# NOTE there are multiple implementations of the MemCache client in Ruby,
# each with slightly different API's and semantics.
# See:
#     http://www.deveiate.org/code/Ruby-MemCache/ (Gem: Ruby-MemCache)
#     http://seattlerb.rubyforge.org/memcache-client/ (Gem: memcache-client)
#     http://github.com/mperham/dalli (Gem: dalli)

module NewRelic
  module Agent
    module Instrumentation
      module Memcache
        module_function
        def instrument_method(the_class, method_name)
          return unless the_class.method_defined? method_name.to_sym          
                     the_class.class_eval <<-EOD
                       def #{method_name}_with_newrelic_trace(*args)
                         metrics = ["MemCache/#{method_name}",
                                    (NewRelic::Agent::Instrumentation::MetricFrame.recording_web_transaction? ? 'MemCache/allWeb' : 'MemCache/allOther')]
                         self.class.trace_execution_scoped(metrics) do
                           t0 = Time.now
                           begin
                             #{method_name}_without_newrelic_trace(*args)
                           ensure
                             #{memcache_key_snippet(method_name)}
                           end
                         end
                       end
                       alias #{method_name}_without_newrelic_trace #{method_name}
                       alias #{method_name} #{method_name}_with_newrelic_trace
                       EOD
        end
        def memcache_key_snippet(method_name)
          return "" unless NewRelic::Control.instance['capture_memcache_keys']
          "NewRelic::Agent.instance.transaction_sampler.notice_nosql(args.first.inspect, (Time.now - t0).to_f) rescue nil"
        end
      end
    end
  end
end




DependencyDetection.defer do
  depends_on do
    !NewRelic::Control.instance['disable_memcache_instrumentation']
  end

  executes do
    %w[get get_multi set add incr decr delete replace append prepend cas].each do | method_name |
      NewRelic::Agent::Instrumentation::Memcache.instrument_method(::MemCache, method_name) if defined? ::MemCache
      NewRelic::Agent::Instrumentation::Memcache.instrument_method(::Memcached, method_name) if defined? ::Memcached
      NewRelic::Agent::Instrumentation::Memcache.instrument_method(::Dalli::Client, method_name) if defined? ::Dalli::Client
    end
  end
end