All of the broken legacy things work.

21 files changed, 692 insertions, 347 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 84eb7665..0be887dc 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -479,6 +479,8 @@ SET(MULTIMC_SOURCES
 	logic/minecraft/OneSixRule.h
 	logic/minecraft/OpSys.cpp
 	logic/minecraft/OpSys.h
+	logic/minecraft/ParseUtils.cpp
+	logic/minecraft/ParseUtils.h
 	logic/minecraft/RawLibrary.cpp
 	logic/minecraft/RawLibrary.h
 	logic/minecraft/VersionBuilder.cpp
@@ -489,10 +491,6 @@ SET(MULTIMC_SOURCES
 	logic/minecraft/VersionFinal.h
 	logic/minecraft/VersionPatch.h
 
-	# Trivial operating system utilities
-	logic/minecraft/OpSys.h
-	logic/minecraft/OpSys.cpp
-
 	# Various base classes
 	logic/BaseInstaller.h
 	logic/BaseInstaller.cpp
diff --git a/depends/launcher/net/minecraft/Launcher.java b/depends/launcher/net/minecraft/Launcher.java
index c9b137e1..a53501ec 100644
--- a/depends/launcher/net/minecraft/Launcher.java
+++ b/depends/launcher/net/minecraft/Launcher.java
@@ -24,6 +24,7 @@ import java.awt.BorderLayout;
 import java.awt.Graphics;
 import java.applet.Applet;
 import java.applet.AppletStub;
+import java.net.MalformedURLException;
 
 public class Launcher extends Applet implements AppletStub
 {
@@ -130,13 +131,23 @@ public class Launcher extends Applet implements AppletStub
 
 	@Override
 	public URL getCodeBase() {
-		return wrappedApplet.getCodeBase();
+		try {
+			return new URL("http://www.minecraft.net/game/");
+		} catch (MalformedURLException e) {
+			e.printStackTrace();
+		}
+		return null;
 	}
 
 	@Override
 	public URL getDocumentBase()
 	{
-		return documentBase;
+		try {
+			return new URL("http://www.minecraft.net/game/");
+		} catch (MalformedURLException e) {
+			e.printStackTrace();
+		}
+		return null;
 	}
 
 	@Override
diff --git a/depends/launcher/org/multimc/onesix/OneSixLauncher.java b/depends/launcher/org/multimc/onesix/OneSixLauncher.java
index 4a0c9589..7bf71b3d 100644
--- a/depends/launcher/org/multimc/onesix/OneSixLauncher.java
+++ b/depends/launcher/org/multimc/onesix/OneSixLauncher.java
@@ -53,7 +53,7 @@ public class OneSixLauncher implements Launcher
 	{
 		libraries = params.all("cp");
 		extlibs = params.all("ext");
-		mcparams = params.all("param");
+		mcparams = params.allSafe("param", new ArrayList<String>() );
 		mainClass = params.firstSafe("mainClass", "net.minecraft.client.Minecraft");
 		appletClass = params.firstSafe("appletClass", "net.minecraft.client.MinecraftApplet");
 		mods = params.allSafe("mods", new ArrayList<String>());
diff --git a/gui/dialogs/NewInstanceDialog.cpp b/gui/dialogs/NewInstanceDialog.cpp
index 3192a1cd..41ae329c 100644
--- a/gui/dialogs/NewInstanceDialog.cpp
+++ b/gui/dialogs/NewInstanceDialog.cpp
@@ -47,7 +47,7 @@ NewInstanceDialog::NewInstanceDialog(QWidget *parent)
 		taskDlg->exec(loadTask);
 	}
 	*/
-	setSelectedVersion(MMC->minecraftlist()->getLatestStable());
+	setSelectedVersion(MMC->minecraftlist()->getLatestStable(), true);
 	InstIconKey = "infinity";
 	ui->iconButton->setIcon(MMC->icons()->getIcon(InstIconKey));
 }
@@ -63,13 +63,17 @@ void NewInstanceDialog::updateDialogState()
 		->setEnabled(!instName().isEmpty() && m_selectedVersion);
 }
 
