Start of factor graph port. Things don't work yet, but a lot of syntax updates towards PHP

PHPSkills/TrueSkill/Layers/PlayerPerformancesToTeamPerformancesLayer.php

@@ -0,0 +1,71 @@
+<?php
+
+namespace Moserware\Skills\TrueSkill\Layers;
+
+class PlayerPerformancesToTeamPerformancesLayer extends TrueSkillFactorGraphLayer
+{
+    public function __construct(TrueSkillFactorGraph $parentGraph)
+    {
+        parent::__construct($parentGraph);
+    }
+
+    public function buildLayer()
+    {
+        foreach ($this->getInputVariablesGroups() as $currentTeam)
+        {
+            $teamPerformance = $this->createOutputVariable($currentTeam);
+            $this->addLayerFactor($this->createPlayerToTeamSumFactor($currentTeam, $teamPerformance));
+
+            // REVIEW: Does it make sense to have groups of one?
+            $this->getOutputVariablesGroups() = $teamPerformance;
+        }
+    }
+
+    public function createPriorSchedule()
+    {
+        return $this->scheduleSequence(
+                array_map(
+                        function($weightedSumFactor)
+                        {
+                            return new ScheduleStep("Perf to Team Perf Step", $weightedSumFactor, 0);
+                        },
+                        $this->getLocalFactors()),
+                "all player perf to team perf schedule");
+    }
+
+    protected function createPlayerToTeamSumFactor($teamMembers, $sumVariable)
+    {
+        return new GaussianWeightedSumFactor(
+                $sumVariable,
+                $teamMembers,
+                array_map(
+                        function($v)
+                        {
+                            return PartialPlay::getPartialPlayPercentage($v->getKey());
+                        },
+                        $teamMembers));
+                                                 
+    }
+
+    public function createPosteriorSchedule()
+    {
+        // BLOG
+        return $this->scheduleSequence(
+                from currentFactor in LocalFactors
+                                from currentIteration in
+                                    Enumerable.Range(1, currentFactor.NumberOfMessages - 1)
+                                select new ScheduleStep<GaussianDistribution>(
+                                    "team sum perf @" + currentIteration,
+                                    currentFactor,
+                                    currentIteration),
+                                "all of the team's sum iterations");
+    }
+
+    private function createOutputVariable($team)
+    {
+        $teamMemberNames = String.Join(", ", team.Select(teamMember => teamMember.Key.ToString()).ToArray());
+        return ParentFactorGraph.VariableFactory.CreateBasicVariable("Team[{0}]'s performance", teamMemberNames);
+    }
+}
+
+?>