@startuml
skinparam classFontSize 8
skinparam classFontName Helvetica
autonumber

box "Application" #LightGreen
    participant "Application" as application
    participant "Callback" as callback
end box

box "Libraries" #LightBlue
    participant "JSON" as json

    participant "Shadow" as shadow

    participant "MQTT" as mqtt

end box

activate application
application -> mqtt : Establish\nMQTT Connection\nwith\ncallback function


activate mqtt
mqtt -> mqtt : Initialization with the callback
mqtt -> : Connect to the broker
mqtt -> application : Return from MQTT library
deactivate mqtt

application -> shadow : Get shadow topics

activate shadow
shadow -> application : Return assembled\nshadow topics
deactivate shadow

application -> mqtt : Subscribe to the shadow topics

activate mqtt
mqtt -> : Subscribe to the\nshadow topic to the broker
mqtt -> application : Return Success
deactivate mqtt
application -> mqtt : Publish messages on\nthe shadow topic


activate mqtt
mqtt -> : Publish message on the shadow topic to the broker
mqtt <- : Incoming message
mqtt -> callback : Trigger callback function
activate callback
callback -> shadow : Parse the topic
activate shadow
shadow -> callback : Return the parsed result
deactivate shadow
callback -> json : Parse key/value from shadow topic payload
activate json
json -> callback : Return parsed key/value
deactivate json
callback -> mqtt : Return from the callback
deactivate callback
mqtt -> application : Return from MQTT library
deactivate mqtt

deactivate application

@enduml