Implement offline POST method for starting an offline participation

app/controllers/contests_controller.rb

@@ -1,6 +1,7 @@
 class ContestsController < ApplicationController
   before_action :set_contest, only: %i[ destroy edit show update ]
-  skip_before_action :require_authentication, only: %i[ scoreboard offline_new ]
+  before_action :offline_setup, only: %i[ offline_new offline_create ]
+  skip_before_action :require_authentication, only: %i[ scoreboard offline_new offline_create ]
 
   def index
     authorize :contest
@@ -100,22 +101,30 @@ class ContestsController < ApplicationController
   end
 
   def offline_new
-    @contest = Contest.find_by(slug: params[:id])
-    unless @contest && @contest.offline_form
-      skip_authorization
-      not_found and return
-    end
-    authorize :contest
-
-    I18n.locale = @contest.lang
-
-    @title = I18n.t("contests.scoreboard.title", name: @contest.name)
-
+    authorize @contest
     @offline = Offline.new
   end
 
+  def offline_create
+    authorize @contest
+    @offline = Offline.new(offline_start_params)
+    @offline.contest = @contest
+    @offline.start_time = Time.now()
+    if @offline.save
+      redirect_to "/public/#{@contest.friendly_id}/offline/test"
+    else
+      render :offline_new, status: :unprocessable_entity
+    end
+  end
+
   private
 
+  def offline_setup
+    @contest = Contest.find_by(slug: params[:id])
+    I18n.locale = @contest.lang
+    @title = I18n.t("contests.scoreboard.title", name: @contest.name)
+  end
+
   def set_badges
     @badges = []
     @badges.push(t("helpers.badges.team")) if @contest.team
@@ -139,4 +148,8 @@ class ContestsController < ApplicationController
       end
     end
   end
+
+  def offline_start_params
+    params.expect(offline: [ :name, :start_image ])
+  end
 end