11 files changed, 1399 insertions, 0 deletions
diff --git a/launcher/meta/BaseEntity.cpp b/launcher/meta/BaseEntity.cpp
new file mode 100644
index 00000000..5ff7a59a
--- /dev/null
+++ b/launcher/meta/BaseEntity.cpp
@@ -0,0 +1,168 @@
+/* Copyright 2015-2021 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 "BaseEntity.h"
+
+#include "Json.h"
+
+#include "net/Download.h"
+#include "net/HttpMetaCache.h"
+#include "net/NetJob.h"
+
+#include "Env.h"
+#include "Json.h"
+
+#include "BuildConfig.h"
+
+class ParsingValidator : public Net::Validator
+{
+public: /* con/des */
+    ParsingValidator(Meta::BaseEntity *entity) : m_entity(entity)
+    {
+    };
+    virtual ~ParsingValidator()
+    {
+    };
+
+public: /* methods */
+    bool init(QNetworkRequest &) override
+    {
+        return true;
+    }
+    bool write(QByteArray & data) override
+    {
+        this->data.append(data);
+        return true;
+    }
+    bool abort() override
+    {
+        return true;
+    }
+    bool validate(QNetworkReply &) override
+    {
+        auto fname = m_entity->localFilename();
+        try
+        {
+            auto doc = Json::requireDocument(data, fname);
+            auto obj = Json::requireObject(doc, fname);
+            m_entity->parse(obj);
+            return true;
+        }
+        catch (const Exception &e)
+        {
+            qWarning() << "Unable to parse response:" << e.cause();
+            return false;
+        }
+    }
+
+private: /* data */
+    QByteArray data;
+    Meta::BaseEntity *m_entity;
+};
+
+Meta::BaseEntity::~BaseEntity()
+{
+}
+
+QUrl Meta::BaseEntity::url() const
+{
+    return QUrl(BuildConfig.META_URL).resolved(localFilename());
+}
+
+bool Meta::BaseEntity::loadLocalFile()
+{
+    const QString fname = QDir("meta").absoluteFilePath(localFilename());
+    if (!QFile::exists(fname))
+    {
+        return false;
+    }
+    // TODO: check if the file has the expected checksum
+    try
+    {
+        auto doc = Json::requireDocument(fname, fname);
+        auto obj = Json::requireObject(doc, fname);
+        parse(obj);
+        return true;
+    }
+    catch (const Exception &e)
+    {
+        qDebug() << QString("Unable to parse file %1: %2").arg(fname, e.cause());
+        // just make sure it's gone and we never consider it again.
+        QFile::remove(fname);
+        return false;
+    }
+}
+
+void Meta::BaseEntity::load(Net::Mode loadType)
+{
+    // load local file if nothing is loaded yet
+    if(!isLoaded())
+    {
+        if(loadLocalFile())
+        {
+            m_loadStatus = LoadStatus::Local;
+        }
+    }
+    // if we need remote update, run the update task
+    if(loadType == Net::Mode::Offline || !shouldStartRemoteUpdate())
+    {
+        return;
+    }
+    NetJob *job = new NetJob(QObject::tr("Download of meta file %1").arg(localFilename()));
+    auto url = this->url();
+    auto entry = ENV.metacache()->resolveEntry("meta", localFilename());
+    entry->setStale(true);
+    auto dl = Net::Download::makeCached(url, entry);
+    /*
+     * The validator parses the file and loads it into the object.
+     * If that fails, the file is not written to storage.
+     */
+    dl->addValidator(new ParsingValidator(this));
+    job->addNetAction(dl);
+    m_updateStatus = UpdateStatus::InProgress;
+    m_updateTask.reset(job);
+    QObject::connect(job, &NetJob::succeeded, [&]()
+    {
+        m_loadStatus = LoadStatus::Remote;
+        m_updateStatus = UpdateStatus::Succeeded;
+        m_updateTask.reset();
+    });
+    QObject::connect(job, &NetJob::failed, [&]()
+    {
+        m_updateStatus = UpdateStatus::Failed;
+        m_updateTask.reset();
+    });
+    m_updateTask->start();
+}
+
+bool Meta::BaseEntity::isLoaded() const
+{
+    return m_loadStatus > LoadStatus::NotLoaded;
+}
+
+bool Meta::BaseEntity::shouldStartRemoteUpdate() const
+{
+    // TODO: version-locks and offline mode?
