/*
 * This file is part of the Flowee project
 * Copyright (c) 2009-2015 The Bitcoin Core developers
 * Copyright (c) 2021-2024 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/>.
 */

#include "PrivateKey.h"

#include <crypto/common.h>
#include <hash.h>
#include <hmac_sha512.h>
#include <random.h>

#include <base58.h>
#include <secp256k1.h>
#include <secp256k1_recovery.h>
#include <secp256k1_schnorr.h>

static secp256k1_context* secp256k1_context_sign = nullptr;

/** These functions are taken from the libsecp256k1 distribution and are very ugly. */
static int ec_privkey_import_der(const secp256k1_context* ctx, unsigned char *out32, const unsigned char *privkey, size_t privkeylen)
{
    const unsigned char *end = privkey + privkeylen;
    int lenb = 0;
    int len = 0;
    memset(out32, 0, 32);
    /* sequence header */
    if (end < privkey+1 || *privkey != 0x30) {
        return 0;
    }
    privkey++;
    /* sequence length constructor */
    if (end < privkey+1 || !(*privkey & 0x80)) {
        return 0;
    }
    lenb = *privkey & ~0x80; privkey++;
    if (lenb < 1 || lenb > 2) {
        return 0;
    }
    if (end < privkey+lenb) {
        return 0;
    }
    /* sequence length */
    len = privkey[lenb-1] | (lenb > 1 ? privkey[lenb-2] << 8 : 0);
    privkey += lenb;
    if (end < privkey+len) {
        return 0;
    }
    /* sequence element 0: version number (=1) */
    if (end < privkey+3 || privkey[0] != 0x02 || privkey[1] != 0x01 || privkey[2] != 0x01) {
        return 0;
    }
    privkey += 3;
    /* sequence element 1: octet string, up to 32 bytes */
    if (end < privkey+2 || privkey[0] != 0x04 || privkey[1] > 0x20 || end < privkey+2+privkey[1]) {
        return 0;
    }
    memcpy(out32 + 32 - privkey[1], privkey + 2, privkey[1]);
    if (!secp256k1_ec_seckey_verify(ctx, out32)) {
        memset(out32, 0, 32);
        return 0;
    }
    return 1;
}

static int ec_privkey_export_der(const secp256k1_context *ctx, unsigned char *privkey, size_t *privkeylen, const unsigned char *key32, int compressed)
{
    secp256k1_pubkey pubkey;
    size_t pubkeylen = 0;
    if (!secp256k1_ec_pubkey_create(ctx, &pubkey, key32)) {
        *privkeylen = 0;
        return 0;
    }
    if (compressed) {
        static const unsigned char begin[] = {
            0x30,0x81,0xD3,0x02,0x01,0x01,0x04,0x20
        };
        static const unsigned char middle[] = {
            0xA0,0x81,0x85,0x30,0x81,0x82,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
            0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
            0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
            0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
            0x21,0x02,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
            0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
            0x17,0x98,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
            0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
            0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x24,0x03,0x22,0x00
        };
        unsigned char *ptr = privkey;
        memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
        memcpy(ptr, key32, 32); ptr += 32;
        memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
        pubkeylen = 33;
        secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_COMPRESSED);
        ptr += pubkeylen;
        *privkeylen = ptr - privkey;
    } else {
        static const unsigned char begin[] = {
            0x30,0x82,0x01,0x13,0x02,0x01,0x01,0x04,0x20
        };
        static const unsigned char middle[] = {
            0xA0,0x81,0xA5,0x30,0x81,0xA2,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
            0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
            0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
            0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
            0x41,0x04,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
            0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
            0x17,0x98,0x48,0x3A,0xDA,0x77,0x26,0xA3,0xC4,0x65,0x5D,0xA4,0xFB,0xFC,0x0E,0x11,
            0x08,0xA8,0xFD,0x17,0xB4,0x48,0xA6,0x85,0x54,0x19,0x9C,0x47,0xD0,0x8F,0xFB,0x10,
            0xD4,0xB8,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
            0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
            0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x44,0x03,0x42,0x00
        };
        unsigned char *ptr = privkey;
        memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
        memcpy(ptr, key32, 32); ptr += 32;
        memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
        pubkeylen = 65;
        secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_UNCOMPRESSED);
        ptr += pubkeylen;
        *privkeylen = ptr - privkey;
    }
    return 1;
}

