/* ====================================================================
   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.poi.ss.util;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * Contains specific examples of {@code double} value pairs and their comparison result according to Excel.
 */
final class NumberComparisonExamples {

    private NumberComparisonExamples() {
        // no instances of this class
    }

    /**
     * represents one comparison test case
     */
    public static final class ComparisonExample {
        private final long _rawBitsA;
        private final long _rawBitsB;
        private final int _expectedResult;

        public ComparisonExample(long rawBitsA, long rawBitsB, int expectedResult) {
            _rawBitsA = rawBitsA;
            _rawBitsB = rawBitsB;
            _expectedResult = expectedResult;
        }

        public double getA() {
            return Double.longBitsToDouble(_rawBitsA);
        }
        public double getB() {
            return Double.longBitsToDouble(_rawBitsB);
        }
        public double getNegA() {
            return -Double.longBitsToDouble(_rawBitsA);
        }
        public double getNegB() {
            return -Double.longBitsToDouble(_rawBitsB);
        }
        public int getExpectedResult() {
            return _expectedResult;
        }
    }

    private static final ComparisonExample[] examples = initExamples();

    private static ComparisonExample[] initExamples() {

        List<ComparisonExample> temp = new ArrayList<>();

        addStepTransition(temp, 0x4010000000000005L);
        addStepTransition(temp, 0x4010000000000010L);
        addStepTransition(temp, 0x401000000000001CL);

        addStepTransition(temp, 0x403CE0FFFFFFFFF1L);

        addStepTransition(temp, 0x5010000000000006L);
        addStepTransition(temp, 0x5010000000000010L);
        addStepTransition(temp, 0x501000000000001AL);

        addStepTransition(temp, 0x544CE6345CF32018L);
        addStepTransition(temp, 0x544CE6345CF3205AL);
        addStepTransition(temp, 0x544CE6345CF3209CL);
        addStepTransition(temp, 0x544CE6345CF320DEL);

        addStepTransition(temp, 0x54B250001000101DL);
        addStepTransition(temp, 0x54B2500010001050L);
        addStepTransition(temp, 0x54B2500010001083L);

        addStepTransition(temp, 0x6230100010001000L);
        addStepTransition(temp, 0x6230100010001005L);
        addStepTransition(temp, 0x623010001000100AL);

        addStepTransition(temp, 0x7F50300020001011L);
        addStepTransition(temp, 0x7F5030002000102BL);
        addStepTransition(temp, 0x7F50300020001044L);


        addStepTransition(temp, 0x2B2BFFFF1000102AL);
        addStepTransition(temp, 0x2B2BFFFF10001079L);
        addStepTransition(temp, 0x2B2BFFFF100010C8L);

        addStepTransition(temp, 0x2B2BFF001000102DL);
        addStepTransition(temp, 0x2B2BFF0010001035L);
        addStepTransition(temp, 0x2B2BFF001000103DL);

        addStepTransition(temp, 0x2B61800040002024L);
        addStepTransition(temp, 0x2B61800040002055L);
        addStepTransition(temp, 0x2B61800040002086L);


        addStepTransition(temp, 0x008000000000000BL);
        // just outside 'subnormal' range
        addStepTransition(temp, 0x0010000000000007L);
        addStepTransition(temp, 0x001000000000001BL);
        addStepTransition(temp, 0x001000000000002FL);

        Collections.addAll(temp, // negative, and exponents differ by more than 1
            ce(0xBF30000000000000L, 0xBE60000000000000L, -1),

            // negative zero *is* less than positive zero, but not easy to get out of calculations
            ce(0x0000000000000000L, 0x8000000000000000L, +1),
            // subnormal numbers compare without rounding for some reason
            ce(0x0000000000000000L, 0x0000000000000001L, -1),
            ce(0x0008000000000000L, 0x0008000000000001L, -1),
            ce(0x000FFFFFFFFFFFFFL, 0x000FFFFFFFFFFFFEL, +1),
            ce(0x000FFFFFFFFFFFFBL, 0x000FFFFFFFFFFFFCL, -1),
            ce(0x000FFFFFFFFFFFFBL, 0x000FFFFFFFFFFFFEL, -1),

            // across subnormal threshold (some mistakes when close)
            ce(0x000FFFFFFFFFFFFFL, 0x0010000000000000L, +1),
            ce(0x000FFFFFFFFFFFFBL, 0x0010000000000007L, +1),
            ce(0x000FFFFFFFFFFFFAL, 0x0010000000000007L, 0),

            // when a bit further apart - normal results
            ce(0x000FFFFFFFFFFFF9L, 0x0010000000000007L, -1),
            ce(0x000FFFFFFFFFFFFAL, 0x0010000000000008L, -1),
            ce(0x000FFFFFFFFFFFFBL, 0x0010000000000008L, -1));

        ComparisonExample[] result = new ComparisonExample[temp.size()];
        temp.toArray(result);
        return result;
    }

    private static ComparisonExample ce(long rawBitsA, long rawBitsB, int expectedResult) {
        return new ComparisonExample(rawBitsA, rawBitsB, expectedResult);
    }

    private static void addStepTransition(List<ComparisonExample> temp, long rawBits) {
        Collections.addAll(temp,
            ce(rawBits - 1, rawBits + 0, 0),
            ce(rawBits + 0, rawBits + 1, -1),
            ce(rawBits + 1, rawBits + 2, 0));

    }

    public static ComparisonExample[] getComparisonExamples() {
        return examples.clone();
    }

}