArrayDownloadPtr changelogDownload;
+	QByteArray changelogData;
 	NetJobPtr dljob;
 	ChangelogType m_changelogType = CHANGELOG_MARKDOWN;
 };
diff --git a/application/pages/global/AccountListPage.cpp b/application/pages/global/AccountListPage.cpp
index eb3ddff9..f4aa58b0 100644
--- a/application/pages/global/AccountListPage.cpp
+++ b/application/pages/global/AccountListPage.cpp
@@ -131,8 +131,7 @@ void AccountListPage::addAccount(const QString &errMsg)
 		for (AccountProfile profile : account->profiles())
 		{
 			auto meta = Env::getInstance().metacache()->resolveEntry("skins", profile.id + ".png");
-			auto action = CacheDownload::make(
-				QUrl("https://" + URLConstants::SKINS_BASE + profile.id + ".png"), meta);
+			auto action = Net::Download::makeCached(QUrl("https://" + URLConstants::SKINS_BASE + profile.id + ".png"), meta);
 			job->addNetAction(action);
 			meta->setStale(true);
 		}