feat: Allow setting acknowledgment fields dynamically based on inbound message

[jtarvainen]

Feature Request

Describe the Feature Request

Version 3.0.0 added support for overriding the acknowledgment message MSH content with the mshOverrides prop (#103). In updating to the new version, I realized that the functionality doesn't allow us to retrieve acknowledgment message field values from the inbound message because the mshOverrides content is specified upon server creation, before any messages are received.

Describe Preferred Solution

I propose that we extend mshOverrides to accept, for each specified acknowledgment field, either field value as a string (as it does now) or a function that takes the inbound message as an optional argument and returns the field value.

Related Code

We would define mshOverrides as follows:

import type { Message } from 'node-hl7-client';

export interface ListenerOptions {
  mshOverrides?: Record<string, string | (message?: Message) => string>;
  // ...
}

And use it like this:

import type { Message } from 'node-hl7-client';

new Server().createInbound({
  mshOverrides: {
    '7': () => format(new Date(), 'yyyyMMddHHmmssxx') // set MSH.7 to formatted timestamp representing time of response creation
    '9.3': 'ACK' // set hardcoded MSH.9.3 field value
    '12': (message: Message) => message.get('MSH.12').toString() // copy MSH.12 value from inbound message to response
  }
});

And internally it would do this:

if (typeof this._mshOverrides === 'object') {
  Object.entries(this._mshOverrides).forEach(([path, override]) => {
    ackMessage.set(`MSH.${path}`, typeof override === 'function' ? override(message) : override);
  });
}

If the feature request is approved, would you be willing to submit a PR?

Yes!

[Bugs5382]

@jtarvainen Looks good. Go ahead and submit one!

[Bugs5382]

Make sure you update the documentation with examples.

[jtarvainen]

Great! I'll get on it after the holidays.

[Bugs5382]

@jtarvainen Enjoy the holidays. :)

[Bugs5382]

@jtarvainen Updates?

[jtarvainen]

@Bugs5382 Thanks for the reminder, I'll get right on it.

[Bugs5382]

@jtarvainen I'll review this weekend during normal coding time!