/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */

package org.elasticsearch.common.time;

import org.elasticsearch.ElasticsearchParseException;
import org.elasticsearch.core.Strings;
import org.elasticsearch.test.ESTestCase;

import java.time.Instant;
import java.time.ZoneId;
import java.time.ZoneOffset;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatterBuilder;
import java.time.format.ResolverStyle;
import java.util.Locale;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.function.LongSupplier;

import static org.hamcrest.Matchers.containsString;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.is;

public class JavaDateMathParserTests extends ESTestCase {

    private final DateFormatter formatter = DateFormatter.forPattern("date_optional_time||epoch_millis");
    private final DateMathParser parser = formatter.toDateMathParser();

    public void testRoundUpParserBasedOnList() {
        DateFormatter formatter = new JavaDateFormatter(
            "test",
            new DateTimeFormatterBuilder().appendPattern("uuuu-MM-dd").toFormatter(Locale.ROOT),
            new DateTimeFormatterBuilder().appendPattern("uuuu-MM-dd'T'HH:mm:ss.S")
                .appendZoneOrOffsetId()
                .toFormatter(Locale.ROOT)
                .withResolverStyle(ResolverStyle.STRICT),
            new DateTimeFormatterBuilder().appendPattern("uuuu-MM-dd'T'HH:mm:ss.S")
                .appendOffset("+HHmm", "Z")
                .toFormatter(Locale.ROOT)
                .withResolverStyle(ResolverStyle.STRICT)
        );
        Instant parsed = formatter.toDateMathParser().parse("1970-01-01T00:00:00.0+0000", () -> 0L, true, (ZoneId) null);
        assertThat(parsed.toEpochMilli(), equalTo(0L));
    }

    public void testMergingOfMultipleParsers() {
        // date_time has 2 parsers, date_time_no_millis has 4. Parsing with rounding should be able to use all of them
        DateFormatter formatter = DateFormatter.forPattern("date_time||date_time_no_millis");
        // date_time 2 parsers
        Instant parsed = formatter.toDateMathParser().parse("1970-01-01T00:00:00.0+00:00", () -> 0L, true, (ZoneId) null);
        assertThat(parsed.toEpochMilli(), equalTo(0L));

        parsed = formatter.toDateMathParser().parse("1970-01-01T00:00:00.0+0000", () -> 0L, true, (ZoneId) null);
        assertThat(parsed.toEpochMilli(), equalTo(0L));

        // date_time_no_millis 4 parsers
        parsed = formatter.toDateMathParser().parse("1970-01-01T00:00:00+00:00", () -> 0L, true, (ZoneId) null);
        assertThat(parsed.toEpochMilli(), equalTo(999L));// defaulting millis

        parsed = formatter.toDateMathParser().parse("1970-01-01T00:00:00+0000", () -> 0L, true, (ZoneId) null);
        assertThat(parsed.toEpochMilli(), equalTo(999L));// defaulting millis

        parsed = formatter.toDateMathParser().parse("1970-01-01T00:00:00UTC+00:00", () -> 0L, true, (ZoneId) null);
        assertThat(parsed.toEpochMilli(), equalTo(999L));// defaulting millis

        // this one is actually still using parser number 3. I don't see a combination to use parser number 4
        parsed = formatter.toDateMathParser().parse("1970-01-01T00:00:00", () -> 0L, true, (ZoneId) null);
        assertThat(parsed.toEpochMilli(), equalTo(999L));// defaulting millis
    }

    public void testOverridingLocaleOrZoneAndCompositeRoundUpParser() {
        // the pattern has to be composite and the match should not be on the first one
        DateFormatter formatter = DateFormatter.forPattern("date||epoch_millis").withLocale(randomLocale(random()));
        DateMathParser parser = formatter.toDateMathParser();
        long gotMillis = parser.parse("297276785531", () -> 0, true, (ZoneId) null).toEpochMilli();
        assertDateEquals(gotMillis, "297276785531", "297276785531");

