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/*
* Copyright 2018 Nafundi
*
* 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.
*/
package org.javarosa.xform.parse;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* This class contains all the code needed to implement the xform randomize()
* function.
*/
public final class RandomizeHelper {
private static final Pattern CHOICE_FILTER_PATTERN = Pattern.compile("randomize\\((.+?),?([^,)\\]]+?)?\\)");
/**
* Cleans an xform randomize() expression to leave only its first argument, which
* should be an xpath expression.
*
* Can throw an {@link IllegalArgumentException} if the expression doesn't conform
* to an xform randomize() call.
*
* @param nodesetStr an xform randomize() expression
* @return a {@link String} with the first argument of the xform randomize() expression
*/
static String cleanNodesetDefinition(String nodesetStr) {
return getArgs(nodesetStr)[0].trim();
}
/**
* Cleans an xform randomize() expression to leave only its second argument, if it exists, which
* should be a number or an xpath expression, or null if there's no second argument present
*
* Can throw an {@link IllegalArgumentException} if the expression doesn't conform
* to an xform randomize() call.
*
* @param nodesetStr an xform randomize() expression
* @return a {@link String} with the second argument of the xform randomize() expression, or
* null, if there's no second argument present
*/
static String cleanSeedDefinition(String nodesetStr) {
String[] args = getArgs(nodesetStr);
return args.length > 1 ? args[1].trim() : null;
}
/**
* This method will return a new list with the same elements, randomly reordered.
* Every call to this method will produce a different random seed, which will
* potentially produce a different ordering each time.
*
* @param elements {@link List} of elements of type T to be shuffled
* @param Type of the elements in the list
* @return a new {@link List} with the same input elements reordered
*/
public static List shuffle(List elements) {
return FisherYates.shuffle(elements);
}
/**
* This method will return a new list with the same elements, randomly reordered.
* Given the same seed, calls to this method will produce exactly the same output.
*
* @param elements {@link List} of elements of type T to be shuffled
* @param seed {@link Long} seed for the Random number generator
* @param Type of the elements in the list
* @return a new {@link List} with the same input elements reordered
*/
public static List shuffle(List elements, Long seed) {
return seed == null ? FisherYates.shuffle(elements) : FisherYates.shuffle(elements, seed);
}
private static String[] getArgs(String nodesetStr) {
nodesetStr = nodesetStr.trim();
if (!nodesetStr.startsWith("randomize(") || !nodesetStr.endsWith(")"))
throw new IllegalArgumentException("Nodeset definition must use randomize(path, seed?) function");
if (!nodesetStr.contains("["))
return nodesetStr.substring(10, nodesetStr.length() - 1).split(",");
Matcher matcher = CHOICE_FILTER_PATTERN.matcher(nodesetStr);
if (!matcher.matches())
throw new IllegalArgumentException("Can't parse the Nodeset definition");
String nodeset = matcher.group(1);
String seed = matcher.group(2);
return seed != null ? new String[]{nodeset, seed} : new String[]{nodeset};
}
}