001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.juneau.svl.vars;
018
019import static org.apache.juneau.commons.utils.AssertionUtils.*;
020import static org.apache.juneau.commons.utils.StringUtils.*;
021
022import java.util.regex.*;
023
024import org.apache.juneau.svl.*;
025
026/**
027 * A basic switch/case logic variable resolver.
028 *
029 * <p>
030 * The format for this var is one of the following:
031 * <ul>
032 *    <li><js>"$SW{stringArg, pattern:thenValue[, pattern:thenValue...]}"</js>
033 *    <li>...
034 * </ul>
035 *
036 * <p>
037 * The pattern can be any string optionally containing <js>'*'</js> or <js>'?'</js> representing any or one character
038 * respectively.
039 *
040 * <h5 class='section'>Example:</h5>
041 * <p class='bjava'>
042 *    <jc>// Create a variable resolver that resolves system properties and $SW vars.</jc>
043 *    VarResolver <jv>varResolver</jv> = VarResolver.<jsm>create</jsm>().vars(SwitchVar.<jk>class</jk>, SystemPropertiesVar.<jk>class</jk>).build();
044 *
045 *    <jc>// Use it!</jc>
046 *    System.<jsf>out</jsf>.println(<jv>varResolver</jv>.resolve(<js>"We are running on $SW{$P{os.name},*win*:Windows,*:Something else}!"</js>));
047 * </p>
048 *
049 * <p>
050 * Since this is a {@link MultipartVar}, any variables contained in the result will be recursively resolved.
051 * <br>Likewise, if the arguments contain any variables, those will be resolved before they are passed to this var.
052 *
053 * <h5 class='section'>See Also:</h5><ul>
054 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/SimpleVariableLanguageBasics">Simple Variable Language Basics</a>
055 * </ul>
056 */
057public class SwitchVar extends MultipartVar {
058
059   /** The name of this variable. */
060   public static final String NAME = "SW";
061
062   /**
063    * Constructor.
064    */
065   public SwitchVar() {
066      super(NAME);
067   }
068
069   @Override /* Overridden from MultipartVar */
070   public String resolve(VarResolverSession session, String[] args) {
071      assertArg(args.length >= 2, "Invalid number of arguments passed to $SW var.  Must have 2 or more arguments.");
072
073      String stringArg = args[0];
074      for (var i = 1; i < args.length; i++) {
075         String pattern = args[i];
076
077         String[] parts = splita(pattern, ':', 2);
078         assertArg(parts.length >= 2, "Invalid arguments passed to $SW var.  Each case statement must contains 'pattern:value'.");
079
080         var p = Pattern.compile(parts[0].replace("*", ".*").replace("?", "."));
081         if (p.matcher(stringArg).matches())
082            return parts[1];
083      }
084
085      // Nothing matched and no else clause.
086      return "";
087   }
088}