/*
    * 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.logging.log4j.core.appender.db.jpa.converter;
  
  import java.io.IOException;
  import java.util.List;
  
  import javax.persistence.AttributeConverter;
  import javax.persistence.Converter;
  import javax.persistence.PersistenceException;
  
  import org.apache.logging.log4j.ThreadContext;
  import org.apache.logging.log4j.spi.DefaultThreadContextStack;
  import org.apache.logging.log4j.util.Strings;
  
  import com.fasterxml.jackson.core.type.TypeReference;
  
  /**
   * A JPA 2.1 attribute converter for 
   * {@link org.apache.logging.log4j.ThreadContext.ContextStack ThreadContext.ContextStack}s in
   * {@link org.apache.logging.log4j.core.LogEvent}s. This converter is capable of converting both to and from
   * {@link String}s.
   *
   * In addition to other optional dependencies required by the JPA appender, this converter requires the Jackson Data
   * Processor.
   */
  @Converter(autoApply = false)
  public class ContextStackJsonAttributeConverter implements AttributeConverter<ThreadContext.ContextStack, String> {
      @Override
      public String convertToDatabaseColumn(final ThreadContext.ContextStack contextStack) {
          if (contextStack == null) {
              return null;
          }
  
          try {
              return ContextMapJsonAttributeConverter.OBJECT_MAPPER.writeValueAsString(contextStack.asList());
          } catch (final IOException e) {
              throw new PersistenceException("Failed to convert stack list to JSON string.", e);
          }
      }
  
      @Override
      public ThreadContext.ContextStack convertToEntityAttribute(final String s) {
          if (Strings.isEmpty(s)) {
              return null;
          }
  
          List<String> list;
          try {
              list = ContextMapJsonAttributeConverter.OBJECT_MAPPER.readValue(s, new TypeReference<List<String>>() { });
          } catch (final IOException e) {
              throw new PersistenceException("Failed to convert JSON string to list for stack.", e);
          }
  
          final DefaultThreadContextStack result = new DefaultThreadContextStack(true);
          result.addAll(list);
          return result;
      }
  }