+    return m_updateStatus != UpdateStatus::InProgress;
+}
+
+shared_qobject_ptr<Task> Meta::BaseEntity::getCurrentTask()
+{
+    if(m_updateStatus == UpdateStatus::InProgress)
+    {
+        return m_updateTask;
+    }
+    return nullptr;
+}
diff --git a/launcher/meta/BaseEntity.h b/launcher/meta/BaseEntity.h
new file mode 100644
index 00000000..eff43879
--- /dev/null
+++ b/launcher/meta/BaseEntity.h
@@ -0,0 +1,67 @@
+/* Copyright 2015-2021 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 <QJsonObject>
+#include <QObject>
+#include "QObjectPtr.h"
+
+#include "net/Mode.h"
+
+class Task;
+namespace Meta
+{
+class BaseEntity
+{
+public: /* types */
+    using Ptr = std::shared_ptr<BaseEntity>;
+    enum class LoadStatus
+    {
+        NotLoaded,
+        Local,
+        Remote
+    };
+    enum class UpdateStatus
+    {
+        NotDone,
+        InProgress,
+        Failed,
+        Succeeded
+    };
+
+public:
+    virtual ~BaseEntity();
+
+    virtual void parse(const QJsonObject &obj) = 0;
+
+    virtual QString localFilename() const = 0;
+    virtual QUrl url() const;
+
+    bool isLoaded() const;
+    bool shouldStartRemoteUpdate() const;
+
+    void load(Net::Mode loadType);
+    shared_qobject_ptr<Task> getCurrentTask();
+
+protected: /* methods */
+    bool loadLocalFile();
+
+private:
+    LoadStatus m_loadStatus = LoadStatus::NotLoaded;
+    UpdateStatus m_updateStatus = UpdateStatus::NotDone;
+    shared_qobject_ptr<Task> m_updateTask;
+};
+}
diff --git a/launcher/meta/Index.cpp b/launcher/meta/Index.cpp
new file mode 100644
index 00000000..6802470d
--- /dev/null
+++ b/launcher/meta/Index.cpp
@@ -0,0 +1,148 @@
+/* Copyright 2015-2021 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 "Index.h"
+
+#include "VersionList.h"
+#include "JsonFormat.h"
+
+namespace Meta
+{
+Index::Index(QObject *parent)
+    : QAbstractListModel(parent)
+{
+}
+Index::Index(const QVector<VersionListPtr> &lists, QObject *parent)
+    : QAbstractListModel(parent), m_lists(lists)
+{
+    for (int i = 0; i < m_lists.size(); ++i)
+    {
+        m_uids.insert(m_lists.at(i)->uid(), m_lists.at(i));
+        connectVersionList(i, m_lists.at(i));
+    }
+}
+
+QVariant Index::data(const QModelIndex &index, int role) const
+{
+    if (index.parent().isValid() || index.row() < 0 || index.row() >= m_lists.size())
+    {
+        return QVariant();
+    }
+
+    VersionListPtr list = m_lists.at(index.row());
+    switch (role)
+    {
+    case Qt::DisplayRole:
+        switch (index.column())
+        {
+        case 0: return list->humanReadable();
+        default: break;
+        }
+    case UidRole: return list->uid();
+    case NameRole: return list->name();
+    case ListPtrRole: return QVariant::fromValue(list);
+    }
+    return QVariant();
+}
+int Index::rowCount(const QModelIndex &parent) const
+{
+    return m_lists.size();
+}
+int Index::columnCount(const QModelIndex &parent) const
+{
+    return 1;
+}
+QVariant Index::headerData(int section, Qt::Orientation orientation, int role) const
+{
+    if (orientation == Qt::Horizontal && role == Qt::DisplayRole && section == 0)
+    {
+        return tr("Name");
+    }
+    else
+    {
+        return QVariant();
+    }
+}
+
+bool Index::hasUid(const QString &uid) const
+{
+    return m_uids.contains(uid);
+}
+
+VersionListPtr Index::get(const QString &uid)
+{
+    VersionListPtr out = m_uids.value(uid, nullptr);
+    if(!out)
+    {
+        out = std::make_shared<VersionList>(uid);
+        m_uids[uid] = out;
+    }
+    return out;
+}
+
+VersionPtr Index::get(const QString &uid, const QString &version)
+{
+    auto list = get(uid);
+    return list->getVersion(version);
+}
+
+void Index::parse(const QJsonObject& obj)
+{
+    parseIndex(obj, this);
+}
+
+void Index::merge(const std::shared_ptr<Index> &other)
+{
+    const QVector<VersionListPtr> lists = std::dynamic_pointer_cast<Index>(other)->m_lists;
+    // initial load, no need to merge
+    if (m_lists.isEmpty())
+    {
+        beginResetModel();
+        m_lists = lists;
+        for (int i = 0; i < lists.size(); ++i)
+        {
+            m_uids.insert(lists.at(i)->uid(), lists.at(i));
+            connectVersionList(i, lists.at(i));
+        }
+        endResetModel();
+    }
+    else
+    {
+        for (const VersionListPtr &list : lists)
+        {
+            if (m_uids.contains(list->uid()))
+            {
+                m_uids[list->uid()]->mergeFromIndex(list);
+            }
+            else
+            {
