// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2014 The Bitcoin Core developers
// Distributed under the GPLv3 software license, see the accompanying
// file COPYING or https://www.gnu.org/licenses/gpl-3.0.en.html

/******************************************************************************
 * Copyright © 2014-2019 The SuperNET Developers.                             *
 *                                                                            *
 * See the AUTHORS, DEVELOPER-AGREEMENT and LICENSE files at                  *
 * the top-level directory of this distribution for the individual copyright  *
 * holder information and the developer policies on copyright and licensing.  *
 *                                                                            *
 * Unless otherwise agreed in a custom licensing agreement, no part of the    *
 * SuperNET software, including this file may be copied, modified, propagated *
 * or distributed except according to the terms contained in the LICENSE file *
 *                                                                            *
 * Removal or modification of this copyright notice is prohibited.            *
 *                                                                            *
 ******************************************************************************/

#include <cryptoconditions.h>

#include "interpreter.h"

#include "consensus/upgrades.h"
#include "primitives/transaction.h"
#include "cc/eval.h"
#include "crypto/ripemd160.h"
#include "crypto/sha1.h"
#include "crypto/sha256.h"
#include "pubkey.h"
#include "script/script.h"
#include "uint256.h"



using namespace std;

typedef vector<unsigned char> valtype;

namespace {

inline bool set_success(ScriptError* ret)
{
    if (ret)
        *ret = SCRIPT_ERR_OK;
    return true;
}

inline bool set_error(ScriptError* ret, const ScriptError serror)
{
    if (ret)
        *ret = serror;
    return false;
}

} // anon namespace

bool CastToBool(const valtype& vch)
{
    for (unsigned int i = 0; i < vch.size(); i++)
    {
        if (vch[i] != 0)
        {
            // Can be negative zero
            if (i == vch.size()-1 && vch[i] == 0x80)
                return false;
            return true;
        }
    }
    return false;
}

/**
 * Script is a stack machine (like Forth) that evaluates a predicate
 * returning a bool indicating valid or not.  There are no loops.
 */
#define stacktop(i)  (stack.at(stack.size()+(i)))
#define altstacktop(i)  (altstack.at(altstack.size()+(i)))
static inline void popstack(vector<valtype>& stack)
{
    if (stack.empty())
        throw runtime_error("popstack(): stack empty");
    stack.pop_back();
}

bool static IsCompressedOrUncompressedPubKey(const valtype &vchPubKey) {
    if (vchPubKey.size() < 33) {
        //  Non-canonical public key: too short
        return false;
    }
    if (vchPubKey[0] == 0x04) {
        if (vchPubKey.size() != 65) {
            //  Non-canonical public key: invalid length for uncompressed key
            return false;
        }
    } else if (vchPubKey[0] == 0x02 || vchPubKey[0] == 0x03) {
        if (vchPubKey.size() != 33) {
            //  Non-canonical public key: invalid length for compressed key
            return false;
        }
    } else {
          //  Non-canonical public key: neither compressed nor uncompressed
          return false;
    }
    return true;
}

/**
 * A canonical signature exists of: <30> <total len> <02> <len R> <R> <02> <len S> <S> <hashtype>
 * Where R and S are not negative (their first byte has its highest bit not set), and not
 * excessively padded (do not start with a 0 byte, unless an otherwise negative number follows,
 * in which case a single 0 byte is necessary and even required).
 * 
 * See https://bitcointalk.org/index.php?topic=8392.msg127623#msg127623
 *
 * This function is consensus-critical since BIP66.
 */
bool static IsValidSignatureEncoding(const std::vector<unsigned char> &sig) {
    // Format: 0x30 [total-length] 0x02 [R-length] [R] 0x02 [S-length] [S] [sighash]
    // * total-length: 1-byte length descriptor of everything that follows,
    //   excluding the sighash byte.
    // * R-length: 1-byte length descriptor of the R value that follows.
    // * R: arbitrary-length big-endian encoded R value. It must use the shortest
    //   possible encoding for a positive integer (which means no null bytes at
    //   the start, except a single one when the next byte has its highest bit set).
    // * S-length: 1-byte length descriptor of the S value that follows.
    // * S: arbitrary-length big-endian encoded S value. The same rules apply.
    // * sighash: 1-byte value indicating what data is hashed (not part of the DER
    //   signature)

    // Minimum and maximum size constraints.
    if (sig.size() < 9) return false;
    if (sig.size() > 73) return false;

    // A signature is of type 0x30 (compound).
    if (sig[0] != 0x30) return false;

    // Make sure the length covers the entire signature.
    if (sig[1] != sig.size() - 3) return false;

    // Extract the length of the R element.
    unsigned int lenR = sig[3];

    // Make sure the length of the S element is still inside the signature.
    if (5 + lenR >= sig.size()) return false;

    // Extract the length of the S element.
    unsigned int lenS = sig[5 + lenR];

    // Verify that the length of the signature matches the sum of the length
    // of the elements.
    if ((size_t)(lenR + lenS + 7) != sig.size()) return false;
 
    // Check whether the R element is an integer.
    if (sig[2] != 0x02) return false;

    // Zero-length integers are not allowed for R.
    if (lenR == 0) return false;

    // Negative numbers are not allowed for R.
    if (sig[4] & 0x80) return false;

    // Null bytes at the start of R are not allowed, unless R would
    // otherwise be interpreted as a negative number.
    if (lenR > 1 && (sig[4] == 0x00) && !(sig[5] & 0x80)) return false;

    // Check whether the S element is an integer.
    if (sig[lenR + 4] != 0x02) return false;

    // Zero-length integers are not allowed for S.
    if (lenS == 0) return false;

    // Negative numbers are not allowed for S.
    if (sig[lenR + 6] & 0x80) return false;

    // Null bytes at the start of S are not allowed, unless S would otherwise be
    // interpreted as a negative number.
    if (lenS > 1 && (sig[lenR + 6] == 0x00) && !(sig[lenR + 7] & 0x80)) return false;

    return true;
}

bool static IsLowDERSignature(const valtype &vchSig, ScriptError* serror) {
    if (!IsValidSignatureEncoding(vchSig)) {
        return set_error(serror, SCRIPT_ERR_SIG_DER);
    }
    // https://bitcoin.stackexchange.com/a/12556:
    //     Also note that inside transaction signatures, an extra hashtype byte
    //     follows the actual signature data.
    std::vector<unsigned char> vchSigCopy(vchSig.begin(), vchSig.begin() + vchSig.size() - 1);
    // If the S value is above the order of the curve divided by two, its
    // complement modulo the order could have been used instead, which is
    // one byte shorter when encoded correctly.
    return CPubKey::CheckLowS(vchSigCopy);
}

bool static IsDefinedHashtypeSignature(const valtype &vchSig) {
    if (vchSig.size() == 0) {
        return false;
    }
    unsigned char nHashType = vchSig[vchSig.size() - 1] & (~(SIGHASH_ANYONECANPAY));
    if (nHashType < SIGHASH_ALL || nHashType > SIGHASH_SINGLE)
        return false;

