MAPG-235 new challenge can be created and is prepared

src/Repository/MapRepository.php

@@ -1,5 +1,7 @@
 <?php namespace MapGuesser\Repository;
 
+use MapGuesser\Database\Query\Select;
+use MapGuesser\PersistentData\Model\Challenge;
 use MapGuesser\PersistentData\Model\Map;
 use MapGuesser\PersistentData\PersistentDataManager;
 
@@ -16,4 +18,15 @@ class MapRepository
     {
         return $this->pdm->selectFromDbById($mapId, Map::class);
     }
+
+    public function getByChallenge(Challenge $challenge): ?Map
+    {
+        $select = new Select(\Container::$dbConnection);
+        $select->innerJoin('places', ['maps', 'id'], '=', ['places', 'map_id']);
+        $select->innerJoin('place_in_challenge', ['places', 'id'], '=', ['place_in_challenge', 'place_id']);
+        $select->where('challenge_id', '=', $challenge->getId());
+        $select->limit(1);
+
+        return $this->pdm->selectFromDb($select, Map::class);
+    }
 }