+                beginInsertRows(QModelIndex(), m_lists.size(), m_lists.size());
+                connectVersionList(m_lists.size(), list);
+                m_lists.append(list);
+                m_uids.insert(list->uid(), list);
+                endInsertRows();
+            }
+        }
+    }
+}
+
+void Index::connectVersionList(const int row, const VersionListPtr &list)
+{
+    connect(list.get(), &VersionList::nameChanged, this, [this, row]()
+    {
+        emit dataChanged(index(row), index(row), QVector<int>() << Qt::DisplayRole);
+    });
+}
+}
diff --git a/launcher/meta/Index.h b/launcher/meta/Index.h
new file mode 100644
index 00000000..d33ab0c8
--- /dev/null
+++ b/launcher/meta/Index.h
@@ -0,0 +1,69 @@
+/* Copyright 2015-2021 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 <QAbstractListModel>
+#include <memory>
+
+#include "BaseEntity.h"
+
+class Task;
+
+namespace Meta
+{
+using VersionListPtr = std::shared_ptr<class VersionList>;
+using VersionPtr = std::shared_ptr<class Version>;
+
+class Index : public QAbstractListModel, public BaseEntity
+{
+    Q_OBJECT
+public:
+    explicit Index(QObject *parent = nullptr);
+    explicit Index(const QVector<VersionListPtr> &lists, QObject *parent = nullptr);
+
+    enum
+    {
+        UidRole = Qt::UserRole,
+        NameRole,
+        ListPtrRole
+    };
+
+    QVariant data(const QModelIndex &index, int role) const override;
+    int rowCount(const QModelIndex &parent) const override;
+    int columnCount(const QModelIndex &parent) const override;
+    QVariant headerData(int section, Qt::Orientation orientation, int role) const override;
+
+    QString localFilename() const override { return "index.json"; }
+
+    // queries
+    VersionListPtr get(const QString &uid);
+    VersionPtr get(const QString &uid, const QString &version);
+    bool hasUid(const QString &uid) const;
+
+    QVector<VersionListPtr> lists() const { return m_lists; }
+
+public: // for usage by parsers only
+    void merge(const std::shared_ptr<Index> &other);
+    void parse(const QJsonObject &obj) override;
+
+private:
+    QVector<VersionListPtr> m_lists;
+    QHash<QString, VersionListPtr> m_uids;
+
+    void connectVersionList(const int row, const VersionListPtr &list);
+};
+}
+
diff --git a/launcher/meta/Index_test.cpp b/launcher/meta/Index_test.cpp
new file mode 100644
index 00000000..b0892070
--- /dev/null
+++ b/launcher/meta/Index_test.cpp
@@ -0,0 +1,44 @@
+#include <QTest>
+#include "TestUtil.h"
+
+#include "meta/Index.h"
+#include "meta/VersionList.h"
+#include "Env.h"
+
+class IndexTest : public QObject
+{
+    Q_OBJECT
+private
+slots:
+    void test_isProvidedByEnv()
+    {
+        QVERIFY(ENV.metadataIndex());
+        QCOMPARE(ENV.metadataIndex(), ENV.metadataIndex());
+    }
+
+    void test_hasUid_and_getList()
+    {
+        Meta::Index windex({std::make_shared<Meta::VersionList>("list1"), std::make_shared<Meta::VersionList>("list2"), std::make_shared<Meta::VersionList>("list3")});
+        QVERIFY(windex.hasUid("list1"));
+        QVERIFY(!windex.hasUid("asdf"));
+        QVERIFY(windex.get("list2") != nullptr);
+        QCOMPARE(windex.get("list2")->uid(), QString("list2"));
+        QVERIFY(windex.get("adsf") != nullptr);
+    }
+
+    void test_merge()
+    {
+        Meta::Index windex({std::make_shared<Meta::VersionList>("list1"), std::make_shared<Meta::VersionList>("list2"), std::make_shared<Meta::VersionList>("list3")});
+        QCOMPARE(windex.lists().size(), 3);
+        windex.merge(std::shared_ptr<Meta::Index>(new Meta::Index({std::make_shared<Meta::VersionList>("list1"), std::make_shared<Meta::VersionList>("list2"), std::make_shared<Meta::VersionList>("list3")})));
+        QCOMPARE(windex.lists().size(), 3);
+        windex.merge(std::shared_ptr<Meta::Index>(new Meta::Index({std::make_shared<Meta::VersionList>("list4"), std::make_shared<Meta::VersionList>("list2"), std::make_shared<Meta::VersionList>("list5")})));
+        QCOMPARE(windex.lists().size(), 5);
+        windex.merge(std::shared_ptr<Meta::Index>(new Meta::Index({std::make_shared<Meta::VersionList>("list6")})));
+        QCOMPARE(windex.lists().size(), 6);
+    }
+};
+
+QTEST_GUILESS_MAIN(IndexTest)
+
+#include "Index_test.moc"
diff --git a/launcher/meta/JsonFormat.cpp b/launcher/meta/JsonFormat.cpp
new file mode 100644
index 00000000..796da4bb
--- /dev/null
+++ b/launcher/meta/JsonFormat.cpp
@@ -0,0 +1,218 @@
+/* Copyright 2015-2021 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 "JsonFormat.h"
+