    return true;
}

bool CheckSignatureEncoding(const vector<unsigned char> &vchSig, unsigned int flags, ScriptError* serror) {
    // Empty signature. Not strictly DER encoded, but allowed to provide a
    // compact way to provide an invalid signature for use with CHECK(MULTI)SIG
    if (vchSig.size() == 0) {
        return true;
    }
    if (!IsValidSignatureEncoding(vchSig)) {
        return set_error(serror, SCRIPT_ERR_SIG_DER);
    } else if ((flags & SCRIPT_VERIFY_LOW_S) != 0 && !IsLowDERSignature(vchSig, serror)) {
        // serror is set
        return false;
    } else if ((flags & SCRIPT_VERIFY_STRICTENC) != 0 && !IsDefinedHashtypeSignature(vchSig)) {
        return set_error(serror, SCRIPT_ERR_SIG_HASHTYPE);
    }
    return true;
}

bool static CheckPubKeyEncoding(const valtype &vchSig, unsigned int flags, ScriptError* serror) {
    if ((flags & SCRIPT_VERIFY_STRICTENC) != 0 && !IsCompressedOrUncompressedPubKey(vchSig)) {
        return set_error(serror, SCRIPT_ERR_PUBKEYTYPE);
    }
    return true;
}

bool static CheckMinimalPush(const valtype& data, opcodetype opcode) {
    if (data.size() == 0) {
        // Could have used OP_0.
        return opcode == OP_0;
    } else if (data.size() == 1 && data[0] >= 1 && data[0] <= 16) {
        // Could have used OP_1 .. OP_16.
        return opcode == OP_1 + (data[0] - 1);
    } else if (data.size() == 1 && data[0] == 0x81) {
        // Could have used OP_1NEGATE.
        return opcode == OP_1NEGATE;
    } else if (data.size() <= 75) {
        // Could have used a direct push (opcode indicating number of bytes pushed + those bytes).
        return opcode == data.size();
    } else if (data.size() <= 255) {
        // Could have used OP_PUSHDATA.
        return opcode == OP_PUSHDATA1;
    } else if (data.size() <= 65535) {
        // Could have used OP_PUSHDATA2.
        return opcode == OP_PUSHDATA2;
    }
    return true;
}

bool EvalScript(
    vector<vector<unsigned char> >& stack,
    const CScript& script,
    unsigned int flags,
    const BaseSignatureChecker& checker,
    uint32_t consensusBranchId,
    ScriptError* serror)
{
    static const CScriptNum bnZero(0);
    static const CScriptNum bnOne(1);
    static const CScriptNum bnFalse(0);
    static const CScriptNum bnTrue(1);
    static const valtype vchFalse(0);
    static const valtype vchZero(0);
    static const valtype vchTrue(1, 1);

    CScript::const_iterator pc = script.begin();
    CScript::const_iterator pend = script.end();
    opcodetype opcode;
    valtype vchPushValue;
    vector<bool> vfExec;
    vector<valtype> altstack;
    set_error(serror, SCRIPT_ERR_UNKNOWN_ERROR);
    if (script.size() > MAX_SCRIPT_SIZE)
        return set_error(serror, SCRIPT_ERR_SCRIPT_SIZE);
    int nOpCount = 0;
    bool fRequireMinimal = (flags & SCRIPT_VERIFY_MINIMALDATA) != 0;

    try
    {
        while (pc < pend)
        {
            bool fExec = !count(vfExec.begin(), vfExec.end(), false);

            //
            // Read instruction
            //
            if (!script.GetOp(pc, opcode, vchPushValue))
                return set_error(serror, SCRIPT_ERR_BAD_OPCODE);
            if (vchPushValue.size() > MAX_SCRIPT_ELEMENT_SIZE)
                return set_error(serror, SCRIPT_ERR_PUSH_SIZE);

            // Note how OP_RESERVED does not count towards the opcode limit.
            if (opcode > OP_16 && ++nOpCount > 201)
                return set_error(serror, SCRIPT_ERR_OP_COUNT);

            if (opcode == OP_CAT ||
                opcode == OP_SUBSTR ||
                opcode == OP_LEFT ||
                opcode == OP_RIGHT ||
                opcode == OP_INVERT ||
                opcode == OP_AND ||
                opcode == OP_OR ||
                opcode == OP_XOR ||
                opcode == OP_2MUL ||
                opcode == OP_2DIV ||
                opcode == OP_MUL ||
                opcode == OP_DIV ||
                opcode == OP_MOD ||
                opcode == OP_LSHIFT ||
                opcode == OP_RSHIFT ||
                opcode == OP_CODESEPARATOR)
                return set_error(serror, SCRIPT_ERR_DISABLED_OPCODE); // Disabled opcodes.

            if (fExec && 0 <= opcode && opcode <= OP_PUSHDATA4) {
                if (fRequireMinimal && !CheckMinimalPush(vchPushValue, opcode)) {
                    return set_error(serror, SCRIPT_ERR_MINIMALDATA);
                }
                stack.push_back(vchPushValue);
            } else if (fExec || (OP_IF <= opcode && opcode <= OP_ENDIF))
            switch (opcode)
            {
                //
                // Push value
                //
                case OP_1NEGATE:
                case OP_1:
                case OP_2:
                case OP_3:
                case OP_4:
                case OP_5:
                case OP_6:
                case OP_7:
                case OP_8:
                case OP_9:
                case OP_10:
                case OP_11:
                case OP_12:
                case OP_13:
                case OP_14:
                case OP_15:
                case OP_16:
                {
                    // ( -- value)
                    CScriptNum bn((int)opcode - (int)(OP_1 - 1));
                    stack.push_back(bn.getvch());
                    // The result of these opcodes should always be the minimal way to push the data
                    // they push, so no need for a CheckMinimalPush here.
                }
                break;


                //
                // Control
                //
                case OP_NOP:
                    break;

                case OP_CHECKLOCKTIMEVERIFY:
                {
                    if (!(flags & SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY)) {
                        // not enabled; treat as a NOP2
                        if (flags & SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS) {
                            return set_error(serror, SCRIPT_ERR_DISCOURAGE_UPGRADABLE_NOPS);
                        }
                        break;
                    }

                    if (stack.size() < 1)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);

                    // Note that elsewhere numeric opcodes are limited to
                    // operands in the range -2**31+1 to 2**31-1, however it is
                    // legal for opcodes to produce results exceeding that
                    // range. This limitation is implemented by CScriptNum's
                    // default 4-byte limit.
                    //
                    // If we kept to that limit we'd have a year 2038 problem,
                    // even though the nLockTime field in transactions
                    // themselves is uint32 which only becomes meaningless
                    // after the year 2106.
                    //
                    // Thus as a special case we tell CScriptNum to accept up
                    // to 5-byte bignums, which are good until 2**39-1, well
                    // beyond the 2**32-1 limit of the nLockTime field itself.
                    const CScriptNum nLockTime(stacktop(-1), fRequireMinimal, 5);

                    // In the rare event that the argument may be < 0 due to
                    // some arithmetic being done first, you can always use
                    // 0 MAX CHECKLOCKTIMEVERIFY.
                    if (nLockTime < 0)
                        return set_error(serror, SCRIPT_ERR_NEGATIVE_LOCKTIME);

