# encoding: utf-8
# This file is distributed under New Relic's license terms.
# See https://github.com/newrelic/rpm/blob/master/LICENSE for complete details.

require 'base64'
require 'new_relic/agent/beacon_configuration'
require 'new_relic/agent/transaction_timings'

module NewRelic
  module Agent
    # This module contains support for Real User Monitoring - the
    # javascript generation and configuration
    #
    # @api public
    module BrowserMonitoring
      include NewRelic::Coerce

      class DummyTransaction

        attr_reader :custom_parameters
        attr_accessor :start_time

        def initialize
          @custom_parameters = {}
        end

        def queue_time
          0.0
        end

        def timings
          NewRelic::Agent::TransactionTimings.new(0.0, NewRelic::Agent::TransactionState.get)
        end

        def name
          ::NewRelic::Agent::UNKNOWN_METRIC
        end
      end

      @@dummy_txn = DummyTransaction.new

      # This method returns a string suitable for inclusion in a page
      # - known as 'manual instrumentation' for Real User
      # Monitoring. Can return either a script tag with associated
      # javascript, or in the case of disabled Real User Monitoring,
      # an empty string
      #
      # This is the header string - it should be placed as high in the
      # page as is reasonably possible - that is, before any style or
      # javascript inclusions, but after any header-related meta tags
      #
      # @api public
      #
      def browser_timing_header
        insert_js? ? header_js_string : ""
      end

      # This method returns a string suitable for inclusion in a page
      # - known as 'manual instrumentation' for Real User
      # Monitoring. Can return either a script tag with associated
      # javascript, or in the case of disabled Real User Monitoring,
      # an empty string
      #
      # This is the footer string - it should be placed as low in the
      # page as is reasonably possible.
      #
      # @api public
      #
      def browser_timing_footer
        if insert_js?
          NewRelic::Agent::Transaction.freeze_name
          generate_footer_js(NewRelic::Agent.instance.beacon_configuration)
        else
          ""
        end
      end

      module_function

      def obfuscate(config, text)
        obfuscated = ""
        if defined?(::Encoding::ASCII_8BIT)
          obfuscated.force_encoding(::Encoding::ASCII_8BIT)
        end
        key_bytes = config.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

      def browser_monitoring_transaction_name
        current_timings.transaction_name || ::NewRelic::Agent::UNKNOWN_METRIC
      end

      def current_transaction
        NewRelic::Agent::TransactionState.get.transaction || @@dummy_txn
      end

      def current_timings
        NewRelic::Agent::TransactionState.get.timings
      end

      private

      # Check whether RUM header and footer should be generated.  Log the
      # reason if they shouldn't.
      def insert_js?
        if NewRelic::Agent.instance.beacon_configuration.nil?
          ::NewRelic::Agent.logger.debug "Beacon configuration is nil. Skipping browser instrumentation."
          false
        elsif ! NewRelic::Agent.instance.beacon_configuration.enabled?
          ::NewRelic::Agent.logger.debug "Beacon configuration is disabled. Skipping browser instrumentation."
          ::NewRelic::Agent.logger.debug NewRelic::Agent.instance.beacon_configuration.inspect
          false
        elsif Agent.config[:browser_key].nil? || Agent.config[:browser_key].empty?
          ::NewRelic::Agent.logger.debug "Browser key is not set. Skipping browser instrumentation."
          false
        elsif ! NewRelic::Agent.is_transaction_traced?
          ::NewRelic::Agent.logger.debug "Transaction is not traced. Skipping browser instrumentation."
          false
        elsif ! NewRelic::Agent.is_execution_traced?
          ::NewRelic::Agent.logger.debug "Execution is not traced. Skipping browser instrumentation."
          false
        elsif NewRelic::Agent::TransactionState.get.request_ignore_enduser
          ::NewRelic::Agent.logger.debug "Ignore end user for this transaction is set. Skipping browser instrumentation."
          false
        else
          true
        end
      end

      def generate_footer_js(config)
        if current_transaction.start_time
          footer_js_string(config)
        else
          ''
        end
      end

