Merge remote-tracking branch 'origin/ws-toilet' into ws-toilet

src/main/scala/LilaWs.scala

@@ -12,6 +12,7 @@ object LilaWs extends App:
   given Executor                      = clientSystem.executionContext
 
   lazy val mongo         = wire[Mongo]
+  lazy val settings      = wire[util.SettingStore]
   lazy val groupedWithin = wire[util.GroupedWithin]
   lazy val lightUserApi  = wire[LightUserApi]
   lazy val lilaRedis     = wire[Lila]

src/main/scala/Mongo.scala

@@ -60,6 +60,7 @@ final class Mongo(config: Config)(using Executor) extends MongoHandlers:
   def oauthColl                                     = collNamed("oauth2_access_token")
   def relayTourColl                                 = collNamed("relay_tour")
   def relayRoundColl                                = collNamed("relay")
+  def settingColl                                   = collNamed("setting")
   def studyColl                                     = studyDb.map(_.collection("study"))(parasitic)
   def evalCacheColl                                 = yoloDb.map(_.collection("eval_cache2"))(parasitic)
 

src/main/scala/util/SettingStore.scala

@@ -0,0 +1,41 @@
+package lila.ws
+package util
+
+import org.apache.pekko.actor.typed.Scheduler
+import reactivemongo.api.bson.*
+
+/* A setting that is read from the database every `ttl`.
+ *
+ * Usage:
+ * val nbDogs: Setting[Int] = settingStore.makeSetting("dogs", 48, 1.minute)
+ * println("dogs: " + nbDogs.get)
+ *
+ * Note that the first reads are not guaranteed to be from the DB,
+ * but could return the hardcoded default value instead.
+ *
+ * To change the value of a setting, you need to update the DB directly, using mongosh:
+ * db.setting.updateOne({_id:'dogs'},{$set:{value:50}})
+ */
+
+case class Setting[A](default: A, ttl: FiniteDuration)(fetch: () => Future[Option[A]])(using
+    ec: Executor,
+    scheduler: Scheduler
+):
+  private var value: A = default
+
+  def get: A = value
+
+  private def readFromDb(): Unit =
+    fetch().foreach: opt =>
+      value = opt | default
+
+  scheduler.scheduleWithFixedDelay(1.millis, ttl)(() => readFromDb())
+
+final class SettingStore(mongo: Mongo)(using Executor, Scheduler):
+
+  def makeSetting[A: BSONReader](key: String, default: A, ttl: FiniteDuration = 10.seconds): Setting[A] =
+    Setting[A](default, ttl): () =>
+      mongo.settingColl.flatMap:
+        _.find(selector = BSONDocument("_id" -> key))
+          .one[BSONDocument]
+          .map(_.flatMap(_.getAsOpt[A]("value")))