I would love to hear some advice from someone who has programmed for Alexa and any other virtual assistant. I'm the only one in my team with experience with Alexa and just recently we have sold our first Alexa product. The client wants to know how expensive it would be to make the app also work for Siri/Google Home/Cortana but I have no idea about other virtual assistants and we don't really have time to dive deep into every assistants documentation.
That's where you could help me. Do you have any experience in programming for Alexa and any other mentioned virtual assistant? Maybe you have even tried them all? Which ones are the most similar (from the development point of view of course)? Do other assistance have the same intent/utterance/slots-logic as Alexa? The most interesting thing I want to find out is how much Alexa code we could actually reuse and how much time I would need to spend if I wanted to learn another frameworks granted that I already know Alexa API. Can you share your experiences on this topic?
Thank you very much for any advises.
PS forgot to mention, for Alexa we have made our own webservice endpoint and used Java