/*
 * LMDB Abstraction Layer.
 * Copyright (C) 2023  Yury Gubich <blue@macaw.me>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "base.h"
#include "exceptions.h"
#include "storage.h"

#define UNUSED(x) (void)(x)

LMDBAL::Base::Base(const QString& p_name, uint16_t mapSize):
    name(p_name.toStdString()),
    opened(false),
    size(mapSize),
    environment(),
    storages(),
    transactions(new Transactions())
{}

LMDBAL::Base::~Base() {
    close();

    delete transactions;

    for (const std::pair<const std::string, iStorage*>& pair : storages)
        delete pair.second;
}

void LMDBAL::Base::close() {
    if (opened) {
        for (LMDBAL::TransactionID id : *transactions)
            abortTransaction(id, emptyName);

        for (const std::pair<const std::string, iStorage*>& pair : storages) {
            iStorage* storage = pair.second;
            mdb_dbi_close(environment, storage->dbi);
        }
        mdb_env_close(environment);
        transactions->clear();
        opened = false;
    }
}

/**
 * Almost every LMDBAL::Base require it to be opened, this function opens it. It laso creates the directory for the database if it was an initial launch
 */
void LMDBAL::Base::open() {
    if (!opened) {
        mdb_env_create(&environment);
        QString path = createDirectory();

        mdb_env_set_maxdbs(environment, storages.size());
        mdb_env_set_mapsize(environment, size * 1024UL * 1024UL);
        mdb_env_open(environment, path.toStdString().c_str(), 0, 0664);

        TransactionID txn = beginPrivateTransaction(emptyName);
        for (const std::pair<const std::string, iStorage*>& pair : storages) {
            iStorage* storage = pair.second;
            int rc = storage->createStorage(txn);
            if (rc)
                throw Unknown(name, mdb_strerror(rc));
        }
        commitPrivateTransaction(txn, emptyName);
        opened = true;
    }
}

bool LMDBAL::Base::removeDirectory() {
    if (opened)
        throw Opened(name, "remove database directory");

    QString path(QStandardPaths::writableLocation(QStandardPaths::CacheLocation));
    path += "/" + getName();
    QDir cache(path);

    if (cache.exists())
        return cache.removeRecursively();
    else
        return true;
}

QString LMDBAL::Base::createDirectory() {
    if (opened)
        throw Opened(name, "create database directory");

    QString path(QStandardPaths::writableLocation(QStandardPaths::CacheLocation));
    path += "/" + getName();
    QDir cache(path);

    if (!cache.exists()) {
        bool res = cache.mkpath(path);
        if (!res)
            throw Directory(path.toStdString());
    }

    return path;
}

QString LMDBAL::Base::getName() const {
    return QString::fromStdString(name);}

bool LMDBAL::Base::ready() const {
    return opened;}

void LMDBAL::Base::drop() {
    if (!opened)
        throw Closed("drop", name);

    TransactionID txn = beginPrivateTransaction(emptyName);
    for (const std::pair<const std::string, iStorage*>& pair : storages) {
        int rc = pair.second->drop(txn);
        if (rc)
            throw Unknown(name, mdb_strerror(rc), pair.first);
    }
    commitPrivateTransaction(txn, emptyName);
}

LMDBAL::TransactionID LMDBAL::Base::beginReadOnlyTransaction() const {
    return beginReadOnlyTransaction(emptyName);}

LMDBAL::TransactionID LMDBAL::Base::beginTransaction() const {
    return beginTransaction(emptyName);}

void LMDBAL::Base::abortTransaction(LMDBAL::TransactionID id) const {
    return abortTransaction(id, emptyName);}

void LMDBAL::Base::commitTransaction(LMDBAL::TransactionID id) const {
    return commitTransaction(id, emptyName);}

LMDBAL::TransactionID LMDBAL::Base::beginReadOnlyTransaction(const std::string& storageName) const {
    if (!opened)
        throw Closed("beginReadOnlyTransaction", name, storageName);

    TransactionID txn = beginPrivateReadOnlyTransaction(storageName);
    transactions->emplace(txn);
    for (const std::pair<const std::string, LMDBAL::iStorage*>& pair : storages)
        pair.second->transactionStarted(txn, true);

    return txn;
}

LMDBAL::TransactionID LMDBAL::Base::beginTransaction(const std::string& storageName) const {
    if (!opened)
        throw Closed("beginTransaction", name, storageName);

    TransactionID txn = beginPrivateTransaction(storageName);
    transactions->emplace(txn);
    for (const std::pair<const std::string, LMDBAL::iStorage*>& pair : storages)
        pair.second->transactionStarted(txn, false);

    return txn;
}

void LMDBAL::Base::abortTransaction(LMDBAL::TransactionID id, const std::string& storageName) const {
    if (!opened)
        throw Closed("abortTransaction", name, storageName);

    Transactions::iterator itr = transactions->find(id);
    if (itr == transactions->end())     //TODO may be it's a good idea to make an exception class for this
        throw Unknown(name, "unable to abort transaction: transaction was not found", storageName);

    abortPrivateTransaction(id, storageName);
    for (const std::pair<const std::string, LMDBAL::iStorage*>& pair : storages)
        pair.second->transactionAborted(id);

    transactions->erase(itr);
}

void LMDBAL::Base::commitTransaction(LMDBAL::TransactionID id, const std::string& storageName) const {
    if (!opened)
        throw Closed("abortTransaction", name, storageName);

    Transactions::iterator itr = transactions->find(id);
    if (itr == transactions->end())     //TODO may be it's a good idea to make an exception class for this
        throw Unknown(name, "unable to commit transaction: transaction was not found", storageName);

    commitPrivateTransaction(id, storageName);
    for (const std::pair<const std::string, LMDBAL::iStorage*>& pair : storages)
        pair.second->transactionCommited(id);

    transactions->erase(itr);
}

LMDBAL::TransactionID LMDBAL::Base::beginPrivateReadOnlyTransaction(const std::string& storageName) const {
    MDB_txn* txn;
    int rc = mdb_txn_begin(environment, NULL, MDB_RDONLY, &txn);
    if (rc) {
        mdb_txn_abort(txn);
        throw Unknown(name, mdb_strerror(rc), storageName);
    }
    return txn;
}

LMDBAL::TransactionID LMDBAL::Base::beginPrivateTransaction(const std::string& storageName) const {
    MDB_txn* txn;
    int rc = mdb_txn_begin(environment, NULL, 0, &txn);
    if (rc) {
        mdb_txn_abort(txn);
        throw Unknown(name, mdb_strerror(rc), storageName);
    }
    return txn;
}

void LMDBAL::Base::abortPrivateTransaction(LMDBAL::TransactionID id, const std::string& storageName) const {
    UNUSED(storageName);
    mdb_txn_abort(id);
}

void LMDBAL::Base::commitPrivateTransaction(LMDBAL::TransactionID id, const std::string& storageName) const {
    int rc = mdb_txn_commit(id);
    if (rc != MDB_SUCCESS)
        throw Unknown(name, mdb_strerror(rc), storageName);
}