                    // Actually compare the specified lock time with the transaction.
                    if (!checker.CheckLockTime(nLockTime))
                        return set_error(serror, SCRIPT_ERR_UNSATISFIED_LOCKTIME);

                    break;
                }

                case OP_NOP1: case OP_NOP3: case OP_NOP4: case OP_NOP5:
                case OP_NOP6: case OP_NOP7: case OP_NOP8: case OP_NOP9: case OP_NOP10:
                {
                    if (flags & SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS)
                        return set_error(serror, SCRIPT_ERR_DISCOURAGE_UPGRADABLE_NOPS);
                }
                break;

                case OP_IF:
                case OP_NOTIF:
                {
                    // <expression> if [statements] [else [statements]] endif
                    bool fValue = false;
                    if (fExec)
                    {
                        if (stack.size() < 1)
                            return set_error(serror, SCRIPT_ERR_UNBALANCED_CONDITIONAL);
                        valtype& vch = stacktop(-1);
                        fValue = CastToBool(vch);
                        if (opcode == OP_NOTIF)
                            fValue = !fValue;
                        popstack(stack);
                    }
                    vfExec.push_back(fValue);
                }
                break;

                case OP_ELSE:
                {
                    if (vfExec.empty())
                        return set_error(serror, SCRIPT_ERR_UNBALANCED_CONDITIONAL);
                    vfExec.back() = !vfExec.back();
                }
                break;

                case OP_ENDIF:
                {
                    if (vfExec.empty())
                        return set_error(serror, SCRIPT_ERR_UNBALANCED_CONDITIONAL);
                    vfExec.pop_back();
                }
                break;

                case OP_VERIFY:
                {
                    // (true -- ) or
                    // (false -- false) and return
                    if (stack.size() < 1)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    bool fValue = CastToBool(stacktop(-1));
                    if (fValue)
                        popstack(stack);
                    else
                        return set_error(serror, SCRIPT_ERR_VERIFY);
                }
                break;

                case OP_RETURN:
                {
                    return set_error(serror, SCRIPT_ERR_OP_RETURN);
                }
                break;


                //
                // Stack ops
                //
                case OP_TOALTSTACK:
                {
                    if (stack.size() < 1)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    altstack.push_back(stacktop(-1));
                    popstack(stack);
                }
                break;

                case OP_FROMALTSTACK:
                {
                    if (altstack.size() < 1)
                        return set_error(serror, SCRIPT_ERR_INVALID_ALTSTACK_OPERATION);
                    stack.push_back(altstacktop(-1));
                    popstack(altstack);
                }
                break;

                case OP_2DROP:
                {
                    // (x1 x2 -- )
                    if (stack.size() < 2)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    popstack(stack);
                    popstack(stack);
                }
                break;

                case OP_2DUP:
                {
                    // (x1 x2 -- x1 x2 x1 x2)
                    if (stack.size() < 2)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    valtype vch1 = stacktop(-2);
                    valtype vch2 = stacktop(-1);
                    stack.push_back(vch1);
                    stack.push_back(vch2);
                }
                break;

                case OP_3DUP:
                {
                    // (x1 x2 x3 -- x1 x2 x3 x1 x2 x3)
                    if (stack.size() < 3)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    valtype vch1 = stacktop(-3);
                    valtype vch2 = stacktop(-2);
                    valtype vch3 = stacktop(-1);
                    stack.push_back(vch1);
                    stack.push_back(vch2);
                    stack.push_back(vch3);
                }
                break;

                case OP_2OVER:
                {
                    // (x1 x2 x3 x4 -- x1 x2 x3 x4 x1 x2)
                    if (stack.size() < 4)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    valtype vch1 = stacktop(-4);
                    valtype vch2 = stacktop(-3);
                    stack.push_back(vch1);
                    stack.push_back(vch2);
                }
                break;

                case OP_2ROT:
                {
                    // (x1 x2 x3 x4 x5 x6 -- x3 x4 x5 x6 x1 x2)
                    if (stack.size() < 6)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    valtype vch1 = stacktop(-6);
                    valtype vch2 = stacktop(-5);
                    stack.erase(stack.end()-6, stack.end()-4);
                    stack.push_back(vch1);
                    stack.push_back(vch2);
                }
                break;

                case OP_2SWAP:
                {
                    // (x1 x2 x3 x4 -- x3 x4 x1 x2)
                    if (stack.size() < 4)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    swap(stacktop(-4), stacktop(-2));
                    swap(stacktop(-3), stacktop(-1));
                }
                break;

                case OP_IFDUP:
                {
                    // (x - 0 | x x)
                    if (stack.size() < 1)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    valtype vch = stacktop(-1);
                    if (CastToBool(vch))
                        stack.push_back(vch);
                }
                break;

                case OP_DEPTH:
                {
                    // -- stacksize
                    CScriptNum bn(stack.size());
                    stack.push_back(bn.getvch());
                }
                break;

                case OP_DROP:
                {
                    // (x -- )
                    if (stack.size() < 1)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    popstack(stack);
                }
                break;

                case OP_DUP:
                {
                    // (x -- x x)
                    if (stack.size() < 1)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    valtype vch = stacktop(-1);
                    stack.push_back(vch);
                }
                break;

                case OP_NIP:
                {
                    // (x1 x2 -- x2)
                    if (stack.size() < 2)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    stack.erase(stack.end() - 2);
                }
                break;

                case OP_OVER:
                {
                    // (x1 x2 -- x1 x2 x1)
                    if (stack.size() < 2)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    valtype vch = stacktop(-2);
                    stack.push_back(vch);
                }
                break;

                case OP_PICK:
                case OP_ROLL:
                {
                    // (xn ... x2 x1 x0 n - xn ... x2 x1 x0 xn)
                    // (xn ... x2 x1 x0 n - ... x2 x1 x0 xn)
                    if (stack.size() < 2)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    int n = CScriptNum(stacktop(-1), fRequireMinimal).getint();
                    popstack(stack);
                    if (n < 0 || n >= (int)stack.size())
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    valtype vch = stacktop(-n-1);
                    if (opcode == OP_ROLL)
                        stack.erase(stack.end()-n-1);
                    stack.push_back(vch);
                }
                break;

                case OP_ROT:
                {
                    // (x1 x2 x3 -- x2 x3 x1)
                    //  x2 x1 x3  after first swap
                    //  x2 x3 x1  after second swap
                    if (stack.size() < 3)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    swap(stacktop(-3), stacktop(-2));
                    swap(stacktop(-2), stacktop(-1));
                }
                break;

                case OP_SWAP:
                {
                    // (x1 x2 -- x2 x1)
                    if (stack.size() < 2)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    swap(stacktop(-2), stacktop(-1));
                }
                break;

                case OP_TUCK:
                {
                    // (x1 x2 -- x2 x1 x2)
                    if (stack.size() < 2)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    valtype vch = stacktop(-1);
                    stack.insert(stack.end()-2, vch);
                }
                break;


                case OP_SIZE:
                {
                    // (in -- in size)
                    if (stack.size() < 1)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    CScriptNum bn(stacktop(-1).size());
                    stack.push_back(bn.getvch());
                }
                break;