        formatter = DateFormatter.forPattern("date||epoch_millis").withZone(ZoneOffset.UTC);
        parser = formatter.toDateMathParser();
        gotMillis = parser.parse("297276785531", () -> 0, true, (ZoneId) null).toEpochMilli();
        assertDateEquals(gotMillis, "297276785531", "297276785531");
    }

    public void testWeekBasedDate() {
        DateFormatter formatter = DateFormatter.forPattern("strict_basic_week_date");// YYYY'W'wwe
        // first week of 2022 is starting on Monday 3rd Jan
        assertDateMathEquals(formatter.toDateMathParser(), "2022W0101", "2022-01-03T23:59:59.999Z", 0, true, ZoneOffset.UTC);

        // defaulting missing day of week
        formatter = DateFormatter.forPattern("YYYY'W'ww[e]");// YYYY'W'wwe
        // second week of 2022 is starting on Monday 10th Jan
        assertDateMathEquals(formatter.toDateMathParser(), "2022W02", "2022-01-10T23:59:59.999Z", 0, true, ZoneOffset.UTC);
    }

    public void testDayOfYear() {
        DateFormatter formatter = DateFormatter.forPattern("yyyy-DDD'T'HH:mm:ss.SSS");
        assertDateMathEquals(formatter.toDateMathParser(), "2022-104T14:08:30.293", "2022-04-14T14:08:30.293", 0, true, ZoneOffset.UTC);
    }

    public void testAMPM() {
        DateFormatter formatter = DateFormatter.forPattern("MM/dd/yyyy hh:mm a"); // h clock-hour-of-am-pm (1-12)
        assertDateMathEquals(formatter.toDateMathParser(), "04/30/2020 12:48 AM", "2020-04-30T00:48:59.999Z", 0, true, ZoneOffset.UTC);

        formatter = DateFormatter.forPattern("MM/dd/yyyy KK:mm a"); // K hour-of-am-pm (0-11)
        assertDateMathEquals(formatter.toDateMathParser(), "04/30/2020 00:48 AM", "2020-04-30T00:48:59.999Z", 0, true, ZoneOffset.UTC);
    }

    public void testAMPMWithTimeMissing() {
        DateFormatter formatter = DateFormatter.forPattern("MM/dd/yyyy[ hh:mm a]"); // h clock-hour-of-am-pm (1-12)
        assertDateMathEquals(formatter.toDateMathParser(), "04/30/2020", "2020-04-30T23:59:59.999Z", 0, true, ZoneOffset.UTC);

        formatter = DateFormatter.forPattern("MM/dd/yyyy[ KK:mm a]"); // K hour-of-am-pm (0-11)
        assertDateMathEquals(formatter.toDateMathParser(), "04/30/2020", "2020-04-30T23:59:59.999Z", 0, true, ZoneOffset.UTC);
    }

    public void testWeekDates() {
        DateFormatter formatter = DateFormatter.forPattern("YYYY-ww");
        assertDateMathEquals(formatter.toDateMathParser(), "2016-01", "2016-01-04T23:59:59.999Z", 0, true, ZoneOffset.UTC);

        formatter = DateFormatter.forPattern("YYYY");
        assertDateMathEquals(formatter.toDateMathParser(), "2016", "2016-01-04T23:59:59.999Z", 0, true, ZoneOffset.UTC);

        formatter = DateFormatter.forPattern("YYYY-ww");
        assertDateMathEquals(formatter.toDateMathParser(), "2015-01", "2014-12-29T23:59:59.999Z", 0, true, ZoneOffset.UTC);

        formatter = DateFormatter.forPattern("YYYY");
        assertDateMathEquals(formatter.toDateMathParser(), "2015", "2014-12-29T23:59:59.999Z", 0, true, ZoneOffset.UTC);
    }