+// FIXME: remove this from here... somehow
+#include "minecraft/OneSixVersionFormat.h"
+#include "Json.h"
+
+#include "Index.h"
+#include "Version.h"
+#include "VersionList.h"
+
+using namespace Json;
+
+namespace Meta
+{
+
+MetadataVersion currentFormatVersion()
+{
+    return MetadataVersion::InitialRelease;
+}
+
+// Index
+static std::shared_ptr<Index> parseIndexInternal(const QJsonObject &obj)
+{
+    const QVector<QJsonObject> objects = requireIsArrayOf<QJsonObject>(obj, "packages");
+    QVector<VersionListPtr> lists;
+    lists.reserve(objects.size());
+    std::transform(objects.begin(), objects.end(), std::back_inserter(lists), [](const QJsonObject &obj)
+    {
+        VersionListPtr list = std::make_shared<VersionList>(requireString(obj, "uid"));
+        list->setName(ensureString(obj, "name", QString()));
+        return list;
+    });
+    return std::make_shared<Index>(lists);
+}
+
+// Version
+static VersionPtr parseCommonVersion(const QString &uid, const QJsonObject &obj)
+{
+    VersionPtr version = std::make_shared<Version>(uid, requireString(obj, "version"));
+    version->setTime(QDateTime::fromString(requireString(obj, "releaseTime"), Qt::ISODate).toMSecsSinceEpoch() / 1000);
+    version->setType(ensureString(obj, "type", QString()));
+    version->setRecommended(ensureBoolean(obj, QString("recommended"), false));
+    version->setVolatile(ensureBoolean(obj, QString("volatile"), false));
+    RequireSet requires, conflicts;
+    parseRequires(obj, &requires, "requires");
+    parseRequires(obj, &conflicts, "conflicts");
+    version->setRequires(requires, conflicts);
+    return version;
+}
+
+static std::shared_ptr<Version> parseVersionInternal(const QJsonObject &obj)
+{
+    VersionPtr version = parseCommonVersion(requireString(obj, "uid"), obj);
+
+    version->setData(OneSixVersionFormat::versionFileFromJson(QJsonDocument(obj),
+                                           QString("%1/%2.json").arg(version->uid(), version->version()),
+                                           obj.contains("order")));
+    return version;
+}
+
+// Version list / package
+static std::shared_ptr<VersionList> parseVersionListInternal(const QJsonObject &obj)
+{
+    const QString uid = requireString(obj, "uid");
+
+    const QVector<QJsonObject> versionsRaw = requireIsArrayOf<QJsonObject>(obj, "versions");
+    QVector<VersionPtr> versions;
+    versions.reserve(versionsRaw.size());
+    std::transform(versionsRaw.begin(), versionsRaw.end(), std::back_inserter(versions), [uid](const QJsonObject &vObj)
+    {
+        auto version = parseCommonVersion(uid, vObj);
+        version->setProvidesRecommendations();
+        return version;
+    });
+
+    VersionListPtr list = std::make_shared<VersionList>(uid);
+    list->setName(ensureString(obj, "name", QString()));
+    list->setVersions(versions);
+    return list;
+}
+
+
+MetadataVersion parseFormatVersion(const QJsonObject &obj, bool required)
+{
+    if (!obj.contains("formatVersion"))
+    {
+        if(required)
+        {
+            return MetadataVersion::Invalid;
+        }
+        return MetadataVersion::InitialRelease;
+    }
+    if (!obj.value("formatVersion").isDouble())
+    {
+        return MetadataVersion::Invalid;
+    }
+    switch(obj.value("formatVersion").toInt())
+    {
+        case 0:
+        case 1:
+            return MetadataVersion::InitialRelease;
+        default:
+            return MetadataVersion::Invalid;
+    }
+}
+
+void serializeFormatVersion(QJsonObject& obj, Meta::MetadataVersion version)
+{
+    if(version == MetadataVersion::Invalid)
+    {
+        return;
+    }
+    obj.insert("formatVersion", int(version));
+}
+
+void parseIndex(const QJsonObject &obj, Index *ptr)
+{
+    const MetadataVersion version = parseFormatVersion(obj);
+    switch (version)
+    {
+    case MetadataVersion::InitialRelease:
+        ptr->merge(parseIndexInternal(obj));
+        break;
+    case MetadataVersion::Invalid:
+        throw ParseException(QObject::tr("Unknown format version!"));
+    }
+}
+
+void parseVersionList(const QJsonObject &obj, VersionList *ptr)
+{
+    const MetadataVersion version = parseFormatVersion(obj);
+    switch (version)
+    {
+    case MetadataVersion::InitialRelease:
+        ptr->merge(parseVersionListInternal(obj));
+        break;
+    case MetadataVersion::Invalid:
+        throw ParseException(QObject::tr("Unknown format version!"));
+    }
+}
+
+void parseVersion(const QJsonObject &obj, Version *ptr)
+{