                //
                // Bitwise logic
                //
                case OP_EQUAL:
                case OP_EQUALVERIFY:
                //case OP_NOTEQUAL: // use OP_NUMNOTEQUAL
                {
                    // (x1 x2 - bool)
                    if (stack.size() < 2)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    valtype& vch1 = stacktop(-2);
                    valtype& vch2 = stacktop(-1);
                    bool fEqual = (vch1 == vch2);
                    // OP_NOTEQUAL is disabled because it would be too easy to say
                    // something like n != 1 and have some wiseguy pass in 1 with extra
                    // zero bytes after it (numerically, 0x01 == 0x0001 == 0x000001)
                    //if (opcode == OP_NOTEQUAL)
                    //    fEqual = !fEqual;
                    popstack(stack);
                    popstack(stack);
                    stack.push_back(fEqual ? vchTrue : vchFalse);
                    if (opcode == OP_EQUALVERIFY)
                    {
                        if (fEqual)
                            popstack(stack);
                        else
                            return set_error(serror, SCRIPT_ERR_EQUALVERIFY);
                    }
                }
                break;


                //
                // Numeric
                //
                case OP_1ADD:
                case OP_1SUB:
                case OP_NEGATE:
                case OP_ABS:
                case OP_NOT:
                case OP_0NOTEQUAL:
                {
                    // (in -- out)
                    if (stack.size() < 1)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    CScriptNum bn(stacktop(-1), fRequireMinimal);
                    switch (opcode)
                    {
                    case OP_1ADD:       bn += bnOne; break;
                    case OP_1SUB:       bn -= bnOne; break;
                    case OP_NEGATE:     bn = -bn; break;
                    case OP_ABS:        if (bn < bnZero) bn = -bn; break;
                    case OP_NOT:        bn = (bn == bnZero); break;
                    case OP_0NOTEQUAL:  bn = (bn != bnZero); break;
                    default:            assert(!"invalid opcode"); break;
                    }
                    popstack(stack);
                    stack.push_back(bn.getvch());
                }
                break;

                case OP_ADD:
                case OP_SUB:
                case OP_BOOLAND:
                case OP_BOOLOR:
                case OP_NUMEQUAL:
                case OP_NUMEQUALVERIFY:
                case OP_NUMNOTEQUAL:
                case OP_LESSTHAN:
                case OP_GREATERTHAN:
                case OP_LESSTHANOREQUAL:
                case OP_GREATERTHANOREQUAL:
                case OP_MIN:
                case OP_MAX:
                {
                    // (x1 x2 -- out)
                    if (stack.size() < 2)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    CScriptNum bn1(stacktop(-2), fRequireMinimal);
                    CScriptNum bn2(stacktop(-1), fRequireMinimal);
                    CScriptNum bn(0);
                    switch (opcode)
                    {
                    case OP_ADD:
                        bn = bn1 + bn2;
                        break;

                    case OP_SUB:
                        bn = bn1 - bn2;
                        break;

                    case OP_BOOLAND:             bn = (bn1 != bnZero && bn2 != bnZero); break;
                    case OP_BOOLOR:              bn = (bn1 != bnZero || bn2 != bnZero); break;
                    case OP_NUMEQUAL:            bn = (bn1 == bn2); break;
                    case OP_NUMEQUALVERIFY:      bn = (bn1 == bn2); break;
                    case OP_NUMNOTEQUAL:         bn = (bn1 != bn2); break;
                    case OP_LESSTHAN:            bn = (bn1 < bn2); break;
                    case OP_GREATERTHAN:         bn = (bn1 > bn2); break;
                    case OP_LESSTHANOREQUAL:     bn = (bn1 <= bn2); break;
                    case OP_GREATERTHANOREQUAL:  bn = (bn1 >= bn2); break;
                    case OP_MIN:                 bn = (bn1 < bn2 ? bn1 : bn2); break;
                    case OP_MAX:                 bn = (bn1 > bn2 ? bn1 : bn2); break;
                    default:                     assert(!"invalid opcode"); break;
                    }
                    popstack(stack);
                    popstack(stack);
                    stack.push_back(bn.getvch());

                    if (opcode == OP_NUMEQUALVERIFY)
                    {
                        if (CastToBool(stacktop(-1)))
                            popstack(stack);
                        else
                            return set_error(serror, SCRIPT_ERR_NUMEQUALVERIFY);
                    }
                }
                break;

                case OP_WITHIN:
                {
                    // (x min max -- out)
                    if (stack.size() < 3)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    CScriptNum bn1(stacktop(-3), fRequireMinimal);
                    CScriptNum bn2(stacktop(-2), fRequireMinimal);
                    CScriptNum bn3(stacktop(-1), fRequireMinimal);
                    bool fValue = (bn2 <= bn1 && bn1 < bn3);
                    popstack(stack);
                    popstack(stack);
                    popstack(stack);
                    stack.push_back(fValue ? vchTrue : vchFalse);
                }
                break;


                //
                // Crypto
                //
                case OP_RIPEMD160:
                case OP_SHA1:
                case OP_SHA256:
                case OP_HASH160:
                case OP_HASH256:
                {
                    // (in -- hash)
                    if (stack.size() < 1)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    valtype& vch = stacktop(-1);
                    valtype vchHash((opcode == OP_RIPEMD160 || opcode == OP_SHA1 || opcode == OP_HASH160) ? 20 : 32);
                    if (opcode == OP_RIPEMD160)
                        CRIPEMD160().Write(begin_ptr(vch), vch.size()).Finalize(begin_ptr(vchHash));
                    else if (opcode == OP_SHA1)
                        CSHA1().Write(begin_ptr(vch), vch.size()).Finalize(begin_ptr(vchHash));
                    else if (opcode == OP_SHA256)
                        CSHA256().Write(begin_ptr(vch), vch.size()).Finalize(begin_ptr(vchHash));
                    else if (opcode == OP_HASH160)
                        CHash160().Write(begin_ptr(vch), vch.size()).Finalize(begin_ptr(vchHash));
                    else if (opcode == OP_HASH256)
                        CHash256().Write(begin_ptr(vch), vch.size()).Finalize(begin_ptr(vchHash));
                    popstack(stack);
                    stack.push_back(vchHash);
                }
                break;

                // script that takes PAXpubkey + real pubkey, verifies output is within acceptable range and sig is for real pubkey. adjust vin amount to fiatvalue
                case OP_CHECKSIG:
                case OP_CHECKSIGVERIFY:
                {
                    // (sig pubkey -- bool)
                    if (stack.size() < 2)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);

                    valtype& vchSig    = stacktop(-2);
                    valtype& vchPubKey = stacktop(-1);

                    if (!CheckSignatureEncoding(vchSig, flags, serror) || !CheckPubKeyEncoding(vchPubKey, flags, serror)) {
                        //serror is set
                        return false;
                    }
                    bool fSuccess = checker.CheckSig(vchSig, vchPubKey, script, consensusBranchId);

