public function computeDelta()
{
// get metric from yesterday
$yesterdaysDate = date('Y-m-d', strtotime('yesterday'));
$stat = Statistic::findOne(['where' => ['metric' => $this->key(), 'day' => $yesterdaysDate]]);
$previous = $stat ? $stat->val : 0;
return $this->computeValue() - $previous;
}
/**
* Saves the Nth previous period. Creates the statistic entry
* if it does not exist, otherwise overwrites the previous value.
*
* @param int $n nth previous period to save
*
* @return bool
*/
public function savePeriod($n = 1)
{
if (!$this->shouldBeCaptured() || $n < 1) {
return false;
}
// compute the period in question
$period = $this->nthPreviousPeriod($n);
// compute the value for that time period
$value = $this->computeValue($period);
// generate the start date for the period
$d = date('Y-m-d', $period['start']);
// save the value
$stat = new Statistic([$this->key(), $d]);
if (!$stat->exists()) {
$stat = new Statistic();
return $stat->create(['metric' => $this->key(), 'day' => $d, 'val' => $value]);
} else {
return $stat->set('val', $value);
}
}
