/*
 * 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.aggregations.bucket.histogram;

import org.elasticsearch.TransportVersion;
import org.elasticsearch.common.Rounding;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.common.io.stream.Writeable;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.search.aggregations.AggregationBuilder;
import org.elasticsearch.search.aggregations.AggregatorFactories.Builder;
import org.elasticsearch.search.aggregations.AggregatorFactory;
import org.elasticsearch.search.aggregations.MultiBucketConsumerService;
import org.elasticsearch.search.aggregations.support.AggregationContext;
import org.elasticsearch.search.aggregations.support.CoreValuesSourceType;
import org.elasticsearch.search.aggregations.support.ValuesSourceAggregationBuilder;
import org.elasticsearch.search.aggregations.support.ValuesSourceAggregatorFactory;
import org.elasticsearch.search.aggregations.support.ValuesSourceConfig;
import org.elasticsearch.search.aggregations.support.ValuesSourceRegistry;
import org.elasticsearch.search.aggregations.support.ValuesSourceType;
import org.elasticsearch.xcontent.ObjectParser;
import org.elasticsearch.xcontent.ParseField;
import org.elasticsearch.xcontent.XContentBuilder;

import java.io.IOException;
import java.time.ZoneId;
import java.util.Arrays;
import java.util.Map;
import java.util.Objects;
import java.util.function.Consumer;

import static java.util.Map.entry;

public class AutoDateHistogramAggregationBuilder extends ValuesSourceAggregationBuilder<AutoDateHistogramAggregationBuilder> {

    public static final String NAME = "auto_date_histogram";
    public static final ValuesSourceRegistry.RegistryKey<AutoDateHistogramAggregatorSupplier> REGISTRY_KEY =
        new ValuesSourceRegistry.RegistryKey<>(NAME, AutoDateHistogramAggregatorSupplier.class);

    private static final ParseField NUM_BUCKETS_FIELD = new ParseField("buckets");
    private static final ParseField MINIMUM_INTERVAL_FIELD = new ParseField("minimum_interval");

    public static final ObjectParser<AutoDateHistogramAggregationBuilder, String> PARSER = ObjectParser.fromBuilder(
        NAME,
        AutoDateHistogramAggregationBuilder::new
    );
    static {
        ValuesSourceAggregationBuilder.declareFields(PARSER, true, true, true);
        PARSER.declareInt(AutoDateHistogramAggregationBuilder::setNumBuckets, NUM_BUCKETS_FIELD);
        PARSER.declareStringOrNull(AutoDateHistogramAggregationBuilder::setMinimumIntervalExpression, MINIMUM_INTERVAL_FIELD);
    }

    public static final Map<Rounding.DateTimeUnit, String> ALLOWED_INTERVALS = Map.ofEntries(
        entry(Rounding.DateTimeUnit.YEAR_OF_CENTURY, "year"),
        entry(Rounding.DateTimeUnit.MONTH_OF_YEAR, "month"),
        entry(Rounding.DateTimeUnit.DAY_OF_MONTH, "day"),
        entry(Rounding.DateTimeUnit.HOUR_OF_DAY, "hour"),
        entry(Rounding.DateTimeUnit.MINUTES_OF_HOUR, "minute"),
        entry(Rounding.DateTimeUnit.SECOND_OF_MINUTE, "second")
    );

    public static void registerAggregators(ValuesSourceRegistry.Builder builder) {
        AutoDateHistogramAggregatorFactory.registerAggregators(builder);
    }

    /**
     *
     * Build roundings, computed dynamically as roundings are time zone dependent.
     * The current implementation probably should not be invoked in a tight loop.
     * @return Array of RoundingInfo
     */
    static RoundingInfo[] buildRoundings(ZoneId timeZone, String minimumInterval) {

        int indexToSliceFrom = 0;

        RoundingInfo[] roundings = new RoundingInfo[6];
        roundings[0] = new RoundingInfo(Rounding.DateTimeUnit.SECOND_OF_MINUTE, timeZone, 1000L, "s", 1, 5, 10, 30);
        roundings[1] = new RoundingInfo(Rounding.DateTimeUnit.MINUTES_OF_HOUR, timeZone, 60 * 1000L, "m", 1, 5, 10, 30);
        roundings[2] = new RoundingInfo(Rounding.DateTimeUnit.HOUR_OF_DAY, timeZone, 60 * 60 * 1000L, "h", 1, 3, 12);
        roundings[3] = new RoundingInfo(Rounding.DateTimeUnit.DAY_OF_MONTH, timeZone, 24 * 60 * 60 * 1000L, "d", 1, 7);
        roundings[4] = new RoundingInfo(Rounding.DateTimeUnit.MONTH_OF_YEAR, timeZone, 30 * 24 * 60 * 60 * 1000L, "M", 1, 3);
        roundings[5] = new RoundingInfo(
            Rounding.DateTimeUnit.YEAR_OF_CENTURY,
            timeZone,
            365 * 24 * 60 * 60 * 1000L,
            "y",
            1,
            5,
            10,
            20,
            50,
            100
        );