-void NewInstanceDialog::setSelectedVersion(BaseVersionPtr version)
+void NewInstanceDialog::setSelectedVersion(BaseVersionPtr version, bool initial)
 {
 	m_selectedVersion = version;
 
 	if (m_selectedVersion)
 	{
 		ui->versionTextBox->setText(version->name());
+		if(ui->instNameTextBox->text().isEmpty() && !initial)
+		{
+			ui->instNameTextBox->setText(version->name());
+		}
 	}
 	else
 	{
diff --git a/gui/dialogs/NewInstanceDialog.h b/gui/dialogs/NewInstanceDialog.h
index 4357c28d..17045ec0 100644
--- a/gui/dialogs/NewInstanceDialog.h
+++ b/gui/dialogs/NewInstanceDialog.h
@@ -33,7 +33,7 @@ public:
 
 	void updateDialogState();
 
-	void setSelectedVersion(BaseVersionPtr version);
+	void setSelectedVersion(BaseVersionPtr version, bool initial = false);
 
 	void loadVersionList();
 
diff --git a/logic/OneSixInstance.cpp b/logic/OneSixInstance.cpp
index 2c67f7a9..574dfc69 100644
--- a/logic/OneSixInstance.cpp
+++ b/logic/OneSixInstance.cpp
@@ -224,7 +224,10 @@ bool OneSixInstance::prepareForLaunch(AuthSessionPtr account, QString &launchScr
 		}
 		launchScript += "cp " + versionsPath().absoluteFilePath(minecraftjarpath) + "\n";
 	}
-	launchScript += "mainClass " + version->mainClass + "\n";
+	if(!version->mainClass.isEmpty())
+	{
+		launchScript += "mainClass " + version->mainClass + "\n";
+	}
 	if(!version->appletClass.isEmpty())
 	{
 		launchScript += "appletClass " + version->appletClass + "\n";
diff --git a/logic/OneSixUpdate.cpp b/logic/OneSixUpdate.cpp
index beb293ff..f77913dc 100644
--- a/logic/OneSixUpdate.cpp
+++ b/logic/OneSixUpdate.cpp
@@ -62,12 +62,14 @@ void OneSixUpdate::executeTask()
 			emitFailed(tr("The specified Minecraft version is invalid. Choose a different one."));
 			return;
 		}
-		versionFileStart();
-	}
-	else
-	{
-		jarlibStart();
+		// builtins need no updates, so only update for Mojang
+		if(targetVersion->m_versionSource == MinecraftVersion::Mojang)
+		{
+			versionFileStart();
+			return;
+		}
 	}
+	jarlibStart();
 }
 
 void OneSixUpdate::versionFileStart()
diff --git a/logic/minecraft/MinecraftVersion.cpp b/logic/minecraft/MinecraftVersion.cpp
index a2e5a50a..2191e8af 100644
--- a/logic/minecraft/MinecraftVersion.cpp
+++ b/logic/minecraft/MinecraftVersion.cpp
@@ -1,2 +1,95 @@
 #include "MinecraftVersion.h"
+#include "VersionFinal.h"
 
