block12.ruby

class Struct
  OPCODES = {
    'OP_DUP' =>  0x76,
    'OP_HASH160' =>  0xA9,
    'OP_EQUAL' =>  0x87,
    'OP_EQUALVERIFY' =>  0x88,
    'OP_CHECKSIG' =>  0xAC
  }.freeze
  def opcode(token)
    raise "opcode #{token} not found" unless OPCODES.include?(token)
    OPCODES[token].to_s 16
  end
  def data(token)
    bin_size = hex_size token
    byte_to_hex(bin_size) + token
  end
  def hex_size(hex)
    [hex].pack('H*').size
  end
  def to_hex(binary_bytes)
    binary_bytes.unpack('H*').first
  end
  def hash_to_hex(value)
    to_hex [value].pack('H*').reverse
  end
  def int_to_hex(value)
    to_hex [value].pack('V')
  end
  def byte_to_hex(value)
    to_hex [value].pack('C')
  end
  def long_to_hex(value)
    to_hex [value].pack('Q<')
  end
  def script_to_hex(script_string)
    script_string.split.map { |token| token.start_with?('OP') ? opcode(token) : data(token) }.join
  end
  def sha256(hex)
    Digest::SHA256.hexdigest([hex].pack('H*'))
  end
end