"Undo" functionality in flash messages (issue #64)

app/controllers/attendees_controller.rb

@@ -2,17 +2,41 @@ class AttendeesController < ApplicationController
   before_action :set_session
 
   def create
-    @session.attendees.push(current_user) if @session.attendees.exclude?(current_user)
-    @user_session_ids = current_user.sessions.pluck(:id)
+    @session.attendees.push(current_user)
+    flash[:notice] = I18n.t("controllers.attendees.add_user.notice")
+
+    session[:last_action] = "create"
+    flash[:undo] = {path: undo_session_attendee_path(session_id: @session.id)}
+
+    redirect_back_or_to(sessions_path, params: params[:starts_at])
   end
 
   def destroy
-    @session.attendees.delete(current_user) if @session.attendees.include?(current_user)
-    @user_session_ids = current_user.sessions.pluck(:id)
-    if URI(request.referer).path == schedule_path
-      flash[:notice] = I18n.t("controllers.attendees.remove_user.notice")
-      redirect_back_or_to(sessions_path, params: params[:starts_at])
+    @session.attendees.delete(current_user)
+    flash[:notice] = I18n.t("controllers.attendees.remove_user.notice")
+
+    session[:last_action] = "destroy"
+    flash[:undo] = {path: undo_session_attendee_path(session_id: @session.id)}
+
+    redirect_back_or_to(sessions_path, params: params[:starts_at])
+  end
+
+  def undo
+    if session[:last_action].present?
+      last_action = session[:last_action]
+
+      if last_action == "create"
+        @session.attendees.delete(current_user)
+      elsif last_action == "destroy"
+        @session.attendees.push(current_user)
+      end
+
+      session[:last_action] = nil
+    else
+      flash[:notice] = I18n.t("controllers.attendees.undo.expired")
     end
+
+    redirect_back_or_to(sessions_path, params: params[:starts_at])
   end
 
   private

app/views/layouts/_flash_message.html.erb

@@ -1,7 +1,10 @@
-<%# locals: (message:) %>
+<%# locals: (message:, type:) %>
 
 <div class="flex flex-col items-center justify-center fixed bottom-[64px] pb-safe-area-1 w-full z-30 px-5">
-  <div data-controller="closable" class="bg-black/70 shadow-simple backdrop-blur-[25px] rounded-lg px-5 py-4 transition-all bottom-0 max-w-screen-sm text-white z-20 sticky">
+  <div data-controller="closable" class="flex justify-between gap-8 bg-black/70 shadow-simple backdrop-blur-[25px] rounded-lg px-5 py-4 transition-all bottom-0 max-w-screen-sm text-white z-20 sticky">
     <%= message %>
+    <% if type == "notice" && flash[:undo].present? %>
+      <%= button_to "Undo", flash[:undo]["path"], class: "italic font-bold" %>
+    <% end %>
   </div>
 </div>

app/views/layouts/application.html.erb

@@ -48,7 +48,7 @@
       <div id="flash_message">
         <% flash.each do |type, message| %>
           <% if message.present? && message.is_a?(String) %>
-            <%= render partial: "layouts/flash_message", locals: { message: message } %>
+            <%= render partial: "layouts/flash_message", locals: { message: message, type: type } %>
           <% end %>
         <% end %>
       </div>

config/locales/en.yml

@@ -32,6 +32,8 @@ en:
         notice: "Session was added to My Schedule"
       remove_user:
         notice: "Session was removed from My Schedule"
+      undo:
+        expired: "The undo action has expired."
   mailers:
     session_mailer:
       reminder:

config/routes.rb

@@ -29,7 +29,9 @@
   resource :schedule, only: [:show]
 
   resources :sessions, only: [:index, :show] do
-    resource :attendee, only: [:create, :destroy]
+    resource :attendee, only: [:create, :destroy] do
+      post "undo", on: :collection
+    end
   end
   resources :speakers, only: [:show]
   resources :profiles, only: [:show, :edit, :update], param: :uuid