/**
 * 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.hive.service.cli;

/**
 * CLIServiceUtils.
 *
 */
public class CLIServiceUtils {


  private static final char SEARCH_STRING_ESCAPE = '\\';

  /**
   * Convert a SQL search pattern into an equivalent Java Regex.
   *
   * @param pattern input which may contain '%' or '_' wildcard characters, or
   * these characters escaped using {@link #getSearchStringEscape()}.
   * @return replace %/_ with regex search characters, also handle escaped
   * characters.
   */
  public static String patternToRegex(String pattern) {
    if (pattern == null) {
      return ".*";
    } else {
      StringBuilder result = new StringBuilder(pattern.length());

      boolean escaped = false;
      for (int i = 0, len = pattern.length(); i < len; i++) {
        char c = pattern.charAt(i);
        if (escaped) {
          if (c != SEARCH_STRING_ESCAPE) {
            escaped = false;
          }
          result.append(c);
        } else {
          if (c == SEARCH_STRING_ESCAPE) {
            escaped = true;
            continue;
          } else if (c == '%') {
            result.append(".*");
          } else if (c == '_') {
            result.append('.');
          } else {
            result.append(Character.toLowerCase(c));
          }
        }
      }
      return result.toString();
    }
  }

}
