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phorge/src/applications/fact/chart/PhabricatorAccumulateChartFunction.php
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PhabricatorAccumulateChartFunction.php
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<?php
final class PhabricatorAccumulateChartFunction
extends PhabricatorHigherOrderChartFunction {
const FUNCTIONKEY = 'accumulate';
protected function newArguments() {
return array(
$this->newArgument()
->setName('x')
->setType('function'),
);
}
public function evaluateFunction(array $xv) {
// First, we're going to accumulate the underlying function. Then
// we'll map the inputs through the accumulation.
$datasource = $this->getArgument('x');
// Use an unconstrained query to pull all the data from the underlying
// source. We need to accumulate data since the beginning of time to
// figure out the right Y-intercept -- otherwise, we'll always start at
// "0" wherever our domain begins.
$empty_query = new PhabricatorChartDataQuery();
$datasource_xv = $datasource->newInputValues($empty_query);
if (!$datasource_xv) {
// When the datasource has no datapoints, we can't evaluate the function
// anywhere.
return array_fill(0, count($xv), null);
}
$yv = $datasource->evaluateFunction($datasource_xv);
$map = array_combine($datasource_xv, $yv);
$accumulator = 0;
foreach ($map as $x => $y) {
$accumulator += $y;
$map[$x] = $accumulator;
}
// The value of "accumulate(x)" is the largest datapoint in the map which
// is no larger than "x".
$map_x = array_keys($map);
$idx = -1;
$max = count($map_x) - 1;
$yv = array();
$value = 0;
foreach ($xv as $x) {
// While the next "x" we need to evaluate the function at lies to the
// right of the next datapoint, move the current datapoint forward until
// we're at the rightmost datapoint which is not larger than "x".
while ($idx < $max) {
if ($map_x[$idx + 1] > $x) {
break;
}
$idx++;
$value = $map[$map_x[$idx]];
}
$yv[] = $value;
}
return $yv;
}
}

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