// Copyright (c) 2012-2022 The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <dbwrapper.h>

#include <logging.h>

#include <random.h>

#include <serialize.h>

#include <span.h>

#include <streams.h>

#include <util/fs.h>

#include <util/fs_helpers.h>

#include <util/strencodings.h>

#include <algorithm>

#include <cassert>

#include <cstdarg>

#include <cstdint>

#include <cstdio>

#include <leveldb/cache.h>

#include <leveldb/db.h>

#include <leveldb/env.h>

#include <leveldb/filter_policy.h>

#include <leveldb/helpers/memenv/memenv.h>

#include <leveldb/iterator.h>

#include <leveldb/options.h>

#include <leveldb/slice.h>

#include <leveldb/status.h>

#include <leveldb/write_batch.h>

#include <memory>

#include <optional>

#include <utility>

static auto CharCast(const std::byte* data) { return reinterpret_cast<const char*>(data); }

bool DestroyDB(const std::string& path_str)

{

    return leveldb::DestroyDB(path_str, {}).ok();

}

/** Handle database error by throwing dbwrapper_error exception.

 */

static void HandleError(const leveldb::Status& status)

{

    if (status.ok())

        return;

    const std::string errmsg = "Fatal LevelDB error: " + status.ToString();

    LogPrintf("%s\n", errmsg);

    LogPrintf("You can use -debug=leveldb to get more complete diagnostic messages\n");

    throw dbwrapper_error(errmsg);

}

class CBitcoinLevelDBLogger : public leveldb::Logger {

public:

    // This code is adapted from posix_logger.h, which is why it is using vsprintf.

    // Please do not do this in normal code

    void Logv(const char * format, va_list ap) override {

            if (!LogAcceptCategory(BCLog::LEVELDB, BCLog::Level::Debug)) {

                return;

            }

            char buffer[500];

            for (int iter = 0; iter < 2; iter++) {

                char* base;

                int bufsize;

                if (iter == 0) {

                    bufsize = sizeof(buffer);

                    base = buffer;

                }

                else {

                    bufsize = 30000;

                    base = new char[bufsize];

                }

                char* p = base;

                char* limit = base + bufsize;

                // Print the message

                if (p < limit) {

                    va_list backup_ap;

                    va_copy(backup_ap, ap);

                    // Do not use vsnprintf elsewhere in bitcoin source code, see above.

                    p += vsnprintf(p, limit - p, format, backup_ap);

                    va_end(backup_ap);

                }

                // Truncate to available space if necessary

                if (p >= limit) {

                    if (iter == 0) {

                        continue;       // Try again with larger buffer

                    }

                    else {

                        p = limit - 1;

                    }

                }

                // Add newline if necessary

                if (p == base || p[-1] != '\n') {

                    *p++ = '\n';

                }

                assert(p <= limit);

                base[std::min(bufsize - 1, (int)(p - base))] = '\0';

                LogDebug(BCLog::LEVELDB, "%s\n", util::RemoveSuffixView(base, "\n"));

                if (base != buffer) {

                    delete[] base;

                }

                break;

            }

    }

};

static void SetMaxOpenFiles(leveldb::Options *options) {

    // On most platforms the default setting of max_open_files (which is 1000)

    // is optimal. On Windows using a large file count is OK because the handles

    // do not interfere with select() loops. On 64-bit Unix hosts this value is

    // also OK, because up to that amount LevelDB will use an mmap

    // implementation that does not use extra file descriptors (the fds are

    // closed after being mmap'ed).

    //

    // Increasing the value beyond the default is dangerous because LevelDB will

    // fall back to a non-mmap implementation when the file count is too large.

    // On 32-bit Unix host we should decrease the value because the handles use

    // up real fds, and we want to avoid fd exhaustion issues.

    //

    // See PR #12495 for further discussion.

    int default_open_files = options->max_open_files;

#ifndef WIN32

    if (sizeof(void*) < 8) {

        options->max_open_files = 64;

    }

#endif

    LogDebug(BCLog::LEVELDB, "LevelDB using max_open_files=%d (default=%d)\n",

             options->max_open_files, default_open_files);

}

static leveldb::Options GetOptions(size_t nCacheSize)

{

    leveldb::Options options;

    options.block_cache = leveldb::NewLRUCache(nCacheSize / 2);

    options.write_buffer_size = nCacheSize / 4; // up to two write buffers may be held in memory simultaneously

    options.filter_policy = leveldb::NewBloomFilterPolicy(10);

    options.compression = leveldb::kNoCompression;

    options.info_log = new CBitcoinLevelDBLogger();

    if (leveldb::kMajorVersion > 1 || (leveldb::kMajorVersion == 1 && leveldb::kMinorVersion >= 16)) {

        // LevelDB versions before 1.16 consider short writes to be corruption. Only trigger error

        // on corruption in later versions.

        options.paranoid_checks = true;

    }

    SetMaxOpenFiles(&options);

    return options;

}

struct CDBBatch::WriteBatchImpl {

    leveldb::WriteBatch batch;

};