+bool MinecraftVersion::usesLegacyLauncher()
+{
+	return m_traits.contains("legacyLaunch") || m_traits.contains("aplhaLaunch");
+}
+QString MinecraftVersion::descriptor()
+{
+	return m_descriptor;
+}
+QString MinecraftVersion::name()
+{
+	return m_name;
+}
+QString MinecraftVersion::typeString() const
+{
+	if (is_latest && is_snapshot)
+	{
+		return QObject::tr("Latest snapshot");
+	}
+	else if (is_latest)
+	{
+		return QObject::tr("Latest release");
+	}
+	else if (is_snapshot)
+	{
+		return QObject::tr("Snapshot");
+	}
+	else
+	{
+		return QObject::tr("Regular release");
+	}
+}
+bool MinecraftVersion::hasJarMods()
+{
+	return false;
+}
+bool MinecraftVersion::isVanilla()
+{
+	return true;
+}
+
+void MinecraftVersion::applyTo(VersionFinal *version)
+{
+	// FIXME: make this work.
+	if(m_versionSource != Builtin)
+	{
+		return;
+	}
+	if (!m_descriptor.isNull())
+	{
+		version->id = m_descriptor;
+	}
+	if (!m_mainClass.isNull())
+	{
+		version->mainClass = m_mainClass;
+	}
+	if (!m_appletClass.isNull())
+	{
+		version->appletClass = m_appletClass;
+	}
+	if (!m_processArguments.isNull())
+	{
+		version->vanillaProcessArguments = m_processArguments;
+		version->processArguments = m_processArguments;
+	}
+	if (!m_type.isNull())
+	{
+		version->type = m_type;
+	}
+	if (!m_releaseTimeString.isNull())
+	{
+		version->m_releaseTimeString = m_releaseTimeString;
+		version->m_releaseTime = m_releaseTime;
+	}
+	if (!m_updateTimeString.isNull())
+	{
+		version->m_updateTimeString = m_updateTimeString;
+		version->m_updateTime = m_updateTime;
+	}
+	version->traits.unite(m_traits);
+}
+int MinecraftVersion::getOrder()
+{
+	return order;
+}
+void MinecraftVersion::setOrder(int order)
+{
+	this->order = order;
+}
+QList<JarmodPtr> MinecraftVersion::getJarMods()
+{
+	return QList<JarmodPtr>();
+}
diff --git a/logic/minecraft/MinecraftVersion.h b/logic/minecraft/MinecraftVersion.h
index dab08bb1..6a1c54cb 100644
--- a/logic/minecraft/MinecraftVersion.h
+++ b/logic/minecraft/MinecraftVersion.h
@@ -15,16 +15,18 @@
 
 #pragma once
 
-#include "logic/BaseVersion.h"
-#include "VersionPatch.h"
 #include <QStringList>
 #include <QSet>
+#include <QDateTime>
+
+#include "logic/BaseVersion.h"
+#include "VersionPatch.h"
+#include "VersionFile.h"
+
+class VersionFinal;
 
 struct MinecraftVersion : public BaseVersion, public VersionPatch
 {
-	/// The version's timestamp - this is primarily used for sorting versions in a list.
-	qint64 timestamp;
-
 	/// The URL that this version will be downloaded from. maybe.
 	QString download_url;
 
@@ -34,16 +36,20 @@ struct MinecraftVersion : public BaseVersion, public VersionPatch
 	/// is this a snapshot?
 	bool is_snapshot = false;
 
-	/// is this a built-in version that comes with MultiMC?
-	bool is_builtin = false;
-	
+	/// where is this from?
+	enum VersionSource
+	{
+		Builtin,
+		Mojang
+	} m_versionSource = Builtin;
+
 	/// the human readable version name
 	QString m_name;
 
 	/// the version ID.
 	QString m_descriptor;
 
-	/// version traits. generally launcher business...
+	/// version traits. added by MultiMC
 	QSet<QString> m_traits;
 
 	/// The main class this version uses (if any, can be empty).
@@ -52,57 +58,47 @@ struct MinecraftVersion : public BaseVersion, public VersionPatch
 	/// The applet class this version uses (if any, can be empty).
 	QString m_appletClass;
 
-	bool usesLegacyLauncher()
-	{
-		return m_traits.contains("legacyLaunch") || m_traits.contains("aplhaLaunch");
-	}
-	
-	virtual QString descriptor() override
-	{
-		return m_descriptor;
-	}
+	/// The process arguments used by this version
+	QString m_processArguments;
 
-	virtual QString name() override
-	{
-		return m_name;
-	}
+	/// The type of this release
+	QString m_type;
 
