/*
 * This file is part of the Flowee project
 * Copyright (C) 2017-2024 Tom Zander <tom@flowee.org>
 *
 * 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 BLOCKSDB_P_H
#define BLOCKSDB_P_H

/*
 * WARNING USAGE OF THIS HEADER IS RESTRICTED.
 * This Header file is part of the private API and is meant to be used solely by the server component.
 *
 * Usage of this API will likely mean your code will break in interesting ways in the future,
 * or even stop to compile.
 *
 * YOU HAVE BEEN WARNED!!
 */

#include "chain.h"
#include "BlocksDB.h"
#include "streaming/ConstBuffer.h"

#include <vector>
#include <mutex>
#include <memory>
#include <list>

#include <boost/unordered_map.hpp>
#include <boost/iostreams/device/mapped_file.hpp>


class CBlockIndex;
class CScheduler;

namespace Blocks {

struct DataFile
{
    DataFile() : filesize(0) {}
    boost::iostreams::mapped_file file;
    std::weak_ptr<char> buffer;
    size_t filesize;
};

enum BlockType {
    ForwardBlock,
    RevertBlock,
    MetaDataForBlock
};

struct FileHistoryEntry
{
    FileHistoryEntry(const std::shared_ptr<char> &dataFile, int64_t lastAccessed)
        : dataFile(dataFile), lastAccessed(lastAccessed) {}

    std::shared_ptr<char> dataFile;
    int64_t lastAccessed = 0;
};

class BlockFileInfo
{
public:
    unsigned int nBlocks;      //! number of blocks stored in file
    unsigned int nSize;        //! number of used bytes of block file
    unsigned int nUndoSize;    //! number of used bytes in the undo file

    ADD_SERIALIZE_METHODS

    template <typename Stream, typename Operation>
    inline void SerializationOp(Stream& s, Operation ser_action, int nType, int nVersion) {
        READWRITE(VARINT(nBlocks));
        READWRITE(VARINT(nSize));
        READWRITE(VARINT(nUndoSize));
    }

     void SetNull() {
         nBlocks = 0;
         nSize = 0;
         nUndoSize = 0;
     }

     BlockFileInfo() {
         SetNull();
     }

     std::string ToString() const;

     /** update statistics (does not update nSize) */
     void AddBlock() {
         nBlocks++;
     }
};

class DBPrivate  : public std::enable_shared_from_this<DBPrivate>
{
public:
    DBPrivate();
    ~DBPrivate();

    Streaming::ConstBuffer loadBlock(CDiskBlockPos pos, BlockType type);
    Streaming::ConstBuffer writeBlock(const std::deque<Streaming::ConstBuffer> &block, CDiskBlockPos &pos, BlockType type);
    void unloadIndexMap();
    void foundBlockFile(int index, const BlockFileInfo &info);

    std::shared_ptr<char> mapFile(int fileIndex, BlockType type, size_t *size_out = 0, bool *isWritable = nullptr);

    // close files from filehistory that have been unused for some time.
    void setScheduler(CScheduler *scheduler);
    void pruneFiles();
    /**
     * @brief allByHeight Sort and return the blocks by height.
     */
    std::vector<std::pair<int, CBlockIndex*> > allByHeight() const;

    CChain headersChain;
    std::list<CBlockIndex*> headerChainTips;

    std::vector<std::string> blocksDataDirs;

    std::recursive_mutex lock;
    bool nextWriteToNewFile = false; // we detected a writing issue with the last file, go to a new data file.
    std::vector<DataFile*> datafiles;
    std::vector<DataFile*> revertDatafiles;
    std::list<FileHistoryEntry> fileHistory; // keep the last opened ones to avoid opening and closing files all the time.

    std::mutex blockIndexLock;

    typedef boost::unordered_map<uint256, CBlockIndex*, HashShortener> BlockMap;
    BlockMap indexMap;

    ReindexingState reindexing = NoReindex;
};
}

// a global owned by main.cpp
extern std::vector<Blocks::BlockFileInfo> vinfoBlockFile;

#endif