+    const MetadataVersion version = parseFormatVersion(obj);
+    switch (version)
+    {
+    case MetadataVersion::InitialRelease:
+        ptr->merge(parseVersionInternal(obj));
+        break;
+    case MetadataVersion::Invalid:
+        throw ParseException(QObject::tr("Unknown format version!"));
+    }
+}
+
+/*
+[
+{"uid":"foo", "equals":"version"}
+]
+*/
+void parseRequires(const QJsonObject& obj, RequireSet* ptr, const char * keyName)
+{
+    if(obj.contains(keyName))
+    {
+        QSet<QString> requires;
+        auto reqArray = requireArray(obj, keyName);
+        auto iter = reqArray.begin();
+        while(iter != reqArray.end())
+        {
+            auto reqObject = requireObject(*iter);
+            auto uid = requireString(reqObject, "uid");
+            auto equals = ensureString(reqObject, "equals", QString());
+            auto suggests = ensureString(reqObject, "suggests", QString());
+            ptr->insert({uid, equals, suggests});
+            iter++;
+        }
+    }
+}
+void serializeRequires(QJsonObject& obj, RequireSet* ptr, const char * keyName)
+{
+    if(!ptr || ptr->empty())
+    {
+        return;
+    }
+    QJsonArray arrOut;
+    for(auto &iter: *ptr)
+    {
+        QJsonObject reqOut;
+        reqOut.insert("uid", iter.uid);
+        if(!iter.equalsVersion.isEmpty())
+        {
+            reqOut.insert("equals", iter.equalsVersion);
+        }
+        if(!iter.suggests.isEmpty())
+        {
+            reqOut.insert("suggests", iter.suggests);
+        }
+        arrOut.append(reqOut);
+    }
+    obj.insert(keyName, arrOut);
+}
+
+}
+
diff --git a/launcher/meta/JsonFormat.h b/launcher/meta/JsonFormat.h
new file mode 100644
index 00000000..93217b7e
--- /dev/null
+++ b/launcher/meta/JsonFormat.h
@@ -0,0 +1,83 @@
+/* Copyright 2015-2021 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 <QJsonObject>
+#include <memory>
+
+#include "Exception.h"
+#include "meta/BaseEntity.h"
+#include <set>
+
+namespace Meta
+{
+class Index;
+class Version;
+class VersionList;
+
+enum class MetadataVersion
+{
+    Invalid = -1,
+    InitialRelease = 1
+};
+
+class ParseException : public Exception
+{
+public:
+    using Exception::Exception;
+};
+struct Require
+{
+    bool operator==(const Require & rhs) const
+    {
+        return uid == rhs.uid;
+    }
+    bool operator<(const Require & rhs) const
+    {
+        return uid < rhs.uid;
+    }
+    bool deepEquals(const Require & rhs) const
+    {
+        return uid == rhs.uid
+            && equalsVersion == rhs.equalsVersion
+            && suggests == rhs.suggests;
+    }
+    QString uid;
+    QString equalsVersion;
+    QString suggests;
+};
+
+inline Q_DECL_PURE_FUNCTION uint qHash(const Require &key, uint seed = 0) Q_DECL_NOTHROW
+{
+    return qHash(key.uid, seed);
+}
+
+using RequireSet = std::set<Require>;
+
+void parseIndex(const QJsonObject &obj, Index *ptr);
+void parseVersion(const QJsonObject &obj, Version *ptr);
+void parseVersionList(const QJsonObject &obj, VersionList *ptr);
+
+MetadataVersion parseFormatVersion(const QJsonObject &obj, bool required = true);
+void serializeFormatVersion(QJsonObject &obj, MetadataVersion version);
+
+// FIXME: this has a different shape than the others...FIX IT!?
+void parseRequires(const QJsonObject &obj, RequireSet * ptr, const char * keyName = "requires");
+void serializeRequires(QJsonObject & objOut, RequireSet* ptr, const char * keyName = "requires");
+MetadataVersion currentFormatVersion();
+}
+
+Q_DECLARE_METATYPE(std::set<Meta::Require>)
diff --git a/launcher/meta/Version.cpp b/launcher/meta/Version.cpp
new file mode 100644
index 00000000..a8dc3169
--- /dev/null
+++ b/launcher/meta/Version.cpp
@@ -0,0 +1,140 @@
+/* Copyright 2015-2021 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 "Version.h"
+
+#include <QDateTime>
+
+#include "JsonFormat.h"
+#include "minecraft/PackProfile.h"
+
+Meta::Version::Version(const QString &uid, const QString &version)
+    : BaseVersion(), m_uid(uid), m_version(version)
+{
+}
+
+Meta::Version::~Version()
+{
+}
+
+QString Meta::Version::descriptor()
+{
+    return m_version;
+}
+QString Meta::Version::name()
+{
+    if(m_data)
+        return m_data->name;
+    return m_uid;
+}
+QString Meta::Version::typeString() const
+{
+    return m_type;
+}
+
+QDateTime Meta::Version::time() const
+{
+    return QDateTime::fromMSecsSinceEpoch(m_time * 1000, Qt::UTC);
+}
+
+void Meta::Version::parse(const QJsonObject& obj)
+{
+    parseVersion(obj, this);
+}
+