-	virtual QString typeString() const override
+	/// the time this version was actually released by Mojang, as string and as QDateTime
+	QString m_releaseTimeString;
+	QDateTime m_releaseTime;
+
+	/// the time this version was last updated by Mojang, as string and as QDateTime
+	QString m_updateTimeString;
+	QDateTime m_updateTime;
+
+	/// order of this file... default = -2
+	int order = -2;
+
+	bool usesLegacyLauncher();
+	virtual QString descriptor() override;
+	virtual QString name() override;
+	virtual QString typeString() const override;
+	virtual bool hasJarMods() override;
+	virtual bool isVanilla() override;
+	virtual void applyTo(VersionFinal *version) override;
+	virtual int getOrder();
+	virtual void setOrder(int order);
+	virtual QList<JarmodPtr> getJarMods() override;
+	virtual QString getPatchID()
 	{
-		if (is_latest && is_snapshot)
-		{
-			return QObject::tr("Latest snapshot");
-		}
-		else if(is_latest)
-		{
-			return QObject::tr("Latest release");
-		}
-		else if(is_snapshot)
-		{
-			return QObject::tr("Snapshot");
-		}
-		else if(is_builtin)
-		{
-			return QObject::tr("Museum piece");
-		}
-		else
-		{
-			return QObject::tr("Regular release");
-		}
+		return "net.minecraft";
 	}
-	
-	virtual bool hasJarMods() override
+	virtual QString getPatchVersion()
 	{
-		return false;
+		return m_descriptor;
 	}
-	
-	virtual bool isVanilla() override
+	virtual QString getPatchName()
 	{
-		return true;
+		return "Minecraft";
 	}
-	
-	virtual void applyTo(VersionFinal *version)
+	virtual QString getPatchFilename()
 	{
-		// umm... what now?
-	}
+		return QString();
+	};
 };
diff --git a/logic/minecraft/MinecraftVersionList.cpp b/logic/minecraft/MinecraftVersionList.cpp
index cdf5fa77..1aa220e8 100644
--- a/logic/minecraft/MinecraftVersionList.cpp
+++ b/logic/minecraft/MinecraftVersionList.cpp
@@ -16,7 +16,8 @@
 #include "MinecraftVersionList.h"
 #include "MultiMC.h"
 #include "logic/net/URLConstants.h"
-#include <logic/MMCJson.h>
+#include "logic/MMCJson.h"
+#include "ParseUtils.h"
 
 #include <QtXml>
 
@@ -30,11 +31,6 @@
 
 #include <QtNetwork>
 
-inline QDateTime timeFromS3Time(QString str)
-{
-	return QDateTime::fromString(str, Qt::ISODate);
-}
-
 MinecraftVersionList::MinecraftVersionList(QObject *parent) : BaseVersionList(parent)
 {
 	loadBuiltinList();
@@ -64,7 +60,7 @@ static bool cmpVersions(BaseVersionPtr first, BaseVersionPtr second)
 {
 	auto left = std::dynamic_pointer_cast<MinecraftVersion>(first);
 	auto right = std::dynamic_pointer_cast<MinecraftVersion>(second);
-	return left->timestamp > right->timestamp;
+	return left->m_releaseTime > right->m_releaseTime;
 }
 
 void MinecraftVersionList::sortInternal()
@@ -79,55 +75,55 @@ void MinecraftVersionList::loadBuiltinList()
 	QFile filez(versionList.absoluteFilePath());
 	filez.open(QIODevice::ReadOnly);
 	auto data = filez.readAll();
-	
+
 	// parse the data as json
 	QJsonParseError jsonError;
 	QJsonDocument jsonDoc = QJsonDocument::fromJson(data, &jsonError);
 	QJsonObject root = jsonDoc.object();
-	
+
 	// parse all the versions
 	for (const auto version : MMCJson::ensureArray(root.value("versions")))
 	{
 		QJsonObject versionObj = version.toObject();
 		QString versionID = versionObj.value("id").toString("");
-		QString versionTimeStr = versionObj.value("releaseTime").toString("");
 		QString versionTypeStr = versionObj.value("type").toString("");
-		QSet<QString> traits;
-		if (versionObj.contains("+traits"))
+		if (versionID.isEmpty() || versionTypeStr.isEmpty())
 		{
-			for (auto traitVal : MMCJson::ensureArray(versionObj.value("+traits")))
-			{
-				traits.insert(MMCJson::ensureString(traitVal));
-			}
-		}
-		if (versionID.isEmpty() || versionTimeStr.isEmpty() || versionTypeStr.isEmpty())
-		{
-			// FIXME: log this somewhere
+			QLOG_ERROR() << "Parsed version is missing ID or type";
 			continue;
 		}
+
+		// Now, we construct the version object and add it to the list.
+		std::shared_ptr<MinecraftVersion> mcVersion(new MinecraftVersion());
+		mcVersion->m_name = mcVersion->m_descriptor = versionID;
+
 		// Parse the timestamp.
-		QDateTime versionTime = timeFromS3Time(versionTimeStr);
-		if (!versionTime.isValid())
+		try
+		{
+			parse_timestamp(versionObj.value("releaseTime").toString(""),
+							mcVersion->m_releaseTimeString, mcVersion->m_releaseTime);
+		}
+		catch (MMCError &e)
 		{
-			// FIXME: log this somewhere
+			QLOG_ERROR() << "Error while parsing version" << versionID << ":" << e.cause();
 			continue;
 		}
-		// Get the download URL.
-		QString dlUrl = "http://" + URLConstants::AWS_DOWNLOAD_VERSIONS + versionID + "/";
 
