treat cable sub/unsub as joined/left map. fixes #1035 (#1047)

app/channels/map_channel.rb

@@ -3,7 +3,15 @@ class MapChannel < ApplicationCable::Channel
   # Called when the consumer has successfully
   # become a subscriber of this channel.
   def subscribed
-    return unless Pundit.policy(current_user, Map.find(params[:id])).show?
+    map = Map.find(params[:id])
+    return unless Pundit.policy(current_user, map).show?
     stream_from "map_#{params[:id]}"
+    Events::UserPresentOnMap.publish!(map, current_user)
+  end
+
+  def unsubscribed
+    map = Map.find(params[:id])
+    return unless Pundit.policy(current_user, map).show?
+    Events::UserNotPresentOnMap.publish!(map, current_user)
   end
 end

app/controllers/maps_controller.rb

@@ -106,9 +106,6 @@ class MapsController < ApplicationController
     if params[:event] == 'conversation'
       Events::ConversationStartedOnMap.publish!(@map, current_user)
       valid_event = true
-    elsif params[:event] == 'user_presence'
-      Events::UserPresentOnMap.publish!(@map, current_user)
-      valid_event = true
     end
 
     respond_to do |format|

app/models/event.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 class Event < ApplicationRecord
-  KINDS = %w(user_present_on_map conversation_started_on_map
+  KINDS = %w(user_present_on_map user_not_present_on_map
+             conversation_started_on_map
              topic_added_to_map topic_moved_on_map topic_removed_from_map
              synapse_added_to_map synapse_removed_from_map
              topic_updated synapse_updated).freeze

app/models/events/user_not_present_on_map.rB

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+module Events
+  class UserNotPresentOnMap < Event
+    # after_create :notify_users!
+
+    def self.publish!(map, user)
+      create!(kind: 'user_not_present_on_map',
+              eventable: map,
+              map: map,
+              user: user)
+    end
+  end
+end

frontend/src/Metamaps/Visualize.js

@@ -149,8 +149,6 @@ const Visualize = {
       self.mGraph.graph.empty()
     }
 
-    if (self.type === 'ForceDirected' && Active.Mapper) $.post('/maps/' + Active.Map.id + '/events/user_presence')
-
     function runAnimation() {
       Loading.hide()
       // load JSON data, if it's not empty