    public void testBasicDates() {
        assertDateMathEquals("2014-05-30", "2014-05-30T00:00:00.000");
        assertDateMathEquals("2014-05-30T20", "2014-05-30T20:00:00.000");
        assertDateMathEquals("2014-05-30T20:21", "2014-05-30T20:21:00.000");
        assertDateMathEquals("2014-05-30T20:21:35", "2014-05-30T20:21:35.000");
        assertDateMathEquals("2014-05-30T20:21:35.123", "2014-05-30T20:21:35.123");
    }

    public void testRoundingDoesNotAffectExactDate() {
        assertDateMathEquals("2014-11-12T22:55:00.000Z", "2014-11-12T22:55:00.000Z", 0, true, null);
        assertDateMathEquals("2014-11-12T22:55:00.000Z", "2014-11-12T22:55:00.000Z", 0, false, null);

        assertDateMathEquals("2014-11-12T22:55:00.000", "2014-11-12T21:55:00.000Z", 0, true, ZoneId.of("+01:00"));
        assertDateMathEquals("2014-11-12T22:55:00.000", "2014-11-12T21:55:00.000Z", 0, false, ZoneId.of("+01:00"));

        assertDateMathEquals("2014-11-12T22:55:00.000+01:00", "2014-11-12T21:55:00.000Z", 0, true, null);
        assertDateMathEquals("2014-11-12T22:55:00.000+01:00", "2014-11-12T21:55:00.000Z", 0, false, null);
    }

    public void testTimezone() {
        // timezone works within date format
        assertDateMathEquals("2014-05-30T20:21+02:00", "2014-05-30T18:21:00.000");

        // test alternative ways of writing zero offsets, according to ISO 8601 +00:00, +00, +0000 should work.
        // joda also seems to allow for -00:00, -00, -0000
        assertDateMathEquals("2014-05-30T18:21+00:00", "2014-05-30T18:21:00.000");
        assertDateMathEquals("2014-05-30T18:21+00", "2014-05-30T18:21:00.000");
        assertDateMathEquals("2014-05-30T18:21+0000", "2014-05-30T18:21:00.000");
        assertDateMathEquals("2014-05-30T18:21-00:00", "2014-05-30T18:21:00.000");
        assertDateMathEquals("2014-05-30T18:21-00", "2014-05-30T18:21:00.000");
        assertDateMathEquals("2014-05-30T18:21-0000", "2014-05-30T18:21:00.000");

        // but also externally
        assertDateMathEquals("2014-05-30T20:21", "2014-05-30T18:21:00.000", 0, false, ZoneId.of("+02:00"));
        assertDateMathEquals("2014-05-30T18:21", "2014-05-30T18:21:00.000", 0, false, ZoneId.of("+00:00"));
        assertDateMathEquals("2014-05-30T18:21", "2014-05-30T18:21:00.000", 0, false, ZoneId.of("+00:00"));
        assertDateMathEquals("2014-05-30T18:21", "2014-05-30T18:21:00.000", 0, false, ZoneId.of("+00"));
        assertDateMathEquals("2014-05-30T18:21", "2014-05-30T18:21:00.000", 0, false, ZoneId.of("+0000"));
        assertDateMathEquals("2014-05-30T18:21", "2014-05-30T18:21:00.000", 0, false, ZoneId.of("-00:00"));
        assertDateMathEquals("2014-05-30T18:21", "2014-05-30T18:21:00.000", 0, false, ZoneId.of("-00"));
        assertDateMathEquals("2014-05-30T18:21", "2014-05-30T18:21:00.000", 0, false, ZoneId.of("-0000"));

