class Utils::SshTunnelSpecification

def interpret_spec(spec_string)
  @local_addr, @local_port, @remote_addr, @remote_port =
    case spec_string
    when /\A(\d+)\z/
      [ 'localhost', $1.to_i, 'localhost', $1.to_i ]
    when /\A(\[[^\]]+\]|[^:]+):(\d+)\z/
      [ 'localhost', $2.to_i, $1, $2.to_i ]
    when /\A(\d+):(\[[^\]]+\]|[^:]+):(\d+)\z/
      [ 'localhost', $1.to_i, $2, $3.to_i ]
    when /\A(\[[^\]]+\]|[^:]+):(\[[^\]]+\]|[^:]+):(\d+)\z/
      [ $1, $3.to_i, $2, $3.to_i ]
    when /\A(\[[^\]]+\]|[^:]+):(\d+):(\[[^\]]+\]|[^:]+):(\d+)\z/
      [ $1, $2.to_i, $3, $4.to_i ]
    end
end