Stack chart functions in a more physical way

Summary:
Ref T13279. See that task for some discussion.

The accumulations of some of the datasets may be negative (e.g., if more tasks are moved out of a project than into it) which can lead to negative area in the stacked chart.

Introduce `min(...)` and `max(...)` to separate a function into points above or below some line, then mangle the areas to pick the negative and positive regions apart so they at least have a plausible physical interpretation and none of the areas are negative.

This is presumably not a final version, I'm just trying to produce a chart that isn't a sequence of overlapping regions with negative areas that is "technically" correct but not really possible to interpret.

Test Plan: {F6439195}

Reviewers: amckinley

Reviewed By: amckinley

Subscribers: yelirekim

Maniphest Tasks: T13279

Differential Revision: https://secure.phabricator.com/D20506

src/__phutil_library_map__.php

@@ -3622,6 +3622,7 @@ phutil_register_library_map(array(
     'PhabricatorMarkupInterface' => 'infrastructure/markup/PhabricatorMarkupInterface.php',
     'PhabricatorMarkupOneOff' => 'infrastructure/markup/PhabricatorMarkupOneOff.php',
     'PhabricatorMarkupPreviewController' => 'infrastructure/markup/PhabricatorMarkupPreviewController.php',
+    'PhabricatorMaxChartFunction' => 'applications/fact/chart/PhabricatorMaxChartFunction.php',
     'PhabricatorMemeEngine' => 'applications/macro/engine/PhabricatorMemeEngine.php',
     'PhabricatorMemeRemarkupRule' => 'applications/macro/markup/PhabricatorMemeRemarkupRule.php',
     'PhabricatorMentionRemarkupRule' => 'applications/people/markup/PhabricatorMentionRemarkupRule.php',
@@ -3676,6 +3677,7 @@ phutil_register_library_map(array(
     'PhabricatorMetronome' => 'infrastructure/util/PhabricatorMetronome.php',
     'PhabricatorMetronomeTestCase' => 'infrastructure/util/__tests__/PhabricatorMetronomeTestCase.php',
     'PhabricatorMetronomicTriggerClock' => 'infrastructure/daemon/workers/clock/PhabricatorMetronomicTriggerClock.php',
+    'PhabricatorMinChartFunction' => 'applications/fact/chart/PhabricatorMinChartFunction.php',
     'PhabricatorModularTransaction' => 'applications/transactions/storage/PhabricatorModularTransaction.php',
     'PhabricatorModularTransactionType' => 'applications/transactions/storage/PhabricatorModularTransactionType.php',
     'PhabricatorMonogramDatasourceEngineExtension' => 'applications/typeahead/engineextension/PhabricatorMonogramDatasourceEngineExtension.php',
@@ -9748,6 +9750,7 @@ phutil_register_library_map(array(
       'PhabricatorMarkupInterface',
     ),
     'PhabricatorMarkupPreviewController' => 'PhabricatorController',
+    'PhabricatorMaxChartFunction' => 'PhabricatorChartFunction',
     'PhabricatorMemeEngine' => 'Phobject',
     'PhabricatorMemeRemarkupRule' => 'PhutilRemarkupRule',
     'PhabricatorMentionRemarkupRule' => 'PhutilRemarkupRule',
@@ -9814,6 +9817,7 @@ phutil_register_library_map(array(
     'PhabricatorMetronome' => 'Phobject',
     'PhabricatorMetronomeTestCase' => 'PhabricatorTestCase',
     'PhabricatorMetronomicTriggerClock' => 'PhabricatorTriggerClock',
+    'PhabricatorMinChartFunction' => 'PhabricatorChartFunction',
     'PhabricatorModularTransaction' => 'PhabricatorApplicationTransaction',
     'PhabricatorModularTransactionType' => 'Phobject',
     'PhabricatorMonogramDatasourceEngineExtension' => 'PhabricatorDatasourceEngineExtension',

src/applications/fact/chart/PhabricatorChartStackedAreaDataset.php

@@ -9,8 +9,10 @@ final class PhabricatorChartStackedAreaDataset
     PhabricatorChartDataQuery $data_query) {
     $functions = $this->getFunctions();
 
+    $reversed_functions = array_reverse($functions, true);
+
     $function_points = array();
-    foreach ($functions as $function_idx => $function) {
+    foreach ($reversed_functions as $function_idx => $function) {
       $function_points[$function_idx] = array();
 
       $datapoints = $function->newDatapoints($data_query);
@@ -36,7 +38,7 @@ final class PhabricatorChartStackedAreaDataset
     }
     ksort($must_define);
 
-    foreach ($functions as $function_idx => $function) {
+    foreach ($reversed_functions as $function_idx => $function) {
       $missing = array();
       foreach ($must_define as $x) {
         if (!isset($function_points[$function_idx][$x])) {
@@ -136,6 +138,8 @@ final class PhabricatorChartStackedAreaDataset
       $series[] = $bounds;
     }
 