        // and timezone in the date has priority
        assertDateMathEquals("2014-05-30T20:21+03:00", "2014-05-30T17:21:00.000", 0, false, ZoneId.of("-08:00"));
        assertDateMathEquals("2014-05-30T20:21Z", "2014-05-30T20:21:00.000", 0, false, ZoneId.of("-08:00"));
    }

    public void testBasicMath() {
        assertDateMathEquals("2014-11-18||+y", "2015-11-18");
        assertDateMathEquals("2014-11-18||-2y", "2012-11-18");

        assertDateMathEquals("2014-11-18||+3M", "2015-02-18");
        assertDateMathEquals("2014-11-18||-M", "2014-10-18");

        assertDateMathEquals("2014-11-18||+1w", "2014-11-25");
        assertDateMathEquals("2014-11-18||-3w", "2014-10-28");

        assertDateMathEquals("2014-11-18||+22d", "2014-12-10");
        assertDateMathEquals("2014-11-18||-423d", "2013-09-21");

        assertDateMathEquals("2014-11-18T14||+13h", "2014-11-19T03");
        assertDateMathEquals("2014-11-18T14||-1h", "2014-11-18T13");
        assertDateMathEquals("2014-11-18T14||+13H", "2014-11-19T03");
        assertDateMathEquals("2014-11-18T14||-1H", "2014-11-18T13");

        assertDateMathEquals("2014-11-18T14:27||+10240m", "2014-11-25T17:07");
        assertDateMathEquals("2014-11-18T14:27||-10m", "2014-11-18T14:17");

        assertDateMathEquals("2014-11-18T14:27:32||+60s", "2014-11-18T14:28:32");
        assertDateMathEquals("2014-11-18T14:27:32||-3600s", "2014-11-18T13:27:32");
    }

    public void testLenientEmptyMath() {
        assertDateMathEquals("2014-05-30T20:21||", "2014-05-30T20:21:00.000");
    }

    public void testMultipleAdjustments() {
        assertDateMathEquals("2014-11-18||+1M-1M", "2014-11-18");
        assertDateMathEquals("2014-11-18||+1M-1m", "2014-12-17T23:59");
        assertDateMathEquals("2014-11-18||-1m+1M", "2014-12-17T23:59");
        assertDateMathEquals("2014-11-18||+1M/M", "2014-12-01");
        assertDateMathEquals("2014-11-18||+1M/M+1h", "2014-12-01T01");
    }

    public void testNow() {
        final long now = parser.parse("2014-11-18T14:27:32", () -> 0, false, (ZoneId) null).toEpochMilli();

        assertDateMathEquals("now", "2014-11-18T14:27:32", now, false, null);
        assertDateMathEquals("now+M", "2014-12-18T14:27:32", now, false, null);
        assertDateMathEquals("now+M", "2014-12-18T14:27:32", now, true, null);
        assertDateMathEquals("now-2d", "2014-11-16T14:27:32", now, false, null);
        assertDateMathEquals("now-2d", "2014-11-16T14:27:32", now, true, null);
        assertDateMathEquals("now/m", "2014-11-18T14:27", now, false, null);
        assertDateMathEquals("now/m", "2014-11-18T14:27:59.999Z", now, true, null);
        assertDateMathEquals("now/M", "2014-11-01T00:00:00", now, false, null);
        assertDateMathEquals("now/M", "2014-11-30T23:59:59.999Z", now, true, null);

        // timezone does not affect now
        assertDateMathEquals("now/m", "2014-11-18T14:27", now, false, ZoneId.of("+02:00"));
    }

    public void testRoundingPreservesEpochAsBaseDate() {
        // If a user only specifies times, then the date needs to always be 1970-01-01 regardless of rounding
        DateFormatter formatter = DateFormatters.forPattern("HH:mm:ss");
        DateMathParser parser = formatter.toDateMathParser();
        ZonedDateTime zonedDateTime = DateFormatters.from(formatter.parse("04:52:20"));
        assertThat(zonedDateTime.getYear(), is(1970));
        Instant millisStart = zonedDateTime.toInstant();
        assertEquals(millisStart, parser.parse("04:52:20", () -> 0, false, (ZoneId) null));
        // due to rounding up, we have to add the number of milliseconds here manually
        long millisEnd = DateFormatters.from(formatter.parse("04:52:20")).toInstant().toEpochMilli() + 999;
        assertEquals(millisEnd, parser.parse("04:52:20", () -> 0, true, (ZoneId) null).toEpochMilli());
    }

