def get_parameter_default(parameter, ctx):
    """
    Get the value for a specific parameter from the computer_builder or the default value of that option

    :param parameter: parameter name
    :param ctx: click context of the command
    :return: parameter default value, or None
    """
    default = None
    for param in ctx.command.get_params(ctx):
        if param.name == parameter:
            default = param.default
    try:
        value = getattr(ctx.computer_builder, parameter)
        if value == '' or value is None:
            value = default
    except KeyError:
        value = default
    return value