+void Meta::Version::mergeFromList(const Meta::VersionPtr& other)
+{
+    if(other->m_providesRecommendations)
+    {
+        if(m_recommended != other->m_recommended)
+        {
+            setRecommended(other->m_recommended);
+        }
+    }
+    if (m_type != other->m_type)
+    {
+        setType(other->m_type);
+    }
+    if (m_time != other->m_time)
+    {
+        setTime(other->m_time);
+    }
+    if (m_requires != other->m_requires)
+    {
+        m_requires = other->m_requires;
+    }
+    if (m_conflicts != other->m_conflicts)
+    {
+        m_conflicts = other->m_conflicts;
+    }
+    if(m_volatile != other->m_volatile)
+    {
+        setVolatile(other->m_volatile);
+    }
+}
+
+void Meta::Version::merge(const VersionPtr &other)
+{
+    mergeFromList(other);
+    if(other->m_data)
+    {
+        setData(other->m_data);
+    }
+}
+
+QString Meta::Version::localFilename() const
+{
+    return m_uid + '/' + m_version + ".json";
+}
+
+void Meta::Version::setType(const QString &type)
+{
+    m_type = type;
+    emit typeChanged();
+}
+
+void Meta::Version::setTime(const qint64 time)
+{
+    m_time = time;
+    emit timeChanged();
+}
+
+void Meta::Version::setRequires(const Meta::RequireSet &requires, const Meta::RequireSet &conflicts)
+{
+    m_requires = requires;
+    m_conflicts = conflicts;
+    emit requiresChanged();
+}
+
+void Meta::Version::setVolatile(bool volatile_)
+{
+    m_volatile = volatile_;
+}
+
+
+void Meta::Version::setData(const VersionFilePtr &data)
+{
+    m_data = data;
+}
+
+void Meta::Version::setProvidesRecommendations()
+{
+    m_providesRecommendations = true;
+}
+
+void Meta::Version::setRecommended(bool recommended)
+{
+    m_recommended = recommended;
+}
diff --git a/launcher/meta/Version.h b/launcher/meta/Version.h
new file mode 100644
index 00000000..dea8dc8a
--- /dev/null
+++ b/launcher/meta/Version.h
@@ -0,0 +1,116 @@
+/* Copyright 2015-2021 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 "BaseVersion.h"
+
+#include <QJsonObject>
+#include <QStringList>
+#include <QVector>
+#include <memory>
+
+#include "minecraft/VersionFile.h"
+
+#include "BaseEntity.h"
+
+#include "JsonFormat.h"
+
+namespace Meta
+{
+using VersionPtr = std::shared_ptr<class Version>;
+
+class Version : public QObject, public BaseVersion, public BaseEntity
+{
+    Q_OBJECT
+
+public: /* con/des */
+    explicit Version(const QString &uid, const QString &version);
+    virtual ~Version();
+
+    QString descriptor() override;
+    QString name() override;
+    QString typeString() const override;
+
+    QString uid() const
+    {
+        return m_uid;
+    }
+    QString version() const
+    {
+        return m_version;
+    }
+    QString type() const
+    {
+        return m_type;
+    }
+    QDateTime time() const;
+    qint64 rawTime() const
+    {
+        return m_time;
+    }
+    const Meta::RequireSet &requires() const
+    {
+        return m_requires;
+    }
+    VersionFilePtr data() const
+    {
+        return m_data;
+    }
+    bool isRecommended() const
+    {
+        return m_recommended;
+    }
+    bool isLoaded() const
+    {
+        return m_data != nullptr;
+    }
+
+    void merge(const VersionPtr &other);
+    void mergeFromList(const VersionPtr &other);
+    void parse(const QJsonObject &obj) override;
+
+    QString localFilename() const override;
+
+public: // for usage by format parsers only
+    void setType(const QString &type);
+    void setTime(const qint64 time);
+    void setRequires(const Meta::RequireSet &requires, const Meta::RequireSet &conflicts);
+    void setVolatile(bool volatile_);
+    void setRecommended(bool recommended);
+    void setProvidesRecommendations();
+    void setData(const VersionFilePtr &data);
+
+signals:
+    void typeChanged();
+    void timeChanged();
+    void requiresChanged();
+
+private:
+    bool m_providesRecommendations = false;
+    bool m_recommended = false;
+    QString m_name;
+    QString m_uid;
+    QString m_version;
+    QString m_type;
+    qint64 m_time = 0;
+    Meta::RequireSet m_requires;
+    Meta::RequireSet m_conflicts;
+    bool m_volatile = false;
+    VersionFilePtr m_data;
+};
+}
+
+Q_DECLARE_METATYPE(Meta::VersionPtr)
diff --git a/launcher/meta/VersionList.cpp b/launcher/meta/VersionList.cpp
new file mode 100644
index 00000000..607007eb
--- /dev/null
+++ b/launcher/meta/VersionList.cpp
@@ -0,0 +1,245 @@
+/* Copyright 2015-2021 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 "VersionList.h"
+
+#include <QDateTime>
+
+#include "Version.h"