CDBBatch::CDBBatch(const CDBWrapper& _parent)

    : parent{_parent},

      m_impl_batch{std::make_unique<CDBBatch::WriteBatchImpl>()} {};

CDBBatch::~CDBBatch() = default;

void CDBBatch::Clear()

{

    m_impl_batch->batch.Clear();

    size_estimate = 0;

}

void CDBBatch::WriteImpl(Span<const std::byte> key, DataStream& ssValue)

{

    leveldb::Slice slKey(CharCast(key.data()), key.size());

    ssValue.Xor(dbwrapper_private::GetObfuscateKey(parent));

    leveldb::Slice slValue(CharCast(ssValue.data()), ssValue.size());

    m_impl_batch->batch.Put(slKey, slValue);

    // LevelDB serializes writes as:

    // - byte: header

    // - varint: key length (1 byte up to 127B, 2 bytes up to 16383B, ...)

    // - byte[]: key

    // - varint: value length

    // - byte[]: value

    // The formula below assumes the key and value are both less than 16k.

    size_estimate += 3 + (slKey.size() > 127) + slKey.size() + (slValue.size() > 127) + slValue.size();

}

void CDBBatch::EraseImpl(Span<const std::byte> key)

{

    leveldb::Slice slKey(CharCast(key.data()), key.size());

    m_impl_batch->batch.Delete(slKey);

    // LevelDB serializes erases as:

    // - byte: header

    // - varint: key length

    // - byte[]: key

    // The formula below assumes the key is less than 16kB.

    size_estimate += 2 + (slKey.size() > 127) + slKey.size();

}

struct LevelDBContext {

    //! custom environment this database is using (may be nullptr 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;

};

CDBWrapper::CDBWrapper(const DBParams& params)

    : m_db_context{std::make_unique<LevelDBContext>()}, m_name{fs::PathToString(params.path.stem())}, m_path{params.path}, m_is_memory{params.memory_only}

{

    DBContext().penv = nullptr;

    DBContext().readoptions.verify_checksums = true;

    DBContext().iteroptions.verify_checksums = true;

    DBContext().iteroptions.fill_cache = false;

    DBContext().syncoptions.sync = true;

    DBContext().options = GetOptions(params.cache_bytes);

    DBContext().options.create_if_missing = true;

    if (params.memory_only) {

        DBContext().penv = leveldb::NewMemEnv(leveldb::Env::Default());

        DBContext().options.env = DBContext().penv;

    } else {

        if (params.wipe_data) {

            LogPrintf("Wiping LevelDB in %s\n", fs::PathToString(params.path));

            leveldb::Status result = leveldb::DestroyDB(fs::PathToString(params.path), DBContext().options);

            HandleError(result);

        }

        TryCreateDirectories(params.path);

        LogPrintf("Opening LevelDB in %s\n", fs::PathToString(params.path));

    }

    // PathToString() return value is safe to pass to leveldb open function,

    // because on POSIX leveldb passes the byte string directly to ::open(), and

    // on Windows it converts from UTF-8 to UTF-16 before calling ::CreateFileW

    // (see env_posix.cc and env_windows.cc).

    leveldb::Status status = leveldb::DB::Open(DBContext().options, fs::PathToString(params.path), &DBContext().pdb);

    HandleError(status);

    LogPrintf("Opened LevelDB successfully\n");

    if (params.options.force_compact) {

        LogPrintf("Starting database compaction of %s\n", fs::PathToString(params.path));

        DBContext().pdb->CompactRange(nullptr, nullptr);

        LogPrintf("Finished database compaction of %s\n", fs::PathToString(params.path));

    }

    // The base-case obfuscation key, which is a noop.

    obfuscate_key = std::vector<unsigned char>(OBFUSCATE_KEY_NUM_BYTES, '\000');

    bool key_exists = Read(OBFUSCATE_KEY_KEY, obfuscate_key);

    if (!key_exists && params.obfuscate && IsEmpty()) {

        // Initialize non-degenerate obfuscation if it won't upset

        // existing, non-obfuscated data.

        std::vector<unsigned char> new_key = CreateObfuscateKey();

        // Write `new_key` so we don't obfuscate the key with itself

        Write(OBFUSCATE_KEY_KEY, new_key);

        obfuscate_key = new_key;

        LogPrintf("Wrote new obfuscate key for %s: %s\n", fs::PathToString(params.path), HexStr(obfuscate_key));

    }

    LogPrintf("Using obfuscation key for %s: %s\n", fs::PathToString(params.path), HexStr(obfuscate_key));

}

CDBWrapper::~CDBWrapper()

{

    delete DBContext().pdb;

    DBContext().pdb = nullptr;

    delete DBContext().options.filter_policy;

    DBContext().options.filter_policy = nullptr;

    delete DBContext().options.info_log;

    DBContext().options.info_log = nullptr;

    delete DBContext().options.block_cache;

    DBContext().options.block_cache = nullptr;

    delete DBContext().penv;

    DBContext().options.env = nullptr;

}

bool CDBWrapper::WriteBatch(CDBBatch& batch, bool fSync)

