/*
 * 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.spark.util.collection.unsafe.sort;

import com.google.common.primitives.UnsignedLongs;

import org.apache.spark.unsafe.types.ByteArray;
import org.apache.spark.unsafe.types.UTF8String;
import org.apache.spark.util.Utils;

public class PrefixComparators {
    private PrefixComparators() {}

    public static final StringPrefixComparator STRING = new StringPrefixComparator();
    public static final StringPrefixComparatorDesc STRING_DESC = new StringPrefixComparatorDesc();
    public static final BinaryPrefixComparator BINARY = new BinaryPrefixComparator();
    public static final BinaryPrefixComparatorDesc BINARY_DESC = new BinaryPrefixComparatorDesc();
    public static final LongPrefixComparator LONG = new LongPrefixComparator();
    public static final LongPrefixComparatorDesc LONG_DESC = new LongPrefixComparatorDesc();
    public static final DoublePrefixComparator DOUBLE = new DoublePrefixComparator();
    public static final DoublePrefixComparatorDesc DOUBLE_DESC = new DoublePrefixComparatorDesc();

    public static final class StringPrefixComparator implements PrefixComparator {
        @Override
        public int compare(long aPrefix, long bPrefix) {
            return UnsignedLongs.compare(aPrefix, bPrefix);
        }

        public static long computePrefix(UTF8String value) {
            return value == null ? 0L : value.getPrefix();
        }
    }

    public static final class StringPrefixComparatorDesc implements PrefixComparator {
        @Override
        public int compare(long bPrefix, long aPrefix) {
            return UnsignedLongs.compare(aPrefix, bPrefix);
        }
    }

    public static final class BinaryPrefixComparator implements PrefixComparator {
        @Override
        public int compare(long aPrefix, long bPrefix) {
            return UnsignedLongs.compare(aPrefix, bPrefix);
        }

        public static long computePrefix(byte[] bytes) {
            return ByteArray.getPrefix(bytes);
        }
    }

    public static final class BinaryPrefixComparatorDesc implements PrefixComparator {
        @Override
        public int compare(long bPrefix, long aPrefix) {
            return UnsignedLongs.compare(aPrefix, bPrefix);
        }
    }

    public static final class LongPrefixComparator implements PrefixComparator {
        @Override
        public int compare(long a, long b) {
            return (a < b) ? -1 : (a > b) ? 1 : 0;
        }
    }

    public static final class LongPrefixComparatorDesc implements PrefixComparator {
        @Override
        public int compare(long b, long a) {
            return (a < b) ? -1 : (a > b) ? 1 : 0;
        }
    }

    public static final class DoublePrefixComparator implements PrefixComparator {
        @Override
        public int compare(long aPrefix, long bPrefix) {
            double a = Double.longBitsToDouble(aPrefix);
            double b = Double.longBitsToDouble(bPrefix);
            return Utils.nanSafeCompareDoubles(a, b);
        }

        public static long computePrefix(double value) {
            return Double.doubleToLongBits(value);
        }
    }

    public static final class DoublePrefixComparatorDesc implements PrefixComparator {
        @Override
        public int compare(long bPrefix, long aPrefix) {
            double a = Double.longBitsToDouble(aPrefix);
            double b = Double.longBitsToDouble(bPrefix);
            return Utils.nanSafeCompareDoubles(a, b);
        }

        public static long computePrefix(double value) {
            return Double.doubleToLongBits(value);
        }
    }
}