                    // comment below when not debugging
                    //printf("OP_CHECKSIG: scriptSig.%s\nscriptPubKey.%s\nbranchid.%x, success: %s\n", 
                    //       CScript(vchSig).ToString().c_str(), CScript(vchPubKey).ToString().c_str(), consensusBranchId, (fSuccess ? "true" : "false"));

                    popstack(stack);
                    popstack(stack);
                    stack.push_back(fSuccess ? vchTrue : vchFalse);
                    if (opcode == OP_CHECKSIGVERIFY)
                    {
                        if (fSuccess)
                            popstack(stack);
                        else
                            return set_error(serror, SCRIPT_ERR_CHECKSIGVERIFY);
                    }
                }
                break;

                case OP_CHECKMULTISIG:
                case OP_CHECKMULTISIGVERIFY:
                {
                    // ([sig ...] num_of_signatures [pubkey ...] num_of_pubkeys -- bool)

                    int i = 1;
                    if ((int)stack.size() < i)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);

                    int nKeysCount = CScriptNum(stacktop(-i), fRequireMinimal).getint();
                    if (nKeysCount < 0 || nKeysCount > 20)
                        return set_error(serror, SCRIPT_ERR_PUBKEY_COUNT);
                    nOpCount += nKeysCount;
                    if (nOpCount > 201)
                        return set_error(serror, SCRIPT_ERR_OP_COUNT);
                    int ikey = ++i;
                    i += nKeysCount;
                    if ((int)stack.size() < i)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);

                    int nSigsCount = CScriptNum(stacktop(-i), fRequireMinimal).getint();
                    if (nSigsCount < 0 || nSigsCount > nKeysCount)
                        return set_error(serror, SCRIPT_ERR_SIG_COUNT);
                    int isig = ++i;
                    i += nSigsCount;
                    if ((int)stack.size() < i)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);

                    bool fSuccess = true;
                    while (fSuccess && nSigsCount > 0)
                    {
                        valtype& vchSig    = stacktop(-isig);
                        valtype& vchPubKey = stacktop(-ikey);

                        // Note how this makes the exact order of pubkey/signature evaluation
                        // distinguishable by CHECKMULTISIG NOT if the STRICTENC flag is set.
                        // See the script_(in)valid tests for details.
                        if (!CheckSignatureEncoding(vchSig, flags, serror) || !CheckPubKeyEncoding(vchPubKey, flags, serror)) {
                            // serror is set
                            return false;
                        }

                        // Check signature
                        bool fOk = checker.CheckSig(vchSig, vchPubKey, script, consensusBranchId);

                        if (fOk) {
                            isig++;
                            nSigsCount--;
                        }
                        ikey++;
                        nKeysCount--;

                        // If there are more signatures left than keys left,
                        // then too many signatures have failed. Exit early,
                        // without checking any further signatures.
                        if (nSigsCount > nKeysCount)
                            fSuccess = false;
                    }

                    // Clean up stack of actual arguments
                    while (i-- > 1)
                        popstack(stack);

                    // A bug causes CHECKMULTISIG to consume one extra argument
                    // whose contents were not checked in any way.
                    //
                    // Unfortunately this is a potential source of mutability,
                    // so optionally verify it is exactly equal to zero prior
                    // to removing it from the stack.
                    if (stack.size() < 1)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    if ((flags & SCRIPT_VERIFY_NULLDUMMY) && stacktop(-1).size())
                        return set_error(serror, SCRIPT_ERR_SIG_NULLDUMMY);
                    popstack(stack);

                    stack.push_back(fSuccess ? vchTrue : vchFalse);

                    if (opcode == OP_CHECKMULTISIGVERIFY)
                    {
                        if (fSuccess)
                            popstack(stack);
                        else
                            return set_error(serror, SCRIPT_ERR_CHECKMULTISIGVERIFY);
                    }
                }
                break;

                case OP_CHECKCRYPTOCONDITION:
                case OP_CHECKCRYPTOCONDITIONVERIFY:
                {
                    if (!IsCryptoConditionsEnabled()) {
                        goto INTERPRETER_DEFAULT;
                    }

                    if (stack.size() < 2)
                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                    //fprintf(stderr,"check cryptocondition\n");
                    int fResult = checker.CheckCryptoCondition(stacktop(-1), stacktop(-2), script, consensusBranchId);
                    if (fResult == -1) {
                        return set_error(serror, SCRIPT_ERR_CRYPTOCONDITION_INVALID_FULFILLMENT);
                    }
                    
                    popstack(stack);
                    popstack(stack);

                    stack.push_back(fResult == 1 ? vchTrue : vchFalse);

                    if (opcode == OP_CHECKCRYPTOCONDITIONVERIFY)
                    {
                        if (fResult == 1)
                            popstack(stack);
                        else
                            return set_error(serror, SCRIPT_ERR_CRYPTOCONDITION_VERIFY);
                    }
                }
                break;

INTERPRETER_DEFAULT:
                default:
                    return set_error(serror, SCRIPT_ERR_BAD_OPCODE);
            }

            // Size limits
            if (stack.size() + altstack.size() > 1000)
                return set_error(serror, SCRIPT_ERR_STACK_SIZE);
        }
    }
    catch (...)
    {
        return set_error(serror, SCRIPT_ERR_UNKNOWN_ERROR);
    }

    if (!vfExec.empty())
        return set_error(serror, SCRIPT_ERR_UNBALANCED_CONDITIONAL);

    return set_success(serror);
}

namespace {

/**
 * Wrapper that serializes like CTransaction, but with the modifications
 *  required for the signature hash done in-place
 */
class CTransactionSignatureSerializer {
private:
    const CTransaction &txTo;  //! reference to the spending transaction (the one being serialized)
    const CScript &scriptCode; //! output script being consumed
    const unsigned int nIn;    //! input index of txTo being signed
    const bool fAnyoneCanPay;  //! whether the hashtype has the SIGHASH_ANYONECANPAY flag set
    const bool fHashSingle;    //! whether the hashtype is SIGHASH_SINGLE
    const bool fHashNone;      //! whether the hashtype is SIGHASH_NONE

public:
    CTransactionSignatureSerializer(const CTransaction &txToIn, const CScript &scriptCodeIn, unsigned int nInIn, int nHashTypeIn) :
        txTo(txToIn), scriptCode(scriptCodeIn), nIn(nInIn),
        fAnyoneCanPay(!!(nHashTypeIn & SIGHASH_ANYONECANPAY)),
        fHashSingle((nHashTypeIn & 0x1f) == SIGHASH_SINGLE),
        fHashNone((nHashTypeIn & 0x1f) == SIGHASH_NONE) {}

    /** Serialize the passed scriptCode */
    template<typename S>
    void SerializeScriptCode(S &s) const {
        auto size = scriptCode.size();
        ::WriteCompactSize(s, size);
        s.write((char*)&scriptCode.begin()[0], size);
    }

    /** Serialize an input of txTo */
    template<typename S>
    void SerializeInput(S &s, unsigned int nInput) const {
        // In case of SIGHASH_ANYONECANPAY, only the input being signed is serialized
        if (fAnyoneCanPay)
            nInput = nIn;
        // Serialize the prevout
        ::Serialize(s, txTo.vin[nInput].prevout);
        // Serialize the script
        assert(nInput != NOT_AN_INPUT);
        if (nInput != nIn)
            // Blank out other inputs' signatures
            ::Serialize(s, CScriptBase());
        else
            SerializeScriptCode(s);
        // Serialize the nSequence
        if (nInput != nIn && (fHashSingle || fHashNone))
            // let the others update at will
            ::Serialize(s, (int)0);
        else
            ::Serialize(s, txTo.vin[nInput].nSequence);
    }

