/*
 * Copyright (C) 2016 Christian Mollekopf <mollekopf@kolabsys.com>
 *
 * 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 "changereplay.h"

#include "entitybuffer.h"
#include "log.h"
#include "definitions.h"
#include "bufferutils.h"

using namespace Sink;

#undef DEBUG_AREA
#define DEBUG_AREA "resource.changereplay"

ChangeReplay::ChangeReplay(const QByteArray &resourceName)
    : mStorage(storageLocation(), resourceName, Storage::ReadOnly), mChangeReplayStore(storageLocation(), resourceName + ".changereplay", Storage::ReadWrite)
{
    Trace() << "Created change replay: " << resourceName;
}

qint64 ChangeReplay::getLastReplayedRevision()
{
    qint64 lastReplayedRevision = 0;
    auto replayStoreTransaction = mChangeReplayStore.createTransaction(Storage::ReadOnly);
    replayStoreTransaction.openDatabase().scan("lastReplayedRevision",
        [&lastReplayedRevision](const QByteArray &key, const QByteArray &value) -> bool {
            lastReplayedRevision = value.toLongLong();
            return false;
        },
        [](const Storage::Error &) {});
    return lastReplayedRevision;
}

bool ChangeReplay::allChangesReplayed()
{
    const qint64 topRevision = Storage::maxRevision(mStorage.createTransaction(Storage::ReadOnly, [](const Sink::Storage::Error &error) {
        Warning() << error.message;
    }));
    const qint64 lastReplayedRevision = getLastReplayedRevision();
    Trace() << "All changes replayed " << topRevision << lastReplayedRevision;
    return (lastReplayedRevision >= topRevision);
}

void ChangeReplay::revisionChanged()
{
    auto mainStoreTransaction = mStorage.createTransaction(Storage::ReadOnly, [](const Sink::Storage::Error &error) {
        Warning() << error.message;
    });
    auto replayStoreTransaction = mChangeReplayStore.createTransaction(Storage::ReadWrite, [](const Sink::Storage::Error &error) {
        Warning() << error.message;
    });
    qint64 lastReplayedRevision = 1;
    replayStoreTransaction.openDatabase().scan("lastReplayedRevision",
        [&lastReplayedRevision](const QByteArray &key, const QByteArray &value) -> bool {
            lastReplayedRevision = value.toLongLong();
            return false;
        },
        [](const Storage::Error &) {});
    const qint64 topRevision = Storage::maxRevision(mainStoreTransaction);

    Trace() << "Changereplay from " << lastReplayedRevision << " to " << topRevision;
    if (lastReplayedRevision <= topRevision) {
        qint64 revision = lastReplayedRevision;
        for (; revision <= topRevision; revision++) {
            const auto uid = Storage::getUidFromRevision(mainStoreTransaction, revision);
            const auto type = Storage::getTypeFromRevision(mainStoreTransaction, revision);
            const auto key = Storage::assembleKey(uid, revision);
            Storage::mainDatabase(mainStoreTransaction, type)
                .scan(key,
                    [&lastReplayedRevision, type, this](const QByteArray &key, const QByteArray &value) -> bool {
                        Trace() << "Replaying " << key;
                        replay(type, key, value).exec();
                        // TODO make for loop async, and pass to async replay function together with type
                        return false;
                    },
                    [key](const Storage::Error &) { ErrorMsg() << "Failed to replay change " << key; });
        }
        revision--;
        replayStoreTransaction.openDatabase().write("lastReplayedRevision", QByteArray::number(revision));
        replayStoreTransaction.commit();
        Trace() << "Replayed until " << revision;
    }
    emit changesReplayed();
}