// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2013 The Bitcoin developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef H_BITCOIN_SCRIPTUTILS
#define H_BITCOIN_SCRIPTUTILS

#include "key.h"
#include "script/script.h"

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

class CKeyStore;
class CTransaction;
struct CMutableTransaction;

static const unsigned int MAX_OP_RETURN_RELAY = 40;      // bytes

/** 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_NOCACHE   = (1U << 3), // do not store results in signature cache (but do query it)
    SCRIPT_VERIFY_NULLDUMMY = (1U << 4), // verify dummy stack item consumed by CHECKMULTISIG is of zero-length
};

/** IsMine() return codes */
enum isminetype
{
    ISMINE_NO = 0,
    ISMINE_WATCH_ONLY = 1,
    ISMINE_SPENDABLE = 2,
    ISMINE_ALL = ISMINE_WATCH_ONLY | ISMINE_SPENDABLE
};
/** used for bitflags of isminetype */
typedef uint8_t isminefilter;

// Mandatory script verification flags that all new blocks must comply with for
// them to be valid. (but old blocks may not comply with) Currently just P2SH,
// but in the future other flags may be added, such as a soft-fork to enforce
// strict DER encoding.
//
// Failing one of these tests may trigger a DoS ban - see CheckInputs() for
// details.
static const unsigned int MANDATORY_SCRIPT_VERIFY_FLAGS = SCRIPT_VERIFY_P2SH;

// Standard script verification flags that standard transactions will comply
// with. However scripts violating these flags may still be present in valid
// blocks and we must accept those blocks.
static const unsigned int STANDARD_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VERIFY_FLAGS |
                                                         SCRIPT_VERIFY_STRICTENC |
                                                         SCRIPT_VERIFY_NULLDUMMY;

// For convenience, standard but not mandatory verify flags.
static const unsigned int STANDARD_NOT_MANDATORY_VERIFY_FLAGS = STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SCRIPT_VERIFY_FLAGS;

enum txnouttype
{
    TX_NONSTANDARD,
    // 'standard' transaction types:
    TX_PUBKEY,
    TX_PUBKEYHASH,
    TX_SCRIPTHASH,
    TX_MULTISIG,
    TX_NULL_DATA,
};

const char* GetTxnOutputType(txnouttype t);

/** Compact serializer for scripts.
 *
 *  It detects common cases and encodes them much more efficiently.
 *  3 special cases are defined:
 *  * Pay to pubkey hash (encoded as 21 bytes)
 *  * Pay to script hash (encoded as 21 bytes)
 *  * Pay to pubkey starting with 0x02, 0x03 or 0x04 (encoded as 33 bytes)
 *
 *  Other scripts up to 121 bytes require 1 byte + script length. Above
 *  that, scripts up to 16505 bytes require 2 bytes + script length.
 */
class CScriptCompressor
{
private:
    // make this static for now (there are only 6 special scripts defined)
    // this can potentially be extended together with a new nVersion for
    // transactions, in which case this value becomes dependent on nVersion
    // and nHeight of the enclosing transaction.
    static const unsigned int nSpecialScripts = 6;

    CScript &script;
protected:
    // These check for scripts for which a special case with a shorter encoding is defined.
    // They are implemented separately from the CScript test, as these test for exact byte
    // sequence correspondences, and are more strict. For example, IsToPubKey also verifies
    // whether the public key is valid (as invalid ones cannot be represented in compressed
    // form).
    bool IsToKeyID(CKeyID &hash) const;
    bool IsToScriptID(CScriptID &hash) const;
    bool IsToPubKey(CPubKey &pubkey) const;

    bool Compress(std::vector<unsigned char> &out) const;
    unsigned int GetSpecialSize(unsigned int nSize) const;
    bool Decompress(unsigned int nSize, const std::vector<unsigned char> &out);
public:
    CScriptCompressor(CScript &scriptIn) : script(scriptIn) { }

    unsigned int GetSerializeSize(int nType, int nVersion) const {
        std::vector<unsigned char> compr;
        if (Compress(compr))
            return compr.size();
        unsigned int nSize = script.size() + nSpecialScripts;
        return script.size() + VARINT(nSize).GetSerializeSize(nType, nVersion);
    }

    template<typename Stream>
    void Serialize(Stream &s, int nType, int nVersion) const {
        std::vector<unsigned char> compr;
        if (Compress(compr)) {
            s << CFlatData(compr);
            return;
        }
        unsigned int nSize = script.size() + nSpecialScripts;
        s << VARINT(nSize);
        s << CFlatData(script);
    }

    template<typename Stream>
    void Unserialize(Stream &s, int nType, int nVersion) {
        unsigned int nSize = 0;
        s >> VARINT(nSize);
        if (nSize < nSpecialScripts) {
            std::vector<unsigned char> vch(GetSpecialSize(nSize), 0x00);
            s >> REF(CFlatData(vch));
            Decompress(nSize, vch);
            return;
        }
        nSize -= nSpecialScripts;
        script.resize(nSize);
        s >> REF(CFlatData(script));
    }
};

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

bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, const CTransaction& txTo, unsigned int nIn, unsigned int flags, int nHashType);
uint256 SignatureHash(const CScript &scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType);
bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<std::vector<unsigned char> >& vSolutionsRet);
int ScriptSigArgsExpected(txnouttype t, const std::vector<std::vector<unsigned char> >& vSolutions);
bool IsStandard(const CScript& scriptPubKey, txnouttype& whichType);
isminetype IsMine(const CKeyStore& keystore, const CScript& scriptPubKey);
isminetype IsMine(const CKeyStore& keystore, const CTxDestination& dest);
void ExtractAffectedKeys(const CKeyStore &keystore, const CScript& scriptPubKey, std::vector<CKeyID> &vKeys);
bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet);
bool ExtractDestinations(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<CTxDestination>& addressRet, int& nRequiredRet);
bool SignSignature(const CKeyStore& keystore, const CScript& fromPubKey, CMutableTransaction& txTo, unsigned int nIn, int nHashType=SIGHASH_ALL);
bool SignSignature(const CKeyStore& keystore, const CTransaction& txFrom, CMutableTransaction& txTo, unsigned int nIn, int nHashType=SIGHASH_ALL);
bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, const CTransaction& txTo, unsigned int nIn, unsigned int flags, int nHashType);

// Given two sets of signatures for scriptPubKey, possibly with OP_0 placeholders,
// combine them intelligently and return the result.
CScript CombineSignatures(CScript scriptPubKey, const CTransaction& txTo, unsigned int nIn, const CScript& scriptSig1, const CScript& scriptSig2);

#endif // H_BITCOIN_SCRIPT