/* Copyright 2013-2018 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 <QDir>
#include <QDirIterator>
#include <QSet>
#include <QFile>
#include <QThread>
#include <QTextStream>
#include <QXmlStreamReader>
#include <QTimer>
#include <QDebug>
#include <QFileSystemWatcher>
#include <QUuid>
#include <QJsonArray>
#include <QJsonDocument>

#include "InstanceList.h"
#include "BaseInstance.h"
#include "InstanceTask.h"
#include "settings/INISettingsObject.h"
#include "minecraft/legacy/LegacyInstance.h"
#include "NullInstance.h"
#include "minecraft/MinecraftInstance.h"
#include "FileSystem.h"
#include "ExponentialSeries.h"
#include "WatchLock.h"

const static int GROUP_FILE_FORMAT_VERSION = 1;

InstanceList::InstanceList(SettingsObjectPtr settings, const QString & instDir, QObject *parent)
    : QAbstractListModel(parent), m_globalSettings(settings)
{
    resumeWatch();
    // Create aand normalize path
    if (!QDir::current().exists(instDir))
    {
        QDir::current().mkpath(instDir);
    }

    connect(this, &InstanceList::instancesChanged, this, &InstanceList::providerUpdated);
    connect(this, &InstanceList::groupsChanged, this, &InstanceList::groupsPublished);

    // NOTE: canonicalPath requires the path to exist. Do not move this above the creation block!
    m_instDir = QDir(instDir).canonicalPath();
    m_watcher = new QFileSystemWatcher(this);
    connect(m_watcher, &QFileSystemWatcher::directoryChanged, this, &InstanceList::instanceDirContentsChanged);
    m_watcher->addPath(m_instDir);
}

InstanceList::~InstanceList()
{
}

int InstanceList::rowCount(const QModelIndex &parent) const
{
    Q_UNUSED(parent);
    return m_instances.count();
}

QModelIndex InstanceList::index(int row, int column, const QModelIndex &parent) const
{
    Q_UNUSED(parent);
    if (row < 0 || row >= m_instances.size())
        return QModelIndex();
    return createIndex(row, column, (void *)m_instances.at(row).get());
}

QVariant InstanceList::data(const QModelIndex &index, int role) const
{
    if (!index.isValid())
    {
        return QVariant();
    }
    BaseInstance *pdata = static_cast<BaseInstance *>(index.internalPointer());
    switch (role)
    {
    case InstancePointerRole:
    {
        QVariant v = qVariantFromValue((void *)pdata);
        return v;
    }
    case InstanceIDRole:
    {
        return pdata->id();
    }
    case Qt::DisplayRole:
    {
        return pdata->name();
    }
    case Qt::ToolTipRole:
    {
        return pdata->instanceRoot();
    }
    case Qt::DecorationRole:
    {
        return pdata->iconKey();
    }
    // HACK: see GroupView.h in gui!
    case GroupRole:
    {
        return pdata->group();
    }
    default:
        break;
    }
    return QVariant();
}

Qt::ItemFlags InstanceList::flags(const QModelIndex &index) const
{
    Qt::ItemFlags f;
    if (index.isValid())
    {
        f |= (Qt::ItemIsEnabled | Qt::ItemIsSelectable);
    }
    return f;
}

QStringList InstanceList::getGroups()
{
    return m_groups.toList();
}

void InstanceList::deleteGroup(const QString& name)
{
    for(auto & instance: m_instances)
    {
        auto instGroupName = instance->group();
        if(instGroupName == name)
        {
            instance->setGroupPost(QString());
        }
    }
}

void InstanceList::deleteInstance(const InstanceId& id)
{
    auto inst = getInstanceById(id);
    if(!inst)
    {
        qDebug() << "Cannot delete instance" << id << " No such instance is present.";
        return;
    }

    qDebug() << "Will delete instance" << id;
    if(!FS::deletePath(inst->instanceRoot()))
    {
        qWarning() << "Deletion of instance" << id << "has not been completely successful ...";
        return;
    }

    qDebug() << "Instance" << id << "has been deleted by MultiMC.";
}

static QMap<InstanceId, InstanceLocator> getIdMapping(const QList<InstancePtr> &list)
{
    QMap<InstanceId, InstanceLocator> out;
    int i = 0;
    for(auto & item: list)
    {
        auto id = item->id();
        if(out.contains(id))
        {
            qWarning() << "Duplicate ID" << id << "in instance list";
        }
        out[id] = std::make_pair(item, i);
        i++;
    }
    return out;
}

