/*
 * 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.phoenix.expression.function;

import java.sql.SQLException;
import java.sql.Timestamp;
import java.util.List;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.phoenix.expression.CoerceExpression;
import org.apache.phoenix.expression.Expression;
import org.apache.phoenix.expression.LiteralExpression;
import org.apache.phoenix.parse.FunctionParseNode.Argument;
import org.apache.phoenix.parse.FunctionParseNode.BuiltInFunction;
import org.apache.phoenix.parse.FunctionParseNode.FunctionClassType;
import org.apache.phoenix.schema.SortOrder;
import org.apache.phoenix.schema.tuple.Tuple;
import org.apache.phoenix.schema.types.PDataType;
import org.apache.phoenix.schema.types.PDataType.PDataCodec;
import org.apache.phoenix.schema.types.PDate;
import org.apache.phoenix.schema.types.PInteger;
import org.apache.phoenix.schema.types.PTimestamp;
import org.apache.phoenix.schema.types.PUnsignedDate;
import org.apache.phoenix.schema.types.PUnsignedTimestamp;
import org.apache.phoenix.schema.types.PVarchar;

import org.apache.phoenix.thirdparty.com.google.common.collect.Lists;

/**
 * Class encapsulating the process for rounding off a column/literal of type
 * {@link org.apache.phoenix.schema.types.PTimestamp} This class only supports rounding off the
 * milliseconds that is for {@link TimeUnit#MILLISECOND}. If you want more options of rounding like
 * using {@link TimeUnit#HOUR} use {@link RoundDateExpression}
 * @since 3.0.0
 */
@BuiltInFunction(name = RoundFunction.NAME,
    args = { @Argument(allowedTypes = { PTimestamp.class }),
      @Argument(allowedTypes = { PVarchar.class, PInteger.class }, defaultValue = "null",
          isConstant = true),
      @Argument(allowedTypes = { PInteger.class }, defaultValue = "1", isConstant = true) },
    classType = FunctionClassType.DERIVED)
public class RoundTimestampExpression extends RoundDateExpression {

  private static final long HALF_OF_NANOS_IN_MILLI =
    java.util.concurrent.TimeUnit.MILLISECONDS.toNanos(1) / 2;

  public RoundTimestampExpression() {
  }

  public RoundTimestampExpression(List<Expression> children) {
    super(children);
  }

  public static Expression create(List<Expression> children) throws SQLException {
    Expression firstChild = children.get(0);
    PDataType firstChildDataType = firstChild.getDataType();
    String timeUnit = (String) ((LiteralExpression) children.get(1)).getValue();
    LiteralExpression multiplierExpr = (LiteralExpression) children.get(2);

    /*
     * When rounding off timestamp to milliseconds, nanos play a part only when the multiplier value
     * is equal to 1. This is because for cases when multiplier value is greater than 1, number of
     * nanos/multiplier will always be less than half the nanos in a millisecond.
     */
    if (
      (timeUnit == null || TimeUnit.MILLISECOND.toString().equalsIgnoreCase(timeUnit))
        && ((Number) multiplierExpr.getValue()).intValue() == 1
    ) {
      return new RoundTimestampExpression(children);
    }
    // Coerce TIMESTAMP to DATE, as the nanos has no affect
    List<Expression> newChildren = Lists.newArrayListWithExpectedSize(children.size());
    newChildren.add(CoerceExpression.create(firstChild,
      firstChildDataType == PTimestamp.INSTANCE ? PDate.INSTANCE : PUnsignedDate.INSTANCE));
    newChildren.addAll(children.subList(1, children.size()));
    return RoundDateExpression.create(newChildren);
  }

  @Override
  protected PDataCodec getKeyRangeCodec(PDataType columnDataType) {
    return columnDataType == PTimestamp.INSTANCE ? PDate.INSTANCE.getCodec()
      : columnDataType == PUnsignedTimestamp.INSTANCE ? PUnsignedDate.INSTANCE.getCodec()
      : super.getKeyRangeCodec(columnDataType);
  }

  @Override
  public boolean evaluate(Tuple tuple, ImmutableBytesWritable ptr) {
    if (children.get(0).evaluate(tuple, ptr)) {
      if (ptr.getLength() == 0) {
        return true;
      }
      SortOrder sortOrder = children.get(0).getSortOrder();
      PDataType dataType = getDataType();
      int nanos = dataType.getNanos(ptr, sortOrder);
      if (nanos >= HALF_OF_NANOS_IN_MILLI) {
        long timeMillis = dataType.getMillis(ptr, sortOrder);
        Timestamp roundedTs = new Timestamp(timeMillis + 1);
        byte[] byteValue = dataType.toBytes(roundedTs);
        ptr.set(byteValue);
      }
      return true; // for timestamp we only support rounding up the milliseconds.
    }
    return false;
  }

}
