/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 * 
 */

package org.apache.jmeter.functions;

import java.util.Collection;
import java.util.List;

import org.apache.jmeter.samplers.SampleResult;
import org.apache.jmeter.samplers.Sampler;

/**
 * Methods that a function must implement
 */
public interface Function {
	/**
	 * Given the previous SampleResult and the current Sampler, return a string
	 * to use as a replacement value for the function call. Assume
	 * "setParameter" was previously called.
	 * 
	 * This method must be threadsafe - multiple threads will be using the same
	 * object.
	 */
	public String execute(SampleResult previousResult, Sampler currentSampler) throws InvalidVariableException;

	/**
	 * A collection of the parameters used to configure your function. Each
	 * parameter is a CompoundFunction and can be resolved by calling the
	 * execute() method of the CompoundFunction (which should be done at
	 * execution.)
	 * 
	 * @param parameters
	 * @throws InvalidVariableException
	 */
	public void setParameters(Collection parameters) throws InvalidVariableException;

	/**
	 * Return the name of your function. Convention is to prepend "__" to the
	 * name (ie "__regexFunction")
	 */
	public String getReferenceKey();

	/**
	 * Return a list of strings briefly describing each parameter your function
	 * takes. Please use JMeterUtils.getResString(resource_name) to grab a
	 * resource string. Otherwise, your help text will be difficult to
	 * internationalize.
	 * 
	 * This list is not optional. If you don't wish to write help, you must at
	 * least return a List containing the correct number of blank strings, one
	 * for each argument.
	 */
	public List getArgumentDesc();
}
