/**
 * 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.hadoop.hive.ql.udf.generic;

import java.sql.Timestamp;
import java.util.TimeZone;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.exec.UDFArgumentLengthException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.serde2.io.TimestampWritable;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.PrimitiveObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorConverter.TextConverter;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorConverter.TimestampConverter;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;
import org.apache.hadoop.io.Text;


public class GenericUDFFromUtcTimestamp extends GenericUDF {

  static final Log LOG = LogFactory.getLog(GenericUDFFromUtcTimestamp.class);

  private PrimitiveObjectInspector[] argumentOIs;
  private TimestampConverter timestampConverter;
  private TextConverter textConverter;

  @Override
  public ObjectInspector initialize(ObjectInspector[] arguments)
      throws UDFArgumentException {
    if (arguments.length < 2) {
      throw new UDFArgumentLengthException(
          "The function " + getName() + " requires at least two "
          + "argument, got " + arguments.length);
    }
    try {
      argumentOIs = new PrimitiveObjectInspector[2];
      argumentOIs[0] = (PrimitiveObjectInspector) arguments[0];
      if (arguments.length > 1) {
        argumentOIs[1] = (PrimitiveObjectInspector) arguments[1];
      }
    } catch (ClassCastException e) {
      throw new UDFArgumentException(
          "The function " + getName() + " takes only primitive types");
    }

    timestampConverter = new TimestampConverter(argumentOIs[0],
        PrimitiveObjectInspectorFactory.writableTimestampObjectInspector);
    textConverter = new TextConverter(argumentOIs[1]);
    return PrimitiveObjectInspectorFactory.javaTimestampObjectInspector;
  }

  @Override
  public Object evaluate(DeferredObject[] arguments) throws HiveException {
    Object o0 = arguments[0].get();
    TimeZone timezone = null;
    if (o0 == null) {
      return null;
    }

    if (arguments.length > 1 && arguments[1] != null) {
      Text text = textConverter.convert(arguments[1].get());
      if (text != null) {
        timezone = TimeZone.getTimeZone(text.toString());
      }
    } else {
      return null;
    }

    Timestamp timestamp = ((TimestampWritable) timestampConverter.convert(o0))
        .getTimestamp();

    int offset = timezone.getOffset(timestamp.getTime());
    if (invert()) {
      offset = -offset;
    }
    return applyOffset(offset, timestamp);
  }

  protected Timestamp applyOffset(long offset, Timestamp t) {
    long newTime = t.getTime() + offset;
    int nanos = (int) (t.getNanos() + (newTime % 1000) * 1000000);
    t.setTime(newTime);
    t.setNanos(nanos);

    return t;
  }

  @Override
  public String getDisplayString(String[] children) {
    StringBuilder sb = new StringBuilder();
    sb.append("Converting field ");
    sb.append(children[0]);
    sb.append(" from UTC to timezone: ");
    if (children.length > 1) {
      sb.append(children[1]);
    }
    return sb.toString();
  }

  public String getName() {
    return "from_utc_timestamp";
  }

  protected boolean invert() {
    return false;
  }
}