Apply changes from team members in own editor

app/assets/javascripts/channels/synchronized_editor_channel.js

@@ -0,0 +1,38 @@
+$(document).on('turbolinks:load', function () {
+
+  if (window.location.pathname.includes('/implement')) {
+    const editor = $('#editor');
+    const exercise_id = editor.data('exercise-id');
+    const current_user_id = editor.data('user-id');
+    const current_contributor_id = editor.data('contributor-id');
+
+    if ($.isController('exercises') && current_user_id !== current_contributor_id) {
+
+      App.synchronized_editor = App.cable.subscriptions.create({
+        channel: "SynchronizedEditorChannel", exercise_id: exercise_id
+      }, {
+
+
+        connected() {
+          // Called when the subscription is ready for use on the server
+        },
+
+        disconnected() {
+          // Called when the subscription has been terminated by the server
+        },
+
+        received(data) {
+          // Called when there's incoming data on the websocket for this channel
+          if (current_user_id !== data['current_user_id']) {
+            CodeOceanEditor.applyChanges(data['delta']['data']);
+          }
+        },
+
+        send_changes(delta) {
+          const delta_with_user_id = {current_user_id: current_user_id, delta: delta}
+          this.perform('send_changes', {delta_with_user_id: delta_with_user_id});
+        }
+      });
+    }
+  }
+});

app/assets/javascripts/editor/editor.js.erb

@@ -29,6 +29,7 @@ var CodeOceanEditor = {
     running: false,
 
     lastCopyText: null,
+    lastDeltaObject: null,
 
     <% self.class.include Rails.application.routes.url_helpers %>
     <% @config ||= CodeOcean::Config.new(:code_ocean).read(erb: false) %>
@@ -334,6 +335,12 @@ var CodeOceanEditor = {
 
             // listener for autosave
             session.on("change", function (deltaObject, session) {
+                if (this.compareDeltaObjects(deltaObject, CodeOceanEditor.lastDeltaObject)) {
+                    CodeOceanEditor.lastDeltaObject = null;
+                    return;
+                }
+                App.synchronized_editor?.send_changes(deltaObject);
+
                 // TODO: This is a workaround for a bug in Ace. Remove when upgrading Ace.
                 this.handleUTF16Surrogates(deltaObject, session);
                 this.resetSaveTimer();
@@ -1015,6 +1022,27 @@ var CodeOceanEditor = {
         }
     },
 
+    applyChanges: function (delta) {
+        this.lastDeltaObject = delta;
+        this.editors[0].session.doc.applyDeltas([delta]);
+    },
+
+    compareDeltaObjects: function (delta, last_delta) {
+        if (delta === null || last_delta === null) {
+            return false;
+        }
+
+        const delta_data = delta.data
+        // We need this manual comparison because the range uses two different classes
+        // and there is no function to compare these two objects.
+        return delta_data.action === last_delta.action &&
+          delta_data.range.start.row === last_delta.range.start.row &&
+          delta_data.range.start.column === last_delta.range.start.column &&
+          delta_data.range.end.row === last_delta.range.end.row &&
+          delta_data.range.end.column === last_delta.range.end.column &&
+          delta_data.text === last_delta.text;
+    },
+
     initializeEverything: function () {
         CodeOceanEditor.editors = [];
         this.initializeRegexes();

app/channels/application_cable/connection.rb

@@ -2,10 +2,12 @@
 
 module ApplicationCable
   class Connection < ActionCable::Connection::Base
-    identified_by :current_user
+    identified_by :current_user, :current_contributor
 
     def connect
+      # The order is important here, because a valid user is required to find a valid contributor.
       self.current_user = find_verified_user
+      self.current_contributor = find_verified_contributor
     end
 
     def disconnect
@@ -24,5 +26,14 @@ module ApplicationCable
       current_user = ExternalUser.find_by(id: session[:external_user_id]) || InternalUser.find_by(id: session[:user_id])
       current_user || reject_unauthorized_connection
     end
+
+    def find_verified_contributor
+      # Finding the current_contributor is similar to the code used in application_controller.rb#current_contributor
+      if session[:pg_id]
+        current_user.programming_groups.find(session[:pg_id])
+      else
+        current_user
+      end
+    end
   end
 end

