Additional Event Firing Fix

[the-c0d3r]

I tested the code and it seem like the event streaming is fired as soon as you start the stream on a reference which already have data in the database. Therefore I modified the code to check for the last_value and only fire the event if the value is changed. I modified this to fit my needs, maybe somebody will find this useful as well. Thanks for your commit adding the SSE client.

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Original comment from this discussion

I tried your fork repo, somehow it fires off an event as soon as I set the stream() and the callback function is called immediately. But the intended listening event is triggered every time when the data is changed in the database side.

>>> ref.stream(callbackfunc)
<firebase_admin.db.Stream object at 0x10c9b7ef0>
>>> {'event': 'put', 'data': True, 'path': '/'}
>>> # The event above is fired off automatically on stream without modification on db

>>> # these 3 events below are fired off by the changes in the db. 
>>> {'event': 'put', 'data': 'true', 'path': '/'}
>>> {'event': 'put', 'data': 'false', 'path': '/'}
>>> {'event': 'put', 'data': 'true', 'path': '/'}

>>> self.db.reference("/users/dev1/successful").stream(callbackfunc)
<firebase_admin.db.Stream object at 0x10ef897f0>
>>> {'event': 'put', 'data': True, 'path': '/'}
>>> # The event above is fired off automatically on stream without modification on db

Is it possible to fix this unexpected behavior? I would like to help fix it, but I have no idea where to start looking and I have never worked with SSE before. If anyone can point me in correct direction, please do.

[the-c0d3r]

Since this feature has been merged into Firebase, I will be closing this.