text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2018 The Bitcoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifndef LEARNCOIN_SCRIPT_STANDARD_H
  #define LEARNCOIN_SCRIPT_STANDARD_H
  
  #include <script/interpreter.h>
  #include <uint256.h>
  
  #include <boost/variant.hpp>
  
  #include <stdint.h>
  
  static const bool DEFAULT_ACCEPT_DATACARRIER = true;
  
  class CKeyID;
  class CScript;
  
  /** A reference to a CScript: the Hash160 of its serialization (see script.h) */
  class CScriptID : public uint160
  {
  public:
      CScriptID() : uint160() {}
      explicit CScriptID(const CScript& in);
      CScriptID(const uint160& in) : uint160(in) {}
  };
  
  /**
   * Default setting for nMaxDatacarrierBytes. 80 bytes of data, +1 for OP_RETURN,
   * +2 for the pushdata opcodes.
   */
  static const unsigned int MAX_OP_RETURN_RELAY = 83;
  
  /**
   * A data carrying output is an unspendable output containing data. The script
   * type is designated as TX_NULL_DATA.
   */
  extern bool fAcceptDatacarrier;
  
  /** Maximum size of TX_NULL_DATA scripts that this node considers standard. */
  extern unsigned nMaxDatacarrierBytes;
  
  /**
   * 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;
  
  enum txnouttype
  {
      TX_NONSTANDARD,
      // 'standard' transaction types:
      TX_PUBKEY,
      TX_PUBKEYHASH,
      TX_SCRIPTHASH,
      TX_MULTISIG,
      TX_NULL_DATA, //!< unspendable OP_RETURN script that carries data
      TX_WITNESS_V0_SCRIPTHASH,
      TX_WITNESS_V0_KEYHASH,
      TX_WITNESS_UNKNOWN, //!< Only for Witness versions not already defined above
  };
  
  class CNoDestination {
  public:
      friend bool operator==(const CNoDestination &a, const CNoDestination &b) { return true; }
      friend bool operator<(const CNoDestination &a, const CNoDestination &b) { return true; }
  };
  
  struct WitnessV0ScriptHash : public uint256
  {
      WitnessV0ScriptHash() : uint256() {}
      explicit WitnessV0ScriptHash(const uint256& hash) : uint256(hash) {}
      explicit WitnessV0ScriptHash(const CScript& script);
      using uint256::uint256;
  };
  
  struct WitnessV0KeyHash : public uint160
  {
      WitnessV0KeyHash() : uint160() {}
      explicit WitnessV0KeyHash(const uint160& hash) : uint160(hash) {}
      using uint160::uint160;
  };
  
  //! CTxDestination subtype to encode any future Witness version
  struct WitnessUnknown
  {
      unsigned int version;
      unsigned int length;
      unsigned char program[40];
  
      friend bool operator==(const WitnessUnknown& w1, const WitnessUnknown& w2) {
          if (w1.version != w2.version) return false;
          if (w1.length != w2.length) return false;
          return std::equal(w1.program, w1.program + w1.length, w2.program);
      }
  
      friend bool operator<(const WitnessUnknown& w1, const WitnessUnknown& w2) {
          if (w1.version < w2.version) return true;
          if (w1.version > w2.version) return false;
          if (w1.length < w2.length) return true;
          if (w1.length > w2.length) return false;
          return std::lexicographical_compare(w1.program, w1.program + w1.length, w2.program, w2.program + w2.length);
      }
  };
  
  /**
   * A txout script template with a specific destination. It is either:
   *  * CNoDestination: no destination set
   *  * CKeyID: TX_PUBKEYHASH destination (P2PKH)
   *  * CScriptID: TX_SCRIPTHASH destination (P2SH)
   *  * WitnessV0ScriptHash: TX_WITNESS_V0_SCRIPTHASH destination (P2WSH)
   *  * WitnessV0KeyHash: TX_WITNESS_V0_KEYHASH destination (P2WPKH)
   *  * WitnessUnknown: TX_WITNESS_UNKNOWN destination (P2W???)
   *  A CTxDestination is the internal data type encoded in a learncoin address
   */
  typedef boost::variant<CNoDestination, CKeyID, CScriptID, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessUnknown> CTxDestination;
  
  /** Check whether a CTxDestination is a CNoDestination. */
  bool IsValidDestination(const CTxDestination& dest);
  
  /** Get the name of a txnouttype as a C string, or nullptr if unknown. */
  const char* GetTxnOutputType(txnouttype t);
  
  /**
   * Parse a scriptPubKey and identify script type for standard scripts. If
   * successful, returns script type and parsed pubkeys or hashes, depending on
   * the type. For example, for a P2SH script, vSolutionsRet will contain the
   * script hash, for P2PKH it will contain the key hash, etc.
   *
   * @param[in]   scriptPubKey   Script to parse
   * @param[out]  typeRet        The script type
   * @param[out]  vSolutionsRet  Vector of parsed pubkeys and hashes
   * @return                     True if script matches standard template
   */
  bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<std::vector<unsigned char> >& vSolutionsRet);
  
  /**
   * Parse a standard scriptPubKey for the destination address. Assigns result to
   * the addressRet parameter and returns true if successful. For multisig
   * scripts, instead use ExtractDestinations. Currently only works for P2PK,
   * P2PKH, P2SH, P2WPKH, and P2WSH scripts.
   */
  bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet);
  
  /**
   * Parse a standard scriptPubKey with one or more destination addresses. For
   * multisig scripts, this populates the addressRet vector with the pubkey IDs
   * and nRequiredRet with the n required to spend. For other destinations,
   * addressRet is populated with a single value and nRequiredRet is set to 1.
   * Returns true if successful. Currently does not extract address from
   * pay-to-witness scripts.
   *
   * Note: this function confuses destinations (a subset of CScripts that are
   * encodable as an address) with key identifiers (of keys involved in a
   * CScript), and its use should be phased out.
   */
  bool ExtractDestinations(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<CTxDestination>& addressRet, int& nRequiredRet);
  
  /**
   * Generate a Learncoin scriptPubKey for the given CTxDestination. Returns a P2PKH
   * script for a CKeyID destination, a P2SH script for a CScriptID, and an empty
   * script for CNoDestination.
   */
  CScript GetScriptForDestination(const CTxDestination& dest);
  
  /** Generate a P2PK script for the given pubkey. */
  CScript GetScriptForRawPubKey(const CPubKey& pubkey);
  
  /** Generate a multisig script. */
  CScript GetScriptForMultisig(int nRequired, const std::vector<CPubKey>& keys);
  
  /**
   * Generate a pay-to-witness script for the given redeem script. If the redeem
   * script is P2PK or P2PKH, this returns a P2WPKH script, otherwise it returns a
   * P2WSH script.
   *
   * TODO: replace calls to GetScriptForWitness with GetScriptForDestination using
   * the various witness-specific CTxDestination subtypes.
   */
  CScript GetScriptForWitness(const CScript& redeemscript);
  
  #endif // LEARNCOIN_SCRIPT_STANDARD_H
  