module ExceptionAlarm
  class Mailer < ActionMailer::Base
    self.mailer_name = 'mailer'
    self.append_view_path "#{File.dirname(__FILE__)}/views"

    thread_local_accessor :prefix, default: '[ERROR]'
    thread_local_accessor :sender, default: 'exception@example.com'
    thread_local_accessor :recipients

    def alarm(env, exception)
      @env = env
      @exception = exception
      @kontroller = env['action_controller.instance']
      @request = ActionDispatch::Request.new(env)

      attachments["exception_#{@request.host.gsub(".", "_")}_#{Time.now.to_i}.txt"] = render(:alarm)
      mail(
        from: self.class.sender,
        to: self.class.recipients,
        subject: "#{self.class.prefix} (#{@exception.class}) #{@exception.message.inspect}",
        body:
          "A #{@exception.class} occurred in #{@kontroller.controller_name}##{@kontroller.action_name}:\n" +
          @exception.backtrace.first.to_s
      )
    end
  end
end