componentClass.py

from mqttClient import MqttClient
from abc import ABCMeta, abstractmethod
import math
import json


class Component:

    __metaclass__ = ABCMeta

    def __init__(self, root):
        self.mqttHandler = MqttClient()
        self.mqttHandler.setup_client()

        self.name = "component"
        self.sampInterval = 1
        self.loopCycles = 1
        self.loopRate = 1
        self.rootTopic = root
        self.config_topic = self.rootTopic + "/components/" + self.name
        self.my_topic = self.rootTopic + "/" + self.name

    # Component specific setup
    # Needs to contain all the code to be executed once
    # before the loop starts
    # Needs to be implemented in order for the main to run correctly
    @abstractmethod
    def setup(self,samplingInterval):
        pass

    # Component specific data handling and MQTT publishing
    # It should receive the main timestamp to stamp the package
    # in order to ensure coherence between components.
    #
    # Needs to be implemented in order for the main to run correctly

    def handleData(self, timestamp):
        pass

    # Run code for components which are supposed to loop in parallel
    # and do not require data acquisition, such as the camera

    def run(self):
        pass

    # Component specific setup JSON payload generation
    # (Good practice to implement it, so it's well organized)

    def gen_payload_message(self, data, timestamp):
        pass

    # Calculate the number of loop cycles before sampling the
    # sensor based on the rate the loop is run and publish
    # the new configuration parameters of the component

    def calculate_loop_cycles(self, loop_rate, timestamp):
        self.loopRate = loop_rate
        self.loopCycles = int(math.ceil(self.sampInterval / self.loopRate))
        self.publishConfiguration(int(timestamp))

    # Publish component configuration values to the
    # root/component/config topic

    def publishConfiguration(self, timestamp):
        self.mqttHandler.publish(self.config_topic, json.dumps(
            self.gen_curr_configuration_message(timestamp)), retain=True)

    # Generate current configuration message

    def gen_curr_configuration_message(self, timestamp):
        return {
            'name': self.name,
            'topic': self.my_topic,
            'pollRate': float(self.sampInterval),
            'loopRate': self.loopRate,
            'cycles': self.loopCycles,
            'timestamp': timestamp
        }

    # Set component topic
    def set_topic(self, component_name):
        self.name = component_name
        self.config_topic = self.rootTopic + "/components/" + self.name
        self.my_topic = self.rootTopic + "/" + self.name