Rewriting the index action of SolutionsController in Rubeque

rubeque_refactor.rb

# the current index action in SolutionsController (for comparison purposes)
# app/controllers/solutions_controller.rb

def index
  @problem = Problem.find(params[:problem_id]) rescue (redirect_to "/" and return)
  if !current_user_admin? && (@problem.nil? || !@problem.solved?(current_user))
    redirect_to @problem and return
  end
  @top_solutions = Solution.where(problem_id: @problem.id, user_id: { "$nin" => [current_user.id] }).
    desc(:score).desc(:updated_at).page(params[:page] || 1)
  @followed_solutions = current_user.users_followed.map {|u| u.solutions.where(problem_id: @problem.id).first}.compact

  respond_to do |format|
    format.html # index.html.erb
    format.json { render json: @solutions }
  end
end

# refactored index action using the service

def index
  @problem = Problem.find(params[:problem_id]) rescue (redirect_to "/" and return)
  if current_user && @problem
    @solutions, @followed_solutions = SolutionService.new(user: current_user, problem: @problem, page: params[:page]).solutions
  else
    redirect to @problem and return
  end

  respond_to do |format|
    format.html # index.html.erb
    format.json { render json: @solutions }
  end
end

# service object
# app/services/solution_service.rb

class SolutionService
  def initialize(args={})
    @user = args.fetch(:user)
    @problem = args.fetch(:problem)
    @page = args.fetch(:page) || 1
  end

  def solutions
    if @problem.solved?(@user) || @user.admin
      # return the top solutions if they solved the problem
      [top_solutions, followed_solutions]
    else
      # else, mark the problem as skipped and show the bottom ones
      skip_problem
      [bottom_solutions]
    end
  end

  def skip_problem
    @user.skipped_problems[@problem.id] = true
    @user.save
  end

  def bottom_solutions
    Solution.where(problem_id: @problem.id).asc(:score).limit(3).page(@page)
  end

  def top_solutions
    Solution.where(problem_id: @problem.id, user_id: { "$nin" => [@user.id] }).
    desc(:score).desc(:updated_at).page(@page)
  end

  def followed_solutions
    @user.users_followed.map {|u| u.solutions.where(problem_id: @problem.id).first}.compact
  end
end