+    $series = array_reverse($series);
+
     $events = array();
     foreach ($raw_points as $function_idx => $points) {
       $event_list = array();

src/applications/fact/chart/PhabricatorMaxChartFunction.php

@@ -0,0 +1,40 @@
+<?php
+
+final class PhabricatorMaxChartFunction
+  extends PhabricatorChartFunction {
+
+  const FUNCTIONKEY = 'max';
+
+  protected function newArguments() {
+    return array(
+      $this->newArgument()
+        ->setName('x')
+        ->setType('function'),
+      $this->newArgument()
+        ->setName('max')
+        ->setType('number'),
+    );
+  }
+
+  public function getDomain() {
+    return $this->getArgument('x')->getDomain();
+  }
+
+  public function newInputValues(PhabricatorChartDataQuery $query) {
+    return $this->getArgument('x')->newInputValues($query);
+  }
+
+  public function evaluateFunction(array $xv) {
+    $yv = $this->getArgument('x')->evaluateFunction($xv);
+    $max = $this->getArgument('max');
+
+    foreach ($yv as $k => $y) {
+      if ($y > $max) {
+        $yv[$k] = null;
+      }
+    }
+
+    return $yv;
+  }
+
+}

src/applications/fact/chart/PhabricatorMinChartFunction.php

@@ -0,0 +1,40 @@
+<?php
+
+final class PhabricatorMinChartFunction
+  extends PhabricatorChartFunction {
+
+  const FUNCTIONKEY = 'min';
+
+  protected function newArguments() {
+    return array(
+      $this->newArgument()
+        ->setName('x')
+        ->setType('function'),
+      $this->newArgument()
+        ->setName('min')
+        ->setType('number'),
+    );
+  }
+
+  public function getDomain() {
+    return $this->getArgument('x')->getDomain();
+  }
+
+  public function newInputValues(PhabricatorChartDataQuery $query) {
+    return $this->getArgument('x')->newInputValues($query);
+  }
+
+  public function evaluateFunction(array $xv) {
+    $yv = $this->getArgument('x')->evaluateFunction($xv);
+    $min = $this->getArgument('min');
+
+    foreach ($yv as $k => $y) {
+      if ($y < $min) {
+        $yv[$k] = null;
+      }
+    }
+
+    return $yv;
+  }
+
+}

src/applications/fact/daemon/PhabricatorFactDaemon.php

@@ -15,7 +15,7 @@ final class PhabricatorFactDaemon extends PhabricatorDaemon {
       }
 
       $this->log(pht('Zzz...'));
-      $this->sleep(60 * 5);
+      $this->sleep(15);
     }
   }
 

src/applications/project/chart/PhabricatorProjectBurndownChartEngine.php

@@ -32,37 +32,62 @@ final class PhabricatorProjectBurndownChartEngine
     if ($project_phids) {
       foreach ($project_phids as $project_phid) {
         $function = $this->newFunction(
-          'accumulate',
-          array('fact', 'tasks.open-count.create.project', $project_phid));
+          'min',
+          array(
+            'accumulate',
+            array('fact', 'tasks.open-count.assign.project', $project_phid),
+          ),
+          0);
 
         $function->getFunctionLabel()
-          ->setName(pht('Tasks Created'))
-          ->setColor('rgba(0, 0, 200, 1)')
-          ->setFillColor('rgba(0, 0, 200, 0.15)');
+          ->setName(pht('Tasks Moved Into Project'))
+          ->setColor('rgba(0, 200, 200, 1)')
+          ->setFillColor('rgba(0, 200, 200, 0.15)');
 
         $functions[] = $function;
 
-
         $function = $this->newFunction(
-          'accumulate',
-          array('fact', 'tasks.open-count.status.project', $project_phid));
+          'min',
+          array(
+            'accumulate',
+            array('fact', 'tasks.open-count.status.project', $project_phid),
+          ),
+          0);
 
         $function->getFunctionLabel()
-          ->setName(pht('Tasks Closed / Reopened'))
+          ->setName(pht('Tasks Reopened'))
           ->setColor('rgba(200, 0, 200, 1)')
           ->setFillColor('rgba(200, 0, 200, 0.15)');
 
         $functions[] = $function;
 
-
         $function = $this->newFunction(
-          'accumulate',
-          array('fact', 'tasks.open-count.assign.project', $project_phid));
+          'sum',
+          array(
+            'accumulate',
+            array('fact', 'tasks.open-count.create.project', $project_phid),
+          ),
+          array(
+            'max',
+            array(
+              'accumulate',
+              array('fact', 'tasks.open-count.status.project', $project_phid),
+            ),
+            0,
+          ),
+          array(
+            'max',
+            array(
+              'accumulate',
+              array('fact', 'tasks.open-count.assign.project', $project_phid),
+            ),
+            0,
+          ));
 
         $function->getFunctionLabel()
-          ->setName(pht('Tasks Rescoped'))
-          ->setColor('rgba(0, 200, 200, 1)')
-          ->setFillColor('rgba(0, 200, 200, 0.15)');
+          ->setName(pht('Tasks Created'))
+          ->setColor('rgba(0, 0, 200, 1)')
+          ->setFillColor('rgba(0, 0, 200, 0.15)');
 
         $functions[] = $function;
       }