// Copyright (c) 2009-2010 Satoshi Nakamoto

// Copyright (c) 2009-2022 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 <common/signmessage.h>

#include <hash.h>

#include <key.h>

#include <key_io.h>

#include <pubkey.h>

#include <uint256.h>

#include <util/strencodings.h>

#include <cassert>

#include <optional>

#include <string>

#include <variant>

#include <vector>

/**

 * Text used to signify that a signed message follows and to prevent

 * inadvertently signing a transaction.

 */

const std::string MESSAGE_MAGIC = "Bitcoin Signed Message:\n";

MessageVerificationResult MessageVerify(

    const std::string& address,

    const std::string& signature,

    const std::string& message)

{

    CTxDestination destination = DecodeDestination(address);

    if (!IsValidDestination(destination)) {

        return MessageVerificationResult::ERR_INVALID_ADDRESS;

    }

    if (std::get_if<PKHash>(&destination) == nullptr) {

        return MessageVerificationResult::ERR_ADDRESS_NO_KEY;

    }

    auto signature_bytes = DecodeBase64(signature);

    if (!signature_bytes) {

        return MessageVerificationResult::ERR_MALFORMED_SIGNATURE;

    }

    CPubKey pubkey;

    if (!pubkey.RecoverCompact(MessageHash(message), *signature_bytes)) {

        return MessageVerificationResult::ERR_PUBKEY_NOT_RECOVERED;

    }

    if (!(PKHash(pubkey) == *std::get_if<PKHash>(&destination))) {

        return MessageVerificationResult::ERR_NOT_SIGNED;

    }

    return MessageVerificationResult::OK;

}

bool MessageSign(

    const CKey& privkey,

    const std::string& message,

    std::string& signature)

{

    std::vector<unsigned char> signature_bytes;

    if (!privkey.SignCompact(MessageHash(message), signature_bytes)) {

        return false;

    }

    signature = EncodeBase64(signature_bytes);

    return true;

}

uint256 MessageHash(const std::string& message)

{

    HashWriter hasher{};

    hasher << MESSAGE_MAGIC << message;

    return hasher.GetHash();

}

std::string SigningResultString(const SigningResult res)

{

    switch (res) {

        case SigningResult::OK:

            return "No error";

        case SigningResult::PRIVATE_KEY_NOT_AVAILABLE:

            return "Private key not available";

        case SigningResult::SIGNING_FAILED:

            return "Sign failed";

        // no default case, so the compiler can warn about missing cases

    }

    assert(false);

}