QList< InstanceId > InstanceList::discoverInstances()
{
    qDebug() << "Discovering instances in" << m_instDir;
    QList<InstanceId> out;
    QDirIterator iter(m_instDir, QDir::Dirs | QDir::NoDot | QDir::NoDotDot | QDir::Readable | QDir::Hidden, QDirIterator::FollowSymlinks);
    while (iter.hasNext())
    {
        QString subDir = iter.next();
        QFileInfo dirInfo(subDir);
        if (!QFileInfo(FS::PathCombine(subDir, "instance.cfg")).exists())
            continue;
        // if it is a symlink, ignore it if it goes to the instance folder
        if(dirInfo.isSymLink())
        {
            QFileInfo targetInfo(dirInfo.symLinkTarget());
            QFileInfo instDirInfo(m_instDir);
            if(targetInfo.canonicalPath() == instDirInfo.canonicalFilePath())
            {
                qDebug() << "Ignoring symlink" << subDir << "that leads into the instances folder";
                continue;
            }
        }
        auto id = dirInfo.fileName();
        out.append(id);
        qDebug() << "Found instance ID" << id;
    }
    instanceSet = out.toSet();
    m_instancesProbed = true;
    return out;
}

InstanceList::InstListError InstanceList::loadList()
{
    auto existingIds = getIdMapping(m_instances);

    QList<InstancePtr> newList;

    for(auto & id: discoverInstances())
    {
        if(existingIds.contains(id))
        {
            auto instPair = existingIds[id];
            existingIds.remove(id);
            qDebug() << "Should keep and soft-reload" << id;
        }
        else
        {
            InstancePtr instPtr = loadInstance(id);
            if(instPtr)
            {
                newList.append(instPtr);
            }
        }
    }

    // TODO: looks like a general algorithm with a few specifics inserted. Do something about it.
    if(!existingIds.isEmpty())
    {
        // get the list of removed instances and sort it by their original index, from last to first
        auto deadList = existingIds.values();
        auto orderSortPredicate = [](const InstanceLocator & a, const InstanceLocator & b) -> bool
        {
            return a.second > b.second;
        };
        std::sort(deadList.begin(), deadList.end(), orderSortPredicate);
        // remove the contiguous ranges of rows
        int front_bookmark = -1;
        int back_bookmark = -1;
        int currentItem = -1;
        auto removeNow = [&]()
        {
            beginRemoveRows(QModelIndex(), front_bookmark, back_bookmark);
            m_instances.erase(m_instances.begin() + front_bookmark, m_instances.begin() + back_bookmark + 1);
            endRemoveRows();
            front_bookmark = -1;
            back_bookmark = currentItem;
        };
        for(auto & removedItem: deadList)
        {
            auto instPtr = removedItem.first;
            instPtr->invalidate();
            currentItem = removedItem.second;
            if(back_bookmark == -1)
            {
                // no bookmark yet
                back_bookmark = currentItem;
            }
            else if(currentItem == front_bookmark - 1)
            {
                // part of contiguous sequence, continue
            }
            else
            {
                // seam between previous and current item
                removeNow();
            }
            front_bookmark = currentItem;
        }
        if(back_bookmark != -1)
        {
            removeNow();
        }
    }
    if(newList.size())
    {
        add(newList);
    }
    m_dirty = false;
    return NoError;
}

void InstanceList::saveNow()
{
    for(auto & item: m_instances)
    {
        item->saveNow();
    }
}

void InstanceList::add(const QList<InstancePtr> &t)
{
    beginInsertRows(QModelIndex(), m_instances.count(), m_instances.count() + t.size() - 1);
    m_instances.append(t);
    for(auto & ptr : t)
    {
        connect(ptr.get(), &BaseInstance::propertiesChanged, this, &InstanceList::propertiesChanged);
    }
    endInsertRows();
}

