/*
 * Copyright (C) 2014 Aaron Seigo <aseigo@kde.org>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) version 3, or any
 * later version accepted by the membership of KDE e.V. (or its
 * successor approved by the membership of KDE e.V.), which shall
 * act as a proxy defined in Section 6 of version 3 of the license.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "pipeline.h"

#include <QByteArray>
#include <QStandardPaths>
#include <QVector>
#include <QUuid>
#include <QDebug>
#include "entity_generated.h"
#include "metadata_generated.h"
#include "createentity_generated.h"
#include "entitybuffer.h"
#include "async/src/async.h"

namespace Akonadi2
{

class Pipeline::Private
{
public:
    Private(const QString &resourceName)
        : storage(QStandardPaths::writableLocation(QStandardPaths::GenericDataLocation) + "/akonadi2/storage", resourceName, Storage::ReadWrite),
          stepScheduled(false)
    {
    }

    Storage storage;
    QHash<QString, QVector<Preprocessor *> > nullPipeline;
    QHash<QString, QVector<Preprocessor *> > newPipeline;
    QHash<QString, QVector<Preprocessor *> > modifiedPipeline;
    QHash<QString, QVector<Preprocessor *> > deletedPipeline;
    QVector<PipelineState> activePipelines;
    bool stepScheduled;
};

Pipeline::Pipeline(const QString &resourceName, QObject *parent)
    : QObject(parent),
      d(new Private(resourceName))
{
}

Pipeline::~Pipeline()
{
    delete d;
}

void Pipeline::setPreprocessors(const QString &entityType, Type pipelineType, const QVector<Preprocessor *> &preprocessors)
{
    switch (pipelineType) {
        case NewPipeline:
            d->newPipeline[entityType] = preprocessors;
            break;
        case ModifiedPipeline:
            d->modifiedPipeline[entityType] = preprocessors;
            break;
        case DeletedPipeline:
            d->deletedPipeline[entityType] = preprocessors;
            break;
        default:
            break;
    };
}

Storage &Pipeline::storage() const
{
    return d->storage;
}

void Pipeline::null()
{
    //TODO: is there really any need for the null pipeline? if so, it should be doing something ;)
    // PipelineState state(this, NullPipeline, QByteArray(), d->nullPipeline);
    // d->activePipelines << state;
    // state.step();
}

Async::Job<void> Pipeline::newEntity(void const *command, size_t size)
{
    qDebug() << "new entity" << size;

    //TODO toRFC4122 would probably be more efficient, but results in non-printable keys.
    const auto key = QUuid::createUuid().toString().toUtf8();

    //TODO figure out if we already have created a revision for the message?
    const qint64 newRevision = storage().maxRevision() + 1;

    {
        flatbuffers::Verifier verifyer(reinterpret_cast<const uint8_t *>(command), size);
        if (!Akonadi2::Commands::VerifyCreateEntityBuffer(verifyer)) {
            qWarning() << "invalid buffer";
            return Async::null<void>();
        }
    }

    auto createEntity = Akonadi2::Commands::GetCreateEntity(command);

    //TODO rename createEntitiy->domainType to bufferType
    const QString entityType = QString::fromUtf8(reinterpret_cast<char const*>(createEntity->domainType()->Data()), createEntity->domainType()->size());
    auto entity = Akonadi2::GetEntity(createEntity->delta()->Data());

    //Add metadata buffer
    flatbuffers::FlatBufferBuilder metadataFbb;
    auto metadataBuilder = Akonadi2::MetadataBuilder(metadataFbb);
    metadataBuilder.add_revision(newRevision);
    metadataBuilder.add_processed(false);
    auto metadataBuffer = metadataBuilder.Finish();
    Akonadi2::FinishMetadataBuffer(metadataFbb, metadataBuffer);
    //TODO we should reserve some space in metadata for in-place updates

    flatbuffers::FlatBufferBuilder fbb;
    EntityBuffer::assembleEntityBuffer(fbb, metadataFbb.GetBufferPointer(), metadataFbb.GetSize(), entity->resource()->Data(), entity->resource()->size(), entity->local()->Data(), entity->local()->size());

    storage().write(key.data(), key.size(), fbb.GetBufferPointer(), fbb.GetSize());
    storage().setMaxRevision(newRevision);

    return Async::start<void>([this, key, entityType](Async::Future<void> &future) {
        PipelineState state(this, NewPipeline, key, d->newPipeline[entityType], [&future]() {
            future.setFinished();
        });
        d->activePipelines << state;
        state.step();
    });
}