bool PrivateKey::check(const uint8_t *vch)
{
    return secp256k1_ec_seckey_verify(secp256k1_context_sign, vch);
}

PrivateKey PrivateKey::fromBase58(const std::string &wif)
{
    PrivateKey privKey;
    CBase58Data data;
    if (data.SetString(wif) && (data.isMainnetPrivKey() || data.isTestnetPrivKey())) {
        const auto &vectorData = data.data();
        privKey.set(vectorData.begin(), vectorData.begin() + 32,
            vectorData.size() > 32 && vectorData.at(32) == 1);
    }
    return privKey;
}

void PrivateKey::makeNewKey(bool fCompressedIn)
{
    RandAddSeedPerfmon();
    do {
        GetRandBytes(keydata.data(), keydata.size());
    } while (!check(keydata.data()));
    fValid = true;
    fCompressed = fCompressedIn;
}

bool PrivateKey::setPrivKey(const CPrivKey &privkey, bool fCompressedIn)
{
    if (!ec_privkey_import_der(secp256k1_context_sign, keydata.data(), &privkey[0], privkey.size()))
        return false;
    fCompressed = fCompressedIn;
    fValid = true;
    return true;
}

CPrivKey PrivateKey::getPrivKey() const
{
    assert(fValid);
    CPrivKey privkey;
    int ret;
    size_t privkeylen;
    privkey.resize(279);
    privkeylen = 279;
    ret = ec_privkey_export_der(secp256k1_context_sign, (unsigned char*)&privkey[0], &privkeylen, begin(), fCompressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
    assert(ret);
    privkey.resize(privkeylen);
    return privkey;
}

PublicKey PrivateKey::getPubKey() const
{
    assert(fValid);
    secp256k1_pubkey pubkey;
    size_t clen = 65;
    PublicKey result;
    int ret = secp256k1_ec_pubkey_create(secp256k1_context_sign, &pubkey, begin());
    assert(ret);
    secp256k1_ec_pubkey_serialize(secp256k1_context_sign, (unsigned char*)result.begin(), &clen, &pubkey, fCompressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
    assert(result.size() == clen);
    assert(result.isValid());
    return result;
}

bool PrivateKey::signECDSA(const uint256 &hash, std::vector<unsigned char> &vchSig, uint32_t test_case) const
{
    if (!fValid)
        return false;
    vchSig.resize(72);
    size_t nSigLen = 72;
    unsigned char extra_entropy[32] = {0};
    WriteLE32(extra_entropy, test_case);
    secp256k1_ecdsa_signature sig;
    int ret = secp256k1_ecdsa_sign(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, test_case ? extra_entropy : nullptr);
    assert(ret);
    secp256k1_ecdsa_signature_serialize_der(secp256k1_context_sign, (unsigned char*)&vchSig[0], &nSigLen, &sig);
    vchSig.resize(nSigLen);
    return true;
}

bool PrivateKey::signSchnorr(const uint256 &hash, std::vector<uint8_t> &vchSig, uint32_t test_case) const
{
    if (!fValid)
        return false;
    vchSig.resize(64);
    uint8_t extra_entropy[32] = {0};
    WriteLE32(extra_entropy, test_case);

    int ret = secp256k1_schnorr_sign(secp256k1_context_sign, &vchSig[0], hash.begin(), begin(), secp256k1_nonce_function_rfc6979, test_case ? extra_entropy : nullptr);
    assert(ret);
    return true;
}

