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package org.apache.juneau.svl.vars;

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

import java.util.regex.*;

import org.apache.juneau.internal.*;
import org.apache.juneau.svl.*;

/**
 * A basic switch/case logic variable resolver.
 * 
 * <p>
 * The format for this var is one of the following:
 * <ul>
 *    <li><js>"$SW{stringArg, pattern:thenValue[, pattern:thenValue...]}"</js>
 *    <li>...
 * </ul>
 * 
 * <p>
 * The pattern can be any string optionally containing <js>'*'</js> or <js>'?'</js> representing any or one character
 * respectively.
 * 
 * <h5 class='section'>Example:</h5>
 * <p class='bcode'>
 *    <jc>// Create a variable resolver that resolves system properties and $SW vars.</jc>
 *    VarResolver r = VarResolver.<jsm>create</jsm>().vars(SwitchVar.<jk>class</jk>, SystemPropertiesVar.<jk>class</jk>).build();
 * 
 *    <jc>// Use it!</jc>
 *    System.<jsf>out</jsf>.println(r.resolve(<js>"We are running on $SW{$P{os.name},*win*:Windows,*:Something else}!"</js>));
 * </p>
 * 
 * <p>
 * Since this is a {@link MultipartVar}, any variables contained in the result will be recursively resolved.
 * <br>Likewise, if the arguments contain any variables, those will be resolved before they are passed to this var.
 * 
 * <h5 class='section'>See Also:</h5>
 * <ul>
 *    <li class='link'><a class="doclink" href="../../../../../overview-summary.html#juneau-svl.SvlVariables">Overview &gt; juneau-svl &gt; SVL Variables</a>
 * </ul>
 */
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 < 2)
         illegalArg("Invalid number of arguments passed to $SW var.  Must have 2 or more arguments.");

      String stringArg = args[0];
      for (int i = 1; i < args.length; i++) {
         String pattern = args[i];
         
         String[] parts = StringUtils.split(pattern, ':', 2);
         if (parts.length < 2)
            illegalArg("Invalid arguments passed to $SW var.  Each case statement must contains 'pattern:value'.");
         
         Pattern p = Pattern.compile(parts[0].replace("*", ".*").replace("?", "."));
         if (p.matcher(stringArg).matches())
            return parts[1];
      }

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