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// ***************************************************************************************************************************
// * 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.juneau.svl.vars;

import static org.apache.juneau.internal.ThrowableUtils.*;

import java.util.regex.*;

import org.apache.juneau.svl.*;

/**
 * A basic switch/case logic variable resolver.
 *
 * 
 * The format for this var is one of the following:
 * 

 * 	"$SW{stringArg,pattern,thenValue}"
 * 	
"$SW{stringArg,pattern,thenValue,elseValue}"
 * 	
"$SW{stringArg,pattern,thenValue,pattern,thenValue}"
 * 	
"$SW{stringArg,pattern,thenValue,pattern,thenValue,elsePattern}"
 * 	
...
 * 
 *
 * 
 * The pattern can be any string optionally containing '*' or '?' representing any or one character
 * respectively.
 *
 * 
Example:
 * 
 * 	// Create a variable resolver that resolves system properties and $SW vars.
 * 	VarResolver r = new VarResolver().addVars(SwitchVar.class, SystemPropertiesVar.class);
 *
 * 	// Use it!
 * 	System.out.println(r.resolve("We are running on $SW{$P{os.name},*win*,Windows,Something else}!"));
 * 
 *
 * 
 * Since this is a {@link MultipartVar}, any variables contained in the result will be recursively resolved.
 * Likewise, if the arguments contain any variables, those will be resolved before they are passed to this var.
 */
public class SwitchVar extends MultipartVar {

	/** The name of this variable. */
	public static final String NAME = "SW";

	/**
	 * Constructor.
	 */
	public SwitchVar() {
		super(NAME);
	}

	@Override /* MultipartVar */
	public String resolve(VarResolverSession session, String[] args) {
		if (args.length < 3)
			illegalArg("Invalid number of arguments passed to $SW var.  Must have 3 or more arguments.");

		String stringArg = args[0];
		for (int i = 1; i < args.length;) {
			String pattern = args[i++];
			if (args.length == i)
				return pattern;  // We've reached an else.

			Pattern p = Pattern.compile(pattern.replace("*", ".*").replace("?", "."));
			if (p.matcher(stringArg).matches())
				return args[i];
			i++;
		}

		// Nothing matched and no else clause.
		return "";
	}
}