module Bitcoin

  COIN = 100_000_000
  MAX_MONEY = 21_000_000 * COIN

  # The maximum allowed size for a serialized block, in bytes (only for buffer size limits)
  MAX_BLOCK_SERIALIZED_SIZE = 4_000_000
  # The maximum allowed weight for a block, see BIP 141 (network rule)
  MAX_BLOCK_WEIGHT = 4_000_000
  # The maximum allowed number of signature check operations in a block (network rule)
  MAX_BLOCK_SIGOPS_COST = 80_000
  # Coinbase transaction outputs can only be spent after this number of new blocks (network rule)
  COINBASE_MATURITY = 100
  WITNESS_SCALE_FACTOR = 4

  # 60 is the lower bound for the size of a valid serialized Tx
  MIN_TRANSACTION_WEIGHT = WITNESS_SCALE_FACTOR * 60
  # 10 is the lower bound for the size of a serialized Tx
  MIN_SERIALIZABLE_TRANSACTION_WEIGHT = WITNESS_SCALE_FACTOR * 10

  # Flags for nSequence and nLockTime locks
  LOCKTIME_VERIFY_SEQUENCE = (1 << 0)
  LOCKTIME_MEDIAN_TIME_PAST = (1 << 1)

  # script verify flags
  SCRIPT_VERIFY_NONE      = 0
  SCRIPT_VERIFY_P2SH      = (1 << 0)
  SCRIPT_VERIFY_STRICTENC = (1 << 1)
  SCRIPT_VERIFY_DERSIG    = (1 << 2)
  SCRIPT_VERIFY_LOW_S     = (1 << 3)
  SCRIPT_VERIFY_NULLDUMMY = (1 << 4)
  SCRIPT_VERIFY_SIGPUSHONLY = (1 << 5)
  SCRIPT_VERIFY_MINIMALDATA = (1 << 6)
  SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS = (1 << 7)
  SCRIPT_VERIFY_CLEANSTACK = (1 << 8)
  SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY = (1 << 9) # Verify CHECKLOCKTIMEVERIFY (BIP-65)
  SCRIPT_VERIFY_CHECKSEQUENCEVERIFY = (1 << 10) # support CHECKSEQUENCEVERIFY opcode (BIP-112)
  SCRIPT_VERIFY_WITNESS = (1 << 11) # Support segregated witness
  SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM = (1 << 12) # Making v1-v16 witness program non-standard
  SCRIPT_VERIFY_MINIMALIF = (1 << 13) # Segwit script only: Require the argument of OP_IF/NOTIF to be exactly 0x01 or empty vector
  SCRIPT_VERIFY_NULLFAIL = (1 << 14) # Signature(s) must be empty vector if an CHECK(MULTI)SIG operation failed
  SCRIPT_VERIFY_WITNESS_PUBKEYTYPE = (1 << 15) # Public keys in segregated witness scripts must be compressed

  MANDATORY_SCRIPT_VERIFY_FLAGS = SCRIPT_VERIFY_P2SH

  # Standard script verification flags that standard transactions will comply with.
  STANDARD_SCRIPT_VERIFY_FLAGS = [MANDATORY_SCRIPT_VERIFY_FLAGS,
                                  SCRIPT_VERIFY_DERSIG,
                                  SCRIPT_VERIFY_STRICTENC,
                                  SCRIPT_VERIFY_MINIMALDATA,
                                  SCRIPT_VERIFY_NULLDUMMY,
                                  SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS,
                                  SCRIPT_VERIFY_CLEANSTACK,
                                  SCRIPT_VERIFY_MINIMALIF,
                                  SCRIPT_VERIFY_NULLFAIL,
                                  SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY,
                                  SCRIPT_VERIFY_CHECKSEQUENCEVERIFY,
                                  SCRIPT_VERIFY_LOW_S,
                                  SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM]

  # for script

  # witness version
  WITNESS_VERSION = 0x00

  # Maximum script length in bytes
  MAX_SCRIPT_SIZE = 10000

  # Maximum number of public keys per multisig
  MAX_PUBKEYS_PER_MULTISIG = 20

  # Maximum number of non-push operations per script
  MAX_OPS_PER_SCRIPT = 201

  # Maximum number of bytes pushable to the stack
  MAX_SCRIPT_ELEMENT_SIZE = 520

  # Maximum number of size in the stack
  MAX_STACK_SIZE = 1000

  # Threshold for nLockTime: below this value it is interpreted as block number, otherwise as UNIX timestamp.
  LOCKTIME_THRESHOLD = 500000000

