As an alternative to building it yourself you can rely on services that do this for you. I've been using the microsoft bot framework together with the luis.ai

As an alternative to building it yourself you can rely on services that do this for you. I've been using the microsoft bot framework together with the luis.ai (azure) service for natural language parsing. Works really well in my experience. It supports bimodal operation where first a regex is attempted and then as a fallback the sentence is passed to the NLP service to parse into action/entities. I can really recommend the microsoft bot framework even without the natural language parsing. It plugs into a range of chat platforms, including sms and email, and you're free to build your bot with node or .net. I went with node and have been pretty happy with it so far.