src/applications/fact/chart/PhabricatorComposeChartFunction.php

   1 <?php
   2
   3 final class PhabricatorComposeChartFunction
   4   extends PhabricatorHigherOrderChartFunction {
   5
   6   const FUNCTIONKEY = 'compose';
   7
   8   protected function newArguments() {
   9     return array(
  10       $this->newArgument()
  11         ->setName('f')
  12         ->setType('function')
  13         ->setRepeatable(true),
  14     );
  15   }
  16
  17   public function evaluateFunction(array $xv) {
  18     $original_positions = array_keys($xv);
  19     $remaining_positions = $original_positions;
  20     foreach ($this->getFunctionArguments() as $function) {
  21       $xv = $function->evaluateFunction($xv);
  22
  23       // If a function evaluates to "null" at some positions, we want to return
  24       // "null" at those positions and stop evaluating the function.
  25
  26       // We also want to pass "evaluateFunction()" a natural list containing
  27       // only values it should evaluate: keys should not be important and we
  28       // should not pass "null". This simplifies implementation of functions.
  29
  30       // To do this, first create a map from original input positions to
  31       // function return values.
  32       $xv = array_combine($remaining_positions, $xv);
  33
  34       // If a function evaluated to "null" at any position where we evaluated
  35       // it, the result will be "null". We remove the position from the
  36       // vector so we stop evaluating it.
  37       foreach ($xv as $x => $y) {
  38         if ($y !== null) {
  39           continue;
  40         }
  41
  42         unset($xv[$x]);
  43       }
  44
  45       // Store the remaining original input positions for the next round, then
  46       // throw away the array keys so we're passing the next function a natural
  47       // list with only non-"null" values.
  48       $remaining_positions = array_keys($xv);
  49       $xv = array_values($xv);
  50
  51       // If we have no more inputs to evaluate, we can bail out early rather
  52       // than passing empty vectors to functions for evaluation.
  53       if (!$xv) {
  54         break;
  55       }
  56     }
  57
  58
  59     $yv = array();
  60     $xv = array_combine($remaining_positions, $xv);
  61     foreach ($original_positions as $position) {
  62       if (isset($xv[$position])) {
  63         $y = $xv[$position];
  64       } else {
  65         $y = null;
  66       }
  67       $yv[$position] = $y;
  68     }
  69
  70     return $yv;
  71   }
  72
  73   public function getDataRefs(array $xv) {
  74     // TODO: This is not entirely correct. The correct implementation would
  75     // map "x -> y" at each stage of composition and pull and aggregate all
  76     // the datapoint refs. In practice, we currently never compose functions
  77     // with a data function somewhere in the middle, so just grabbing the first
  78     // result is close enough.
  79
  80     // In the future, we may: notably, "x -> shift(-1 month) -> ..." to
  81     // generate a month-over-month overlay is a sensible operation which will
  82     // source data from the middle of a function composition.
  83
  84     foreach ($this->getFunctionArguments() as $function) {
  85       return $function->getDataRefs($xv);
  86     }
  87
  88     return array();
  89   }
  90
  91 }