GDPR erasure: private messages

modules/message/src/main/Env.scala

@@ -45,6 +45,12 @@ final class Env(
     blocks = blocks,
     getPref = getPref
   )
+
+  system.lilaBus.subscribe(system.actorOf(Props(new Actor {
+    def receive = {
+      case lila.user.User.GDPRErase(user) => api erase user
+    }
+  })), 'gdprErase)
 }
 
 object Env {

modules/message/src/main/MessageApi.scala

@@ -133,4 +133,10 @@ final class MessageApi(
         )
       )
     }
+
+  def erase(user: User) = ThreadRepo.byAndForWithoutIndex(user) flatMap { threads =>
+    lila.common.Future.applySequentially(threads) { thread =>
+      coll.update($id(thread.id), thread erase user).void
+    }
+  }
 }

modules/message/src/main/Post.scala

@@ -16,6 +16,8 @@ case class Post(
   def isUnRead = !isRead
 
   def similar(other: Post) = text == other.text && isByCreator == other.isByCreator
+
+  def erase = copy(text = "<deleted>")
 }
 
 object Post {

modules/message/src/main/Thread.scala

@@ -11,9 +11,9 @@ case class Thread(
     createdAt: DateTime,
     updatedAt: DateTime,
     posts: List[Post],
-    creatorId: String,
-    invitedId: String,
-    visibleByUserIds: List[String],
+    creatorId: User.ID,
+    invitedId: User.ID,
+    visibleByUserIds: List[User.ID],
     mod: Option[Boolean]
 ) {
 
@@ -89,6 +89,14 @@ case class Thread(
   def hasPostsWrittenBy(userId: User.ID) = posts exists (_.isByCreator == (creatorId == userId))
 
   def endsWith(post: Post) = posts.lastOption ?? post.similar
+
+  def erase(user: User) = copy(
+    posts = posts.map {
+      case p if p.isByCreator && user.id == creatorId => p.erase
+      case p if !p.isByCreator && user.id == invitedId => p.erase
+      case p => p
+    }
+  )
 }
 
 object Thread {

modules/message/src/main/ThreadRepo.scala

@@ -1,5 +1,6 @@
 package lila.message
 
+import reactivemongo.api.ReadPreference
 import lila.db.dsl._
 import lila.user.User
 
@@ -22,6 +23,13 @@ object ThreadRepo {
   def createdByUser(user: ID): Fu[List[Thread]] =
     coll.find(visibleByUserQuery(user) ++ $doc("creatorId" -> user)).list[Thread]()
 
+  // super heavy. For GDPR only.
+  private[message] def byAndForWithoutIndex(user: User): Fu[List[Thread]] =
+    coll.find($or(
+      $doc("creatorId" -> user.id),
+      $doc("invitedId" -> user.id)
+    )).list[Thread](999, readPreference = ReadPreference.secondaryPreferred)
+
   def setReadFor(user: User)(thread: Thread): Funit = {
     val indexes = thread.unreadIndexesBy(user)
     indexes.nonEmpty ?? coll.update($id(thread.id), $doc("$set" -> indexes.foldLeft($empty) {