    // Implicit rounding happening when parts of the date are not specified
    public void testImplicitRounding() {
        assertDateMathEquals("2014-11-18", "2014-11-18", 0, false, null);
        assertDateMathEquals("2014-11-18", "2014-11-18T23:59:59.999Z", 0, true, null);

        assertDateMathEquals("2014-11-18T09:20", "2014-11-18T09:20", 0, false, null);
        assertDateMathEquals("2014-11-18T09:20", "2014-11-18T09:20:59.999Z", 0, true, null);

        assertDateMathEquals("2014-11-18", "2014-11-17T23:00:00.000Z", 0, false, ZoneId.of("CET"));
        assertDateMathEquals("2014-11-18", "2014-11-18T22:59:59.999Z", 0, true, ZoneId.of("CET"));

        assertDateMathEquals("2014-11-18T09:20", "2014-11-18T08:20:00.000Z", 0, false, ZoneId.of("CET"));
        assertDateMathEquals("2014-11-18T09:20", "2014-11-18T08:20:59.999Z", 0, true, ZoneId.of("CET"));

        // implicit rounding with explicit timezone in the date format
        DateFormatter formatter = DateFormatters.forPattern("yyyy-MM-ddXXX");
        DateMathParser parser = formatter.toDateMathParser();
        Instant time = parser.parse("2011-10-09+01:00", () -> 0, false, (ZoneId) null);
        assertEquals(this.parser.parse("2011-10-09T00:00:00.000+01:00", () -> 0), time);
        time = DateFormatter.forPattern("strict_date_optional_time_nanos")
            .toDateMathParser()
            .parse("2011-10-09T23:59:59.999+01:00", () -> 0, false, (ZoneId) null);
        assertEquals(this.parser.parse("2011-10-09T23:59:59.999+01:00", () -> 0), time);
    }

    // Explicit rounding using the || separator
    public void testExplicitRounding() {
        assertDateMathEquals("2014-11-18||/y", "2014-01-01", 0, false, null);
        assertDateMathEquals("2014-11-18||/y", "2014-12-31T23:59:59.999", 0, true, null);
        assertDateMathEquals("2014-01-01T00:00:00.001||/y", "2014-12-31T23:59:59.999", 0, true, null);
        // rounding should also take into account time zone
        assertDateMathEquals("2014-11-18||/y", "2013-12-31T23:00:00.000Z", 0, false, ZoneId.of("CET"));
        assertDateMathEquals("2014-11-18||/y", "2014-12-31T22:59:59.999Z", 0, true, ZoneId.of("CET"));

        assertDateMathEquals("2014-11-18||/M", "2014-11-01", 0, false, null);
        assertDateMathEquals("2014-11-18||/M", "2014-11-30T23:59:59.999", 0, true, null);
        assertDateMathEquals("2014-11||/M", "2014-11-01", 0, false, null);
        assertDateMathEquals("2014-11||/M", "2014-11-30T23:59:59.999", 0, true, null);
        assertDateMathEquals("2014-11-18||/M", "2014-10-31T23:00:00.000Z", 0, false, ZoneId.of("CET"));
        assertDateMathEquals("2014-11-18||/M", "2014-11-30T22:59:59.999Z", 0, true, ZoneId.of("CET"));

