Move custom app code

Move custom app code (the `src` and `tests` directories) into `app`.

app/src/TwigExtension/Talk/TalksExtension.php

@@ -0,0 +1,113 @@
+<?php
+
+namespace App\TwigExtension\Talk;
+
+use Sculpin\Contrib\ProxySourceCollection\ProxySourceCollection;
+use Tightenco\Collect\Support\Collection;
+use Twig\Extension\AbstractExtension;
+use Twig\TwigFilter;
+use Twig\TwigFunction;
+
+class TalksExtension extends AbstractExtension
+{
+    /**
+     * @var int The current date.
+     */
+    private $today;
+
+    public function __construct()
+    {
+        $this->today = (new \DateTime())
+            ->modify('today')
+            ->setTimezone(new \DateTimeZone('Europe/London'))
+            ->getTimestamp();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getFunctions()
+    {
+        return [
+            new TwigFunction('getTalks', [$this, 'getTalks']),
+        ];
+    }
+
+    public function getFilters()
+    {
+        return [
+            new TwigFilter('pastEvents', [$this, 'filterPastEvents']),
+            new TwigFilter('pastTalks', [$this, 'filterPastTalks']),
+            new TwigFilter('upcomingEvents', [$this, 'filterUpcomingEvents']),
+            new TwigFilter('upcomingTalks', [$this, 'filterUpcomingTalks']),
+        ];
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getName()
+    {
+        return 'app.talks';
+    }
+
+    /**
+     * Get all upcoming and previous talks.
+     *
+     * @param ProxySourceCollection|array $talks All talk nodes.
+     *
+     * @return Collection A sorted collection of talks.
+     */
+    public function getTalks($talks): Collection
+    {
+        return (new Collection($talks))->sortBy(function ($talk) {
+            return $this->getLastDate($talk);
+        });
+    }
+
+    public function filterUpcomingTalks(Collection $talks): Collection
+    {
+        return $talks->filter(function ($talk): bool {
+            return $this->getLastDate($talk) >= $this->today;
+        })->values();
+    }
+
+    public function filterPastTalks(Collection $talks): Collection
+    {
+        return $talks->filter(function ($talk): bool {
+            return $this->getLastDate($talk) < $this->today;
+        })->values();
+    }
+
+    private function getLastDate($talk): string
+    {
+        return $this->eventsFromTalks(new Collection([$talk]))
+            ->pluck('date')->max();
+    }
+
+    public function filterUpcomingEvents($talks): Collection
+    {
+        return $this->eventsFromTalks($talks)->filter(function ($event): bool {
+            return $event['date'] >= $this->today;
+        })->sortBy('date');
+    }
+
+    public function filterPastEvents($talks): Collection
+    {
+        return $this->eventsFromTalks($talks)->filter(function ($event): bool {
+            return $event['date'] < $this->today;
+        })->sortBy('date');
+    }
+
+    private function eventsFromTalks($talks): Collection
+    {
+        return (new Collection($talks))->flatMap(function ($talk): array {
+            return $talk['events'];
+        });
+    }
+
+    public function getAllEvents($talks): Collection
+    {
+        return $this->eventsFromTalks($talks);
+    }
+}