Add public preview links for drafts

Lets editors share a draft with people outside the admin system, via a
random per-page token rather than an enumerable id - /preview/<token>.
shared_previews#show is intentionally unauthenticated. Redirects to the
real public URL once the page is published. Surfaced on nodes#show
(Admin Preview + Public Preview, next to Public Link) as generate/revoke
buttons.

2 files changed, 31 insertions, 0 deletions

diff --git a/app/controllers/nodes_controller.rb b/app/controllers/nodes_controller.rb
index 380a659..69aa268 100644
--- a/app/controllers/nodes_controller.rb
+++ b/app/controllers/nodes_controller.rb
@@ -104,6 +104,24 @@ class NodesController < ApplicationController
     redirect_to node_path(@node)
   end
 
+  def generate_shared_preview
+    @node = Node.find(params[:id])
+    if @node.draft
+      @node.draft.ensure_preview_token!
+      flash[:notice] = "Shareable preview link created - see below."
+    else
+      flash[:notice] = "Create or edit a draft first - shared preview links are only available for pages with an active draft."
+    end
+    redirect_to node_path(@node)
+  end
+
+  def revoke_shared_preview
+    @node = Node.find(params[:id])
+    @node.draft.revoke_preview_token! if @node.draft
+    flash[:notice] = "Shareable preview link revoked."
+    redirect_to node_path(@node)
+  end
+
   def parameterize_preview
     render plain: slug_for(params[:title])
   end
diff --git a/app/controllers/shared_previews_controller.rb b/app/controllers/shared_previews_controller.rb
new file mode 100644
index 0000000..a8a540f
--- /dev/null
+++ b/app/controllers/shared_previews_controller.rb
@@ -0,0 +1,13 @@
+class SharedPreviewsController < ApplicationController
+  def show
+    @page = Page.find_by!(preview_token: params[:token])
+
+    if @page.node && @page.node.head_id == @page.id
+      redirect_to node_path(@page.node)
+      return
+    end
+
+    response.headers['X-Robots-Tag'] = 'noindex'
+    render template: @page.valid_template, layout: "application"
+  end
+end