package jdk.test;

import org.openjdk.jmh.annotations.*;

import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.util.Date;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.TimeUnit;

/*

Original:

Benchmark                               Mode   Samples        Score  Score error    Units
j.t.ZipUtilsTest.dosToJavaTime_Date     avgt        15       95.644        4.241    ns/op
j.t.ZipUtilsTest.dosToJavaTime_LDT      avgt        15      118.155        2.980    ns/op
j.t.ZipUtilsTest.dosToJavaTime_ZDT      avgt        15      131.456        3.586    ns/op
j.t.ZipUtilsTest.javaToDosTime_Date     avgt        15       74.692        1.709    ns/op
j.t.ZipUtilsTest.javaToDosTime_LDT      avgt        15      134.116        4.396    ns/op
j.t.ZipUtilsTest.javaToDosTime_ZDT      avgt        15      141.987        8.697    ns/op

Patched TimeZone:

Benchmark                               Mode   Samples        Score  Score error    Units
j.t.ZipUtilsTest.dosToJavaTime_Date     avgt        15       95.590        2.354    ns/op
j.t.ZipUtilsTest.dosToJavaTime_LDT      avgt        15       79.682        3.572    ns/op
j.t.ZipUtilsTest.dosToJavaTime_ZDT      avgt        15       86.801        2.081    ns/op
j.t.ZipUtilsTest.javaToDosTime_Date     avgt        15       75.096        1.178    ns/op
j.t.ZipUtilsTest.javaToDosTime_LDT      avgt        15       91.919        2.191    ns/op
j.t.ZipUtilsTest.javaToDosTime_ZDT      avgt        15       92.037        2.054    ns/op

Patched TimeZone & ZoneOffsetTransition:

Benchmark                               Mode   Samples        Score  Score error    Units
j.t.ZipUtilsTest.dosToJavaTime_Date     avgt        15       92.291        2.903    ns/op
j.t.ZipUtilsTest.dosToJavaTime_LDT      avgt        15       79.765        3.106    ns/op
j.t.ZipUtilsTest.dosToJavaTime_ZDT      avgt        15       87.282        2.967    ns/op
j.t.ZipUtilsTest.javaToDosTime_Date     avgt        15       76.235        2.651    ns/op
j.t.ZipUtilsTest.javaToDosTime_LDT      avgt        15       73.115        2.567    ns/op
j.t.ZipUtilsTest.javaToDosTime_ZDT      avgt        15       75.701        2.226    ns/op

 */

@BenchmarkMode(Mode.AverageTime)
@Fork(3)
@Warmup(iterations = 5)
@Measurement(iterations = 5)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@State(Scope.Thread)
public class ZipUtilsTest {

    static final int LEN = 1 << 10;

    long[] dosTimes, javaTimes;

    @Setup
    public void setup() {
        dosTimes = new long[LEN];
        javaTimes = new long[LEN];
        for (int i = 0; i < LEN; i++) {
            javaTimes[i] = System.currentTimeMillis() -
                ThreadLocalRandom.current().nextLong(5L * 365L * 24L * 60L * 60L * 1000L);
            dosTimes[i] = javaToDosTime0(javaTimes[i]);
        }
    }

    int i;

    @Benchmark
    public long javaToDosTime_Date() {
        return javaToDosTime0(javaTimes[(i++) & (LEN - 1)]);
    }

    @Benchmark
    public long dosToJavaTime_Date() {
        return dosToJavaTime0(dosTimes[(i++) & (LEN - 1)]);
    }

    @Benchmark
    public long javaToDosTime_ZDT() {
        return javaToDosTime1(javaTimes[(i++) & (LEN - 1)]);
    }

    @Benchmark
    public long dosToJavaTime_ZDT() {
        return dosToJavaTime1(dosTimes[(i++) & (LEN - 1)]);
    }

    @Benchmark
    public long javaToDosTime_LDT() {
        return javaToDosTime2(javaTimes[(i++) & (LEN - 1)]);
    }

