/*
 * Copyright 2017 Sai Pullabhotla.
 *
 * 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 com.jmethods.catatumbo.mappers;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;
import java.util.Locale;

import com.google.cloud.datastore.NullValue;
import com.google.cloud.datastore.StringValue;
import com.google.cloud.datastore.Value;
import com.google.cloud.datastore.ValueBuilder;
import com.jmethods.catatumbo.Mapper;
import com.jmethods.catatumbo.MappingException;

/**
 * An implementation of {@link Mapper} for mapping {@link LocalDateTime} to/from Cloud Datastore.
 * {@link LocalDateTime} types are mapped to String type in the Cloud Datastore.
 * {@link LocalDateTime} objects are persisted into the datastore with a nano-second precision in
 * the <code>uuuu-MM-dd'T'HH:mm:ss.nnnnnnnnn</code> format.
 * 
 * @author Sai Pullabhotla
 *
 */
public class LocalDateTimeMapper implements Mapper {

  /**
   * The formatter to use for converting LocalTime to String and vice versa.
   */
  public static final DateTimeFormatter FORMATTER = DateTimeFormatter
      .ofPattern("uuuu-MM-dd'T'HH:mm:ss.nnnnnnnnn", Locale.ENGLISH);

  @Override
  public ValueBuilder<?, ?, ?> toDatastore(Object input) {
    if (input == null) {
      return NullValue.newBuilder();
    }
    return StringValue.newBuilder(((LocalDateTime) input).format(FORMATTER));
  }

  @Override
  public Object toModel(Value<?> input) {
    if (input instanceof NullValue) {
      return null;
    }
    try {
      return LocalDateTime.parse(((StringValue) input).get(), FORMATTER);
    } catch (ClassCastException exp) {
      String pattern = "Mapping of type %s to %s is not supported";
      throw new MappingException(
          String.format(pattern, input.getClass().getName(), LocalDateTime.class.getName()), exp);
    } catch (DateTimeParseException exp) {
      throw new MappingException(exp);
    }
  }

}