/*
    *    Copyright 2009-2021 the original author or authors.
    *
    *    Licensed 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.ibatis.parsing;
  
  /**
   * @author Clinton Begin
   */
  public class GenericTokenParser {
  
    private final String openToken;
    private final String closeToken;
    private final TokenHandler handler;
  
    public GenericTokenParser(String openToken, String closeToken, TokenHandler handler) {
      this.openToken = openToken;
      this.closeToken = closeToken;
      this.handler = handler;
    }
  
    public String parse(String text) {
      if (text == null || text.isEmpty()) {
        return "";
      }
      // search open token
      int start = text.indexOf(openToken);
      if (start == -1) {
        return text;
      }
      char[] src = text.toCharArray();
      int offset = 0;
      final StringBuilder builder = new StringBuilder();
      StringBuilder expression = null;
      do {
        if (start > 0 && src[start - 1] == '\\') {
          // this open token is escaped. remove the backslash and continue.
          builder.append(src, offset, start - offset - 1).append(openToken);
          offset = start + openToken.length();
        } else {
          // found open token. let's search close token.
          if (expression == null) {
            expression = new StringBuilder();
          } else {
            expression.setLength(0);
          }
          builder.append(src, offset, start - offset);
          offset = start + openToken.length();
          int end = text.indexOf(closeToken, offset);
          while (end > -1) {
            if (end > offset && src[end - 1] == '\\') {
              // this close token is escaped. remove the backslash and continue.
              expression.append(src, offset, end - offset - 1).append(closeToken);
              offset = end + closeToken.length();
              end = text.indexOf(closeToken, offset);
            } else {
              expression.append(src, offset, end - offset);
              break;
            }
          }
          if (end == -1) {
            // close token was not found.
            builder.append(src, start, src.length - start);
            offset = src.length;
          } else {
            builder.append(handler.handleToken(expression.toString()));
            offset = end + closeToken.length();
          }
        }
        start = text.indexOf(openToken, offset);
      } while (start > -1);
      if (offset < src.length) {
        builder.append(src, offset, src.length - offset);
      }
      return builder.toString();
    }
  }