  # Signature hash types/flags
  SIGHASH_TYPE = { all: 1, none: 2, single: 3, anyonecanpay: 128 }

  # Maximum number length in bytes
  DEFAULT_MAX_NUM_SIZE = 4

  # 80 bytes of data, +1 for OP_RETURN, +2 for the pushdata opcodes.
  MAX_OP_RETURN_RELAY = 83

  SIG_VERSION = [:base, :witness_v0]

  # for script error
  SCRIPT_ERR_OK = 0
  SCRIPT_ERR_UNKNOWN_ERROR = 1
  SCRIPT_ERR_EVAL_FALSE = 2
  SCRIPT_ERR_OP_RETURN = 3

  # Max sizes
  SCRIPT_ERR_SCRIPT_SIZE = 10
  SCRIPT_ERR_PUSH_SIZE = 11
  SCRIPT_ERR_OP_COUNT = 12
  SCRIPT_ERR_STACK_SIZE = 13
  SCRIPT_ERR_SIG_COUNT = 14
  SCRIPT_ERR_PUBKEY_COUNT = 15

  # Failed verify operations
  SCRIPT_ERR_VERIFY = 20
  SCRIPT_ERR_EQUALVERIFY = 21
  SCRIPT_ERR_CHECKMULTISIGVERIFY = 22
  SCRIPT_ERR_CHECKSIGVERIFY = 23
  SCRIPT_ERR_NUMEQUALVERIFY = 24

  # Logical/Format/Canonical errors
  SCRIPT_ERR_BAD_OPCODE = 30
  SCRIPT_ERR_DISABLED_OPCODE = 31
  SCRIPT_ERR_INVALID_STACK_OPERATION = 32
  SCRIPT_ERR_INVALID_ALTSTACK_OPERATION = 33
  SCRIPT_ERR_UNBALANCED_CONDITIONAL = 34

  # CHECKLOCKTIMEVERIFY and CHECKSEQUENCEVERIFY
  SCRIPT_ERR_NEGATIVE_LOCKTIME = 40
  SCRIPT_ERR_UNSATISFIED_LOCKTIME = 41

  # Malleability
  SCRIPT_ERR_SIG_HASHTYPE = 50
  SCRIPT_ERR_SIG_DER = 51
  SCRIPT_ERR_MINIMALDATA = 52
  SCRIPT_ERR_SIG_PUSHONLY = 53
  SCRIPT_ERR_SIG_HIGH_S = 54
  SCRIPT_ERR_SIG_NULLDUMMY = 55
  SCRIPT_ERR_PUBKEYTYPE = 56
  SCRIPT_ERR_CLEANSTACK = 56
  SCRIPT_ERR_MINIMALIF = 57
  SCRIPT_ERR_SIG_NULLFAIL = 58

  # softfork safeness
  SCRIPT_ERR_DISCOURAGE_UPGRADABLE_NOPS = 60
  SCRIPT_ERR_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM = 61

  # segregated witness
  SCRIPT_ERR_WITNESS_PROGRAM_WRONG_LENGTH = 70
  SCRIPT_ERR_WITNESS_PROGRAM_WITNESS_EMPTY = 71
  SCRIPT_ERR_WITNESS_PROGRAM_MISMATCH = 72
  SCRIPT_ERR_WITNESS_MALLEATED = 73
  SCRIPT_ERR_WITNESS_MALLEATED_P2SH = 74
  SCRIPT_ERR_WITNESS_UNEXPECTED = 75
  SCRIPT_ERR_WITNESS_PUBKEYTYPE = 76

  SCRIPT_ERR_ERROR_COUNT = 80

  ERRCODES_MAP = Hash[*constants.grep(/^SCRIPT_ERR_/).map { |c| [const_get(c), c.to_s] }.flatten]
  NAME_MAP = Hash[*constants.grep(/^SCRIPT_ERR_/).map { |c| [c.to_s, const_get(c)] }.flatten]

end