      def tt_guid
        state = NewRelic::Agent::TransactionState.get
        return state.request_guid if include_guid?(state)
        ""
      end

      def include_guid?(state)
        state.request_token &&
          state.timings.app_time_in_seconds > state.transaction.apdex_t
      end

      def tt_token
        return NewRelic::Agent::TransactionState.get.request_token
      end

      def js_agent_loader
        Agent.config[:js_agent_loader].to_s
      end

      def has_loader?
        !js_agent_loader.empty?
      end

      # NOTE: Internal prototyping often overrides this, so leave name stable!
      def header_js_string
        return "" unless has_loader?
        html_safe_if_needed("\n<script type=\"text/javascript\">#{js_agent_loader}</script>")
      end

      # NOTE: Internal prototyping often overrides this, so leave name stable!
      def footer_js_string(config)
        data = js_data(config)
        html_safe_if_needed("\n<script type=\"text/javascript\">window.NREUM||(NREUM={});NREUM.info=#{NewRelic.json_dump(data)}</script>")
      end

      BEACON_KEY           = "beacon".freeze
      ERROR_BEACON_KEY     = "errorBeacon".freeze
      LICENSE_KEY_KEY      = "licenseKey".freeze
      APPLICATIONID_KEY    = "applicationID".freeze
      TRANSACTION_NAME_KEY = "transactionName".freeze
      QUEUE_TIME_KEY       = "queueTime".freeze
      APPLICATION_TIME_KEY = "applicationTime".freeze
      TT_GUID_KEY          = "ttGuid".freeze
      AGENT_TOKEN_KEY      = "agentToken".freeze
      AGENT_KEY            = "agent".freeze
      EXTRA_KEY            = "extra".freeze

      # NOTE: Internal prototyping may override this, so leave name stable!
      def js_data(config)
        {
          BEACON_KEY           => NewRelic::Agent.config[:beacon],
          ERROR_BEACON_KEY     => NewRelic::Agent.config[:error_beacon],
          LICENSE_KEY_KEY      => NewRelic::Agent.config[:browser_key],
          APPLICATIONID_KEY    => NewRelic::Agent.config[:application_id],
          TRANSACTION_NAME_KEY => obfuscate(config, browser_monitoring_transaction_name),
          QUEUE_TIME_KEY       => current_timings.queue_time_in_millis,
          APPLICATION_TIME_KEY => current_timings.app_time_in_millis,
          TT_GUID_KEY          => tt_guid,
          AGENT_TOKEN_KEY      => tt_token,
          AGENT_KEY            => NewRelic::Agent.config[:js_agent_file],
          EXTRA_KEY            => obfuscate(config, format_extra_data(extra_data))
        }
      end

      ANALYTICS_ENABLED = :'analytics_events.enabled'
      ANALYTICS_TXN_ENABLED = :'analytics_events.transactions.enabled'
      ANALYTICS_TXN_IN_PAGE = :'capture_attributes.page_view_events'

      # NOTE: Internal prototyping may override this, so leave name stable!
      def extra_data
        return {} unless include_custom_parameters_in_extra?
        current_transaction.custom_parameters.dup
      end

      def include_custom_parameters_in_extra?
        NewRelic::Agent.config[ANALYTICS_ENABLED] &&
          NewRelic::Agent.config[ANALYTICS_TXN_ENABLED] &&
          NewRelic::Agent.config[ANALYTICS_TXN_IN_PAGE]
      end

      # Format the props using semicolon separated pairs separated by '=':
      #   product=pro;user=bill@microsoft.com
      def format_extra_data(extra_props)
        extra_props = event_params(extra_props)
        extra_props.map do |k, v|
          key = escape_special_characters(k)
          value = format_value(v)
          "#{key}=#{value}"
        end.join(';')
      end

      def escape_special_characters(string)
        string.to_s.tr("\";=", "':-" )
      end

      def format_value(v)
        # flag numeric values with `#' prefix
        if v.is_a? Numeric
          value = "##{v}"
        else
          value = escape_special_characters(v)
        end
      end

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