// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2014 The Bitcoin developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef H_BITCOIN_SCRIPT_INTERPRETER
#define H_BITCOIN_SCRIPT_INTERPRETER

#include <vector>
#include <stdint.h>
#include <string>

class CPubKey;
class CScript;
class CTransaction;
class uint256;

/** Signature hash types/flags */
enum
{
    SIGHASH_ALL = 1,
    SIGHASH_NONE = 2,
    SIGHASH_SINGLE = 3,
    SIGHASH_ANYONECANPAY = 0x80,
};

/** Script verification flags */
enum
{
    SCRIPT_VERIFY_NONE      = 0,
    SCRIPT_VERIFY_P2SH      = (1U << 0), // evaluate P2SH (BIP16) subscripts
    SCRIPT_VERIFY_STRICTENC = (1U << 1), // enforce strict conformance to DER and SEC2 for signatures and pubkeys
    SCRIPT_VERIFY_LOW_S     = (1U << 2), // enforce low S values (<n/2) in signatures (depends on STRICTENC)
    SCRIPT_VERIFY_NULLDUMMY = (1U << 3), // verify dummy stack item consumed by CHECKMULTISIG is of zero-length
};

bool IsCanonicalPubKey(const std::vector<unsigned char> &vchPubKey, unsigned int flags);
bool IsCanonicalSignature(const std::vector<unsigned char> &vchSig, unsigned int flags);

uint256 SignatureHash(const CScript &scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType);

class BaseSignatureChecker
{
public:
    virtual bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode) const
    {
        return false;
    }

    virtual ~BaseSignatureChecker() {}
};

class SignatureChecker : public BaseSignatureChecker
{
private:
    const CTransaction& txTo;
    unsigned int nIn;

protected:
    virtual bool VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& vchPubKey, const uint256& sighash) const;

public:
    SignatureChecker(const CTransaction& txToIn, unsigned int nInIn) : txTo(txToIn), nIn(nInIn) {}
    bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode) const;
};

bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const BaseSignatureChecker& checker);
bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, unsigned int flags, const BaseSignatureChecker& checker);

#endif // H_BITCOIN_SCRIPT_INTERPRETER