Add realtime events with SSE

[relekang]

This is very much work in progress, but wanted to open a pr so that we can get this right.

• [x] Add server-sent events
• [x] Add observables to flat-file-db adapter
• [x] Decide what to do with options etc in the cli
• [x] Add documentation
• [x] Decide what to call the event of a new view

Relates to #16

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How to use this

const sse = new EventSource('/sse')
sse.onopen = function () { console.log('sse open') }
sse.onerror = function (error) { console.error('[sse error]', error) }
sse.addEventlistener('new-event', function (e) { console.log(e) })

Rendered version of updated readme

[mxstbr]

Awesome, can't wait to see this! Reminds me I still need to figure out how to get #31 to work…

[relekang]

Unfortunately I haven't had the time to put into this lately, will hopefully have more time next week.

[mxstbr]

How are we looking with this PR? Would love to land this!

[relekang]

@mxstbr I am working through the last of the issues now. Have any inputs on the event name at the moment it is new-event.

[codecov-io]

Codecov Report

Merging #41 into master will decrease coverage by 12.5%. The diff coverage is 66.66%.

@@             Coverage Diff             @@
##           master      #41       +/-   ##
===========================================
- Coverage   83.63%   71.13%   -12.51%     
===========================================
  Files           3        6        +3     
  Lines          55       97       +42     
  Branches       13       20        +7     
===========================================
+ Hits           46       69       +23     
- Misses          9       28       +19

Impacted Files	Coverage Δ
src/parseArgs.js	100% <100%> (ø)
src/index.js	7.69% <7.69%> (-78.03%)	:arrow_down:
src/handler.js	72.97% <72.97%> (ø)
src/db.js	83.33% <81.25%> (+13.33%)	:arrow_up:
src/sse.js	83.33% <83.33%> (ø)

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[relekang]

Just need to look into some tests for the sse parts now. Will try to do it tomorrow.

[mxstbr]

Hmm, in terms of names, do they need to be unique? How about micro-analytics-ping?

[relekang]

I think this is ready for review, one of the tests will fail until we release and upgrade adapter-flat-file-db. It needs subscribe from micro-analytics/adapter-flat-file-db#2

[relekang]

Hmm, in terms of names, do they need to be unique? How about micro-analytics-ping?

No, the is just what is passed to the event listener:

sse.addEventlistener('micro-analytics-ping', function (event) { console.log(event) })

The only thing I think we need to consider about the name is that it should describe what you get in the data field of the event passed to the callback of the listener. I think micro-analytics-ping works, will change to use that.

[relekang]

@mxstbr I think this is ready, it only needs a release of flat-file-adapter to make the tests pass. Could you do a release?

[mxstbr]

I did a npm owner add relekang so you should be able to publish it!

[relekang]

@mxstbr It is green now, the decrease in coverage is mostly because of the manuall creation of the server and custom cli. I guess we could ship this?

[mxstbr]

Is this ready to go?

[relekang]

Yes ✌️

[mxstbr]

Merging this tomorrow with a big PR push around the release 👌 Great work man!