Implement undoing

app/controllers/admin/base_controller.rb

@@ -1,3 +1,11 @@
 class Admin::BaseController < ApplicationController
   layout 'admin'
+
+  private
+
+  def undo_link(item)
+    view_context.link_to('Undo this change',
+                         admin_revert_version_path(id: item.version.last),
+                         method: :post)
+  end
 end

app/controllers/admin/cards_controller.rb

@@ -24,7 +24,8 @@ class Admin::CardsController < Admin::BaseController
     authorize @card
 
     if @card.save
-      redirect_to admin_cards_path, notice: 'Card was created'
+      redirect_to admin_cards_path,
+        notice: "Card was created. #{undo_link(@card)}"
     else
       render :new
     end
@@ -40,7 +41,8 @@ class Admin::CardsController < Admin::BaseController
     authorize @card
 
     if @card.update(card_params)
-      redirect_to admin_cards_path, notice: 'Card was updated'
+      redirect_to admin_cards_path,
+        notice: "Card was updated. #{undo_link(@card)}"
     else
       render :edit
     end
@@ -51,7 +53,8 @@ class Admin::CardsController < Admin::BaseController
 
     @card.destroy
 
-    redirect_to admin_cards_path, notice: 'Card was deleted'
+    redirect_to admin_cards_path,
+      notice: "Card was deleted. #{undo_link(@card)}"
   end
 
   private

app/controllers/admin/versions_controller.rb

@@ -1,16 +1,27 @@
 class Admin::VersionsController < Admin::BaseController
-  before_action :set_version, only: [:show]
-
   def show
+    @version = PaperTrail::Version.find(params[:id]).reify(has_one: true)
+
     type = @version.class.to_s.underscore
     instance_variable_set('@' + type, @version)
 
     render "admin/#{type.pluralize}/show"
   end
 
+  def revert
+    @version = PaperTrail::Version.find(params[:id])
+
+    if @version.reify(has_one: true)
+      @version.reify(has_one: true).save!
+    else
+      @version.item.destroy
+    end
+
+    redirect_to :back, notice: "Undid #{@version.event}!"
+  end
+
   private
 
   def set_version
-    @version = PaperTrail::Version.find(params[:id]).reify(has_one: true)
   end
 end

app/views/application/_flash_message.html.slim

@@ -2,4 +2,4 @@
   button.close type='button' data-dismiss='alert'
     span aria-hidden='true' ×
     span.sr-only Close
-  = message
+  = raw(message)

config/routes.rb

@@ -12,6 +12,8 @@ Rails.application.routes.draw do
 
     get '/dashboard', to: 'dashboard#index'
 
+    post '/versions/revert', to: 'versions#revert', as: 'revert_version'
+
     resources :awaken_types
     resources :cards
     resources :characters