#include "ComponentUpdateTask.h"

#include "ComponentList_p.h"
#include "ComponentList.h"
#include "Component.h"
#include <Env.h>
#include <meta/Index.h>
#include <meta/VersionList.h>
#include <meta/Version.h>
#include "ComponentUpdateTask_p.h"
#include <cassert>
#include <Version.h>
#include "net/Mode.h"
#include "OneSixVersionFormat.h"

/*
 * This is responsible for loading the components of a component list AND resolving dependency issues between them
 */

/*
 * FIXME: the 'one shot async task' nature of this does not fit the intended usage
 * Really, it should be a reactor/state machine that receives input from the application
 * and dynamically adapts to changing requirements...
 *
 * The reactor should be the only entry into manipulating the ComponentList.
 * See: https://en.wikipedia.org/wiki/Reactor_pattern
 */

/*
 * Or make this operate on a snapshot of the ComponentList state, then merge results in as long as the snapshot and ComponentList didn't change?
 * If the component list changes, start over.
 */

ComponentUpdateTask::ComponentUpdateTask(Mode mode, Net::Mode netmode, ComponentList* list, QObject* parent)
    : Task(parent)
{
    d.reset(new ComponentUpdateTaskData);
    d->m_list = list;
    d->mode = mode;
    d->netmode = netmode;
}

ComponentUpdateTask::~ComponentUpdateTask()
{
}

void ComponentUpdateTask::executeTask()
{
    qDebug() << "Loading components";
    loadComponents();
}

namespace
{
enum class LoadResult
{
    LoadedLocal,
    RequiresRemote,
    Failed
};

LoadResult composeLoadResult(LoadResult a, LoadResult b)
{
    if (a < b)
    {
        return b;
    }
    return a;
}

static LoadResult loadComponent(ComponentPtr component, shared_qobject_ptr<Task>& loadTask, Net::Mode netmode)
{
    if(component->m_loaded)
    {
        qDebug() << component->getName() << "is already loaded";
        return LoadResult::LoadedLocal;
    }

    LoadResult result = LoadResult::Failed;
    auto customPatchFilename = component->getFilename();
    if(QFile::exists(customPatchFilename))
    {
        // if local file exists...

        // check for uid problems inside...
        bool fileChanged = false;
        auto file = ProfileUtils::parseJsonFile(QFileInfo(customPatchFilename), false);
        if(file->uid != component->m_uid)
        {
            file->uid = component->m_uid;
            fileChanged = true;
        }
        if(fileChanged)
        {
            // FIXME: @QUALITY do not ignore return value
            ProfileUtils::saveJsonFile(OneSixVersionFormat::versionFileToJson(file), customPatchFilename);
        }

        component->m_file = file;
        component->m_loaded = true;
        result = LoadResult::LoadedLocal;
    }
    else
    {
        auto metaVersion = ENV.metadataIndex()->get(component->m_uid, component->m_version);
        component->m_metaVersion = metaVersion;
        if(metaVersion->isLoaded())
        {
            component->m_loaded = true;
            result = LoadResult::LoadedLocal;
        }
        else
        {
            metaVersion->load(netmode);
            loadTask = metaVersion->getCurrentTask();
            if(loadTask)
                result = LoadResult::RequiresRemote;
            else if (metaVersion->isLoaded())
                result = LoadResult::LoadedLocal;
            else
                result = LoadResult::Failed;
        }
    }
    return result;
}

// FIXME: dead code. determine if this can still be useful?
/*
static LoadResult loadComponentList(ComponentPtr component, shared_qobject_ptr<Task>& loadTask, Net::Mode netmode)
{
    if(component->m_loaded)
    {
        qDebug() << component->getName() << "is already loaded";
        return LoadResult::LoadedLocal;
    }

