firestore.rules

service cloud.firestore {
  match /databases/{database}/documents {
    // Make sure the uid of the requesting user matches name of the user
    // document. The wildcard expression {userId} makes the userId variable
    // available in rules.
    match /users/{userID} {
      allow read: if resource.data.privacy == 'public';
      allow read, update, delete: if request.auth.uid == userID;
      allow create: if request.auth.uid != null;
        match /events/{eventID} {
          allow read: if resource.data.privacy == 'public';
          allow read, write, create, update, delete: if request.auth.uid == userID;
          function eventData() {
            return get(/databases/$(database)/documents/users/$(userID)/events/$(eventID)).data
          }
          match /activities/{activityID} {
            allow read: if eventData().privacy == 'public'
            allow read, write, create, update, delete: if request.auth.uid == userID;
            match /streams/{streamID} {
              allow read: if eventData().privacy == 'public'
              allow read, write, create, update, delete: if request.auth.uid == userID;
            }
          }
        }
    }
  }
}