require 'base64'
require 'new_relic/agent/beacon_configuration'
module NewRelic
  module Agent
    module BrowserMonitoring

      def browser_timing_header
        return "" if NewRelic::Agent.instance.beacon_configuration.nil?
        return "" if !NewRelic::Agent.is_transaction_traced? || !NewRelic::Agent.is_execution_traced?

        NewRelic::Agent.instance.beacon_configuration.browser_timing_header
      end

      def browser_timing_footer
        config = NewRelic::Agent.instance.beacon_configuration
        return "" if config.nil? || !config.rum_enabled || config.browser_monitoring_key.nil?
        return "" if !NewRelic::Agent.is_transaction_traced? || !NewRelic::Agent.is_execution_traced?
        generate_footer_js
      end

      private

      def generate_footer_js
        if browser_monitoring_start_time
          config = NewRelic::Agent.instance.beacon_configuration
          application_id = config.application_id
          beacon = config.beacon
          license_key = config.browser_monitoring_key

          footer_js_string(beacon, license_key, application_id)
        else
          ''
        end
      end

      def browser_monitoring_transaction_name
        Thread.current[:newrelic_most_recent_transaction] || "<unknown>"
      end

      def browser_monitoring_start_time
        Thread.current[:newrelic_start_time]
      end

      def clamp_to_positive(value)
        return 0.0 if value < 0
        value
      end

      def browser_monitoring_app_time
        clamp_to_positive(((Time.now - browser_monitoring_start_time).to_f * 1000.0).round)
      end

      def browser_monitoring_queue_time
        clamp_to_positive((Thread.current[:newrelic_queue_time].to_f * 1000.0).round)
      end

      def footer_js_string(beacon, license_key, application_id)
        obfuscated_transaction_name = obfuscate(browser_monitoring_transaction_name)
        html_safe_if_needed("<script>#{NewRelic::Agent.instance.beacon_configuration.browser_timing_static_footer}NREUMQ.push([\"nrf2\",\"#{beacon}\",\"#{license_key}\",#{application_id},\"#{obfuscated_transaction_name}\",#{browser_monitoring_queue_time},#{browser_monitoring_app_time},new Date().getTime()])</script>")
      end

      def html_safe_if_needed(string)
        if string.respond_to?(:html_safe)
          string.html_safe
        else
          string
        end
      end

      def obfuscate(text)
        obfuscated = ""
        key_bytes = NewRelic::Agent.instance.beacon_configuration.license_bytes
        index = 0
        text.each_byte{|byte|
          obfuscated.concat((byte ^ key_bytes[index % 13].to_i))
          index+=1
        }

        [obfuscated].pack("m0").gsub("\n", '')
      end
    end
  end
end