Thanks for submitting this. I'll take a closer look at it this weekend.

I've been thinking for a while that the time series functionality would be better suited as part of the existing gateways instead of in separate gateways. For example, instead of ActivityTimeSeriesGateway or the existing TimeGateway, ActivityGateway itself should implement the methods needed for the series data.

Something like this:

$activities = $factory->getActivityGateway();
$activities->getTimeSeries('distance', 'today', '7d');

public function getTimeSeries($type, $base_date = null, $end_date = null)
{
    $url = '/activities/log/' . $type;
    return $this->makeTimeSeriesApiRequest($url, $base_date, $end_date);
}

What do you think? EndpointGateway would end up with a bit more functionality than every gateway needs, but the benefit would be fewer gateways.

I'd also get rid of the magic methods, favoring explicitly defined methods like this instead:

$activities->getMinutesVeryActive();

public function getMinutesVeryActive($base_date = null, $end_date = null)
{
    return $this->getTimeSeries('minutesVeryActive', $base_date, $end_date);
}
public function getTrackerCalories($base_date = null, $end_date = null)
{
    return $this->getTimeSeries('tracker/calories', $base_date, $end_date);
}