/*
 * 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/>.
 */

#ifndef LMDBAL_CURSOR_HPP
#define LMDBAL_CURSOR_HPP

#include "cursor.h"

template<class K, class V>
LMDBAL::Cursor<K, V>::Cursor(Storage<K, V>* parent):
    storage(parent),
    cursor(nullptr),
    state(closed)
{

}

template<class K, class V>
LMDBAL::Cursor<K, V>::~Cursor () {
    close();
}

template<class K, class V>
void LMDBAL::Cursor<K, V>::terminated () const {
    close();        //for now it's the same, but if I ever going to make writable cursor - here is where it's gonna be different
}

template<class K, class V>
void LMDBAL::Cursor<K, V>::open () const {
    storage->ensureOpened(openCursorMethodName);
    switch (state) {
        case closed: {
            TransactionID txn = storage->beginReadOnlyTransaction();
            int result = mdb_cursor_open(txn, storage->dbi, &cursor);
            if (result != MDB_SUCCESS)
                storage->throwUnknown(result, txn);

            storage->transactionStarted(txn, true);
            state = openedPrivate;
        } break;
        default:
            break;
    }
}

template<class K, class V>
void LMDBAL::Cursor<K, V>::open (TransactionID txn) const {
    storage->ensureOpened(openCursorMethodName);
    switch (state) {
        case closed: {
            int result = mdb_cursor_open(txn, storage->dbi, &cursor);
            if (result != MDB_SUCCESS)
                storage->throwUnknown(result);

            state = openedPublic;
        } break;
        default:
            break;
    }
}

template<class K, class V>
void LMDBAL::Cursor<K, V>::renew () const {
    storage->ensureOpened(renewCursorMethodName);
    switch (state) {
        case openedPrivate: {
            TransactionID txn = mdb_cursor_txn(cursor);
            storage->abortTransaction(txn);
            storage->transactionAborted(txn);
            [[fallthrough]];
        }
        case openedPublic: {
            TransactionID txn = storage->beginReadOnlyTransaction();
            int result = mdb_cursor_renew(txn, cursor);
            if (result != MDB_SUCCESS)
                storage->throwUnknown(result, txn);

            storage->transactionStarted(txn, true);
            state = openedPrivate;
        } break;
        default:
            break;
    }
}

template<class K, class V>
void LMDBAL::Cursor<K, V>::renew (TransactionID txn) const {
    storage->ensureOpened(renewCursorMethodName);
    switch (state) {
        case openedPrivate: {
            TransactionID txn = mdb_cursor_txn(cursor);
            storage->abortTransaction(txn);
            storage->transactionAborted(txn);
            [[fallthrough]];
        }
        case openedPublic: {
            int result = mdb_cursor_renew(txn, cursor);
            if (result != MDB_SUCCESS)
                storage->throwUnknown(result);

            state = openedPublic;
        } break;
        default:
            break;
    }
}

template<class K, class V>
void LMDBAL::Cursor<K, V>::close () const {
    switch (state) {
        case openedPublic: {
            mdb_cursor_close(cursor);

            state = closed;
        } break;
        case openedPrivate: {
            TransactionID txn = mdb_cursor_txn(cursor);
            mdb_cursor_close(cursor);
            storage->abortTransaction(txn);
            storage->transactionAborted(txn);

            state = closed;
        } break;
        default:
            break;
    }
}

template<class K, class V>
void LMDBAL::Cursor<K, V>::first (K& key, V& value) const {
    operateCursorRead(key, value, MDB_FIRST, firstMethodName, firstOperationName);
}

template<class K, class V>
void LMDBAL::Cursor<K, V>::last (K& key, V& value) const {
    operateCursorRead(key, value, MDB_LAST, lastMethodName, lastOperationName);
}

template<class K, class V>
void LMDBAL::Cursor<K, V>::next (K& key, V& value) const {
    operateCursorRead(key, value, MDB_NEXT, nextMethodName, nextOperationName);
}

template<class K, class V>
void LMDBAL::Cursor<K, V>::prev (K& key, V& value) const {
    operateCursorRead(key, value, MDB_PREV, prevMethodName, prevOperationName);
}

template<class K, class V>
void LMDBAL::Cursor<K, V>::current (K& key, V& value) const {
    operateCursorRead(key, value, MDB_GET_CURRENT, currentMethodName, currentOperationName);
}

template<class K, class V>
std::pair<K, V> LMDBAL::Cursor<K, V>::first () const {
    std::pair<K, V> result;
    operateCursorRead(result.first, result.second, MDB_FIRST, firstMethodName, firstOperationName);
    return result;
}

template<class K, class V>
std::pair<K, V> LMDBAL::Cursor<K, V>::last () const {
    std::pair<K, V> result;
    operateCursorRead(result.first, result.second, MDB_LAST, lastMethodName, lastOperationName);
    return result;
}

template<class K, class V>
std::pair<K, V> LMDBAL::Cursor<K, V>::next () const {
    std::pair<K, V> result;
    operateCursorRead(result.first, result.second, MDB_NEXT, nextMethodName, nextOperationName);
    return result;
}

template<class K, class V>
std::pair<K, V> LMDBAL::Cursor<K, V>::prev () const {
    std::pair<K, V> result;
    operateCursorRead(result.first, result.second, MDB_PREV, prevMethodName, prevOperationName);
    return result;
}

template<class K, class V>
std::pair<K, V> LMDBAL::Cursor<K, V>::current () const {
    std::pair<K, V> result;
    operateCursorRead(result.first, result.second, MDB_GET_CURRENT, currentMethodName, currentOperationName);
    return result;
}


template<class K, class V>
void LMDBAL::Cursor<K, V>::operateCursorRead(
    K& key,
    V& value,
    MDB_cursor_op operation,
    const std::string& methodName,
    const std::string& operationName
) const {
    if (state == closed)
        storage->throwCursorNotReady(methodName);

    MDB_val mdbKey, mdbValue;
    int result = mdb_cursor_get(cursor, &mdbKey, &mdbValue, operation);
    if (result != MDB_SUCCESS)
        storage->throwNotFoundOrUnknown(result, operationName);

    storage->keySerializer.deserialize(mdbKey, key);
    storage->valueSerializer.deserialize(mdbValue, value);

    if (state == openedPrivate)
        storage->discoveredRecord(key, value);
    else
        storage->discoveredRecord(key, value, mdb_cursor_txn(cursor));
}

#endif //LMDBAL_CURSOR_HPP