void InstanceList::resumeWatch()
{
    if(m_watchLevel > 0)
    {
        qWarning() << "Bad suspend level resume in instance list";
        return;
    }
    m_watchLevel++;
    if(m_watchLevel > 0 && m_dirty)
    {
        loadList();
    }
}

void InstanceList::suspendWatch()
{
    m_watchLevel --;
}

void InstanceList::providerUpdated()
{
    m_dirty = true;
    if(m_watchLevel == 1)
    {
        loadList();
    }
}

void InstanceList::groupsPublished(QSet<QString> newGroups)
{
    m_groups.unite(newGroups);
}

InstancePtr InstanceList::getInstanceById(QString instId) const
{
    if(instId.isEmpty())
        return InstancePtr();
    for(auto & inst: m_instances)
    {
        if (inst->id() == instId)
        {
            return inst;
        }
    }
    return InstancePtr();
}

QModelIndex InstanceList::getInstanceIndexById(const QString &id) const
{
    return index(getInstIndex(getInstanceById(id).get()));
}

int InstanceList::getInstIndex(BaseInstance *inst) const
{
    int count = m_instances.count();
    for (int i = 0; i < count; i++)
    {
        if (inst == m_instances[i].get())
        {
            return i;
        }
    }
    return -1;
}

void InstanceList::propertiesChanged(BaseInstance *inst)
{
    int i = getInstIndex(inst);
    if (i != -1)
    {
        emit dataChanged(index(i), index(i));
    }
}

InstancePtr InstanceList::loadInstance(const InstanceId& id)
{
    if(!m_groupsLoaded)
    {
        loadGroupList();
    }

    auto instanceRoot = FS::PathCombine(m_instDir, id);
    auto instanceSettings = std::make_shared<INISettingsObject>(FS::PathCombine(instanceRoot, "instance.cfg"));
    InstancePtr inst;

    instanceSettings->registerSetting("InstanceType", "Legacy");

    QString inst_type = instanceSettings->get("InstanceType").toString();

    if (inst_type == "OneSix" || inst_type == "Nostalgia")
    {
        inst.reset(new MinecraftInstance(m_globalSettings, instanceSettings, instanceRoot));
    }
    else if (inst_type == "Legacy")
    {
        inst.reset(new LegacyInstance(m_globalSettings, instanceSettings, instanceRoot));
    }
    else
    {
        inst.reset(new NullInstance(m_globalSettings, instanceSettings, instanceRoot));
    }
    inst->init();
    auto iter = groupMap.find(id);
    if (iter != groupMap.end())
    {
        inst->setGroupInitial((*iter));
    }
    connect(inst.get(), &BaseInstance::groupChanged, this, &InstanceList::groupChanged);
    qDebug() << "Loaded instance " << inst->name() << " from " << inst->instanceRoot();
    return inst;
}

void InstanceList::saveGroupList()
{
    qDebug() << "Will save group list now.";
    if(!m_instancesProbed)
    {
        qDebug() << "Group saving prevented because we don't know the full list of instances yet.";
        return;
    }
    WatchLock foo(m_watcher, m_instDir);
    QString groupFileName = m_instDir + "/instgroups.json";
    QMap<QString, QSet<QString>> reverseGroupMap;
    for (auto iter = groupMap.begin(); iter != groupMap.end(); iter++)
    {
        QString id = iter.key();
        QString group = iter.value();
        if (group.isEmpty())
            continue;
        if(!instanceSet.contains(id))
        {
            qDebug() << "Skipping saving missing instance" << id << "to groups list.";
            continue;
        }

