/*
    * 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.Iterator;
  import java.util.Map;
  import javax.persistence.AttributeConverter;
  import javax.persistence.Converter;
  import javax.persistence.PersistenceException;
  
  import org.apache.logging.log4j.util.ReadOnlyStringMap;
  import org.apache.logging.log4j.core.impl.ContextDataFactory;
  import org.apache.logging.log4j.util.StringMap;
  import org.apache.logging.log4j.util.BiConsumer;
  import org.apache.logging.log4j.util.Strings;
  
  import com.fasterxml.jackson.databind.JsonNode;
  import com.fasterxml.jackson.databind.ObjectMapper;
  import com.fasterxml.jackson.databind.node.JsonNodeFactory;
  import com.fasterxml.jackson.databind.node.ObjectNode;
  
  /**
   * A JPA 2.1 attribute converter for {@link ReadOnlyStringMap}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 ContextDataJsonAttributeConverter implements AttributeConverter<ReadOnlyStringMap, String> {
      static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();
  
      @Override
      public String convertToDatabaseColumn(final ReadOnlyStringMap contextData) {
          if (contextData == null) {
              return null;
          }
  
          try {
              final JsonNodeFactory factory = OBJECT_MAPPER.getNodeFactory();
              final ObjectNode root = factory.objectNode();
              contextData.forEach(new BiConsumer<String, Object>() {
                  @Override
                  public void accept(final String key, final Object value) {
                      // we will cheat here and write the toString of the Object... meh, but ok.
                      root.put(key, String.valueOf(value));
                  }
              });
              return OBJECT_MAPPER.writeValueAsString(root);
          } catch (final Exception e) {
              throw new PersistenceException("Failed to convert contextData to JSON string.", e);
          }
      }
  
      @Override
      public ReadOnlyStringMap convertToEntityAttribute(final String s) {
          if (Strings.isEmpty(s)) {
              return null;
          }
          try {
              final StringMap result = ContextDataFactory.createContextData();
              final ObjectNode root = (ObjectNode) OBJECT_MAPPER.readTree(s);
              final Iterator<Map.Entry<String, JsonNode>> entries = root.fields();
              while (entries.hasNext()) {
                  final Map.Entry<String, JsonNode> entry = entries.next();
  
                  // Don't know what to do with non-text values.
                  // Maybe users who need this need to provide custom converter?
                  final Object value = entry.getValue().textValue();
                  result.putValue(entry.getKey(), value);
              }
              return result;
          } catch (final IOException e) {
              throw new PersistenceException("Failed to convert JSON string to map.", e);
          }
      }
  }