    /** Serialize an output of txTo */
    template<typename S>
    void SerializeOutput(S &s, unsigned int nOutput) const {
        if (fHashSingle && nOutput != nIn)
            // Do not lock-in the txout payee at other indices as txin
            ::Serialize(s, CTxOut());
        else
            ::Serialize(s, txTo.vout[nOutput]);
    }

    /** Serialize txTo */
    template<typename S>
    void Serialize(S &s) const {
        // Serialize nVersion
        ::Serialize(s, txTo.nVersion);
        // Serialize vin
        unsigned int nInputs = fAnyoneCanPay ? 1 : txTo.vin.size();
        ::WriteCompactSize(s, nInputs);
        for (unsigned int nInput = 0; nInput < nInputs; nInput++)
             SerializeInput(s, nInput);
        // Serialize vout
        unsigned int nOutputs = fHashNone ? 0 : (fHashSingle ? nIn+1 : txTo.vout.size());
        ::WriteCompactSize(s, nOutputs);
        for (unsigned int nOutput = 0; nOutput < nOutputs; nOutput++)
             SerializeOutput(s, nOutput);
        // Serialize nLockTime
        ::Serialize(s, txTo.nLockTime);

        // Serialize vjoinsplit
        if (txTo.nVersion >= 2) {
            //
            // SIGHASH_* functions will hash portions of
            // the transaction for use in signatures. This
            // keeps the JoinSplit cryptographically bound
            // to the transaction.
            //
            ::Serialize(s, txTo.vjoinsplit);
            if (txTo.vjoinsplit.size() > 0) {
                ::Serialize(s, txTo.joinSplitPubKey);

                CTransaction::joinsplit_sig_t nullSig = {};
                ::Serialize(s, nullSig);
            }
        }
    }
};

const unsigned char ZCASH_PREVOUTS_HASH_PERSONALIZATION[crypto_generichash_blake2b_PERSONALBYTES] =
    {'Z','c','a','s','h','P','r','e','v','o','u','t','H','a','s','h'};
const unsigned char ZCASH_SEQUENCE_HASH_PERSONALIZATION[crypto_generichash_blake2b_PERSONALBYTES] =
    {'Z','c','a','s','h','S','e','q','u','e','n','c','H','a','s','h'};
const unsigned char ZCASH_OUTPUTS_HASH_PERSONALIZATION[crypto_generichash_blake2b_PERSONALBYTES] =
    {'Z','c','a','s','h','O','u','t','p','u','t','s','H','a','s','h'};
const unsigned char ZCASH_JOINSPLITS_HASH_PERSONALIZATION[crypto_generichash_blake2b_PERSONALBYTES] =
    {'Z','c','a','s','h','J','S','p','l','i','t','s','H','a','s','h'};
const unsigned char ZCASH_SHIELDED_SPENDS_HASH_PERSONALIZATION[crypto_generichash_blake2b_PERSONALBYTES] =
    {'Z','c','a','s','h','S','S','p','e','n','d','s','H','a','s','h'};
const unsigned char ZCASH_SHIELDED_OUTPUTS_HASH_PERSONALIZATION[crypto_generichash_blake2b_PERSONALBYTES] =
    {'Z','c','a','s','h','S','O','u','t','p','u','t','H','a','s','h'};

uint256 GetPrevoutHash(const CTransaction& txTo) {
    CBLAKE2bWriter ss(SER_GETHASH, 0, ZCASH_PREVOUTS_HASH_PERSONALIZATION);
    for (unsigned int n = 0; n < txTo.vin.size(); n++) {
        ss << txTo.vin[n].prevout;
    }
    return ss.GetHash();
}

uint256 GetSequenceHash(const CTransaction& txTo) {
    CBLAKE2bWriter ss(SER_GETHASH, 0, ZCASH_SEQUENCE_HASH_PERSONALIZATION);
    for (unsigned int n = 0; n < txTo.vin.size(); n++) {
        ss << txTo.vin[n].nSequence;
    }
    return ss.GetHash();
}

uint256 GetOutputsHash(const CTransaction& txTo) {
    CBLAKE2bWriter ss(SER_GETHASH, 0, ZCASH_OUTPUTS_HASH_PERSONALIZATION);
    for (unsigned int n = 0; n < txTo.vout.size(); n++) {
        ss << txTo.vout[n];
    }
    return ss.GetHash();
}

uint256 GetJoinSplitsHash(const CTransaction& txTo) {
    CBLAKE2bWriter ss(SER_GETHASH, static_cast<int>(txTo.GetHeader()), ZCASH_JOINSPLITS_HASH_PERSONALIZATION);
    for (unsigned int n = 0; n < txTo.vjoinsplit.size(); n++) {
        ss << txTo.vjoinsplit[n];
    }
    ss << txTo.joinSplitPubKey;
    return ss.GetHash();
}

uint256 GetShieldedSpendsHash(const CTransaction& txTo) {
    CBLAKE2bWriter ss(SER_GETHASH, 0, ZCASH_SHIELDED_SPENDS_HASH_PERSONALIZATION);
    for (unsigned int n = 0; n < txTo.vShieldedSpend.size(); n++) {
        ss << txTo.vShieldedSpend[n].cv;
        ss << txTo.vShieldedSpend[n].anchor;
        ss << txTo.vShieldedSpend[n].nullifier;
        ss << txTo.vShieldedSpend[n].rk;
        ss << txTo.vShieldedSpend[n].zkproof;
    }
    return ss.GetHash();
}

uint256 GetShieldedOutputsHash(const CTransaction& txTo) {
    CBLAKE2bWriter ss(SER_GETHASH, 0, ZCASH_SHIELDED_OUTPUTS_HASH_PERSONALIZATION);
    for (unsigned int n = 0; n < txTo.vShieldedOutput.size(); n++) {
        ss << txTo.vShieldedOutput[n];
    }
    return ss.GetHash();
}

} // anon namespace

PrecomputedTransactionData::PrecomputedTransactionData(const CTransaction& txTo)
{
    hashPrevouts = GetPrevoutHash(txTo);
    hashSequence = GetSequenceHash(txTo);
    hashOutputs = GetOutputsHash(txTo);
    hashJoinSplits = GetJoinSplitsHash(txTo);
    hashShieldedSpends = GetShieldedSpendsHash(txTo);
    hashShieldedOutputs = GetShieldedOutputsHash(txTo);
}