+#include "JsonFormat.h"
+#include "Version.h"
+
+namespace Meta
+{
+VersionList::VersionList(const QString &uid, QObject *parent)
+    : BaseVersionList(parent), m_uid(uid)
+{
+    setObjectName("Version list: " + uid);
+}
+
+shared_qobject_ptr<Task> VersionList::getLoadTask()
+{
+    load(Net::Mode::Online);
+    return getCurrentTask();
+}
+
+bool VersionList::isLoaded()
+{
+    return BaseEntity::isLoaded();
+}
+
+const BaseVersionPtr VersionList::at(int i) const
+{
+    return m_versions.at(i);
+}
+int VersionList::count() const
+{
+    return m_versions.size();
+}
+
+void VersionList::sortVersions()
+{
+    beginResetModel();
+    std::sort(m_versions.begin(), m_versions.end(), [](const VersionPtr &a, const VersionPtr &b)
+    {
+        return *a.get() < *b.get();
+    });
+    endResetModel();
+}
+
+QVariant VersionList::data(const QModelIndex &index, int role) const
+{
+    if (!index.isValid() || index.row() < 0 || index.row() >= m_versions.size() || index.parent().isValid())
+    {
+        return QVariant();
+    }
+
+    VersionPtr version = m_versions.at(index.row());
+
+    switch (role)
+    {
+    case VersionPointerRole: return QVariant::fromValue(std::dynamic_pointer_cast<BaseVersion>(version));
+    case VersionRole:
+    case VersionIdRole:
+        return version->version();
+    case ParentVersionRole:
+    {
+        // FIXME: HACK: this should be generic and be replaced by something else. Anything that is a hard 'equals' dep is a 'parent uid'.
+        auto & reqs = version->requires();
+        auto iter = std::find_if(reqs.begin(), reqs.end(), [](const Require & req)
+        {
+            return req.uid == "net.minecraft";
+        });
+        if (iter != reqs.end())
+        {
+            return (*iter).equalsVersion;
+        }
+        return QVariant();
+    }
+    case TypeRole: return version->type();
+
+    case UidRole: return version->uid();
+    case TimeRole: return version->time();
+    case RequiresRole: return QVariant::fromValue(version->requires());
+    case SortRole: return version->rawTime();
+    case VersionPtrRole: return QVariant::fromValue(version);
+    case RecommendedRole: return version->isRecommended();
+    // FIXME: this should be determined in whatever view/proxy is used...
+    // case LatestRole: return version == getLatestStable();
+    default: return QVariant();
+    }
+}
+
+BaseVersionList::RoleList VersionList::providesRoles() const
+{
+    return {VersionPointerRole, VersionRole, VersionIdRole, ParentVersionRole,
+                TypeRole, UidRole, TimeRole, RequiresRole, SortRole,
+                RecommendedRole, LatestRole, VersionPtrRole};
+}
+
+QHash<int, QByteArray> VersionList::roleNames() const
+{
+    QHash<int, QByteArray> roles = BaseVersionList::roleNames();
+    roles.insert(UidRole, "uid");
+    roles.insert(TimeRole, "time");
+    roles.insert(SortRole, "sort");
+    roles.insert(RequiresRole, "requires");
+    return roles;
+}
+
+QString VersionList::localFilename() const
+{
+    return m_uid + "/index.json";
+}
+
+QString VersionList::humanReadable() const
+{
+    return m_name.isEmpty() ? m_uid : m_name;
+}
+
+VersionPtr VersionList::getVersion(const QString &version)
+{
+    VersionPtr out = m_lookup.value(version, nullptr);
+    if(!out)
+    {
+        out = std::make_shared<Version>(m_uid, version);
+        m_lookup[version] = out;
+    }
+    return out;
+}
+
+void VersionList::setName(const QString &name)
+{
+    m_name = name;
+    emit nameChanged(name);
+}
+
+void VersionList::setVersions(const QVector<VersionPtr> &versions)
+{
+    beginResetModel();
+    m_versions = versions;
+    std::sort(m_versions.begin(), m_versions.end(), [](const VersionPtr &a, const VersionPtr &b)
+    {
+        return a->rawTime() > b->rawTime();
+    });
+    for (int i = 0; i < m_versions.size(); ++i)
+    {
+        m_lookup.insert(m_versions.at(i)->version(), m_versions.at(i));
+        setupAddedVersion(i, m_versions.at(i));
+    }
+
+    // FIXME: this is dumb, we have 'recommended' as part of the metadata already...
+    auto recommendedIt = std::find_if(m_versions.constBegin(), m_versions.constEnd(), [](const VersionPtr &ptr) { return ptr->type() == "release"; });
+    m_recommended = recommendedIt == m_versions.constEnd() ? nullptr : *recommendedIt;
+    endResetModel();
+}
+
+void VersionList::parse(const QJsonObject& obj)
+{
+    parseVersionList(obj, this);
+}
+
+// FIXME: this is dumb, we have 'recommended' as part of the metadata already...
