/*
 * 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/>.
 */

#pragma once

#include <map>
#include <set>
#include <string>
#include <optional>
#include <limits>

#include <QString>
#include <QStandardPaths>
#include <QDir>

#include <lmdb.h>

#include "exceptions.h"

namespace LMDBAL {

class iStorage;
class Transaction;
class WriteTransaction;

template<class T>
class Serializer;

template <class K, class V>
class Storage;

template <class K, class V>
class Cache;

typedef MDB_txn* TransactionID;                         /**<\brief I'm going to use transaction pointers as transaction IDs*/
typedef uint32_t SizeType;                              /**<\brief All LMDBAL sizes are uint32_t*/

class Base {
    friend class iStorage;
    friend class Transaction;
    friend class WriteTransaction;
public:

    Base(const QString& name, uint16_t mapSize = 10);
    ~Base();

    void open();
    void close();
    bool ready() const;
    bool removeDirectory();
    QString createDirectory();
    QString getName() const;
    QString getPath() const;
    void drop();

    Transaction beginReadOnlyTransaction() const;
    WriteTransaction beginTransaction();

    template <class K, class V>
    LMDBAL::Storage<K, V>* addStorage(const std::string& storageName, bool duplicates = false);

    template <class K, class V>
    LMDBAL::Cache<K, V>* addCache(const std::string& storageName);

    template <class K, class V>
    LMDBAL::Storage<K, V>* getStorage(const std::string& storageName);

    template <class K, class V>
    LMDBAL::Cache<K, V>* getCache(const std::string& storageName);

private:
    typedef std::map<std::string, LMDBAL::iStorage*> Storages;  /**<\brief Storage and Cache pointers are saved in the std::map*/
    typedef std::map<TransactionID, Transaction*> Transactions; /**<\brief Piblic transaction IDs are saved in the std::set*/

    void commitTransaction(TransactionID id);
    void abortTransaction(TransactionID id) const;
    TransactionID beginReadOnlyTransaction(const std::string& storageName) const;
    TransactionID beginTransaction(const std::string& storageName) const;
    void commitTransaction(TransactionID id, const std::string& storageName);
    void abortTransaction(TransactionID id, const std::string& storageName) const;

    TransactionID beginPrivateReadOnlyTransaction(const std::string& storageName) const;
    TransactionID beginPrivateTransaction(const std::string& storageName) const;
    void commitPrivateTransaction(TransactionID id, const std::string& storageName);
    void abortPrivateTransaction(TransactionID id, const std::string& storageName) const;

private:
    std::string name;                                           /**<\brief Name of this database*/
    bool opened;                                                /**<\brief State of this database*/
    uint16_t size;                                              /**<\brief lmdb map size in MiB*/
    MDB_env* environment;                                       /**<\brief lmdb environment handle*/
    Storages storages;                                          /**<\brief Registered storages and caches*/
    mutable Transactions transactions;                          /**<\brief Active public transactions*/

    inline static const std::string emptyName = "";             /**<\brief Empty string for general fallback purposes*/
};

}
#include "operators.hpp"

/**
 * \brief Adds LMDBAL::Storage to the database
 *
 * Defines that the database is going to have the following storage.
 * The LMDBAL::Base must be closed
 *
 * \param[in]   storageName     - storage name
 * \param[in]   duplicates      - true if key duplicates are allowed (false by default)
 *
 * \returns     storage pointer. LMDBAL::Base keeps the ownership of the added storage, you don't need to destoroy it
 *
 * \tparam K    -   key type of the storage
 * \tparam V    -   value type of the storage
 *
 * \exception LMDBAL::Opened            thrown if this method is called on the opened database
 * \exception LMDBAL::StorageDuplicate  thrown if somebody tries to add storage with repeating name
 */
template <class K, class V>
LMDBAL::Storage<K, V>* LMDBAL::Base::addStorage(const std::string& storageName, bool duplicates) {
    if (opened)
        throw Opened(name, "add storage " + storageName);

    Storage<K, V>* storage = new Storage<K, V>(this, storageName, duplicates);
    std::pair<Storages::const_iterator, bool> pair = storages.insert(std::make_pair(storageName, (iStorage*)storage));
    if (!pair.second)
        throw StorageDuplicate(name, storageName);

    return storage;
}

/**
 * \brief Adds LMDBAL::Cache to the database
 *
 * Defines that the database is going to have the following cache.
 * The LMDBAL::Base must be closed
 *
 * \param[in]   storageName     - cache name
 * \returns     cache pointer. LMDBAL::Base keeps the ownership of the added cache, you don't need to destoroy it
 *
 * \tparam K    -   key type of the cache
 * \tparam V    -   value type of the cahce
 *
 * \exception LMDBAL::Opened            thrown if this method is called on the opened database
 * \exception LMDBAL::StorageDuplicate  thrown if somebody tries to add cache with repeating name
 */
template<class K, class V>
LMDBAL::Cache<K, V> * LMDBAL::Base::addCache(const std::string& storageName) {
    if (opened)
        throw Opened(name, "add cache " + storageName);

    Cache<K, V>* cache = new Cache<K, V>(this, storageName, false);
    std::pair<Storages::const_iterator, bool> pair = storages.insert(std::make_pair(storageName, (iStorage*)cache));
    if (!pair.second)
        throw StorageDuplicate(name, storageName);

    return cache;
}

/**
 * \brief Returns LMDBAL::Storage handle
 *
 * Requested storage must have been added before opening database
 * Note that template parameters is user responsibility zone!
 * If user, for instance, had added storage <int, int> but calling
 * this method with template parameters <std::string, std::string>
 * on the same name of the previously added storage, or calling it on cache - the behaviour is undefined
 *
 * \param[in]   storageName - storage name
 * \returns     storage pointer. LMDBAL::Base keeps the ownership of the added storage, you don't need to destoroy it
 *
 * \tparam K    -   key type of the storage
 * \tparam V    -   value type of the storage
 *
 * \exception std::out_of_range thrown if storage with the given name was not found
 */
template <class K, class V>
LMDBAL::Storage<K, V>* LMDBAL::Base::getStorage(const std::string& storageName) {
    return static_cast<Storage<K, V>*>(storages.at(storageName));
}

/**
 * \brief Returns LMDBAL::Cache handle
 *
 * Requested cache must have been added before opening database
 * Note that template parameters is user responsibility zone!
 * If user, for instance, had added cache <int, int> but calling
 * this method with template parameters <std::string, std::string>
 * on the same name of the previously added cache, or calling it on storage - the behaviour is undefined
 *
 * \param[in]   storageName - cache name
 * \returns     cache pointer. LMDBAL::Base keeps the ownership of the added cache, you don't need to destoroy it
 *
 * \tparam K    -   key type of the cache
 * \tparam V    -   value type of the cahce
 *
 * \exception std::out_of_range thrown if cache with the given name was not found
 */
template <class K, class V>
LMDBAL::Cache<K, V>* LMDBAL::Base::getCache(const std::string& storageName) {
    return static_cast<Cache<K, V>*>(storages.at(storageName));
}