SigVersion SignatureHashVersion(const CTransaction& txTo)
{
    if (txTo.fOverwintered) {
        if (txTo.nVersionGroupId == SAPLING_VERSION_GROUP_ID) {
            return SIGVERSION_SAPLING;
        } else {
            return SIGVERSION_OVERWINTER;
        }
    } else {
        return SIGVERSION_SPROUT;
    }
}

uint256 SignatureHash(
    const CScript& scriptCode,
    const CTransaction& txTo,
    unsigned int nIn,
    int nHashType,
    const CAmount& amount,
    uint32_t consensusBranchId,
    const PrecomputedTransactionData* cache)
{
    if (nIn >= txTo.vin.size() && nIn != NOT_AN_INPUT) {
        //  nIn out of range
        throw logic_error("input index is out of range");
    }

    auto sigversion = SignatureHashVersion(txTo);

    if (sigversion == SIGVERSION_OVERWINTER || sigversion == SIGVERSION_SAPLING) {
        uint256 hashPrevouts;
        uint256 hashSequence;
        uint256 hashOutputs;
        uint256 hashJoinSplits;
        uint256 hashShieldedSpends;
        uint256 hashShieldedOutputs;

        if (!(nHashType & SIGHASH_ANYONECANPAY)) {
            hashPrevouts = cache ? cache->hashPrevouts : GetPrevoutHash(txTo);
        }

        if (!(nHashType & SIGHASH_ANYONECANPAY) && (nHashType & 0x1f) != SIGHASH_SINGLE && (nHashType & 0x1f) != SIGHASH_NONE) {
            hashSequence = cache ? cache->hashSequence : GetSequenceHash(txTo);
        }

        if ((nHashType & 0x1f) != SIGHASH_SINGLE && (nHashType & 0x1f) != SIGHASH_NONE) {
            hashOutputs = cache ? cache->hashOutputs : GetOutputsHash(txTo);
        } else if ((nHashType & 0x1f) == SIGHASH_SINGLE && nIn < txTo.vout.size()) {
            CBLAKE2bWriter ss(SER_GETHASH, 0, ZCASH_OUTPUTS_HASH_PERSONALIZATION);
            ss << txTo.vout[nIn];
            hashOutputs = ss.GetHash();
        }

        if (!txTo.vjoinsplit.empty()) {
            hashJoinSplits = cache ? cache->hashJoinSplits : GetJoinSplitsHash(txTo);
        }

        if (!txTo.vShieldedSpend.empty()) {
            hashShieldedSpends = cache ? cache->hashShieldedSpends : GetShieldedSpendsHash(txTo);
        }

        if (!txTo.vShieldedOutput.empty()) {
            hashShieldedOutputs = cache ? cache->hashShieldedOutputs : GetShieldedOutputsHash(txTo);
        }

        uint32_t leConsensusBranchId = htole32(consensusBranchId);
        unsigned char personalization[16] = {};
        memcpy(personalization, "ZcashSigHash", 12);
        memcpy(personalization+12, &leConsensusBranchId, 4);

        CBLAKE2bWriter ss(SER_GETHASH, 0, personalization);
        // Header
        ss << txTo.GetHeader();
        // Version group ID
        ss << txTo.nVersionGroupId;
        // Input prevouts/nSequence (none/all, depending on flags)
        ss << hashPrevouts;
        ss << hashSequence;
        // Outputs (none/one/all, depending on flags)
        ss << hashOutputs;
        // JoinSplits
        ss << hashJoinSplits;
        if (sigversion == SIGVERSION_SAPLING) {
            // Spend descriptions
            ss << hashShieldedSpends;
            // Output descriptions
            ss << hashShieldedOutputs;
        }
        // Locktime
        ss << txTo.nLockTime;
        // Expiry height
        ss << txTo.nExpiryHeight;
        if (sigversion == SIGVERSION_SAPLING) {
            // Sapling value balance
            ss << txTo.valueBalance;
        }
        // Sighash type
        ss << nHashType;

        // If this hash is for a transparent input signature
        // (i.e. not for txTo.joinSplitSig):
        if (nIn != NOT_AN_INPUT){
            // The input being signed (replacing the scriptSig with scriptCode + amount)
            // The prevout may already be contained in hashPrevout, and the nSequence
            // may already be contained in hashSequence.
            ss << txTo.vin[nIn].prevout;
            ss << static_cast<const CScriptBase&>(scriptCode);
            ss << amount;
            ss << txTo.vin[nIn].nSequence;
        }

        return ss.GetHash();
    }

    // Check for invalid use of SIGHASH_SINGLE
    if ((nHashType & 0x1f) == SIGHASH_SINGLE) {
        if (nIn >= txTo.vout.size()) {
            //  nOut out of range
            throw logic_error("no matching output for SIGHASH_SINGLE");
        }
    }

    // Wrapper to serialize only the necessary parts of the transaction being signed
    CTransactionSignatureSerializer txTmp(txTo, scriptCode, nIn, nHashType);

    // Serialize and hash
    CHashWriter ss(SER_GETHASH, 0);
    ss << txTmp << nHashType;
    return ss.GetHash();
}

bool TransactionSignatureChecker::VerifySignature(
    const std::vector<unsigned char>& vchSig, const CPubKey& pubkey, const uint256& sighash) const
{
    return pubkey.Verify(sighash, vchSig);
}

bool TransactionSignatureChecker::CheckSig(
    const vector<unsigned char>& vchSigIn,
    const vector<unsigned char>& vchPubKey,
    const CScript& scriptCode,
    uint32_t consensusBranchId) const
{
    CPubKey pubkey(vchPubKey);
    if (!pubkey.IsValid())
        return false;

    // Hash type is one byte tacked on to the end of the signature
    vector<unsigned char> vchSig(vchSigIn);
    if (vchSig.empty())
        return false;
    int nHashType = vchSig.back();
    vchSig.pop_back();

    uint256 sighash;
    try {
        sighash = SignatureHash(scriptCode, *txTo, nIn, nHashType, amount, consensusBranchId, this->txdata);
    } catch (logic_error ex) {
        return false;
    }

    if (!VerifySignature(vchSig, pubkey, sighash))
        return false;

    return true;
}


int TransactionSignatureChecker::CheckCryptoCondition(
        const std::vector<unsigned char>& condBin,
        const std::vector<unsigned char>& ffillBin,
        const CScript& scriptCode,
        uint32_t consensusBranchId) const
{
    // Hash type is one byte tacked on to the end of the fulfillment
    if (ffillBin.empty())
        return false;

    CC *cond;
    int error = cc_readFulfillmentBinaryExt((unsigned char*)ffillBin.data(), ffillBin.size()-1, &cond);
    if (error || !cond) return -1;

    if (!IsSupportedCryptoCondition(cond)) return 0;
    if (!IsSignedCryptoCondition(cond)) return 0;
    
    uint256 sighash;
    int nHashType = ffillBin.back();
    try {
        sighash = SignatureHash(CCPubKey(cond), *txTo, nIn, nHashType, amount, consensusBranchId, this->txdata);
    } catch (logic_error ex) {
        return 0;
    }
    /*int32_t z; uint8_t *ptr;
    ptr = (uint8_t *)scriptCode.data();
    for (z=0; z<scriptCode.size(); z++)
        fprintf(stderr,"%02x",ptr[z]);
    fprintf(stderr," <- CScript\n");
    for (z=0; z<32; z++)
        fprintf(stderr,"%02x",((uint8_t *)&sighash)[z]);
    fprintf(stderr," sighash nIn.%d nHashType.%d %.8f id.%d\n",(int32_t)nIn,(int32_t)nHashType,(double)amount/COIN,(int32_t)consensusBranchId);
     */
    VerifyEval eval = [] (CC *cond, void *checker) {
        //fprintf(stderr,"checker.%p\n",(TransactionSignatureChecker*)checker);
        return ((TransactionSignatureChecker*)checker)->CheckEvalCondition(cond);
    };
    //fprintf(stderr,"non-checker path\n");
    int out = cc_verify(cond, (const unsigned char*)&sighash, 32, 0,
                        condBin.data(), condBin.size(), eval, (void*)this);
    //fprintf(stderr,"out.%d from cc_verify\n",(int32_t)out);
    cc_free(cond);
    return out;
}