    LoadResult result = LoadResult::Failed;
    auto metaList = ENV.metadataIndex()->get(component->m_uid);
    if(metaList->isLoaded())
    {
        component->m_loaded = true;
        result = LoadResult::LoadedLocal;
    }
    else
    {
        metaList->load(netmode);
        loadTask = metaList->getCurrentTask();
        result = LoadResult::RequiresRemote;
    }
    return result;
}
*/

static LoadResult loadIndex(shared_qobject_ptr<Task>& loadTask, Net::Mode netmode)
{
    // FIXME: DECIDE. do we want to run the update task anyway?
    if(ENV.metadataIndex()->isLoaded())
    {
        qDebug() << "Index is already loaded";
        return LoadResult::LoadedLocal;
    }
    ENV.metadataIndex()->load(netmode);
    loadTask = ENV.metadataIndex()->getCurrentTask();
    if(loadTask)
    {
        return LoadResult::RequiresRemote;
    }
    // FIXME: this is assuming the load succeeded... did it really?
    return LoadResult::LoadedLocal;
}
}

void ComponentUpdateTask::loadComponents()
{
    LoadResult result = LoadResult::LoadedLocal;
    size_t taskIndex = 0;
    size_t componentIndex = 0;
    d->remoteLoadSuccessful = true;
    // load the main index (it is needed to determine if components can revert)
    {
        // FIXME: tear out as a method? or lambda?
        shared_qobject_ptr<Task> indexLoadTask;
        auto singleResult = loadIndex(indexLoadTask, d->netmode);
        result = composeLoadResult(result, singleResult);
        if(indexLoadTask)
        {
            qDebug() << "Remote loading is being run for metadata index";
            RemoteLoadStatus status;
            status.type = RemoteLoadStatus::Type::Index;
            d->remoteLoadStatusList.append(status);
            connect(indexLoadTask.get(), &Task::succeeded, [=]()
            {
                remoteLoadSucceeded(taskIndex);
            });
            connect(indexLoadTask.get(), &Task::failed, [=](const QString & error)
            {
                remoteLoadFailed(taskIndex, error);
            });
            taskIndex++;
        }
    }
    // load all the components OR their lists...
    for (auto component: d->m_list->d->components)
    {
        shared_qobject_ptr<Task> loadTask;
        LoadResult singleResult;
        RemoteLoadStatus::Type loadType;
        // FIXME: to do this right, we need to load the lists and decide on which versions to use during dependency resolution. For now, ignore all that...
#if 0
        switch(d->mode)
        {
            case Mode::Launch:
            {
                singleResult = loadComponent(component, loadTask, d->netmode);
                loadType = RemoteLoadStatus::Type::Version;
                break;
            }
            case Mode::Resolution:
            {
                singleResult = loadComponentList(component, loadTask, d->netmode);
                loadType = RemoteLoadStatus::Type::List;
                break;
            }
        }
#else
        singleResult = loadComponent(component, loadTask, d->netmode);
        loadType = RemoteLoadStatus::Type::Version;
#endif
        if(singleResult == LoadResult::LoadedLocal)
        {
            component->updateCachedData();
        }
        result = composeLoadResult(result, singleResult);
        if (loadTask)
        {
            qDebug() << "Remote loading is being run for" << component->getName();
            connect(loadTask.get(), &Task::succeeded, [=]()
            {
                remoteLoadSucceeded(taskIndex);
            });
            connect(loadTask.get(), &Task::failed, [=](const QString & error)
            {
                remoteLoadFailed(taskIndex, error);
            });
            RemoteLoadStatus status;
            status.type = loadType;
            status.componentListIndex = componentIndex;
            d->remoteLoadStatusList.append(status);
            taskIndex++;
        }
        componentIndex++;
    }
    d->remoteTasksInProgress = taskIndex;
    switch(result)
    {
        case LoadResult::LoadedLocal:
        {
            // Everything got loaded. Advance to dependency resolution.
            resolveDependencies(d->mode == Mode::Launch || d->netmode == Net::Mode::Offline);
            break;
        }
        case LoadResult::RequiresRemote:
        {
            // we wait for signals.
            break;
        }
        case LoadResult::Failed:
        {
            emitFailed(tr("Some component metadata load tasks failed."));
            break;
        }
    }
}

namespace
{
    struct RequireEx : public Meta::Require
    {
        size_t indexOfFirstDependee = 0;
    };
    struct RequireCompositionResult
    {
        bool ok;
        RequireEx outcome;
    };
    using RequireExSet = std::set<RequireEx>;
}

