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	// Copyright (c) 2012-2015 The Bitcoin Core developers
	// Distributed under the MIT software license, see the accompanying
	// file COPYING or http://www.opensource.org/licenses/mit-license.php.

	#ifndef BITCOIN_DBWRAPPER_H
	#define BITCOIN_DBWRAPPER_H

	#include "clientversion.h"
	#include "serialize.h"
	#include "streams.h"
	#include "util.h"
	#include "utilstrencodings.h"
	#include "version.h"

	#include <boost/filesystem/path.hpp>

	#include <leveldb/db.h>
	#include <leveldb/write_batch.h>

	static const size_t DBWRAPPER_PREALLOC_KEY_SIZE = 64;
	static const size_t DBWRAPPER_PREALLOC_VALUE_SIZE = 1024;

	class dbwrapper_error : public std::runtime_error
	{
	public:
	dbwrapper_error(const std::string& msg) : std::runtime_error(msg) {}
	};

	class CDBWrapper;

	/** These should be considered an implementation detail of the specific database.
	*/
	namespace dbwrapper_private {

	/** Handle database error by throwing dbwrapper_error exception.
	*/
	void HandleError(const leveldb::Status& status);

	/** Work around circular dependency, as well as for testing in dbwrapper_tests.
	* Database obfuscation should be considered an implementation detail of the
	* specific database.
	*/
	const std::vector<unsigned char>& GetObfuscateKey(const CDBWrapper &w);

	};

	/** Batch of changes queued to be written to a CDBWrapper */
	class CDBBatch
	{
	friend class CDBWrapper;

	private:
	const CDBWrapper &parent;
	leveldb::WriteBatch batch;

	public:
	/**
	* @param[in] _parent CDBWrapper that this batch is to be submitted to
	*/
	CDBBatch(const CDBWrapper &_parent) : parent(_parent) { };

	template <typename K, typename V>
	void Write(const K& key, const V& value)
	{
	CDataStream ssKey(SER_DISK, CLIENT_VERSION);
	ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
	ssKey << key;
	leveldb::Slice slKey(&ssKey[0], ssKey.size());

	CDataStream ssValue(SER_DISK, CLIENT_VERSION);
	ssValue.reserve(DBWRAPPER_PREALLOC_VALUE_SIZE);
	ssValue << value;
	ssValue.Xor(dbwrapper_private::GetObfuscateKey(parent));
	leveldb::Slice slValue(&ssValue[0], ssValue.size());

	batch.Put(slKey, slValue);
	}

	template <typename K>
	void Erase(const K& key)
	{
	CDataStream ssKey(SER_DISK, CLIENT_VERSION);
	ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
	ssKey << key;
	leveldb::Slice slKey(&ssKey[0], ssKey.size());

	batch.Delete(slKey);
	}
	};

	class CDBIterator
	{
	private:
	const CDBWrapper &parent;
	leveldb::Iterator *piter;

	public:

	/**
	* @param[in] _parent Parent CDBWrapper instance.
	* @param[in] _piter The original leveldb iterator.
	*/
	CDBIterator(const CDBWrapper &_parent, leveldb::Iterator *_piter) :
	parent(_parent), piter(_piter) { };
	~CDBIterator();

	bool Valid();

	void SeekToFirst();

	template<typename K> void Seek(const K& key) {
	CDataStream ssKey(SER_DISK, CLIENT_VERSION);
	ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
	ssKey << key;
	leveldb::Slice slKey(&ssKey[0], ssKey.size());
	piter->Seek(slKey);
	}

	void Next();

	template<typename K> bool GetKey(K& key) {
	leveldb::Slice slKey = piter->key();
	try {
	CDataStream ssKey(slKey.data(), slKey.data() + slKey.size(), SER_DISK, CLIENT_VERSION);
	ssKey >> key;
	} catch (const std::exception&) {
	return false;
	}
	return true;
	}

	unsigned int GetKeySize() {
	return piter->key().size();
	}

	template<typename V> bool GetValue(V& value) {
	leveldb::Slice slValue = piter->value();
	try {
	CDataStream ssValue(slValue.data(), slValue.data() + slValue.size(), SER_DISK, CLIENT_VERSION);
	ssValue.Xor(dbwrapper_private::GetObfuscateKey(parent));
	ssValue >> value;
	} catch (const std::exception&) {
	return false;
	}
	return true;
	}

	unsigned int GetValueSize() {
	return piter->value().size();
	}

	};

	class CDBWrapper
	{
	friend const std::vector<unsigned char>& dbwrapper_private::GetObfuscateKey(const CDBWrapper &w);
	private:
	//! custom environment this database is using (may be NULL in case of default environment)
	leveldb::Env* penv;