app/channels/synchronized_editor_channel.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+class SynchronizedEditorChannel < ApplicationCable::Channel
+  def subscribed
+    stream_from specific_channel
+  end
+
+  def unsubscribed
+    # Any cleanup needed when channel is unsubscribed
+    stop_all_streams
+  end
+
+  def specific_channel
+    reject unless ProgrammingGroupPolicy.new(current_user, programming_group).stream_sync_editor?
+    "synchronized_editor_channel_group_#{programming_group.id}"
+  end
+
+  def programming_group
+    current_contributor if current_contributor.programming_group?
+  end
+
+  def send_changes(message)
+    ActionCable.server.broadcast(specific_channel, message['delta_with_user_id'])
+  end
+end

app/policies/application_policy.rb

@@ -50,14 +50,15 @@ class ApplicationPolicy
   private :teacher_in_study_group?
 
   def author_in_programming_group?
+    # !! Order is important !!
     if @record.respond_to? :contributor # e.g. submission
       possible_programming_group = @record.contributor
-
     elsif @record.respond_to? :context # e.g. file
       possible_programming_group = @record.context.contributor
-
     elsif @record.respond_to? :submission # e.g. request_for_comment
       possible_programming_group = @record.submission.contributor
+    elsif @record.respond_to? :users # e.g. programming_group
+      possible_programming_group = @record
     else
       return false
     end

app/policies/programming_group_policy.rb

@@ -8,4 +8,8 @@ class ProgrammingGroupPolicy < ApplicationPolicy
   def create?
     everyone
   end
+
+  def stream_sync_editor?
+    admin? || author_in_programming_group?
+  end
 end

app/views/exercises/_editor.html.slim

@@ -4,7 +4,7 @@
 - show_tips_interventions = @show_tips_interventions || "false"
 - hide_rfc_button = @hide_rfc_button || false
 
-#editor.row data-exercise-id=@exercise.id data-message-depleted=t('exercises.editor.depleted') data-message-timeout=t('exercises.editor.timeout',  permitted_execution_time: @exercise.execution_environment.permitted_execution_time) data-message-out-of-memory=t('exercises.editor.out_of_memory',  memory_limit: @exercise.execution_environment.memory_limit) data-submissions-url=submissions_path data-user-id=current_user.id data-user-external-id=external_user_external_id data-working-times-url=working_times_exercise_path(@exercise) data-intervention-save-url=intervention_exercise_path(@exercise) data-rfc-interventions=show_rfc_interventions data-break-interventions=show_break_interventions data-tips-interventions=show_tips_interventions
+#editor.row data-exercise-id=@exercise.id data-message-depleted=t('exercises.editor.depleted') data-message-timeout=t('exercises.editor.timeout',  permitted_execution_time: @exercise.execution_environment.permitted_execution_time) data-message-out-of-memory=t('exercises.editor.out_of_memory',  memory_limit: @exercise.execution_environment.memory_limit) data-submissions-url=submissions_path data-user-id=current_user.id data-contributor-id=current_contributor.id data-user-external-id=external_user_external_id data-working-times-url=working_times_exercise_path(@exercise) data-intervention-save-url=intervention_exercise_path(@exercise) data-rfc-interventions=show_rfc_interventions data-break-interventions=show_break_interventions data-tips-interventions=show_tips_interventions
   - unless @embed_options[:hide_sidebar]
     - additional_classes = 'sidebar-col'
     - if @tips.blank?

spec/policies/programming_group_policy_spec.rb

@@ -15,5 +15,21 @@ describe ProgrammingGroupPolicy do
         end
       end
     end
+
+    permissions(:stream_sync_editor?) do
+      it 'grants access to admins' do
+        expect(policy).to permit(create(:admin), programming_group)
+      end
+
+      it 'grants access to members of the programming group' do
+        programming_group.users do |user|
+          expect(policy).to permit(user, programming_group)
+        end
+      end
+
+      it 'does not grant access to someone who is not a member of the programming group' do
+        expect(policy).not_to permit(create(:external_user), programming_group)
+      end
+    end
   end
 end