REST Thermostat - Siri to Alexa

Hi I have created a REST API server on a raspberry pi, which interfaces with my home thermostat. I am able to request current and target temperature and also set temperature. Using HomeBridge I am able to control this from Siri.

I have recently purchased an echo dot and would be interested in getting the same functionality as I do with Siri with it. Ideally I would like to keep all the traffic in my LAN, so do not really want to use could service (if possible) to achieve this.

I am lost where to start, I’m sure home assistant will play a part in it! If any one could point me in the right direct on what technologies would help me achieve this, that would be a huge help.

You will have to use a cloud service to make this work.
It looks daunting, but once you get started, it’s pretty straightforward.

In a nutshell:
create a developer account with amazon.
Set up an amazon skill that points to your home assistant instance that describes what Alexa will listen for.
Create a yaml file in home assistant that tells HA what to do when the query comes from Alexa.