Improvements to createAckMessage

[codyebberson]

Hello, thank you for this wonderful library.

Here are some changes to the createAckMessage that we often have to do manually:

• Use the version ID from the input MSH.12 rather than fixed "2.3" (or maybe a config option)
• If the input includes MSH.9.2 (Message Type Trigger Event), then include it in the response
• If the input includes MSH.9.3 (Message Type Message Structure), then include "ACK" in MSH.9.3 in the response
• If the input includes MSH.18 (Character Set), then include it in the response (perhaps with some validation)
• If the input includes MSH.21 (Conformance Statement ID), then include it in the response

In my experience, these improve the likelihood of the ACK working out of the box.

If these are acceptable, then I would be happy to submit a pull request.

Thanks!

[hitgeek]

thanks for the kind words.

all great ideas... some of these I think are added in v4

https://github.com/hitgeek/simple-hl7/blob/v4.0/lib/server/tcp-server.js#L88

definitely would be open to PRs on v4 branch. you can install v4 with npm install simple-hl7@next

I am hesitant to make any potentially breaking changes to v3 branch.