Add create note subscription api endpoint

app/abilities/api_capability.rb

@@ -9,6 +9,7 @@ def initialize(token)
 
       if user&.active?
         can [:create, :comment, :close, :reopen], Note if scope?(token, :write_notes)
+        can :create, NoteSubscription if scope?(token, :write_notes)
         can [:show, :data], Trace if scope?(token, :read_gpx)
         can [:create, :update, :destroy], Trace if scope?(token, :write_gpx)
         can [:details], User if scope?(token, :read_prefs)

app/controllers/api/note_subscriptions_controller.rb

@@ -0,0 +1,18 @@
+module Api
+  class NoteSubscriptionsController < ApiController
+    before_action :check_api_writable
+    before_action :authorize
+
+    authorize_resource
+
+    def create
+      note_id = params[:note_id].to_i
+      note = Note.find(note_id)
+      note.subscribers << current_user
+    rescue ActiveRecord::RecordNotFound
+      report_error "Note #{note_id} not found.", :not_found
+    rescue ActiveRecord::RecordNotUnique
+      report_error "You are already subscribed to note #{note_id}.", :conflict
+    end
+  end
+end

config/routes.rb

@@ -108,6 +108,8 @@
         post "close"
         post "reopen"
       end
+
+      resource :subscription, :only => :create, :controller => "note_subscriptions"
     end
 
     resources :user_blocks, :only => :show, :id => /\d+/, :controller => "user_blocks"

test/controllers/api/note_subscriptions_controller_test.rb

@@ -0,0 +1,77 @@
+require "test_helper"
+
+module Api
+  class NoteSubscriptionsControllerTest < ActionDispatch::IntegrationTest
+    def test_routes
+      assert_routing(
+        { :path => "/api/0.6/notes/1/subscription", :method => :post },
+        { :controller => "api/note_subscriptions", :action => "create", :note_id => "1" }
+      )
+    end
+
+    def test_create
+      user = create(:user)
+      auth_header = bearer_authorization_header user
+      note = create(:note_with_comments)
+      assert_empty note.subscribers
+
+      assert_difference "NoteSubscription.count", 1 do
+        assert_difference "note.subscribers.count", 1 do
+          post api_note_subscription_path(note), :headers => auth_header
+          assert_response :success
+        end
+      end
+      assert_equal user, note.subscribers.last
+    end
+
+    def test_create_fail_anonymous
+      note = create(:note_with_comments)
+
+      assert_no_difference "NoteSubscription.count" do
+        assert_no_difference "note.subscribers.count" do
+          post api_note_subscription_path(note)
+          assert_response :unauthorized
+        end
+      end
+    end
+
+    def test_create_fail_no_scope
+      user = create(:user)
+      auth_header = bearer_authorization_header user, :scopes => %w[read_prefs]
+      note = create(:note_with_comments)
+
+      assert_no_difference "NoteSubscription.count" do
+        assert_no_difference "note.subscribers.count" do
+          post api_note_subscription_path(note), :headers => auth_header
+          assert_response :forbidden
+        end
+      end
+    end
+
+    def test_create_fail_note_not_found
+      user = create(:user)
+      auth_header = bearer_authorization_header user
+
+      assert_no_difference "NoteSubscription.count" do
+        post api_note_subscription_path(999111), :headers => auth_header
+        assert_response :not_found
+      end
+      assert_match "not found", @response.body
+    end
+
+    def test_create_fail_already_subscribed
+      user = create(:user)
+      auth_header = bearer_authorization_header user
+      note = create(:note_with_comments)
+      create(:note_subscription, :user => user, :note => note)
+
+      assert_no_difference "NoteSubscription.count" do
+        assert_no_difference "note.subscribers.count" do
+          post api_note_subscription_path(note), :headers => auth_header
+          assert_response :conflict
+        end
+      end
+      assert_match "already subscribed", @response.body
+    end
+  end
+end