-		// main class and applet class
-		QString mainClass = versionObj.value("type").toString("");
-		QString appletClass = versionObj.value("type").toString("");
+		// Get the download URL.
+		mcVersion->download_url =
+			"http://" + URLConstants::AWS_DOWNLOAD_VERSIONS + versionID + "/";
 
-		// Now, we construct the version object and add it to the list.
-		std::shared_ptr<MinecraftVersion> mcVersion(new MinecraftVersion());
-		mcVersion->m_name = mcVersion->m_descriptor = versionID;
-		mcVersion->timestamp = versionTime.toMSecsSinceEpoch();
-		mcVersion->download_url = dlUrl;
-		mcVersion->is_builtin = true;
-		mcVersion->m_appletClass = appletClass;
-		mcVersion->m_mainClass = mainClass;
-		mcVersion->m_traits = traits;
+		mcVersion->m_versionSource = MinecraftVersion::Builtin;
+		mcVersion->m_appletClass = versionObj.value("appletClass").toString("");
+		mcVersion->m_mainClass = versionObj.value("mainClass").toString("");
+		mcVersion->m_processArguments = versionObj.value("processArguments").toString("legacy");
+		if (versionObj.contains("+traits"))
+		{
+			for (auto traitVal : MMCJson::ensureArray(versionObj.value("+traits")))
+			{
+				mcVersion->m_traits.insert(MMCJson::ensureString(traitVal));
+			}
+		}
 		m_vlist.append(mcVersion);
 	}
 }
@@ -265,62 +261,77 @@ void MCVListLoadTask::list_downloaded()
 		// Load the version info.
 		if (!version.isObject())
 		{
-			// FIXME: log this somewhere
+			QLOG_ERROR() << "Error while parsing version list : invalid JSON structure";
 			continue;
 		}
 		QJsonObject versionObj = version.toObject();
 		QString versionID = versionObj.value("id").toString("");
-		QString versionTimeStr = versionObj.value("releaseTime").toString("");
-		QString versionTypeStr = versionObj.value("type").toString("");
-		if (versionID.isEmpty() || versionTimeStr.isEmpty() || versionTypeStr.isEmpty())
+		if (versionID.isEmpty())
 		{
-			// FIXME: log this somewhere
+			QLOG_ERROR() << "Error while parsing version : version ID is missing";
 			continue;
 		}
+		// Get the download URL.
+		QString dlUrl = "http://" + URLConstants::AWS_DOWNLOAD_VERSIONS + versionID + "/";
 