	//! database options used
	leveldb::Options options;

	//! options used when reading from the database
	leveldb::ReadOptions readoptions;

	//! options used when iterating over values of the database
	leveldb::ReadOptions iteroptions;

	//! options used when writing to the database
	leveldb::WriteOptions writeoptions;

	//! options used when sync writing to the database
	leveldb::WriteOptions syncoptions;

	//! the database itself
	leveldb::DB* pdb;

	//! a key used for optional XOR-obfuscation of the database
	std::vector<unsigned char> obfuscate_key;

	//! the key under which the obfuscation key is stored
	static const std::string OBFUSCATE_KEY_KEY;

	//! the length of the obfuscate key in number of bytes
	static const unsigned int OBFUSCATE_KEY_NUM_BYTES;

	std::vector<unsigned char> CreateObfuscateKey() const;

	public:
	/**
	* @param[in] path Location in the filesystem where leveldb data will be stored.
	* @param[in] nCacheSize Configures various leveldb cache settings.
	* @param[in] fMemory If true, use leveldb's memory environment.
	* @param[in] fWipe If true, remove all existing data.
	* @param[in] obfuscate If true, store data obfuscated via simple XOR. If false, XOR
	* with a zero'd byte array.
	*/
	CDBWrapper(const boost::filesystem::path& path, size_t nCacheSize, bool fMemory = false, bool fWipe = false, bool obfuscate = false);
	~CDBWrapper();

	template <typename K, typename V>
	bool Read(const K& key, V& value) const
	{
	CDataStream ssKey(SER_DISK, CLIENT_VERSION);
	ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
	ssKey << key;
	leveldb::Slice slKey(&ssKey[0], ssKey.size());

	std::string strValue;
	leveldb::Status status = pdb->Get(readoptions, slKey, &strValue);
	if (!status.ok()) {
	if (status.IsNotFound())
	return false;
	LogPrintf("LevelDB read failure: %s\n", status.ToString());
	dbwrapper_private::HandleError(status);
	}
	try {
	CDataStream ssValue(strValue.data(), strValue.data() + strValue.size(), SER_DISK, CLIENT_VERSION);
	ssValue.Xor(obfuscate_key);
	ssValue >> value;
	} catch (const std::exception&) {
	return false;
	}
	return true;
	}

	template <typename K, typename V>
	bool Write(const K& key, const V& value, bool fSync = false)
	{
	CDBBatch batch(*this);
	batch.Write(key, value);
	return WriteBatch(batch, fSync);
	}

	template <typename K>
	bool Exists(const K& key) const
	{
	CDataStream ssKey(SER_DISK, CLIENT_VERSION);
	ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
	ssKey << key;
	leveldb::Slice slKey(&ssKey[0], ssKey.size());

	std::string strValue;
	leveldb::Status status = pdb->Get(readoptions, slKey, &strValue);
	if (!status.ok()) {
	if (status.IsNotFound())
	return false;
	LogPrintf("LevelDB read failure: %s\n", status.ToString());
	dbwrapper_private::HandleError(status);
	}
	return true;
	}

	template <typename K>
	bool Erase(const K& key, bool fSync = false)
	{
	CDBBatch batch(*this);
	batch.Erase(key);
	return WriteBatch(batch, fSync);
	}

	bool WriteBatch(CDBBatch& batch, bool fSync = false);

	// not available for LevelDB; provide for compatibility with BDB
	bool Flush()
	{
	return true;
	}

	bool Sync()
	{
	CDBBatch batch(*this);
	return WriteBatch(batch, true);
	}

	CDBIterator *NewIterator()
	{
	return new CDBIterator(*this, pdb->NewIterator(iteroptions));
	}

	/**
	* Return true if the database managed by this class contains no entries.
	*/
	bool IsEmpty();
	};

	#endif // BITCOIN_DBWRAPPER_H

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