/*
 * 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.util;

import org.apache.hadoop.hbase.util.Pair;

/**
 * @since 1.2.1
 */
public class BigDecimalUtil {

  /**
   * Calculates the precision and scale for BigDecimal arithmetic operation results. It uses the
   * algorithm mentioned <a href=
   * "http://db.apache.org/derby/docs/10.0/manuals/reference/sqlj124.html#HDRSII-SQLJ-36146">here</a>
   * @param lp precision of the left operand
   * @param ls scale of the left operand
   * @param rp precision of the right operand
   * @param rs scale of the right operand
   * @param op The operation type
   * @return {@link Pair} comprising of the precision and scale.
   */
  public static Pair<Integer, Integer> getResultPrecisionScale(int lp, int ls, int rp, int rs,
    Operation op) {
    int resultPrec = 0, resultScale = 0;
    switch (op) {
      case MULTIPLY:
        resultPrec = lp + rp;
        resultScale = ls + rs;
        break;
      case DIVIDE:
        resultPrec = lp - ls + rp + Math.max(ls + rp - rs + 1, 4);
        resultScale = 31 - lp + ls - rs;
        break;
      case ADD:
        resultPrec = 2 * (lp - ls) + ls; // Is this correct? The page says addition -> 2 * (p - s) +
                                         // s.
        resultScale = Math.max(ls, rs);
        break;
      case AVG:
        resultPrec = Math.max(lp - ls, rp - rs) + 1 + Math.max(ls, rs);
        resultScale = Math.max(Math.max(ls, rs), 4);
        break;
      case OTHERS:
        resultPrec = Math.max(lp - ls, rp - rs) + 1 + Math.max(ls, rs);
        resultScale = Math.max(ls, rs);
    }
    return new Pair<Integer, Integer>(resultPrec, resultScale);
  }

  public static enum Operation {
    MULTIPLY,
    DIVIDE,
    ADD,
    AVG,
    OTHERS;
  }
}