-		// Parse the timestamp.
-		QDateTime versionTime = timeFromS3Time(versionTimeStr);
-		if (!versionTime.isValid())
-		{
-			// FIXME: log this somewhere
-			continue;
-		}
-		// OneSix or Legacy. use filter to determine type
-		if (versionTypeStr == "release")
-		{
-			is_latest = (versionID == latestReleaseID);
-			is_snapshot = false;
-		}
-		else if (versionTypeStr == "snapshot") // It's a snapshot... yay
-		{
-			is_latest = (versionID == latestSnapshotID);
-			is_snapshot = true;
-		}
-		else if (versionTypeStr == "old_alpha")
-		{
-			is_latest = false;
-			is_snapshot = false;
-		}
-		else if (versionTypeStr == "old_beta")
+		// Now, we construct the version object and add it to the list.
+		std::shared_ptr<MinecraftVersion> mcVersion(new MinecraftVersion());
+		mcVersion->m_name = mcVersion->m_descriptor = versionID;
+
+		try
 		{
-			is_latest = false;
-			is_snapshot = false;
+			// Parse the timestamps.
+			parse_timestamp(versionObj.value("releaseTime").toString(""),
+							mcVersion->m_releaseTimeString, mcVersion->m_releaseTime);
+
+			parse_timestamp(versionObj.value("time").toString(""),
+							mcVersion->m_updateTimeString, mcVersion->m_updateTime);
 		}
-		else
+		catch (MMCError &e)
 		{
-			// FIXME: log this somewhere
+			QLOG_ERROR() << "Error while parsing version" << versionID << ":" << e.cause();
 			continue;
 		}
-		// Get the download URL.
-		QString dlUrl = "http://" + URLConstants::AWS_DOWNLOAD_VERSIONS + versionID + "/";
 
-		// Now, we construct the version object and add it to the list.
-		std::shared_ptr<MinecraftVersion> mcVersion(new MinecraftVersion());
-		mcVersion->m_name = mcVersion->m_descriptor = versionID;
-		mcVersion->timestamp = versionTime.toMSecsSinceEpoch();
+		mcVersion->m_versionSource = MinecraftVersion::Builtin;
 		mcVersion->download_url = dlUrl;
-		mcVersion->is_latest = is_latest;
-		mcVersion->is_snapshot = is_snapshot;
+		{
+			QString versionTypeStr = versionObj.value("type").toString("");
+			if (versionTypeStr.isEmpty())
+			{
+				// FIXME: log this somewhere
+				continue;
+			}
+			// OneSix or Legacy. use filter to determine type
+			if (versionTypeStr == "release")
+			{
+				is_latest = (versionID == latestReleaseID);
+				is_snapshot = false;
+			}
+			else if (versionTypeStr == "snapshot") // It's a snapshot... yay
+			{
+				is_latest = (versionID == latestSnapshotID);
+				is_snapshot = true;
+			}
+			else if (versionTypeStr == "old_alpha")
+			{
+				is_latest = false;
+				is_snapshot = false;
+			}
+			else if (versionTypeStr == "old_beta")
+			{
+				is_latest = false;
+				is_snapshot = false;
+			}
+			else
+			{
+				// FIXME: log this somewhere
+				continue;
+			}
+			mcVersion->m_type = versionTypeStr;
+			mcVersion->is_latest = is_latest;
+			mcVersion->is_snapshot = is_snapshot;
+		}
 		tempList.append(mcVersion);
 	}
 	m_list->updateListData(tempList);
diff --git a/logic/minecraft/ParseUtils.cpp b/logic/minecraft/ParseUtils.cpp
new file mode 100644
index 00000000..67460ca4
--- /dev/null
+++ b/logic/minecraft/ParseUtils.cpp
@@ -0,0 +1,23 @@
+#include <QDateTime>
+#include <QString>
+#include "ParseUtils.h"
+#include <logic/MMCJson.h>
+
+QDateTime timeFromS3Time(QString str)
+{
+	return QDateTime::fromString(str, Qt::ISODate);
+}
+
+void parse_timestamp (const QString & raw, QString & save_here, QDateTime & parse_here)
+{
+	save_here = raw;
+	if (save_here.isEmpty())
+	{
+		throw JSONValidationError("The timestamp is empty!");
+	}
+	parse_here = timeFromS3Time(save_here);
+	if (!parse_here.isValid())
+	{
+		throw JSONValidationError("The timestamp not a valid timestamp!");
+	}
+}
diff --git a/logic/minecraft/ParseUtils.h b/logic/minecraft/ParseUtils.h
new file mode 100644
index 00000000..73cf526a
--- /dev/null
+++ b/logic/minecraft/ParseUtils.h
@@ -0,0 +1,14 @@
+#pragma once
+#include <QString>
+#include <QDateTime>
+
+/**
+ * parse the S3 timestamp in 'raw' and fill the forwarded variables.
+ * return true/false for success/failure
+ */
+void parse_timestamp (const QString &raw, QString &save_here, QDateTime &parse_here);
+
+/**
+ * take the timestamp used by S3 and turn it into QDateTime
+ */
+QDateTime timeFromS3Time(QString str);
diff --git a/logic/minecraft/VersionBuildError.h b/logic/minecraft/VersionBuildError.h
new file mode 100644
index 00000000..ae479851
--- /dev/null
+++ b/logic/minecraft/VersionBuildError.h
@@ -0,0 +1,58 @@
+#include "MMCError.h"
+
+class VersionBuildError : public MMCError
+{
+public:
+	VersionBuildError(QString cause) : MMCError(cause) {};
+	virtual ~VersionBuildError() noexcept
+	{
+	}
+};
+
+/**
+ * the base version file was meant for a newer version of the vanilla launcher than we support
+ */
+class LauncherVersionError : public VersionBuildError
+{
+public:
+	LauncherVersionError(int actual, int supported)
+		: VersionBuildError(QObject::tr(
+			  "The base version file of this instance was meant for a newer (%1) "
+			  "version of the vanilla launcher than this version of MultiMC supports (%2).")
+								.arg(actual)
+								.arg(supported)) {};
+	virtual ~LauncherVersionError() noexcept
+	{
+	}
+};
+
+/**
+ * some patch was intended for a different version of minecraft
+ */
+class MinecraftVersionMismatch : public VersionBuildError
+{
+public:
+	MinecraftVersionMismatch(QString fileId, QString mcVersion, QString parentMcVersion)
+		: VersionBuildError(QObject::tr("The patch %1 is for a different version of Minecraft "
+										"(%2) than that of the instance (%3).")
+								.arg(fileId)
+								.arg(mcVersion)
+								.arg(parentMcVersion)) {};
+	virtual ~MinecraftVersionMismatch() noexcept
+	{
+	}
+};
+
+/**
+ * files required for the version are not (yet?) present
+ */
+class VersionIncomplete : public VersionBuildError
+{
+public:
+	VersionIncomplete(QString missingPatch)
+		: VersionBuildError(QObject::tr("Version is incomplete: missing %1.")
+								.arg(missingPatch)) {};
+	virtual ~VersionIncomplete() noexcept
+	{
+	}
+};
\ No newline at end of file
diff --git a/logic/minecraft/VersionBuilder.cpp b/logic/minecraft/VersionBuilder.cpp
index 56eef424..d19c2877 100644
--- a/logic/minecraft/VersionBuilder.cpp
+++ b/logic/minecraft/VersionBuilder.cpp
@@ -23,12 +23,17 @@
 #include <QObject>
 #include <QDir>
 #include <QDebug>
+#include <qresource.h>
 #include <modutils.h>
 
