Survey handler functionality to fetch available surveys

[eliasyishak]

Relevant issue:

• ☂️ Create a survey handler class to enable package to share surveys #81

This PR will add functionality to enable tools using this package (flutter-tools, analyzer, etc.) to share available surveys with our users. It will enable the Analytics class to fetch the available surveys from https://docs.flutter.dev/f/contextual-survey-metadata.json and parse the conditions (if applicable) using the locally persisted log file. If the conditions are met, then this package will return the relevant information (url, description, etc.) to the tool so that it can prompt the user with a survey link.

Example of what the survey metadata file will look like:

[
    {
        "uniqueId": "test_channel",
        "url": "xxxxx",
        "startDate": "2000-03-01T09:00:00-07:00",
        "endDate": "2000-06-30T09:00:00-07:00",
	"description": "Contextual message explaining the survey",
	"dismissForDays": "10",
	"moreInfoURL": "xxxxxxx",
	"samplingRate": "0.1",
	"conditions": [
	    {
	        "field": "logFileStats.recordCount",
	        "operator": ">=",
	        "value": 1000
            }
	]
    }
]

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[christopherfujino]

what happens if we fall through and don't hit any of the cases (that is, condition.operatorString is invalid)? I'm guessing we should have a default that throws?

[eliasyishak]

If for some reason the operator in the metadata file wasn't accounted for in this switch statement, then the survey would not be delivered to the end user, which i think is preferable over an error getting surfaced?

But like you mentioned in your other comment, we will look into creating something that properly vets each time we upload metadata files so that package:unified_analytics is able to parse them

[christopherfujino]

I think you should consider where to document these keys (I'm thinking specifically if some noogler in a few months writes a new survey condition where startDateTime < Jan 1 2023, they would need to know to put the condition in millisecondsSinceEpoch.

Could we add a test script to the website CI that validates the contextual-survey-metadata.json file is parseable by package:unified_analytics before publishing the website?

[eliasyishak]

Yeah that's a good point, I have added an additional item in the tracker issue to add automated checks for the metadata file in the flutter/website repo

[christopherfujino]

LGTM