    @Benchmark
    public long dosToJavaTime_LDT() {
        return dosToJavaTime2(dosTimes[(i++) & (LEN - 1)]);
    }

    /**
     * Converts DOS time to Java time (number of milliseconds since epoch).
     */
    public static long dosToJavaTime0(long dtime) {
        @SuppressWarnings("deprecation")
        Date d = new Date(
            (int) (((dtime >> 25) & 0x7f) + 80),
            (int) (((dtime >> 21) & 0x0f) - 1),
            (int) ((dtime >> 16) & 0x1f),
            (int) ((dtime >> 11) & 0x1f),
            (int) ((dtime >> 5) & 0x3f),
            (int) ((dtime << 1) & 0x3e)
        );
        return d.getTime();
    }

    /**
     * Converts Java time to DOS time.
     */
    @SuppressWarnings("deprecation")
    public static long javaToDosTime0(long time) {
        Date d = new Date(time);
        int year = d.getYear() + 1900;
        if (year < 1980) {
            return (1 << 21) | (1 << 16);
        }
        return (year - 1980) << 25 | (d.getMonth() + 1) << 21 |
            d.getDate() << 16 | d.getHours() << 11 | d.getMinutes() << 5 |
            d.getSeconds() >> 1;
    }

    // variants using new java.time API

    /**
     * Converts DOS time to Java time (number of milliseconds since epoch).
     */
    public static long dosToJavaTime1(long dtime) {
        ZonedDateTime zdt = ZonedDateTime.of(
            (int) (((dtime >> 25) & 0x7f) + 1980),
            (int) ((dtime >> 21) & 0x0f),
            (int) ((dtime >> 16) & 0x1f),
            (int) ((dtime >> 11) & 0x1f),
            (int) ((dtime >> 5) & 0x3f),
            (int) ((dtime << 1) & 0x3e),
            0,
            ZoneId.systemDefault()
        );
        return zdt.toInstant().toEpochMilli();
    }

    /**
     * Converts Java time to DOS time.
     */
    public static long javaToDosTime1(long time) {
        ZonedDateTime zdt = ZonedDateTime.ofInstant(
            Instant.ofEpochMilli(time),
            ZoneId.systemDefault()
        );
        int year = zdt.getYear() - 1980;
        if (year < 0) {
            return (1 << 21) | (1 << 16);
        }
        return year << 25 |
            zdt.getMonthValue() << 21 |
            zdt.getDayOfMonth() << 16 |
            zdt.getHour() << 11 |
            zdt.getMinute() << 5 |
            Math.min(59, zdt.getSecond()) >> 1;
    }


    /**
     * Converts DOS time to Java time (number of milliseconds since epoch).
     */
    public static long dosToJavaTime2(long dtime) {
        LocalDateTime ldt = LocalDateTime.of(
            (int) (((dtime >> 25) & 0x7f) + 1980),
            (int) ((dtime >> 21) & 0x0f),
            (int) ((dtime >> 16) & 0x1f),
            (int) ((dtime >> 11) & 0x1f),
            (int) ((dtime >> 5) & 0x3f),
            (int) ((dtime << 1) & 0x3e)
        );
        return ldt.toEpochSecond(
            ZoneId.systemDefault().getRules().getOffset(ldt)) * 1000L;
    }

    /**
     * Converts Java time to DOS time.
     */
    public static long javaToDosTime2(long time) {
        Instant instant = Instant.ofEpochMilli(time);
        LocalDateTime ldt = LocalDateTime.ofInstant(
            instant, ZoneId.systemDefault());
        int year = ldt.getYear() - 1980;
        if (year < 0) {
            return (1 << 21) | (1 << 16);
        }
        return year << 25 |
            ldt.getMonthValue() << 21 |
            ldt.getDayOfMonth() << 16 |
            ldt.getHour() << 11 |
            ldt.getMinute() << 5 |
            ldt.getSecond() >> 1;
    }
}