int TransactionSignatureChecker::CheckEvalCondition(const CC *cond) const
{
    //fprintf(stderr, "Cannot check crypto-condition Eval outside of server, returning true in pre-checks\n");
    return true;
}


bool TransactionSignatureChecker::CheckLockTime(const CScriptNum& nLockTime) const
{
    // There are two times of nLockTime: lock-by-blockheight
    // and lock-by-blocktime, distinguished by whether
    // nLockTime < LOCKTIME_THRESHOLD.
    //
    // We want to compare apples to apples, so fail the script
    // unless the type of nLockTime being tested is the same as
    // the nLockTime in the transaction.
    if (!(
        (txTo->nLockTime <  LOCKTIME_THRESHOLD && nLockTime <  LOCKTIME_THRESHOLD) ||
        (txTo->nLockTime >= LOCKTIME_THRESHOLD && nLockTime >= LOCKTIME_THRESHOLD)
    ))
        return false;

    // Now that we know we're comparing apples-to-apples, the
    // comparison is a simple numeric one.
    if (nLockTime > (int64_t)txTo->nLockTime)
    {
        //fprintf(stderr,"CLTV error: nLockTime %llu > %u txTo->nLockTime\n",*(long long *)&nLockTime,(uint32_t)txTo->nLockTime);
        return false;
    }

    // Finally the nLockTime feature can be disabled and thus
    // CHECKLOCKTIMEVERIFY bypassed if every txin has been
    // finalized by setting nSequence to maxint. The
    // transaction would be allowed into the blockchain, making
    // the opcode ineffective.
    //
    // Testing if this vin is not final is sufficient to
    // prevent this condition. Alternatively we could test all
    // inputs, but testing just this input minimizes the data
    // required to prove correct CHECKLOCKTIMEVERIFY execution.
    if (txTo->vin[nIn].IsFinal())
    {
        //fprintf(stderr,"CLTV error: nonfinal vin.%d nSequence.%u vs %u\n",(int32_t)nIn,(uint32_t)txTo->vin[nIn].nSequence,(uint32_t)std::numeric_limits<uint32_t>::max());
        return false;
    }

    return true;
}


/*
 * Allow larger opcode in case of crypto condition scriptSig
 */
bool EvalCryptoConditionSig(
    vector<vector<unsigned char> >& stack,
    const CScript& scriptSig,
    ScriptError* serror)
{
    CScript::const_iterator pc = scriptSig.begin();
    opcodetype opcode;
    valtype vchPushValue;
    set_error(serror, SCRIPT_ERR_UNKNOWN_ERROR);

    if (!scriptSig.GetOp(pc, opcode, vchPushValue))
        return set_error(serror, SCRIPT_ERR_BAD_OPCODE);

    if (opcode == 0 || opcode > OP_PUSHDATA4)
        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);

    if (pc != scriptSig.end())
        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);

    if (vchPushValue.size() > MAX_SCRIPT_CRYPTOCONDITION_FULFILLMENT_SIZE)
        return set_error(serror, SCRIPT_ERR_PUSH_SIZE);

    stack.push_back(vchPushValue);
    
    return true;
}


bool VerifyScript(
    const CScript& scriptSig,
    const CScript& scriptPubKey,
    unsigned int flags,
    const BaseSignatureChecker& checker,
    uint32_t consensusBranchId,
    ScriptError* serror)
{
    set_error(serror, SCRIPT_ERR_UNKNOWN_ERROR);

    if ((flags & SCRIPT_VERIFY_SIGPUSHONLY) != 0 && !scriptSig.IsPushOnly()) {
        return set_error(serror, SCRIPT_ERR_SIG_PUSHONLY);
    }

    vector<vector<unsigned char> > stack, stackCopy;
    if (IsCryptoConditionsEnabled() && scriptPubKey.IsPayToCryptoCondition()) {
        if (!EvalCryptoConditionSig(stack, scriptSig, serror))
            // serror is set
            return false;
    }
    else if (!EvalScript(stack, scriptSig, flags, checker, consensusBranchId, serror))
        // serror is set
        return false;
    if (flags & SCRIPT_VERIFY_P2SH)
        stackCopy = stack;
    if (!EvalScript(stack, scriptPubKey, flags, checker, consensusBranchId, serror))
        // serror is set
        return false;
    if (stack.empty())
    {
        //printf("interpreter stack is empty, comment this debugging message\nscriptSig: %s\nscriptPubKey: %s\n",scriptSig.ToString().c_str(),scriptPubKey.ToString().c_str());
        return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
    }
    if (CastToBool(stack.back()) == false)
    {
        //printf("false return value, comment this debugging message\nscriptSig: %s\nscriptPubKey: %s\n",scriptSig.ToString().c_str(),scriptPubKey.ToString().c_str());
        return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
    }

    // Additional validation for spend-to-script-hash transactions:
    if ((flags & SCRIPT_VERIFY_P2SH) && scriptPubKey.IsPayToScriptHash())
    {
        // scriptSig must be literals-only or validation fails
        if (!scriptSig.IsPushOnly())
            return set_error(serror, SCRIPT_ERR_SIG_PUSHONLY);

        // Restore stack.
        swap(stack, stackCopy);

        // stack cannot be empty here, because if it was the
        // P2SH  HASH <> EQUAL  scriptPubKey would be evaluated with
        // an empty stack and the EvalScript above would return false.
        assert(!stack.empty());

        const valtype& pubKeySerialized = stack.back();
        CScript pubKey2(pubKeySerialized.begin(), pubKeySerialized.end());
        popstack(stack);

        if (!EvalScript(stack, pubKey2, flags, checker, consensusBranchId, serror))
            // serror is set
            return false;
        if (stack.empty())
        {
            //printf("interpreter stack is empty #2, comment this debugging message\nscriptSig: %s\nscriptPubKey: %s\n",scriptSig.ToString().c_str(),scriptPubKey.ToString().c_str());
            return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
        }
        if (!CastToBool(stack.back()))
        {
            //printf("false return value #2, comment this debugging message\nscriptSig: %s\nscriptPubKey: %s\n",scriptSig.ToString().c_str(),scriptPubKey.ToString().c_str());
            return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
        }
    }

    // The CLEANSTACK check is only performed after potential P2SH evaluation,
    // as the non-P2SH evaluation of a P2SH script will obviously not result in
    // a clean stack (the P2SH inputs remain).
    if ((flags & SCRIPT_VERIFY_CLEANSTACK) != 0) {
        // Disallow CLEANSTACK without P2SH, as otherwise a switch CLEANSTACK->P2SH+CLEANSTACK
        // would be possible, which is not a softfork (and P2SH should be one).
        assert((flags & SCRIPT_VERIFY_P2SH) != 0);
        if (stack.size() != 1) {
            return set_error(serror, SCRIPT_ERR_CLEANSTACK);
        }
    }

    return set_success(serror);
}