001// ***************************************************************************************************************************
002// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
003// * distributed with this work for additional information regarding copyright ownership.  The ASF licenses this file        *
004// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance            *
005// * with the License.  You may obtain a copy of the License at                                                              *
006// *                                                                                                                         *
007// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
008// *                                                                                                                         *
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010// * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the License for the        *
011// * specific language governing permissions and limitations under the License.                                              *
012// ***************************************************************************************************************************
013package org.apache.juneau.svl.vars;
014
015import static org.apache.juneau.internal.ThrowableUtils.*;
016
017import org.apache.juneau.svl.*;
018
019/**
020 * A basic if-else logic variable resolver.
021 * 
022 * <p>
023 * The format for this var is one of the following:
024 * <ul>
025 *    <li><js>"$IF{booleanArg,thenValue}"</js>
026 *    <li><js>"$IF{booleanArg,thenValue,elseValue}"</js>
027 * </ul>
028 * 
029 * <p>
030 * The boolean argument is any string.
031 * <br>The following values are interpreted as <jk>true</jk>:  <js>"true"</js>,<js>"TRUE"</js>,<js>"t"</js>,
032 * <js>"T"</js>,<js>"1"</js>.
033 * <br>All else are interpreted as <jk>false</jk>
034 * 
035 * <h5 class='section'>Example:</h5>
036 * <p class='bcode'>
037 *    <jc>// Create a variable resolver that resolves system properties and $IF vars.</jc>
038 *    VarResolver r = VarResolver.<jsm>create</jsm>().vars(IfVar.<jk>class</jk>, SystemPropertiesVar.<jk>class</jk>).build();
039 * 
040 *    <jc>// Use it!</jc>
041 *    System.<jsf>out</jsf>.println(r.resolve(<js>"Property $IF{$S{someBooleanFlag},IS,IS NOT} set!"</js>));
042 * </p>
043 * 
044 * <p>
045 * Since this is a {@link MultipartVar}, any variables contained in the result will be recursively resolved.
046 * <br>Likewise, if the arguments contain any variables, those will be resolved before they are passed to this var.
047 * 
048 * <h5 class='section'>See Also:</h5>
049 * <ul>
050 *    <li class='link'><a class="doclink" href="../../../../../overview-summary.html#juneau-svl.SvlVariables">Overview &gt; juneau-svl &gt; SVL Variables</a>
051 * </ul>
052 */
053public class IfVar extends MultipartVar {
054
055   /** The name of this variable. */
056   public static final String NAME = "IF";
057
058   /**
059    * Constructor.
060    */
061   public IfVar() {
062      super(NAME);
063   }
064
065   @Override /* MultipartVar */
066   public String resolve(VarResolverSession session, String[] args) {
067      if (args.length < 2 || args.length > 3)
068         illegalArg("Invalid number of arguments passed to $IF var.  Must be either $IF{booleanArg,thenValue} or $IF{booleanArg,thenValue,elseValue}");
069
070      String b = args[0].toLowerCase();
071      if ("1".equals(b) || "t".equals(b) || "true".equals(b))
072         return args[1];
073      return args.length == 2 ? "" : args[2];
074   }
075}