+static const Meta::VersionPtr &getBetterVersion(const Meta::VersionPtr &a, const Meta::VersionPtr &b)
+{
+    if(!a)
+        return b;
+    if(!b)
+        return a;
+    if(a->type() == b->type())
+    {
+        // newer of same type wins
+        return (a->rawTime() > b->rawTime() ? a : b);
+    }
+    // 'release' type wins
+    return (a->type() == "release" ? a : b);
+}
+
+void VersionList::mergeFromIndex(const VersionListPtr &other)
+{
+    if (m_name != other->m_name)
+    {
+        setName(other->m_name);
+    }
+}
+
+void VersionList::merge(const VersionListPtr &other)
+{
+    if (m_name != other->m_name)
+    {
+        setName(other->m_name);
+    }
+
+    // TODO: do not reset the whole model. maybe?
+    beginResetModel();
+    m_versions.clear();
+    if(other->m_versions.isEmpty())
+    {
+        qWarning() << "Empty list loaded ...";
+    }
+    for (const VersionPtr &version : other->m_versions)
+    {
+        // we already have the version. merge the contents
+        if (m_lookup.contains(version->version()))
+        {
+            m_lookup.value(version->version())->mergeFromList(version);
+        }
+        else
+        {
+            m_lookup.insert(version->uid(), version);
+        }
+        // connect it.
+        setupAddedVersion(m_versions.size(), version);
+        m_versions.append(version);
+        m_recommended = getBetterVersion(m_recommended, version);
+    }
+    endResetModel();
+}
+
+void VersionList::setupAddedVersion(const int row, const VersionPtr &version)
+{
+    // FIXME: do not disconnect from everythin, disconnect only the lambdas here
+    version->disconnect();
+    connect(version.get(), &Version::requiresChanged, this, [this, row]() { emit dataChanged(index(row), index(row), QVector<int>() << RequiresRole); });
+    connect(version.get(), &Version::timeChanged, this, [this, row]() { emit dataChanged(index(row), index(row), QVector<int>() << TimeRole << SortRole); });
+    connect(version.get(), &Version::typeChanged, this, [this, row]() { emit dataChanged(index(row), index(row), QVector<int>() << TypeRole); });
+}
+
+BaseVersionPtr VersionList::getRecommended() const
+{
+    return m_recommended;
+}
+
+}
diff --git a/launcher/meta/VersionList.h b/launcher/meta/VersionList.h
new file mode 100644
index 00000000..58cdafe7
--- /dev/null
+++ b/launcher/meta/VersionList.h
@@ -0,0 +1,101 @@
+/* Copyright 2015-2021 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 "BaseEntity.h"
+#include "BaseVersionList.h"
+#include <QJsonObject>
+#include <memory>
+
+namespace Meta
+{
+using VersionPtr = std::shared_ptr<class Version>;
+using VersionListPtr = std::shared_ptr<class VersionList>;
+
+class VersionList : public BaseVersionList, public BaseEntity
+{
+    Q_OBJECT
+    Q_PROPERTY(QString uid READ uid CONSTANT)
+    Q_PROPERTY(QString name READ name NOTIFY nameChanged)
+public:
+    explicit VersionList(const QString &uid, QObject *parent = nullptr);
+
+    enum Roles
+    {
+        UidRole = Qt::UserRole + 100,
+        TimeRole,
+        RequiresRole,
+        VersionPtrRole
+    };
+
+    shared_qobject_ptr<Task> getLoadTask() override;
+    bool isLoaded() override;
+    const BaseVersionPtr at(int i) const override;
+    int count() const override;
+    void sortVersions() override;
+
+    BaseVersionPtr getRecommended() const override;
+
+    QVariant data(const QModelIndex &index, int role) const override;
+    RoleList providesRoles() const override;
+    QHash<int, QByteArray> roleNames() const override;
+
+    QString localFilename() const override;
+
+    QString uid() const
+    {
+        return m_uid;
+    }
+    QString name() const
+    {
+        return m_name;
+    }
+    QString humanReadable() const;
+
+    VersionPtr getVersion(const QString &version);
+
+    QVector<VersionPtr> versions() const
+    {
+        return m_versions;
+    }
+
+public: // for usage only by parsers
+    void setName(const QString &name);
+    void setVersions(const QVector<VersionPtr> &versions);
+    void merge(const VersionListPtr &other);
+    void mergeFromIndex(const VersionListPtr &other);
+    void parse(const QJsonObject &obj) override;
+
+signals:
+    void nameChanged(const QString &name);
+
+protected slots:
+    void updateListData(QList<BaseVersionPtr>) override
+    {
+    }
+
+private:
+    QVector<VersionPtr> m_versions;
+    QHash<QString, VersionPtr> m_lookup;
+    QString m_uid;
+    QString m_name;
+
+    VersionPtr m_recommended;
+
+    void setupAddedVersion(const int row, const VersionPtr &version);
+};
+}
+Q_DECLARE_METATYPE(Meta::VersionListPtr)