# encoding: utf-8
module OneApm
  module Agent
    module Instrumentation
      module ActiveRecordHelper
        module_function

        def metric_for_name(name)
          return unless name && name.respond_to?(:split)
          parts = name.split(' ')
          if parts.size == 2
            model = parts.first
            operation = parts.last.downcase
            case operation
            when 'load', 'count', 'exists'
              op_name = 'find'
            when 'indexes', 'columns'
              op_name = nil # fall back to DirectSQL
            when 'destroy', 'find', 'save', 'create'
              op_name = operation
            when 'update'
              op_name = 'save'
            else
              if model == 'Join'
                op_name = operation
              end
            end
            "ActiveRecord/#{model}/#{op_name}" if op_name
          end
        end

        def metric_for_sql(sql) #THREAD_LOCAL_ACCESS
          txn = OneApm::Transaction.tl_current
          metric = txn && txn.database_metric_name
          if metric.nil?
            operation = OneApm::Agent::Database.parse_operation_from_query(sql)
            if operation
              # Could not determine the model/operation so use a fallback metric
              metric = "Database/SQL/#{operation}"
            else
              metric = "Database/SQL/other"
            end
          end
          metric
        end

        # Given a metric name such as "ActiveRecord/model/action" this
        # returns an array of rollup metrics:
        # [ "Database/all", "ActiveRecord/all", "ActiveRecord/action" ]
        # If the metric name is in the form of "ActiveRecord/action"
        # this returns merely: [ "Database/all", "ActiveRecord/all" ]
        def rollup_metrics_for(metric)
          metrics = ["Database/all"]

          # If we're outside of a web transaction, don't record any rollup
          # database metrics. This is to prevent metrics from background tasks
          # from polluting the metrics used to drive overview graphs.
          if OneApm::Transaction.recording_web_transaction?
            metrics << "ActiveRecord/all"
          else
            metrics << "Database/allOther"
          end
          metrics << "ActiveRecord/#{$1}" if metric =~ /ActiveRecord\/[\w|\:]+\/(\w+)/

          metrics
        end

        # Given a database adapter name and a database server host
        # this returns a metric name in the form:
        # "RemoteService/sql/adapter/host"
        # Host defaults to "localhost".
        def remote_service_metric(adapter, host)
          host ||= 'localhost'
          type = adapter.to_s.sub(/\d*/, '')
          "RemoteService/sql/#{type}/#{host}"
        end
      end
    end
  end
end