static List parse()

in java/tsfile/src/main/java/org/apache/tsfile/common/regexp/LikeMatcher.java [186:260]
63 lines of code
20 McCabe index (conditional complexity)

  static List<Pattern> parse(String pattern, Optional<Character> escape) {
    List<Pattern> result = new ArrayList<>();

    StringBuilder literal = new StringBuilder();
    int anyCount = 0;
    boolean anyUnbounded = false;
    boolean inEscape = false;
    for (int i = 0; i < pattern.length(); i++) {
      char character = pattern.charAt(i);

      if (inEscape) {
        if (character != '%' && character != '_' && character != escape.get()) {
          throw new IllegalArgumentException(
              "Escape character must be followed by '%', '_' or the escape character itself");
        }

        literal.append(character);
        inEscape = false;
      } else if (escape.isPresent() && character == escape.get()) {
        inEscape = true;

        if (anyCount != 0) {
          result.add(new Any(anyCount));
          anyCount = 0;
        }

        if (anyUnbounded) {
          result.add(new ZeroOrMore());
          anyUnbounded = false;
        }
      } else if (character == '%' || character == '_') {
        if (literal.length() != 0) {
          result.add(new Literal(literal.toString()));
          literal.setLength(0);
        }

        if (character == '%') {
          anyUnbounded = true;
        } else {
          anyCount++;
        }
      } else {
        if (anyCount != 0) {
          result.add(new Any(anyCount));
          anyCount = 0;
        }

        if (anyUnbounded) {
          result.add(new ZeroOrMore());
          anyUnbounded = false;
        }

        literal.append(character);
      }
    }

    if (inEscape) {
      throw new IllegalArgumentException(
          "Escape character must be followed by '%', '_' or the escape character itself");
    }

    if (literal.length() != 0) {
      result.add(new Literal(literal.toString()));
    } else {
      if (anyCount != 0) {
        result.add(new Any(anyCount));
      }

      if (anyUnbounded) {
        result.add(new ZeroOrMore());
      }
    }

    return result;
  }