# encoding: utf-8

require 'one_apm/agent/datastore/metric_helper'

module OneApm
  module Agent
    module Instrumentation
      module Memcache
        module_function

        def enabled?
          !OneApm::Manager.config[:disable_memcache]
        end

        METHODS = [:get, :get_multi, :set, :add, :incr, :decr, :delete, :replace, :append,
                   :prepend, :cas, :single_get, :multi_get, :single_cas, :multi_cas]

        def supported_methods_for(client_class, methods)
          methods.select do |method_name|
            client_class.method_defined?(method_name) || client_class.private_method_defined?(method_name)
          end
        end

        def instrument_methods(client_class, requested_methods = METHODS)
          supported_methods_for(client_class, requested_methods).each do |method_name|

            visibility = OneApm::Helper.instance_method_visibility client_class, method_name
            method_name_without = :"#{method_name}_without_oneapm_trace"

            client_class.class_eval do
              alias_method method_name_without, method_name

              define_method method_name do |*args, &block|
                metrics = Datastore::MetricHelper.metrics_for("Memcached", method_name)

                OneApm::Support::MethodTracer.trace_execution_scoped(metrics) do
                  t0 = Time.now
                  begin
                    send method_name_without, *args, &block
                  ensure
                    if OneApm::Manager.config[:capture_memcache_keys]
                      OneApm::Manager.agent.transaction_sampler.notice_nosql(args.first.inspect, (Time.now - t0).to_f) rescue nil
                    end
                  end
                end
              end

              send visibility, method_name
              send visibility, method_name_without
            end
          end
        end

      end
    end
  end
end

LibraryDetection.defer do
  named :memcache_client

  depends_on do
    OneApm::Agent::Instrumentation::Memcache.enabled?
  end

  depends_on do
    defined?(::MemCache)
  end

  executes do
    OneApm::Manager.logger.info 'Installing Memcached instrumentation for memcache-client gem'
    OneApm::Agent::Instrumentation::Memcache.instrument_methods(::MemCache)
  end
end

LibraryDetection.defer do
  named :memcached

  depends_on do
    OneApm::Agent::Instrumentation::Memcache.enabled?
  end

  depends_on do
    defined?(::Memcached)
  end

  executes do
    OneApm::Manager.logger.info 'Installing Memcached instrumentation for memcached gem'
    ::OneApm::Agent::Instrumentation::Memcache.instrument_methods(::Memcached)
  end
end

LibraryDetection.defer do
  named :dalli

  depends_on do
    OneApm::Agent::Instrumentation::Memcache.enabled?
  end

  depends_on do
    defined?(::Dalli::Client)
  end

  executes do
    OneApm::Manager.logger.info 'Installing Memcache instrumentation for dalli gem'
    ::OneApm::Agent::Instrumentation::Memcache.instrument_methods(::Dalli::Client)
  end
end

LibraryDetection.defer do
  named :dalli_cas_client

  depends_on do
    OneApm::Agent::Instrumentation::Memcache.enabled?
  end

  depends_on do
    # These CAS client methods are only optionally defined if users require
    # dalli/cas/client. Use a separate dependency block so it can potentially
    # re-evaluate after they've done that require.
    defined?(::Dalli::Client) &&
      ::OneApm::Agent::Instrumentation::Memcache.supported_methods_for(::Dalli::Client,
                                                                         CAS_CLIENT_METHODS).any?
  end

  CAS_CLIENT_METHODS = [:get_cas, :get_multi_cas, :set_cas, :replace_cas,
                        :delete_cas]

  executes do
    OneApm::Manager.logger.info 'Installing Dalli CAS Client Memcache instrumentation'
    ::OneApm::Agent::Instrumentation::Memcache.instrument_methods(::Dalli::Client,
                                                                    CAS_CLIENT_METHODS)
  end
end