        assertDateMathEquals("2014-11-18T14||/w", "2014-11-17", 0, false, null);
        assertDateMathEquals("2014-11-18T14||/w", "2014-11-23T23:59:59.999", 0, true, null);
        assertDateMathEquals("2014-11-17T14||/w", "2014-11-17", 0, false, null);
        assertDateMathEquals("2014-11-18T14||/w", "2014-11-17", 0, false, null);
        assertDateMathEquals("2014-11-19T14||/w", "2014-11-17", 0, false, null);
        assertDateMathEquals("2014-11-20T14||/w", "2014-11-17", 0, false, null);
        assertDateMathEquals("2014-11-21T14||/w", "2014-11-17", 0, false, null);
        assertDateMathEquals("2014-11-22T14||/w", "2014-11-17", 0, false, null);
        assertDateMathEquals("2014-11-23T14||/w", "2014-11-17", 0, false, null);
        assertDateMathEquals("2014-11-18||/w", "2014-11-23T23:59:59.999", 0, true, null);
        assertDateMathEquals("2014-11-18||/w", "2014-11-16T23:00:00.000Z", 0, false, ZoneId.of("+01:00"));
        assertDateMathEquals("2014-11-18||/w", "2014-11-17T01:00:00.000Z", 0, false, ZoneId.of("-01:00"));
        assertDateMathEquals("2014-11-18||/w", "2014-11-16T23:00:00.000Z", 0, false, ZoneId.of("CET"));
        assertDateMathEquals("2014-11-18||/w", "2014-11-23T22:59:59.999Z", 0, true, ZoneId.of("CET"));
        assertDateMathEquals("2014-07-22||/w", "2014-07-20T22:00:00.000Z", 0, false, ZoneId.of("CET")); // with DST

        assertDateMathEquals("2014-11-18T14||/d", "2014-11-18", 0, false, null);
        assertDateMathEquals("2014-11-18T14||/d", "2014-11-18T23:59:59.999", 0, true, null);
        assertDateMathEquals("2014-11-18||/d", "2014-11-18", 0, false, null);
        assertDateMathEquals("2014-11-18||/d", "2014-11-18T23:59:59.999", 0, true, null);

        assertDateMathEquals("2014-11-18T14:27||/h", "2014-11-18T14", 0, false, null);
        assertDateMathEquals("2014-11-18T14:27||/h", "2014-11-18T14:59:59.999", 0, true, null);
        assertDateMathEquals("2014-11-18T14||/H", "2014-11-18T14", 0, false, null);
        assertDateMathEquals("2014-11-18T14||/H", "2014-11-18T14:59:59.999", 0, true, null);
        assertDateMathEquals("2014-11-18T14:27||/h", "2014-11-18T14", 0, false, null);
        assertDateMathEquals("2014-11-18T14:27||/h", "2014-11-18T14:59:59.999", 0, true, null);
        assertDateMathEquals("2014-11-18T14||/H", "2014-11-18T14", 0, false, null);
        assertDateMathEquals("2014-11-18T14||/H", "2014-11-18T14:59:59.999", 0, true, null);

        assertDateMathEquals("2014-11-18T14:27:32||/m", "2014-11-18T14:27", 0, false, null);
        assertDateMathEquals("2014-11-18T14:27:32||/m", "2014-11-18T14:27:59.999", 0, true, null);
        assertDateMathEquals("2014-11-18T14:27||/m", "2014-11-18T14:27", 0, false, null);
        assertDateMathEquals("2014-11-18T14:27||/m", "2014-11-18T14:27:59.999", 0, true, null);

        assertDateMathEquals("2014-11-18T14:27:32.123||/s", "2014-11-18T14:27:32", 0, false, null);
        assertDateMathEquals("2014-11-18T14:27:32.123||/s", "2014-11-18T14:27:32.999", 0, true, null);
        assertDateMathEquals("2014-11-18T14:27:32||/s", "2014-11-18T14:27:32", 0, false, null);
        assertDateMathEquals("2014-11-18T14:27:32||/s", "2014-11-18T14:27:32.999", 0, true, null);
    }

    public void testTimestamps() {
        assertDateMathEquals("1418248078000", "2014-12-10T21:47:58.000");
        assertDateMathEquals("32484216259000", "2999-05-20T17:24:19.000");
        assertDateMathEquals("253382837059000", "9999-05-20T17:24:19.000");

