Update the destination category id when a user changes it

app/assets/javascripts/discourse/components/shared-draft-controls.js.es6

@@ -1,4 +1,5 @@
 import computed from 'ember-addons/ember-computed-decorators';
+import { ajax } from 'discourse/lib/ajax';
 
 export default Ember.Component.extend({
   tagName: '',
@@ -11,8 +12,14 @@ export default Ember.Component.extend({
   },
 
   actions: {
-    publish() {
+    updateDestinationCategory(category) {
+      ajax(`/t/${this.get('topic.id')}/shared-draft`, {
+        method: 'PUT',
+        data: { category_id: category.get('id') }
+      });
+    },
 
+    publish() {
       bootbox.confirm(I18n.t('shared_drafts.confirm_publish'), result => {
         if (result) {
           this.set('publishing', true);

app/assets/javascripts/discourse/templates/components/shared-draft-controls.hbs

@@ -6,7 +6,9 @@
 
     <div class='publish-field'>
       <label>{{i18n "shared_drafts.destination_category"}}</label>
-      {{category-chooser value=topic.destination_category_id}}
+      {{category-chooser
+        value=topic.destination_category_id
+        onChooseCategory=(action "updateDestinationCategory")}}
     </div>
 
     <div class='publish-field'>

app/assets/javascripts/select-kit/components/category-chooser.js.es6

@@ -98,6 +98,12 @@ export default ComboBoxComponent.extend({
     this.appEvents.off("composer:resized");
   },
 
+  didSelect(computedContentItem) {
+    if (this.attrs.onChooseCategory) {
+      this.attrs.onChooseCategory(computedContentItem.originalContent);
+    }
+  },
+
   computeContent() {
     const categories = Discourse.SiteSettings.fixed_category_positions_on_create ?
       Category.list() :

app/controllers/topics_controller.rb

@@ -11,6 +11,7 @@ class TopicsController < ApplicationController
     :timings,
     :destroy_timings,
     :update,
+    :update_shared_draft,
     :destroy,
     :recover,
     :status,
@@ -236,6 +237,17 @@ class TopicsController < ApplicationController
     render body: nil
   end
 
+  def update_shared_draft
+    topic = Topic.find_by(id: params[:id])
+    guardian.ensure_can_edit!(topic)
+    guardian.ensure_can_create_shared_draft!
+    raise Discourse::NotFound unless topic.shared_draft.present?
+
+    SharedDraft.where(topic_id: topic.id).update_all(category_id: params[:category_id].to_i)
+
+    render json: success_json
+  end
+
   def update
     topic = Topic.find_by(id: params[:topic_id])
     guardian.ensure_can_edit!(topic)

config/routes.rb

@@ -599,6 +599,7 @@ Discourse::Application.routes.draw do
   put "t/:id/move-to-inbox" => "topics#move_to_inbox"
   put "t/:id/convert-topic/:type" => "topics#convert_topic"
   put "t/:id/publish" => "topics#publish"
+  put "t/:id/shared-draft" => "topics#update_shared_draft"
   put "topics/bulk"
   put "topics/reset-new" => 'topics#reset_new'
   post "topics/timings"

spec/requests/topics_controller_spec.rb

@@ -464,6 +464,36 @@ RSpec.describe TopicsController do
       SiteSetting.shared_drafts_category = shared_drafts_category.id
     end
 
+    describe "#update_shared_draft" do
+      let(:category) { Fabricate(:category) }
+      let(:other_cat) { Fabricate(:category) }
+      let(:topic) { Fabricate(:topic, category: shared_drafts_category, visible: false) }
+      let!(:shared_draft) { Fabricate(:shared_draft, topic: topic, category: category) }
+      let(:moderator) { Fabricate(:moderator) }
+
+      context "anonymous" do
+        it "doesn't allow staff to update the shared draft" do
+          put "/t/#{topic.id}/shared-draft.json", params: { category_id: other_cat.id }
+          expect(response.code.to_i).to eq(403)
+          topic.reload
+          expect(topic.shared_draft.category_id).to eq(category.id)
+        end
+      end
+
+      context "as a moderator" do
+        before do
+          sign_in(moderator)
+        end
+
+        it "allows staff to update the category id" do
+          put "/t/#{topic.id}/shared-draft.json", params: { category_id: other_cat.id }
+          expect(response).to be_success
+          topic.reload
+          expect(topic.shared_draft.category_id).to eq(other_cat.id)
+        end
+      end
+    end
+
     describe "#publish" do
       let(:category) { Fabricate(:category) }
       let(:topic) { Fabricate(:topic, category: shared_drafts_category, visible: false) }