Sampling rate functionality added

[eliasyishak]

This addresses part of the umbrella issue:

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

This feature adds a utility function that can take two different strings and return a decimal value that we can compare against the sampling rate found in the remotely hosted metadata survey file (sample below)

[
    {
        "uniqueId": "test_channel",
        "url": "https://google.qualtrics.com/jfe/form/SV_5gsB2EuG5Et5Yy2",
        "startDate": "2023-06-01T09:00:00-07:00",
        "endDate": "2023-06-30T09:00:00-07:00",
	"description": "Help improve Flutter's release builds with this 3-question survey!",
	"dismissForDays": "10",
	"moreInfoURL": "https://docs.flutter.dev/reference/crash-reporting",
	"samplingRate": "0.1",    <---- the newly generated decimal value will be compared against value
	"conditions": [
	    {
	        "field": "logFileStats.recordCount",
	        "operator": ">=",
	        "value": 1000
            }
	]
    }
]

Sample usage of the new utility function

/// Will use two strings to produce a double for applying a sampling
/// rate for [Survey] to be returned to the user
double sampleRate(String string1, String string2) {
  final int1 = string1.codeUnits.reduce((a, b) => a + b);
  final int2 = string2.codeUnits.reduce((a, b) => a + b);

  return ((int1 * int2) % 100) / 100;
}

// Very simplified example to show usage
void main() {
  final sampleRate = 0.30;

  final producedValue = sampleRate('string1', 'string2');
  // Suppose the above output was 0.25

  if (sampleRate >= producedValue) passSurveyToUser();  // sudo code
}

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[eliasyishak]

@bwilkerson any thoughts on how I implemented the algorithm to produce a decimal value to compare against a given survey's sampling rate?

[bwilkerson]

Sorry for the slow response.

I'm not sure that I have the context to understand what you're trying to accomplish (beyond the obvious intent of deciding when to display a survey). In particular, I don't understand what the 'sample rate' is suppose to represent.

[eliasyishak]

@bwilkerson this feature is part of the larger issue #81 which is to enable unified analytics to provide the user surveys based on the data found in the log file (which contains all the events sent from a client). This PR is for surveys that use a sampling rate for delivering surveys since we may not want to send it all users.

Examples of a survey for this is if we wanted to ask 15% of users about which flutter channel (master, stable, beta) they should experiment with based on their historical events in the log file. Does that help?

[bwilkerson]

Not sure how this produces the linear distribution we want, but it appears to do so, so lgtm.