        // datemath still works on timestamps
        assertDateMathEquals("1418248078000||/m", "2014-12-10T21:47:00.000");

        // also check other time units
        DateMathParser parser = DateFormatter.forPattern("epoch_second||date_optional_time").toDateMathParser();
        long datetime = parser.parse("1418248078", () -> 0).toEpochMilli();
        assertDateEquals(datetime, "1418248078", "2014-12-10T21:47:58.000");

        // for date_optional_time a timestamp with more than 9digits is epoch
        assertDateMathEquals("9999", "9999-01-01T00:00:00.000");
        assertDateMathEquals("10000", "10000-01-01T00:00:00.000");
        assertDateMathEquals("1000000000", "1970-01-12T13:46:40.000Z");

        // but 10000 with T is still a date format
        assertDateMathEquals("10000-01-01T", "10000-01-01T00:00:00.000");
    }

    void assertParseException(String msg, String date, String exc) {
        ElasticsearchParseException e = expectThrows(ElasticsearchParseException.class, () -> parser.parse(date, () -> 0));
        assertThat(msg, e.getMessage(), containsString(exc));
    }

    public void testIllegalMathFormat() {
        assertParseException("Expected date math unsupported operator exception", "2014-11-18||*5", "operator not supported");
        assertParseException("Expected date math incompatible rounding exception", "2014-11-18||/2m", "rounding");
        assertParseException("Expected date math illegal unit type exception", "2014-11-18||+2a", "unit [a] not supported");
        assertParseException("Expected date math truncation exception", "2014-11-18||+12", "truncated");
        assertParseException("Expected date math truncation exception", "2014-11-18||-", "truncated");
    }

    public void testIllegalDateFormat() {
        assertParseException("Expected bad timestamp exception", Long.toString(Long.MAX_VALUE) + "0", "failed to parse date field");
        assertParseException("Expected bad date format exception", "123bogus", "failed to parse date field [123bogus]");
    }

    public void testOnlyCallsNowIfNecessary() {
        final AtomicBoolean called = new AtomicBoolean();
        final LongSupplier now = () -> {
            called.set(true);
            return 42L;
        };
        parser.parse("2014-11-18T14:27:32", now, false, (ZoneId) null);
        assertFalse(called.get());
        parser.parse("now/d", now, false, (ZoneId) null);
        assertTrue(called.get());
    }

    private void assertDateMathEquals(String toTest, String expected) {
        assertDateMathEquals(toTest, expected, 0, false, null);
    }

    private void assertDateMathEquals(String toTest, String expected, final long now, boolean roundUp, ZoneId timeZone) {
        assertDateMathEquals(parser, toTest, expected, now, roundUp, timeZone);
    }

    private void assertDateMathEquals(
        DateMathParser parser,
        String toTest,
        String expected,
        final long now,
        boolean roundUp,
        ZoneId timeZone
    ) {
        long gotMillis = parser.parse(toTest, () -> now, roundUp, timeZone).toEpochMilli();
        assertDateEquals(gotMillis, toTest, expected);
    }

    private void assertDateEquals(long gotMillis, String original, String expected) {
        long expectedMillis = parser.parse(expected, () -> 0).toEpochMilli();
        if (gotMillis != expectedMillis) {
            ZonedDateTime zonedDateTime = ZonedDateTime.ofInstant(Instant.ofEpochMilli(gotMillis), ZoneOffset.UTC);
            fail(Strings.format("""
                Date math not equal
                Original              : %s
                Parsed                : %s
                Expected              : %s
                Expected milliseconds : %s
                Actual milliseconds   : %s
                """, original, formatter.format(zonedDateTime), expected, expectedMillis, gotMillis));
        }
    }
}
