fix unread count of compat msg API - closes veloce/lichobile#1561

messages that you never read end up being moved down the list
by newer messages.
stop counting them as unread after a while.

Better fix: use the new inbox API and the lichess notification system

app/controllers/Msg.scala

@@ -60,7 +60,7 @@ final class Msg(
   def unreadCount =
     Auth { ctx => me =>
       JsonOk {
-        env.msg.api unreadCount me
+        env.msg.compat unreadCount me
       }
     }
 

modules/msg/src/main/MsgApi.scala

@@ -15,7 +15,6 @@ import lila.user.{ User, UserRepo }
 final class MsgApi(
     colls: MsgColls,
     userRepo: UserRepo,
-    cacheApi: lila.memo.CacheApi,
     lightUserApi: lila.user.LightUserApi,
     relationApi: lila.relation.RelationApi,
     json: MsgJson,
@@ -203,15 +202,6 @@ final class MsgApi(
         notifier.deleteAllBy(threads, user)
     }
 
-  def unreadCount(me: User): Fu[Int] = unreadCountCache.get(me.id)
-
-  private val unreadCountCache = cacheApi[User.ID, Int](256, "message.unreadCount") {
-    _.expireAfterWrite(10 seconds)
-      .buildAsyncFuture[User.ID, Int] { userId =>
-        colls.thread.countSel($doc("users" -> userId, "lastMsg.read" -> false, "lastMsg.user" $ne userId))
-      }
-  }
-
   private val msgProjection = $doc("_id" -> false, "tid" -> false).some
 
   private def threadMsgsFor(threadId: MsgThread.Id, me: User, before: Option[DateTime]): Fu[List[Msg]] =

modules/msg/src/main/MsgCompat.scala

@@ -3,17 +3,21 @@ package lila.msg
 import play.api.data._
 import play.api.data.Forms._
 import play.api.libs.json._
+import reactivemongo.api.ReadPreference
 import scala.concurrent.duration._
 
 import lila.common.config._
 import lila.common.Json.jodaWrites
 import lila.common.LightUser
 import lila.common.paginator._
+import lila.db.dsl._
 import lila.user.{ LightUserApi, User }
 
 final class MsgCompat(
     api: MsgApi,
+    colls: MsgColls,
     security: MsgSecurity,
+    cacheApi: lila.memo.CacheApi,
     isOnline: lila.socket.IsOnline,
     lightUserApi: LightUserApi
 )(implicit ec: scala.concurrent.ExecutionContext) {
@@ -48,6 +52,25 @@ final class MsgCompat(
     }
   }
 
+  def unreadCount(me: User): Fu[Int] = unreadCountCache.get(me.id)
+
+  private val unreadCountCache = cacheApi[User.ID, Int](256, "message.unreadCount") {
+    _.expireAfterWrite(10 seconds)
+      .buildAsyncFuture[User.ID, Int] { userId =>
+        colls.thread
+          .aggregateOne(ReadPreference.secondaryPreferred) { framework =>
+            import framework._
+            Match($doc("users" -> userId)) -> List(
+              Sort(Descending("lastMsg.date")),
+              Limit(maxPerPage.value),
+              Match($doc("lastMsg.read" -> false, "lastMsg.user" $ne userId)),
+              Count("nb")
+            )
+          }
+          .map(~_.flatMap(_.getAsOpt[Int]("nb")))
+      }
+  }
+
   def thread(me: User, c: MsgConvo): JsObject =
     Json.obj(
       "id"   -> c.contact.id,