static RequireCompositionResult composeRequirement(const RequireEx & a, const RequireEx & b)
{
    assert(a.uid == b.uid);
    RequireEx out;
    out.uid = a.uid;
    out.indexOfFirstDependee = std::min(a.indexOfFirstDependee, b.indexOfFirstDependee);
    if(a.equalsVersion.isEmpty())
    {
        out.equalsVersion = b.equalsVersion;
    }
    else if (b.equalsVersion.isEmpty())
    {
        out.equalsVersion = a.equalsVersion;
    }
    else if (a.equalsVersion == b.equalsVersion)
    {
        out.equalsVersion = a.equalsVersion;
    }
    else
    {
        // FIXME: mark error as explicit version conflict
        return {false, out};
    }

    if(a.suggests.isEmpty())
    {
        out.suggests = b.suggests;
    }
    else if (b.suggests.isEmpty())
    {
        out.suggests = a.suggests;
    }
    else
    {
        Version aVer(a.suggests);
        Version bVer(b.suggests);
        out.suggests = (aVer < bVer ? b.suggests : a.suggests);
    }
    return {true, out};
}

// gather the requirements from all components, finding any obvious conflicts
static bool gatherRequirementsFromComponents(const ComponentContainer & input, RequireExSet & output)
{
    bool succeeded = true;
    size_t componentNum = 0;
    for(auto component: input)
    {
        auto &componentRequires = component->m_cachedRequires;
        for(const auto & componentRequire: componentRequires)
        {
            auto found = std::find_if(output.cbegin(), output.cend(), [componentRequire](const Meta::Require & req){
                return req.uid == componentRequire.uid;
            });

            RequireEx componenRequireEx;
            componenRequireEx.uid = componentRequire.uid;
            componenRequireEx.suggests = componentRequire.suggests;
            componenRequireEx.equalsVersion = componentRequire.equalsVersion;
            componenRequireEx.indexOfFirstDependee = componentNum;

            if(found != output.cend())
            {
                // found... process it further
                auto result = composeRequirement(componenRequireEx, *found);
                if(result.ok)
                {
                    output.erase(componenRequireEx);
                    output.insert(result.outcome);
                }
                else
                {
                    qCritical()
                        << "Conflicting requirements:"
                        << componentRequire.uid
                        << "versions:"
                        << componentRequire.equalsVersion
                        << ";"
                        << (*found).equalsVersion;
                }
                succeeded &= result.ok;
            }
            else
            {
                // not found, accumulate
                output.insert(componenRequireEx);
            }
        }
        componentNum++;
    }
    return succeeded;
}

/// Get list of uids that can be trivially removed because nothing is depending on them anymore (and they are installed as deps)
static void getTrivialRemovals(const ComponentContainer & components, const RequireExSet & reqs, QStringList &toRemove)
{
    for(const auto & component: components)
    {
        if(!component->m_dependencyOnly)
            continue;
        if(!component->m_cachedVolatile)
            continue;
        RequireEx reqNeedle;
        reqNeedle.uid = component->m_uid;
        const auto iter = reqs.find(reqNeedle);
        if(iter == reqs.cend())
        {
            toRemove.append(component->m_uid);
        }
    }
}

/**
 * handles:
 * - trivial addition (there is an unmet requirement and it can be trivially met by adding something)
 * - trivial version conflict of dependencies == explicit version required and installed is different
 *
 * toAdd - set of requirements than mean adding a new component
 * toChange - set of requirements that mean changing version of an existing component
 */
static bool getTrivialComponentChanges(const ComponentIndex & index, const RequireExSet & input, RequireExSet & toAdd, RequireExSet & toChange)
{
    enum class Decision
    {
        Undetermined,
        Met,
        Missing,
        VersionNotSame,
        LockedVersionNotSame
    } decision = Decision::Undetermined;

