/*
 * 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 "transaction.h"

#include "cursorcommon.h"

/**
 * \class LMDBAL::Transaction
 * \brief Public read only transaction
 *
 * This class provides read only transactions you can use
 * to speed to your queries keeping them thread safe.
 * LMDBAL::Transaction is <b>NOT COPYABLE</b> but <b>MOVABLE</b>.
 * Transaction can be in one of two states: active or terminated.
 * The way to receive an active LMDBAL::Transaction is to call LMDBAL::Base::beginReadOnlyTransaction.
 *
 * Active transactions become terminated upon the call of LMDBAL::Transaction::terminate.
 * Active transactions automaticaly terminate themselves upon destruction.
 *
 * You <b>CAN NOT</b> use inactive transactions for any query.
 */

/**
 * \brief Constructs inactive transaction
 */
LMDBAL::Transaction::Transaction():
    txn(nullptr),
    active(false),
    parent(nullptr),
    cursors()
{}

/**
 * \brief Constructs an active transaction
 */
LMDBAL::Transaction::Transaction(TransactionID txn, const Base* parent) :
    txn(txn),
    active(true),
    parent(parent),
    cursors()
{
    parent->transactions[txn] = this;
}

/**
 * \brief Moves transaction to a new object
 */
LMDBAL::Transaction::Transaction(Transaction&& other):
    txn(other.txn),
    active(other.active),
    parent(other.parent),
    cursors(other.cursors)
{
    if (active) {
        parent->transactions[txn] = this;

        other.reset();
    }
}

/**
 * \brief Destroys transaction
 */
LMDBAL::Transaction::~Transaction() {
    terminate();
}

/**
 * \brief Move-assigns transaction to the new object
 */
LMDBAL::Transaction& LMDBAL::Transaction::operator=(Transaction&& other) {
    if (this == &other)
        return *this;

    terminate();

    txn = other.txn;
    active = other.active;
    parent = other.parent;
    cursors = other.cursors;

    if (active) {
        parent->transactions[txn] = this;

        other.reset();
    }

    return *this;
}

/**
 * \brief Terminates transaction if it was active
 *
 * Transaction becomes terminated after calling this method
 */
void LMDBAL::Transaction::terminate() {
    if (active) {
        closeCursors();
        parent->abortTransaction(txn);
        parent->transactions.erase(txn);
        reset();
    }
}


/**
 * \brief Resets inner transaction properties to inactive state
 */
void LMDBAL::Transaction::reset() {
    active = false;
    txn = nullptr;
    parent = nullptr;
    cursors.clear();
}

/**
 * \brief Closes attached curors;
 */
void LMDBAL::Transaction::closeCursors () {
    for (const std::pair<const uint32_t, CursorCommon*>& pair : cursors)
        pair.second->terminated();
}

/**
 * \brief Returns transaction states
 *
 * \returns true if the transaction is active, false otherwise
 */
bool LMDBAL::Transaction::isActive() const {
    return active;      //todo may be it's better if I query it from DB?
}


/**
 * \class LMDBAL::WriteTransaction
 * \brief Public writable transaction
 *
 * This class provides writable transactions you can use
 * to speed to your queries and modifications keeping them thread safe.
 * LMDBAL::WriteTransaction is <b>NOT COPYABLE</b> but <b>MOVABLE</b>.
 * Transaction can be in one of two states: active or terminated.
 * The way to receive an active LMDBAL::WriteTransaction is to call LMDBAL::Base::beginTransaction.
 * You can use LMDBAL::WriteTransaction for everything instead of LMDBAL::Transaction
 *
 * Active transactions become terminated upon the call of
 * LMDBAL::WriteTransaction::abort or LMDBAL::WriteTransaction::commit.
 * Calling LMDBAL::Transaction::terminate on LMDBAL::WriteTransaction
 * is exactly the same as calling LMDBAL::WriteTransaction::abort.
 *
 * Active transactions automaticaly terminate themselves upon destruction.
 * <b>For LMDBAL::WriteTransaction default behaviour upon destruction is to abort.</b>
 *
 * You <b>CAN NOT</b> use inactive transactions for any query.
 */

/**
 * \brief Constructs active write transaction
 */
LMDBAL::WriteTransaction::WriteTransaction(TransactionID txn, Base* parent):
    Transaction(txn, parent)
{}

/**
 * \brief Constructs inactive write transaction
 */
LMDBAL::WriteTransaction::WriteTransaction():
    Transaction()
{}

/**
 * \brief Moves transaction to the new object
 */
LMDBAL::WriteTransaction::WriteTransaction(WriteTransaction&& other):
    Transaction(std::move(other))
{}

LMDBAL::WriteTransaction& LMDBAL::WriteTransaction::operator=(WriteTransaction&& other) {
    Transaction::operator=(std::move(other));

    return *this;
}

/**
 * \brief Aborts transaction cancelling all changes
 *
 * Transaction becomes terminated after calling this method
 */
void LMDBAL::WriteTransaction::abort() {
    terminate();
}

/**
 * \brief Commits transaction submitting all changes
 *
 * Transaction becomes terminated after calling this method
 */
void LMDBAL::WriteTransaction::commit() {
    if (active) {
        closeCursors();
        const_cast<Base*>(parent)->commitTransaction(txn);
        parent->transactions.erase(txn);
        reset();
    }
}