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 org.apache.juneau.common.utils.*;
020import org.apache.juneau.svl.*;
021
022/**
023 * A basic if-else logic variable resolver.
024 *
025 * <p>
026 * The format for this var is one of the following:
027 * <ul>
028 *    <li><js>"$IF{booleanArg,thenValue}"</js>
029 *    <li><js>"$IF{booleanArg,thenValue,elseValue}"</js>
030 * </ul>
031 *
032 * <p>
033 * The boolean argument is any string.
034 * <br>The following values are interpreted as <jk>true</jk>:  <js>"true"</js>,<js>"TRUE"</js>,<js>"t"</js>,
035 * <js>"T"</js>,<js>"1"</js>.
036 * <br>All else are interpreted as <jk>false</jk>
037 *
038 * <h5 class='section'>Example:</h5>
039 * <p class='bjava'>
040 *    <jc>// Create a variable resolver that resolves system properties and $IF vars.</jc>
041 *    VarResolver <jv>varResolver</jv> = VarResolver.<jsm>create</jsm>().vars(IfVar.<jk>class</jk>, SystemPropertiesVar.<jk>class</jk>).build();
042 *
043 *    <jc>// Use it!</jc>
044 *    System.<jsf>out</jsf>.println(<jv>varResolver</jv>.resolve(<js>"Property $IF{$S{someBooleanFlag},IS,IS NOT} set!"</js>));
045 * </p>
046 *
047 * <p>
048 * Since this is a {@link MultipartVar}, any variables contained in the result will be recursively resolved.
049 * <br>Likewise, if the arguments contain any variables, those will be resolved before they are passed to this var.
050 *
051 * <h5 class='section'>See Also:</h5><ul>
052 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/SimpleVariableLanguageBasics">Simple Variable Language Basics</a>
053 * </ul>
054 */
055public class IfVar extends MultipartVar {
056
057   /** The name of this variable. */
058   public static final String NAME = "IF";
059
060   /**
061    * Constructor.
062    */
063   public IfVar() {
064      super(NAME);
065   }
066
067   @Override /* MultipartVar */
068   public String resolve(VarResolverSession session, String[] args) {
069      Utils.assertArg(args.length >= 2 && args.length <= 3, "Invalid number of arguments passed to $IF var.  Must be either $IF{booleanArg,thenValue} or $IF{booleanArg,thenValue,elseValue}");
070
071      String b = args[0].toLowerCase();
072      if ("1".equals(b) || "t".equals(b) || "true".equals(b))
073         return args[1];
074      return args.length == 2 ? "" : args[2];
075   }
076}