Add State machine to sensors

[yatharthranjan]

Adding a state machine to sensors will help in keeping track of any changes in sensors.
This will also help in reporting these to a status/<sensor-name> in the pub sub system similar to #5 .

State machine libraries for py-

• https://github.com/pytransitions/transitions
• https://pypi.org/project/python-statemachine/

Custom Implementation -

• https://python-3-patterns-idioms-test.readthedocs.io/en/latest/StateMachine.html
• https://dev.to/karn/building-a-simple-state-machine-in-python
• https://www.python-course.eu/finite_state_machine.php

EDIT- A really simple way would be using http://liftoff.github.io/onoff/

EDIT 2 - Nice tutorial using the python-statemachine library -- https://www.askpython.com/python-modules/state-machines-python

Tasks

Beta Give feedback

1. Read the code and understand what needs to be changed and come up with an plan for implementation. Only the python module is involved in this currently.
2. Add new abstract functions in the sensor class to expose the states
3. Add states that a sensor can use.
4. Push sensor states when a state change happens (can also use pull using functions above)
5. Publish to the pub/sub broker using Publisher, similar to the way other data is published.