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/* $Id: RegexInfixPatternCompiler.java 369 2007-11-12 18:50:49Z hohwille $
 * Copyright (c) The m-m-m Team, Licensed under the Apache License, Version 2.0
 * http://www.apache.org/licenses/LICENSE-2.0 */
package net.sf.mmm.util.pattern;

import java.util.regex.Pattern;

/**
 * This implementation of the {@link PatternCompiler} interface compiles the
 * pattern given as string in a way similar to GNU-utilities like
 * sed or grep. This means that if no leading "^"
 * (or ".*") or no trailing "$" (or ".*") is present, an according ".*" prefix
 * and suffix is added implicit. This causes that "\.xml$" matches "config.xml"
 * and "^/etc/" matches "/etc/passwd".

 * ATTENTION:

 * On the {@link Pattern#matcher(CharSequence) matcher} of the produced
 * {@link Pattern} you may want to use {@link java.util.regex.Matcher#find()}
 * instead of {@link java.util.regex.Matcher#matches()}.
 * 
 * @author Joerg Hohwiller (hohwille at users.sourceforge.net)
 */
public class RegexInfixPatternCompiler extends RegexPatternCompiler {

  /** A singleton instance of this implementation. */
  public static final PatternCompiler INSTANCE = new RegexInfixPatternCompiler();

  /**
   * The constructor.
   */
  public RegexInfixPatternCompiler() {

    super();
  }

  /**
   * The constructor.
   * 
   * @param flags are the {@link Pattern#compile(String, int) compiler flags}.
   */
  public RegexInfixPatternCompiler(int flags) {

    super(flags);
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public Pattern compile(String pattern) throws IllegalArgumentException {

    StringBuilder buffer = new StringBuilder(pattern.length() + 4);
    if (!pattern.startsWith("^") && !pattern.startsWith(".*")) {
      buffer.append(".*");
    }
    buffer.append(pattern);
    if (!pattern.endsWith("$") && !pattern.endsWith(".*")) {
      buffer.append(".*");
    }
    return super.compile(buffer.toString());
  }

}