// Copyright (c) 2009-2010 Satoshi Nakamoto

// Copyright (c) 2009-present 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_NODE_UTXO_SNAPSHOT_H

#define BITCOIN_NODE_UTXO_SNAPSHOT_H

#include <kernel/chainparams.h>

#include <kernel/cs_main.h>

#include <kernel/messagestartchars.h>

#include <sync.h>

#include <tinyformat.h>

#include <uint256.h>

#include <util/chaintype.h>

#include <util/fs.h>

#include <algorithm>

#include <array>

#include <cstdint>

#include <ios>

#include <optional>

#include <set>

#include <string>

#include <string_view>

// UTXO set snapshot magic bytes

static constexpr std::array<uint8_t, 5> SNAPSHOT_MAGIC_BYTES = {'u', 't', 'x', 'o', 0xff};

class Chainstate;

namespace node {

//! Metadata describing a serialized version of a UTXO set from which an

//! assumeutxo Chainstate can be constructed.

//! All metadata fields come from an untrusted file, so must be validated

//! before being used. Thus, new fields should be added only if needed.

class SnapshotMetadata

{

    inline static const uint16_t VERSION{2};

    const std::set<uint16_t> m_supported_versions{VERSION};

    const MessageStartChars m_network_magic;

public:

    //! The hash of the block that reflects the tip of the chain for the

    //! UTXO set contained in this snapshot.

    uint256 m_base_blockhash;

    //! The number of coins in the UTXO set contained in this snapshot. Used

    //! during snapshot load to estimate progress of UTXO set reconstruction.

    uint64_t m_coins_count = 0;

    SnapshotMetadata(

        const MessageStartChars network_magic) :

            m_network_magic(network_magic) { }

    SnapshotMetadata(

        const MessageStartChars network_magic,

        const uint256& base_blockhash,

        uint64_t coins_count) :

            m_network_magic(network_magic),

            m_base_blockhash(base_blockhash),

            m_coins_count(coins_count) { }

    template <typename Stream>

    inline void Serialize(Stream& s) const {

        s << SNAPSHOT_MAGIC_BYTES;

        s << VERSION;

        s << m_network_magic;

        s << m_base_blockhash;

        s << m_coins_count;

    }

    template <typename Stream>

    inline void Unserialize(Stream& s) {

        // Read the snapshot magic bytes

        std::array<uint8_t, SNAPSHOT_MAGIC_BYTES.size()> snapshot_magic;

        s >> snapshot_magic;

        if (snapshot_magic != SNAPSHOT_MAGIC_BYTES) {

            throw std::ios_base::failure("Invalid UTXO set snapshot magic bytes. Please check if this is indeed a snapshot file or if you are using an outdated snapshot format.");

        }

        // Read the version

        uint16_t version;

        s >> version;

        if (!m_supported_versions.contains(version)) {

            throw std::ios_base::failure(strprintf("Version of snapshot %s does not match any of the supported versions.", version));

        }

        // Read the network magic (pchMessageStart)

        MessageStartChars message;

        s >> message;

        if (!std::equal(message.begin(), message.end(), m_network_magic.data())) {

            auto metadata_network{GetNetworkForMagic(message)};

            if (metadata_network) {

                std::string network_string{ChainTypeToString(metadata_network.value())};

                auto node_network{GetNetworkForMagic(m_network_magic)};

                std::string node_network_string{ChainTypeToString(node_network.value())};

                throw std::ios_base::failure(strprintf("The network of the snapshot (%s) does not match the network of this node (%s).", network_string, node_network_string));

            } else {

                throw std::ios_base::failure("This snapshot has been created for an unrecognized network. This could be a custom signet, a new testnet or possibly caused by data corruption.");

            }

        }

        s >> m_base_blockhash;

        s >> m_coins_count;

    }

};

//! The file in the snapshot chainstate dir which stores the base blockhash. This is

//! needed to reconstruct snapshot chainstates on init.

//!

//! Because we only allow loading a single snapshot at a time, there will only be one

//! chainstate directory with this filename present within it.

const fs::path SNAPSHOT_BLOCKHASH_FILENAME{"base_blockhash"};

//! Write out the blockhash of the snapshot base block that was used to construct

//! this chainstate. This value is read in during subsequent initializations and

//! used to reconstruct snapshot-based chainstates.

bool WriteSnapshotBaseBlockhash(Chainstate& snapshot_chainstate)

    EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

//! Read the blockhash of the snapshot base block that was used to construct the

//! chainstate.

std::optional<uint256> ReadSnapshotBaseBlockhash(fs::path chaindir)

    EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

//! Suffix appended to the chainstate (leveldb) dir when created based upon

//! a snapshot.

constexpr std::string_view SNAPSHOT_CHAINSTATE_SUFFIX = "_snapshot";

//! Return a path to the snapshot-based chainstate dir, if one exists.

std::optional<fs::path> FindAssumeutxoChainstateDir(const fs::path& data_dir);

} // namespace node

#endif // BITCOIN_NODE_UTXO_SNAPSHOT_H