void Pipeline::modifiedEntity(const QString &entityType, const QByteArray &key, void *data, size_t size)
{
    PipelineState state(this, ModifiedPipeline, key, d->modifiedPipeline[entityType], [](){});
    d->activePipelines << state;
    state.step();
}

void Pipeline::deletedEntity(const QString &entityType, const QByteArray &key)
{
    PipelineState state(this, DeletedPipeline, key, d->deletedPipeline[entityType], [](){});
    d->activePipelines << state;
    state.step();
}

void Pipeline::pipelineStepped(const PipelineState &state)
{
    scheduleStep();
}

void Pipeline::scheduleStep()
{
    // if (!d->stepScheduled) {
    //     d->stepScheduled = true;
    //     QMetaObject::invokeMethod(this, "stepPipelines", Qt::QueuedConnection);
    // }
    //FIXME make async again. For some reason the job in newEntity crashes if pipeline processing is async.
    stepPipelines();
}

void Pipeline::stepPipelines()
{
    for (PipelineState &state: d->activePipelines) {
        if (state.isIdle()) {
            state.step();
        }
    }

    d->stepScheduled = false;
}

void Pipeline::pipelineCompleted(const PipelineState &state)
{
    //TODO finalize the datastore, inform clients of the new rev
    const int index = d->activePipelines.indexOf(state);
    if (index > -1) {
        d->activePipelines.remove(index);
    }

    if (state.type() != NullPipeline) {
        //TODO what revision is finalized?
        emit revisionUpdated();
    }
    scheduleStep();
    if (d->activePipelines.isEmpty()) {
        emit pipelinesDrained();
    }
}


class PipelineState::Private : public QSharedData
{
public:
    Private(Pipeline *p, Pipeline::Type t, const QByteArray &k, QVector<Preprocessor *> filters, const std::function<void()> &c)
        : pipeline(p),
          type(t),
          key(k),
          filterIt(filters),
          idle(true),
          callback(c)
    {}

    Private()
        : pipeline(0),
          filterIt(QVector<Preprocessor *>()),
          idle(true)
    {}

    Pipeline *pipeline;
    Pipeline::Type type;
    QByteArray key;
    QVectorIterator<Preprocessor *> filterIt;
    bool idle;
    std::function<void()> callback;
};

PipelineState::PipelineState()
    : d(new Private())
{

}

PipelineState::PipelineState(Pipeline *pipeline, Pipeline::Type type, const QByteArray &key, const QVector<Preprocessor *> &filters, const std::function<void()> &callback)
    : d(new Private(pipeline, type, key, filters, callback))
{
}

PipelineState::PipelineState(const PipelineState &other)
    : d(other.d)
{
}

PipelineState::~PipelineState()
{
}

PipelineState &PipelineState::operator=(const PipelineState &rhs)
{
    d = rhs.d;
    return *this;
}

bool PipelineState::operator==(const PipelineState &rhs)
{
    return d == rhs.d;
}

bool PipelineState::isIdle() const
{
    return d->idle;
}

QByteArray PipelineState::key() const
{
    return d->key;
}

Pipeline::Type PipelineState::type() const
{
    return d->type;
}

void PipelineState::step()
{
    if (!d->pipeline) {
        return;
    }

    d->idle = false;
    if (d->filterIt.hasNext()) {
        //TODO skip step if already processed
        d->pipeline->storage().scan(d->key.toStdString(), [this](void *keyValue, int keySize, void *dataValue, int dataSize) -> bool {
            auto entity = Akonadi2::GetEntity(dataValue);
            d->filterIt.next()->process(*this, *entity);
            return false;
        });
    } else {
        d->pipeline->pipelineCompleted(*this);
        d->callback();
    }
}

void PipelineState::processingCompleted(Preprocessor *filter)
{
    //TODO record processing progress
    if (d->pipeline && filter == d->filterIt.peekPrevious()) {
        d->idle = true;
        d->pipeline->pipelineStepped(*this);
    }
}

Preprocessor::Preprocessor()
    : d(0)
{
}

Preprocessor::~Preprocessor()
{
}

void Preprocessor::process(PipelineState state, const Akonadi2::Entity &)
{
    processingCompleted(state);
}

void Preprocessor::processingCompleted(PipelineState state)
{
    state.processingCompleted(this);
}

} // namespace Akonadi2