+#include "MultiMC.h"
 #include "logic/minecraft/VersionBuilder.h"
 #include "logic/minecraft/VersionFinal.h"
 #include "logic/minecraft/OneSixRule.h"
+#include "logic/minecraft/VersionPatch.h"
 #include "logic/minecraft/VersionFile.h"
+#include "VersionBuildError.h"
+#include "MinecraftVersionList.h"
 
 #include "logic/OneSixInstance.h"
 #include "logic/MMCJson.h"
@@ -39,16 +44,17 @@ VersionBuilder::VersionBuilder()
 {
 }
 
-void VersionBuilder::build(VersionFinal *version, OneSixInstance *instance, const QStringList &external)
+void VersionBuilder::build(VersionFinal *version, OneSixInstance *instance,
+						   const QStringList &external)
 {
 	VersionBuilder builder;
 	builder.m_version = version;
 	builder.m_instance = instance;
-	builder.buildInternal(external);
+	builder.external_patches = external;
+	builder.buildInternal();
 }
 
-void VersionBuilder::readJsonAndApplyToVersion(VersionFinal *version,
-													 const QJsonObject &obj)
+void VersionBuilder::readJsonAndApplyToVersion(VersionFinal *version, const QJsonObject &obj)
 {
 	VersionBuilder builder;
 	builder.m_version = version;
@@ -56,88 +62,143 @@ void VersionBuilder::readJsonAndApplyToVersion(VersionFinal *version,
 	builder.readJsonAndApply(obj);
 }
 
