import yaml


class MQTT_ROS_Config:
    """
    MQTT_ROS_Config configuration class
    """
    # class variables
    sectionName='MQTT_ROS'
    options={
            'msg_format': (str,True),
            'MQTTClientNamePub': (str,True),
            'MQTTClientNameSub': (str,True),
            'host': (str,True),
            'port': (int,True),
            'keepalive': (int,True),
            'willTopic':(str,True),
            'lwt':(str, True),
            'willRetain':(bool,False),
            'willTopicQOS':(int,True),
            'Flight_Information_topicToMqtt': (str,False),
            'Fly_Formation_topicToMqtt': (str,False),
            'Fly_Formation_topicToMqtt_QOS':(int,False),
            'ROSClientNamePub': (str,False),
            'ROSClientNameSub': (str,False),
            'ROStopicName_Flight_Information': (str,False),
            'ROStopicName_Fly_Formation': (str,False)}
     
    #constructor
    def __init__(self, inFileName):
        #read YAML config and get EV3 section
        infile=open(inFileName,'r')
        ymlcfg=yaml.safe_load(infile)
        infile.close()
        eccfg=ymlcfg.get(self.sectionName,None)
        if eccfg is None: raise Exception('Missing {} section in cfg file'.format(self.sectionName))
         
        #iterate over options
        for opt in self.options:
            if opt in eccfg:
                optval=eccfg[opt]
 
                #verify parameter type
                if type(optval) != self.options[opt][0]:
                    raise Exception('Parameter "{}" has wrong type'.format(opt))
                 
                #create attributes on the fly
                setattr(self,opt,optval)
            else:
                if self.options[opt][1]:
                    raise Exception('Missing mandatory parameter "{}"'.format(opt))
                else:
                    setattr(self,opt,None)
     
    #string representation for class data    
    def __str__(self):
        return str(yaml.dump(self.__dict__,default_flow_style=False))

   

if __name__ == '__main__':
    cfg=MQTT_ROS_Config("mqttConfig.yml")
    print(cfg)