        if (!reverseGroupMap.count(group))
        {
            QSet<QString> set;
            set.insert(id);
            reverseGroupMap[group] = set;
        }
        else
        {
            QSet<QString> &set = reverseGroupMap[group];
            set.insert(id);
        }
    }
    QJsonObject toplevel;
    toplevel.insert("formatVersion", QJsonValue(QString("1")));
    QJsonObject groupsArr;
    for (auto iter = reverseGroupMap.begin(); iter != reverseGroupMap.end(); iter++)
    {
        auto list = iter.value();
        auto name = iter.key();
        QJsonObject groupObj;
        QJsonArray instanceArr;
        groupObj.insert("hidden", QJsonValue(QString("false")));
        for (auto item : list)
        {
            instanceArr.append(QJsonValue(item));
        }
        groupObj.insert("instances", instanceArr);
        groupsArr.insert(name, groupObj);
    }
    toplevel.insert("groups", groupsArr);
    QJsonDocument doc(toplevel);
    try
    {
        FS::write(groupFileName, doc.toJson());
        qDebug() << "Group list saved.";
    }
    catch (const FS::FileSystemException &e)
    {
        qCritical() << "Failed to write instance group file :" << e.cause();
    }
}

void InstanceList::loadGroupList()
{
    qDebug() << "Will load group list now.";
    QSet<QString> groupSet;

    QString groupFileName = m_instDir + "/instgroups.json";

    // if there's no group file, fail
    if (!QFileInfo(groupFileName).exists())
        return;

    QByteArray jsonData;
    try
    {
        jsonData = FS::read(groupFileName);
    }
    catch (const FS::FileSystemException &e)
    {
        qCritical() << "Failed to read instance group file :" << e.cause();
        return;
    }

    QJsonParseError error;
    QJsonDocument jsonDoc = QJsonDocument::fromJson(jsonData, &error);

    // if the json was bad, fail
    if (error.error != QJsonParseError::NoError)
    {
        qCritical() << QString("Failed to parse instance group file: %1 at offset %2")
                            .arg(error.errorString(), QString::number(error.offset))
                            .toUtf8();
        return;
    }

    // if the root of the json wasn't an object, fail
    if (!jsonDoc.isObject())
    {
        qWarning() << "Invalid group file. Root entry should be an object.";
        return;
    }

    QJsonObject rootObj = jsonDoc.object();

    // Make sure the format version matches, otherwise fail.
    if (rootObj.value("formatVersion").toVariant().toInt() != GROUP_FILE_FORMAT_VERSION)
        return;

    // Get the groups. if it's not an object, fail
    if (!rootObj.value("groups").isObject())
    {
        qWarning() << "Invalid group list JSON: 'groups' should be an object.";
        return;
    }

    groupMap.clear();

    // Iterate through all the groups.
    QJsonObject groupMapping = rootObj.value("groups").toObject();
    for (QJsonObject::iterator iter = groupMapping.begin(); iter != groupMapping.end(); iter++)
    {
        QString groupName = iter.key();

        // If not an object, complain and skip to the next one.
        if (!iter.value().isObject())
        {
            qWarning() << QString("Group '%1' in the group list should "
                                   "be an object.")
                               .arg(groupName)
                               .toUtf8();
            continue;
        }

        QJsonObject groupObj = iter.value().toObject();
        if (!groupObj.value("instances").isArray())
        {
            qWarning() << QString("Group '%1' in the group list is invalid. "
                                   "It should contain an array "
                                   "called 'instances'.")
                               .arg(groupName)
                               .toUtf8();
            continue;
        }

        // keep a list/set of groups for choosing
        groupSet.insert(groupName);

        // Iterate through the list of instances in the group.
        QJsonArray instancesArray = groupObj.value("instances").toArray();

        for (QJsonArray::iterator iter2 = instancesArray.begin(); iter2 != instancesArray.end(); iter2++)
        {
            groupMap[(*iter2).toString()] = groupName;
        }
    }
    m_groupsLoaded = true;
    emit groupsChanged(groupSet);
    qDebug() << "Group list loaded.";
}

void InstanceList::groupChanged()
{
    // save the groups. save all of them.
    auto instance = (BaseInstance *) QObject::sender();
    auto id = instance->id();
    groupMap[id] = instance->group();
    emit groupsChanged({instance->group()});
    saveGroupList();
}


void InstanceList::instanceDirContentsChanged(const QString& path)
{
    Q_UNUSED(path);
    emit instancesChanged();
}