{

    const bool log_memory = LogAcceptCategory(BCLog::LEVELDB, BCLog::Level::Debug);

    double mem_before = 0;

    if (log_memory) {

        mem_before = DynamicMemoryUsage() / 1024.0 / 1024;

    }

    leveldb::Status status = DBContext().pdb->Write(fSync ? DBContext().syncoptions : DBContext().writeoptions, &batch.m_impl_batch->batch);

    HandleError(status);

    if (log_memory) {

        double mem_after = DynamicMemoryUsage() / 1024.0 / 1024;

        LogDebug(BCLog::LEVELDB, "WriteBatch memory usage: db=%s, before=%.1fMiB, after=%.1fMiB\n",

                 m_name, mem_before, mem_after);

    }

    return true;

}

size_t CDBWrapper::DynamicMemoryUsage() const

{

    std::string memory;

    std::optional<size_t> parsed;

    if (!DBContext().pdb->GetProperty("leveldb.approximate-memory-usage", &memory) || !(parsed = ToIntegral<size_t>(memory))) {

        LogDebug(BCLog::LEVELDB, "Failed to get approximate-memory-usage property\n");

        return 0;

    }

    return parsed.value();

}

// Prefixed with null character to avoid collisions with other keys

//

// We must use a string constructor which specifies length so that we copy

// past the null-terminator.

const std::string CDBWrapper::OBFUSCATE_KEY_KEY("\000obfuscate_key", 14);

const unsigned int CDBWrapper::OBFUSCATE_KEY_NUM_BYTES = 8;

/**

 * Returns a string (consisting of 8 random bytes) suitable for use as an

 * obfuscating XOR key.

 */

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

{

    std::vector<uint8_t> ret(OBFUSCATE_KEY_NUM_BYTES);

    GetRandBytes(ret);

    return ret;

}

std::optional<std::string> CDBWrapper::ReadImpl(Span<const std::byte> key) const

{

    leveldb::Slice slKey(CharCast(key.data()), key.size());

    std::string strValue;

    leveldb::Status status = DBContext().pdb->Get(DBContext().readoptions, slKey, &strValue);

    if (!status.ok()) {

        if (status.IsNotFound())

            return std::nullopt;

        LogPrintf("LevelDB read failure: %s\n", status.ToString());

        HandleError(status);

    }

    return strValue;

}

bool CDBWrapper::ExistsImpl(Span<const std::byte> key) const

{

    leveldb::Slice slKey(CharCast(key.data()), key.size());

    std::string strValue;

    leveldb::Status status = DBContext().pdb->Get(DBContext().readoptions, slKey, &strValue);

    if (!status.ok()) {

        if (status.IsNotFound())

            return false;

        LogPrintf("LevelDB read failure: %s\n", status.ToString());

        HandleError(status);

    }

    return true;

}

size_t CDBWrapper::EstimateSizeImpl(Span<const std::byte> key1, Span<const std::byte> key2) const

{

    leveldb::Slice slKey1(CharCast(key1.data()), key1.size());

    leveldb::Slice slKey2(CharCast(key2.data()), key2.size());

    uint64_t size = 0;

    leveldb::Range range(slKey1, slKey2);

    DBContext().pdb->GetApproximateSizes(&range, 1, &size);

    return size;

}

bool CDBWrapper::IsEmpty()

{

    std::unique_ptr<CDBIterator> it(NewIterator());

    it->SeekToFirst();

    return !(it->Valid());

}

struct CDBIterator::IteratorImpl {

    const std::unique_ptr<leveldb::Iterator> iter;

    explicit IteratorImpl(leveldb::Iterator* _iter) : iter{_iter} {}

};

CDBIterator::CDBIterator(const CDBWrapper& _parent, std::unique_ptr<IteratorImpl> _piter) : parent(_parent),

                                                                                            m_impl_iter(std::move(_piter)) {}

CDBIterator* CDBWrapper::NewIterator()

{

    return new CDBIterator{*this, std::make_unique<CDBIterator::IteratorImpl>(DBContext().pdb->NewIterator(DBContext().iteroptions))};

}

void CDBIterator::SeekImpl(Span<const std::byte> key)

{

    leveldb::Slice slKey(CharCast(key.data()), key.size());

    m_impl_iter->iter->Seek(slKey);

}

Span<const std::byte> CDBIterator::GetKeyImpl() const

{

    return MakeByteSpan(m_impl_iter->iter->key());

}

Span<const std::byte> CDBIterator::GetValueImpl() const

{

    return MakeByteSpan(m_impl_iter->iter->value());

}

CDBIterator::~CDBIterator() = default;

bool CDBIterator::Valid() const { return m_impl_iter->iter->Valid(); }

void CDBIterator::SeekToFirst() { m_impl_iter->iter->SeekToFirst(); }

void CDBIterator::Next() { m_impl_iter->iter->Next(); }

namespace dbwrapper_private {

const std::vector<unsigned char>& GetObfuscateKey(const CDBWrapper &w)

{

    return w.obfuscate_key;

}

} // namespace dbwrapper_private