bool PrivateKey::verifyPubKey(const PublicKey &pubkey) const
{
    if (pubkey.isCompressed() != fCompressed) {
        return false;
    }
    unsigned char rnd[8];
    std::string str = "Bitcoin key verification\n";
    GetRandBytes(rnd, sizeof(rnd));
    uint256 hash;
    CHash256().write((unsigned char*)str.data(), str.size()).write(rnd, sizeof(rnd)).finalize(hash.begin());
    std::vector<unsigned char> vchSig;
    signECDSA(hash, vchSig);
    return pubkey.verifyECDSA(hash, vchSig);
}

bool PrivateKey::signCompact(const uint256 &hash, std::vector<unsigned char> &vchSig) const
{
    if (!fValid)
        return false;
    vchSig.resize(65);
    int rec = -1;
    secp256k1_ecdsa_recoverable_signature sig;
    int ret = secp256k1_ecdsa_sign_recoverable(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, nullptr);
    assert(ret);
    secp256k1_ecdsa_recoverable_signature_serialize_compact(secp256k1_context_sign, (unsigned char*)&vchSig[1], &rec, &sig);
    assert(ret);
    assert(rec != -1);
    vchSig[0] = 27 + rec + (fCompressed ? 4 : 0);
    return true;
}

bool PrivateKey::load(CPrivKey &privkey, PublicKey &vchPubKey, bool fSkipCheck=false) {
    if (!ec_privkey_import_der(secp256k1_context_sign, (unsigned char*)begin(), &privkey[0], privkey.size()))
        return false;
    fCompressed = vchPubKey.isCompressed();
    fValid = true;

    if (fSkipCheck)
        return true;

    return verifyPubKey(vchPubKey);
}

PrivateKey &PrivateKey::operator=(const PrivateKey &other)
{
    fValid = other.fValid;
    fCompressed = other.fCompressed;
    assert(keydata.size() == 32);
    assert(other.keydata.size() == 32);
    memcpy(keydata.data(), other.keydata.data(), 32);
    return *this;
}

bool PrivateKey::derive(PrivateKey &keyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode &cc) const
{
    assert(isValid());
    assert(isCompressed());
    std::vector<uint8_t, secure_allocator<uint8_t>> vout(64);
    if ((nChild >> 31) == 0) {
        PublicKey pubkey = getPubKey();
        assert(pubkey.begin() + 33 == pubkey.end());
        BIP32Hash(cc, nChild, *pubkey.begin(), pubkey.begin()+1, vout.data());
    } else {
        assert(begin() + 32 == end());
        BIP32Hash(cc, nChild, 0, begin(), vout.data());
    }
    memcpy(ccChild.begin(), vout.data()+32, 32);
    memcpy((unsigned char*)keyChild.begin(), begin(), 32);
    bool ret = secp256k1_ec_privkey_tweak_add(secp256k1_context_sign, (unsigned char*)keyChild.begin(), vout.data());
    keyChild.fCompressed = true;
    keyChild.fValid = ret;
    return ret;
}

bool ECC_InitSanityCheck() {
    PrivateKey key;
    key.makeNewKey();
    PublicKey pubkey = key.getPubKey();
    return key.verifyPubKey(pubkey);
}

void ECC_Start() {
    assert(secp256k1_context_sign == nullptr);

    secp256k1_context *ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
    assert(ctx != nullptr);

    {
        // Pass in a random blinding seed to the secp256k1 context.
        std::vector<uint8_t, secure_allocator<uint8_t>> vseed(32);
        GetRandBytes(vseed.data(), 32);
        bool ret = secp256k1_context_randomize(ctx, vseed.data());
        assert(ret);
    }

    secp256k1_context_sign = ctx;
}

void ECC_Stop() {
    secp256k1_context *ctx = secp256k1_context_sign;
    secp256k1_context_sign = nullptr;

    if (ctx) {
        secp256k1_context_destroy(ctx);
    }
}