        for (int i = 0; i < roundings.length; i++) {
            RoundingInfo roundingInfo = roundings[i];
            if (roundingInfo.getDateTimeUnit().equals(minimumInterval)) {
                indexToSliceFrom = i;
                break;
            }
        }
        return Arrays.copyOfRange(roundings, indexToSliceFrom, roundings.length);
    }

    private int numBuckets = 10;

    private String minimumIntervalExpression;

    /** Create a new builder with the given name. */
    public AutoDateHistogramAggregationBuilder(String name) {
        super(name);
    }

    /** Read from a stream, for internal use only. */
    public AutoDateHistogramAggregationBuilder(StreamInput in) throws IOException {
        super(in);
        numBuckets = in.readVInt();
        if (in.getTransportVersion().onOrAfter(TransportVersion.V_7_3_0)) {
            minimumIntervalExpression = in.readOptionalString();
        }
    }

    @Override
    protected void innerWriteTo(StreamOutput out) throws IOException {
        out.writeVInt(numBuckets);
        if (out.getTransportVersion().onOrAfter(TransportVersion.V_7_3_0)) {
            out.writeOptionalString(minimumIntervalExpression);
        }
    }

    protected AutoDateHistogramAggregationBuilder(
        AutoDateHistogramAggregationBuilder clone,
        Builder factoriesBuilder,
        Map<String, Object> metadata
    ) {
        super(clone, factoriesBuilder, metadata);
        this.numBuckets = clone.numBuckets;
        this.minimumIntervalExpression = clone.minimumIntervalExpression;
    }

    @Override
    public boolean supportsSampling() {
        return true;
    }

    @Override
    protected ValuesSourceType defaultValueSourceType() {
        return CoreValuesSourceType.DATE;
    }

    @Override
    protected AggregationBuilder shallowCopy(Builder factoriesBuilder, Map<String, Object> metadata) {
        return new AutoDateHistogramAggregationBuilder(this, factoriesBuilder, metadata);
    }

    @Override
    public String getType() {
        return NAME;
    }

    @Override
    protected ValuesSourceRegistry.RegistryKey<?> getRegistryKey() {
        return REGISTRY_KEY;
    }

    public String getMinimumIntervalExpression() {
        return minimumIntervalExpression;
    }

    public AutoDateHistogramAggregationBuilder setMinimumIntervalExpression(String minimumIntervalExpression) {
        if (minimumIntervalExpression != null && ALLOWED_INTERVALS.containsValue(minimumIntervalExpression) == false) {
            throw new IllegalArgumentException(
                MINIMUM_INTERVAL_FIELD.getPreferredName() + " must be one of [" + ALLOWED_INTERVALS.values().toString() + "]"
            );
        }
        this.minimumIntervalExpression = minimumIntervalExpression;
        return this;
    }

    public AutoDateHistogramAggregationBuilder setNumBuckets(int numBuckets) {
        if (numBuckets <= 0) {
            throw new IllegalArgumentException(NUM_BUCKETS_FIELD.getPreferredName() + " must be greater than 0 for [" + name + "]");
        }
        this.numBuckets = numBuckets;
        return this;
    }

    public int getNumBuckets() {
        return numBuckets;
    }

    @Override
    public BucketCardinality bucketCardinality() {
        return BucketCardinality.MANY;
    }

    @Override
    protected ValuesSourceAggregatorFactory innerBuild(
        AggregationContext context,
        ValuesSourceConfig config,
        AggregatorFactory parent,
        Builder subFactoriesBuilder
    ) throws IOException {
        AutoDateHistogramAggregatorSupplier aggregatorSupplier = context.getValuesSourceRegistry().getAggregator(REGISTRY_KEY, config);