    QString reqStr;
    bool succeeded = true;
    // list the composed requirements and say if they are met or unmet
    for(auto & req: input)
    {
        do
        {
            if(req.equalsVersion.isEmpty())
            {
                reqStr = QString("Req: %1").arg(req.uid);
                if(index.contains(req.uid))
                {
                    decision = Decision::Met;
                }
                else
                {
                    toAdd.insert(req);
                    decision = Decision::Missing;
                }
                break;
            }
            else
            {
                reqStr = QString("Req: %1 == %2").arg(req.uid, req.equalsVersion);
                const auto & compIter = index.find(req.uid);
                if(compIter == index.cend())
                {
                    toAdd.insert(req);
                    decision = Decision::Missing;
                    break;
                }
                auto & comp = (*compIter);
                if(comp->getVersion() != req.equalsVersion)
                {
                    if(comp->isCustom()) {
                        decision = Decision::LockedVersionNotSame;
                    } else {
                        if(comp->m_dependencyOnly)
                        {
                            decision = Decision::VersionNotSame;
                        }
                        else
                        {
                            decision = Decision::LockedVersionNotSame;
                        }
                    }
                    break;
                }
                decision = Decision::Met;
            }
        } while(false);
        switch(decision)
        {
            case Decision::Undetermined:
                qCritical() << "No decision for" << reqStr;
                succeeded = false;
                break;
            case Decision::Met:
                qDebug() << reqStr << "Is met.";
                break;
            case Decision::Missing:
                qDebug() << reqStr << "Is missing and should be added at" << req.indexOfFirstDependee;
                toAdd.insert(req);
                break;
            case Decision::VersionNotSame:
                qDebug() << reqStr << "already has different version that can be changed.";
                toChange.insert(req);
                break;
            case Decision::LockedVersionNotSame:
                qDebug() << reqStr << "already has different version that cannot be changed.";
                succeeded = false;
                break;
        }
    }
    return succeeded;
}

// FIXME, TODO: decouple dependency resolution from loading
// FIXME: This works directly with the ComponentList internals. It shouldn't! It needs richer data types than ComponentList uses.
// FIXME: throw all this away and use a graph
void ComponentUpdateTask::resolveDependencies(bool checkOnly)
{
    qDebug() << "Resolving dependencies";
    /*
     * this is a naive dependency resolving algorithm. all it does is check for following conditions and react in simple ways:
     * 1. There are conflicting dependencies on the same uid with different exact version numbers
     *    -> hard error
     * 2. A dependency has non-matching exact version number
     *    -> hard error
     * 3. A dependency is entirely missing and needs to be injected before the dependee(s)
     *    -> requirements are injected
     *
     * NOTE: this is a placeholder and should eventually be replaced with something 'serious'
     */
    auto & components = d->m_list->d->components;
    auto & componentIndex = d->m_list->d->componentIndex;

    RequireExSet allRequires;
    QStringList toRemove;
    do
    {
        allRequires.clear();
        toRemove.clear();
        if(!gatherRequirementsFromComponents(components, allRequires))
        {
            emitFailed(tr("Conflicting requirements detected during dependency checking!"));
            return;
        }
        getTrivialRemovals(components, allRequires, toRemove);
        if(!toRemove.isEmpty())
        {
            qDebug() << "Removing obsolete components...";
            for(auto & remove : toRemove)
            {
                qDebug() << "Removing" << remove;
                d->m_list->remove(remove);
            }
        }
    } while (!toRemove.isEmpty());
    RequireExSet toAdd;
    RequireExSet toChange;
    bool succeeded = getTrivialComponentChanges(componentIndex, allRequires, toAdd, toChange);
    if(!succeeded)
    {
        emitFailed(tr("Instance has conflicting dependencies."));
        return;
    }
    if(checkOnly)
    {
        if(toAdd.size() || toChange.size())
        {
            emitFailed(tr("Instance has unresolved dependencies while loading/checking for launch."));
        }
        else
        {
            emitSucceeded();
        }
        return;
    }

