text: /*******************************************************************************
   * Copyright 2015 IBM Corp.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   *******************************************************************************/
  var Probe = require('../lib/probe.js');
  var aspect = require('../lib/aspect.js');
  var request = require('../lib/request.js');
  var util = require('util');
  var am = require('..');
  
  function MemcachedProbe() {
  	Probe.call(this, 'memcached');
  }
  util.inherits(MemcachedProbe, Probe);
  
  MemcachedProbe.prototype.attach = function(name, target) {
  	var that = this;
  	if( name != "memcached" ) return target;
  	target.__ddProbeAttached__ = true;
  
  	var methods = [
  	// args: key, callback
  	'get', 'gets', 'getMulti',
  	// args: key, value, lifetime, callback
  	'set', 'replace', 'add',
  	// args: key, value, lifetime, cas, callback
  	'cas',
  	// args: key, value, callback
  	'append', 'prepend',
  	// args: key, amount, callback
  	'increment', 'decrement', 'incr', 'decr',
  	// args: key, callback
  	'touch',
  	// args: key, lifetime, callback
  	'del', 'delete'
  	// args: callback
  	// 'version', 'flush', 'samples', 'slabs', 'items'
  	];
  
  	aspect.around(target.prototype, methods,
  		function(target, methodName, methodArgs, context) {
  			that.metricsProbeStart(context, methodName, methodArgs);
  			that.requestProbeStart(context, methodName, methodArgs);
  			aspect.aroundCallback(methodArgs, context,
  				function(target, callbackArgs, context) {
  
  					//Call the transaction link with a name and the callback for strong trace
  					var callbackPosition = aspect.findCallbackArg(methodArgs);
  					if (typeof(callbackPosition) != 'undefined') {
  						aspect.strongTraceTransactionLink('memcached: ', methodName, methodArgs[callbackPosition]);
  					}
  					
  					that.metricsProbeEnd(context, methodName, methodArgs);
  					that.requestProbeEnd(context, methodName, methodArgs);
  				}
  			);
  		}, function (target, methodName, methodArgs, context, rc) {
  			if (aspect.findCallbackArg(methodArgs) == undefined) {
  				that.metricsProbeEnd(context, methodName, methodArgs);
  				that.requestProbeEnd(context, methodName, methodArgs);
  			}
  			return rc;
  		}
  	);
      return target;
  };
  
  /*
   * Lightweight metrics probe for Memcached data store
   * 
   * These provide:
   * 		time:		time event started
   * 		method:		the API method/function being used
   * 		key:		The data key being used
   * 		duration:	the time for the request to respond
   */
  MemcachedProbe.prototype.metricsEnd = function(context, method, methodArgs) {
      if(context && context.timer) {
  	    context.timer.stop();
  	    am.emit('memcached', {time: context.timer.startTimeMillis, method: method, key: methodArgs[0], duration: context.timer.timeDelta});
      }
  };
  
  /*
   * Heavyweight request probes for Memcached data store
   */
  MemcachedProbe.prototype.requestStart = function (context, methodName, methodArgs) {
  	context.req = request.startRequest( 'memcached', methodName, false, context.timer);
  };
  
  MemcachedProbe.prototype.requestEnd = function (context, methodName, methodArgs) {
      if(context && context.req)
  	    context.req.stop({key: methodArgs[0]});
  };
  
  module.exports = MemcachedProbe;
  