sessions_controller.rb

class SessionsController < ApplicationController
  rescue_from Mutations::ValidationException, with: :validation_handler

  def create
    with_param :session do |params|
      session[:user_id] = SessionCreator.run! params
    end

    render_success
  end

  def new
    @auth_action = request[:auth_action] || root_path
  end

  def destroy
    session[:user_id] = nil

    redirect_to root_path, notice: 'You have been signed out.'
  end

  def validation_handler(exception)
    error_hash = Hash[exception.errors.map{|(k,v)| [k, v.message]}]
    error_hash = {@current_param_key => error_hash} if @current_param_key

    respond_to do |format|
      format.json do
        render json: {errors: error_hash}, status: :bad_request
      end
      format.all { raise }
    end
  end

  def render_success
    render json: {message: 'Success.'}
  end

  def with_param(key)
    @current_param_key = key

    yield params[key]

    @current_param_key = nil
  end
end