    bool recursionNeeded = false;
    if(toAdd.size())
    {
        // add stuff...
        for(auto &add: toAdd)
        {
            ComponentPtr component = new Component(d->m_list, add.uid);
            if(!add.equalsVersion.isEmpty())
            {
                // exact version
                qDebug() << "Adding" << add.uid << "version" << add.equalsVersion << "at position" << add.indexOfFirstDependee;
                component->m_version = add.equalsVersion;
            }
            else
            {
                // version needs to be decided
                qDebug() << "Adding" << add.uid << "at position" << add.indexOfFirstDependee;
// ############################################################################################################
// HACK HACK HACK HACK FIXME: this is a placeholder for deciding what version to use. For now, it is hardcoded.
                if(!add.suggests.isEmpty())
                {
                    component->m_version = add.suggests;
                }
                else
                {
                    if(add.uid == "org.lwjgl")
                    {
                        component->m_version = "2.9.1";
                    }
                    else if (add.uid == "org.lwjgl3")
                    {
                        component->m_version = "3.1.2";
                    }
                    else if (add.uid == "net.fabricmc.intermediary")
                    {
                        auto minecraft = std::find_if(components.begin(), components.end(), [](ComponentPtr & cmp){
                            return cmp->getID() == "net.minecraft";
                        });
                        if(minecraft != components.end()) {
                            component->m_version = (*minecraft)->getVersion();
                        }
                    }
                }
// HACK HACK HACK HACK FIXME: this is a placeholder for deciding what version to use. For now, it is hardcoded.
// ############################################################################################################
            }
            component->m_dependencyOnly = true;
            // FIXME: this should not work directly with the component list
            d->m_list->insertComponent(add.indexOfFirstDependee, component);
            componentIndex[add.uid] = component;
        }
        recursionNeeded = true;
    }
    if(toChange.size())
    {
        // change a version of something that exists
        for(auto &change: toChange)
        {
            // FIXME: this should not work directly with the component list
            qDebug() << "Setting version of " << change.uid << "to" << change.equalsVersion;
            auto component = componentIndex[change.uid];
            component->setVersion(change.equalsVersion);
        }
        recursionNeeded = true;
    }

    if(recursionNeeded)
    {
        loadComponents();
    }
    else
    {
        emitSucceeded();
    }
}

void ComponentUpdateTask::remoteLoadSucceeded(size_t taskIndex)
{
    auto &taskSlot = d->remoteLoadStatusList[taskIndex];
    if(taskSlot.finished)
    {
        qWarning() << "Got multiple results from remote load task" << taskIndex;
        return;
    }
    qDebug() << "Remote task" << taskIndex << "succeeded";
    taskSlot.succeeded = false;
    taskSlot.finished = true;
    d->remoteTasksInProgress --;
    // update the cached data of the component from the downloaded version file.
    if (taskSlot.type == RemoteLoadStatus::Type::Version)
    {
        auto component = d->m_list->getComponent(taskSlot.componentListIndex);
        component->m_loaded = true;
        component->updateCachedData();
    }
    checkIfAllFinished();
}


void ComponentUpdateTask::remoteLoadFailed(size_t taskIndex, const QString& msg)
{
    auto &taskSlot = d->remoteLoadStatusList[taskIndex];
    if(taskSlot.finished)
    {
        qWarning() << "Got multiple results from remote load task" << taskIndex;
        return;
    }
    qDebug() << "Remote task" << taskIndex << "failed: " << msg;
    d->remoteLoadSuccessful = false;
    taskSlot.succeeded = false;
    taskSlot.finished = true;
    taskSlot.error = msg;
    d->remoteTasksInProgress --;
    checkIfAllFinished();
}

void ComponentUpdateTask::checkIfAllFinished()
{
    if(d->remoteTasksInProgress)
    {
        // not yet...
        return;
    }
    if(d->remoteLoadSuccessful)
    {
        // nothing bad happened... clear the temp load status and proceed with looking at dependencies
        d->remoteLoadStatusList.clear();
        resolveDependencies(d->mode == Mode::Launch);
    }
    else
    {
        // remote load failed... report error and bail
        QStringList allErrorsList;
        for(auto & item: d->remoteLoadStatusList)
        {
            if(!item.succeeded)
            {
                allErrorsList.append(item.error);
            }
        }
        auto allErrors = allErrorsList.join("\n");
        emitFailed(tr("Component metadata update task failed while downloading from remote server:\n%1").arg(allErrors));
        d->remoteLoadStatusList.clear();
    }
}