-void VersionBuilder::buildInternal(const QStringList &external)
+void VersionBuilder::buildFromCustomJson()
 {
-	m_version->versionFiles.clear();
+	QLOG_INFO() << "Building version from custom.json within the instance.";
+	QLOG_INFO() << "Reading custom.json";
+	auto file = parseJsonFile(QFileInfo(instance_root.absoluteFilePath("custom.json")), false);
+	file->name = "custom.json";
+	file->filename = "custom.json";
+	file->fileId = "org.multimc.custom.json";
+	file->order = -1;
+	file->version = QString();
+	m_version->VersionPatches.append(file);
+	// QObject::tr("The version descriptors of this instance are not compatible with the
+	// current version of MultiMC"));
+	// QObject::tr("Error while applying %1. Please check MultiMC-0.log for more info.")
+	// some final touches
+	m_version->finalize();
+	return;
+}
 
-	QDir root(m_instance->instanceRoot());
-	QDir patches(root.absoluteFilePath("patches/"));
+void VersionBuilder::buildFromVersionJson()
+{
+	QLOG_INFO() << "Building version from version.json and patches within the instance.";
+	QLOG_INFO() << "Reading version.json";
+	auto file = parseJsonFile(QFileInfo(instance_root.absoluteFilePath("version.json")), false);
+	file->name = "Minecraft";
+	file->fileId = "org.multimc.version.json";
+	file->order = -1;
+	file->version = m_instance->intendedVersionId();
+	file->mcVersion = m_instance->intendedVersionId();
+	m_version->VersionPatches.append(file);
 
-	// if we do external files, do just those.
-	if (!external.isEmpty())
+	// load all patches, put into map for ordering, apply in the right order
+	readInstancePatches();
+
+	// some final touches
+	m_version->finalize();
+}
+
+void VersionBuilder::readInstancePatches()
+{
+	QDir patches(instance_root.absoluteFilePath("patches/"));
+	QMap<int, QPair<QString, VersionFilePtr>> files;
+	for (auto info : patches.entryInfoList(QStringList() << "*.json", QDir::Files))
 	{
-		int externalOrder = -1;
-		for (auto fileName : external)
+		QLOG_INFO() << "Reading" << info.fileName();
+		auto file = parseJsonFile(info, true);
+		if(file->fileId == "net.minecraft")
+			continue;
+		if(file->fileId == "org.lwjgl")
+			continue;
+		if (files.contains(file->order))
 		{
-			QLOG_INFO() << "Reading" << fileName;
-			auto file =
-				parseJsonFile(QFileInfo(fileName), false, fileName.endsWith("pack.json"));
-			file->name = QFileInfo(fileName).fileName();
-			file->fileId = "org.multimc.external." + file->name;
-			file->order = (externalOrder += 1);
-			file->version = QString();
-			file->mcVersion = QString();
-			m_version->versionFiles.append(file);
+			throw VersionBuildError(QObject::tr("%1 has the same order as %2")
+										.arg(file->fileId, files[file->order].second->fileId));
 		}
+		files.insert(file->order, qMakePair(info.fileName(), file));
 	}
-	// else, if there's custom json, we just do that.
-	else if (QFile::exists(root.absoluteFilePath("custom.json")))
-	{
-		QLOG_INFO() << "Reading custom.json";
-		auto file = parseJsonFile(QFileInfo(root.absoluteFilePath("custom.json")), false);
-		file->name = "custom.json";
-		file->filename = "custom.json";
-		file->fileId = "org.multimc.custom.json";
-		file->order = -1;
-		file->version = QString();
-		m_version->versionFiles.append(file);
-		// QObject::tr("The version descriptors of this instance are not compatible with the
-		// current version of MultiMC"));
-		// QObject::tr("Error while applying %1. Please check MultiMC-0.log for more info.")
+	for (auto order : files.keys())
+	{
+		auto &filePair = files[order];
+		m_version->VersionPatches.append(filePair.second);
 	}
-	// version.json -> patches/*.json -> user.json
-	else
-		do
-		{
-			// version.json
-			QLOG_INFO() << "Reading version.json";
-			auto file = parseJsonFile(QFileInfo(