/*
    * 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.shardingsphere.mask.algorithm.cover;
  
  import com.google.common.base.Strings;
  import org.apache.shardingsphere.mask.algorithm.MaskAlgorithmPropertiesChecker;
  import org.apache.shardingsphere.mask.spi.MaskAlgorithm;
  
  import java.util.Properties;
  
  /**
   * Keep first n last m algorithm.
   */
  public final class KeepFirstNLastMMaskAlgorithm implements MaskAlgorithm<Object, String> {
      
      private static final String FIRST_N = "first-n";
      
      private static final String LAST_M = "last-m";
      
      private static final String REPLACE_CHAR = "replace-char";
      
      private Integer firstN;
      
      private Integer lastM;
      
      private Character replaceChar;
      
      @Override
      public void init(final Properties props) {
          firstN = createFirstN(props);
          lastM = createLastM(props);
          replaceChar = createReplaceChar(props);
      }
      
      private Integer createFirstN(final Properties props) {
          MaskAlgorithmPropertiesChecker.checkPositiveInteger(props, FIRST_N, this);
          return Integer.parseInt(props.getProperty(FIRST_N));
      }
      
      private Integer createLastM(final Properties props) {
          MaskAlgorithmPropertiesChecker.checkPositiveInteger(props, LAST_M, this);
          return Integer.parseInt(props.getProperty(LAST_M));
      }
      
      private Character createReplaceChar(final Properties props) {
          MaskAlgorithmPropertiesChecker.checkSingleChar(props, REPLACE_CHAR, this);
          return props.getProperty(REPLACE_CHAR).charAt(0);
      }
      
      @Override
      public String mask(final Object plainValue) {
          String result = null == plainValue ? null : String.valueOf(plainValue);
          if (Strings.isNullOrEmpty(result)) {
              return result;
          }
          if (result.length() < firstN + lastM) {
              return result;
          }
          char[] chars = result.toCharArray();
          for (int i = firstN; i < result.length() - lastM; i++) {
              chars[i] = replaceChar;
          }
          return new String(chars);
      }
      
      @Override
      public String getType() {
          return "KEEP_FIRST_N_LAST_M";
      }
  }