Glob Java

Glob.java

import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

public class Glob {
  public static Glob compile(String pattern) {
    return new Glob(Pattern.compile(globToRegex(pattern)));
  }
  
  private final Pattern pattern;
  
  private Glob(Pattern pattern) {
    this.pattern = pattern;
  }
  
  public boolean matches(CharSequence input) {
    return pattern.matcher(input).matches();
  }
  
  private static final String REGEX_META = ".^$+{[]|()";
  private static final String GLOB_META = "\\*?{";

  
  
  static String globToRegex(final String glob) {

    CharIterator chars = new CharIterator(glob);
    boolean inGroup = false;
    StringBuilder regex = new StringBuilder("^");

    while (chars.hasNext()) {
      char c = chars.next();
      switch (c) {
        case '\\':
          if (!chars.hasNext()) {
            throw new PatternSyntaxException("No character to escape", glob, chars.index - 1);
          }
          char next = chars.next();
          if (GLOB_META.indexOf(next) >= 0 || REGEX_META.indexOf(next) >= 0) {
            regex.append('\\');
          }
          regex.append(next);
          break;
        case '/':
          regex.append('/');
          break;
        case '{':
          if (inGroup) {
            throw new PatternSyntaxException("Cannot nest groups", glob, chars.index - 1);
          }
          regex.append("(?:(?:");
          inGroup = true;
          break;
        case '}':
          if (inGroup) {
            regex.append("))");
            inGroup = false;
          } else {
            regex.append('}');
          }
          break;
        case ',':
          if (inGroup) {
            regex.append(")|(?:");
          } else {
            regex.append(',');
          }
          break;
        case '*':
          if (chars.peekNext() == '*') {
            regex.append(".*");
            chars.next();
          } else {
            regex.append("[^/]*");
          }
          break;
        case '?':
          regex.append("[^/]");
          break;
        default:
          if (REGEX_META.indexOf(c) >= 0) {
            regex.append('\\');
          }
          regex.append(c);
      }
    }
    if (inGroup) {
      throw new PatternSyntaxException("Missing '}", glob, chars.index - 1);
    }
    return regex.append('$').toString();
  }

  private static class CharIterator {

    char[] chars;
    int index = 0;

    CharIterator(String s) {
      chars = s.toCharArray();
    }

    boolean hasNext() {
      return index < chars.length;
    }

    char next() {
      return chars[index++];
    }

    char peekNext() {
      return index + 1 < chars.length ? chars[index] : (char) 0xFFFF;
    }
  }
}