void InstanceList::on_InstFolderChanged(const Setting &setting, QVariant value)
{
    QString newInstDir = QDir(value.toString()).canonicalPath();
    if(newInstDir != m_instDir)
    {
        if(m_groupsLoaded)
        {
            saveGroupList();
        }
        m_instDir = newInstDir;
        m_groupsLoaded = false;
        emit instancesChanged();
    }
}

class InstanceStaging : public Task
{
Q_OBJECT
    const unsigned minBackoff = 1;
    const unsigned maxBackoff = 16;
public:
    InstanceStaging (
        InstanceList * parent,
        Task * child,
        const QString & stagingPath,
        const QString& instanceName,
        const QString& groupName )
    : backoff(minBackoff, maxBackoff)
    {
        m_parent = parent;
        m_child.reset(child);
        connect(child, &Task::succeeded, this, &InstanceStaging::childSucceded);
        connect(child, &Task::failed, this, &InstanceStaging::childFailed);
        connect(child, &Task::status, this, &InstanceStaging::setStatus);
        connect(child, &Task::progress, this, &InstanceStaging::setProgress);
        m_instanceName = instanceName;
        m_groupName = groupName;
        m_stagingPath = stagingPath;
        m_backoffTimer.setSingleShot(true);
        connect(&m_backoffTimer, &QTimer::timeout, this, &InstanceStaging::childSucceded);
    }

    virtual ~InstanceStaging() {};

protected:
    virtual void executeTask() override
    {
        m_child->start();
    }
    QStringList warnings() const override
    {
        return m_child->warnings();
    }

private slots:
    void childSucceded()
    {
        unsigned sleepTime = backoff();
        if(m_parent->commitStagedInstance(m_stagingPath, m_instanceName, m_groupName))
        {
            emitSucceeded();
            return;
        }
        // we actually failed, retry?
        if(sleepTime == maxBackoff)
        {
            emitFailed(tr("Failed to commit instance, even after multiple retries. It is being blocked by something."));
            return;
        }
        qDebug() << "Failed to commit instance" << m_instanceName << "Initiating backoff:" << sleepTime;
        m_backoffTimer.start(sleepTime * 500);
    }
    void childFailed(const QString & reason)
    {
        m_parent->destroyStagingPath(m_stagingPath);
        emitFailed(reason);
    }

private:
    /*
     * WHY: the whole reason why this uses an exponential backoff retry scheme is antivirus on Windows.
     * Basically, it starts messing things up while MultiMC is extracting/creating instances
     * and causes that horrible failure that is NTFS to lock files in place because they are open.
     */
    ExponentialSeries backoff;
    QString m_stagingPath;
    InstanceList * m_parent;
    unique_qobject_ptr<Task> m_child;
    QString m_instanceName;
    QString m_groupName;
    QTimer m_backoffTimer;
};

Task * InstanceList::wrapInstanceTask(InstanceTask * task)
{
    auto stagingPath = getStagedInstancePath();
    task->setStagingPath(stagingPath);
    task->setParentSettings(m_globalSettings);
    return new InstanceStaging(this, task, stagingPath, task->name(), task->group());
}

QString InstanceList::getStagedInstancePath()
{
    QString key = QUuid::createUuid().toString();
    QString relPath = FS::PathCombine("_MMC_TEMP/" , key);
    QDir rootPath(m_instDir);
    auto path = FS::PathCombine(m_instDir, relPath);
    if(!rootPath.mkpath(relPath))
    {
        return QString();
    }
    return path;
}

bool InstanceList::commitStagedInstance(const QString& path, const QString& instanceName, const QString& groupName)
{
    QDir dir;
    QString instID = FS::DirNameFromString(instanceName, m_instDir);
    {
        WatchLock lock(m_watcher, m_instDir);
        QString destination = FS::PathCombine(m_instDir, instID);
        if(!dir.rename(path, destination))
        {
            qWarning() << "Failed to move" << path << "to" << destination;
            return false;
        }
        groupMap[instID] = groupName;
        instanceSet.insert(instID);
        emit groupsChanged({groupName});
        emit instancesChanged();
    }
    saveGroupList();
    return true;
}

bool InstanceList::destroyStagingPath(const QString& keyPath)
{
    return FS::deletePath(keyPath);
}

#include "InstanceList.moc"