        RoundingInfo[] roundings = buildRoundings(timeZone(), getMinimumIntervalExpression());
        int maxRoundingInterval = Arrays.stream(roundings, 0, roundings.length - 1)
            .map(rounding -> rounding.innerIntervals)
            .flatMapToInt(Arrays::stream)
            .boxed()
            .reduce(Integer::max)
            .get();
        Settings settings = context.getIndexSettings().getNodeSettings();
        int maxBuckets = MultiBucketConsumerService.MAX_BUCKET_SETTING.get(settings);
        int bucketCeiling = maxBuckets / maxRoundingInterval;
        if (numBuckets > bucketCeiling) {
            throw new IllegalArgumentException(NUM_BUCKETS_FIELD.getPreferredName() + " must be less than " + bucketCeiling);
        }
        return new AutoDateHistogramAggregatorFactory(
            name,
            config,
            numBuckets,
            roundings,
            context,
            parent,
            subFactoriesBuilder,
            metadata,
            aggregatorSupplier
        );
    }

    static Rounding createRounding(Rounding.DateTimeUnit interval, ZoneId timeZone) {
        Rounding.Builder tzRoundingBuilder = Rounding.builder(interval);
        if (timeZone != null) {
            tzRoundingBuilder.timeZone(timeZone);
        }
        Rounding rounding = tzRoundingBuilder.build();
        return rounding;
    }

    @Override
    protected XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException {
        builder.field(NUM_BUCKETS_FIELD.getPreferredName(), numBuckets);
        builder.field(MINIMUM_INTERVAL_FIELD.getPreferredName(), minimumIntervalExpression);
        return builder;
    }

    @Override
    public int hashCode() {
        return Objects.hash(super.hashCode(), numBuckets, minimumIntervalExpression);
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj == null || getClass() != obj.getClass()) return false;
        if (super.equals(obj) == false) return false;
        AutoDateHistogramAggregationBuilder other = (AutoDateHistogramAggregationBuilder) obj;
        return Objects.equals(numBuckets, other.numBuckets) && Objects.equals(minimumIntervalExpression, other.minimumIntervalExpression);
    }

    @Override
    public TransportVersion getMinimalSupportedVersion() {
        return TransportVersion.ZERO;
    }

    public static class RoundingInfo implements Writeable {
        final Rounding rounding;
        final int[] innerIntervals;
        final long roughEstimateDurationMillis;
        final String unitAbbreviation;
        final String dateTimeUnit;

        public RoundingInfo(
            Rounding.DateTimeUnit dateTimeUnit,
            ZoneId timeZone,
            long roughEstimateDurationMillis,
            String unitAbbreviation,
            int... innerIntervals
        ) {
            this.rounding = createRounding(dateTimeUnit, timeZone);
            this.roughEstimateDurationMillis = roughEstimateDurationMillis;
            this.unitAbbreviation = unitAbbreviation;
            this.innerIntervals = innerIntervals;
            Objects.requireNonNull(dateTimeUnit, "dateTimeUnit cannot be null");
            if (ALLOWED_INTERVALS.containsKey(dateTimeUnit) == false) {
                throw new IllegalArgumentException("dateTimeUnit must be one of " + ALLOWED_INTERVALS.keySet().toString());
            }
            this.dateTimeUnit = ALLOWED_INTERVALS.get(dateTimeUnit);
        }

        public RoundingInfo(StreamInput in) throws IOException {
            rounding = Rounding.read(in);
            roughEstimateDurationMillis = in.readVLong();
            innerIntervals = in.readIntArray();
            unitAbbreviation = in.readString();
            dateTimeUnit = in.readString();
        }

        @Override
        public void writeTo(StreamOutput out) throws IOException {
            rounding.writeTo(out);
            out.writeVLong(roughEstimateDurationMillis);
            out.writeIntArray(innerIntervals);
            out.writeString(unitAbbreviation);
            out.writeString(dateTimeUnit);
        }

        public int getMaximumInnerInterval() {
            return innerIntervals[innerIntervals.length - 1];
        }

        public String getDateTimeUnit() {
            return this.dateTimeUnit;
        }

        public long getRoughEstimateDurationMillis() {
            return roughEstimateDurationMillis;
        }

        public long getMaximumRoughEstimateDurationMillis() {
            return getRoughEstimateDurationMillis() * getMaximumInnerInterval();
        }

        @Override
        public int hashCode() {
            return Objects.hash(rounding, Arrays.hashCode(innerIntervals), dateTimeUnit);
        }

        @Override
        public boolean equals(Object obj) {
            if (obj == null) {
                return false;
            }
            if (obj.getClass() != getClass()) {
                return false;
            }
            RoundingInfo other = (RoundingInfo) obj;
            return Objects.equals(rounding, other.rounding)
                && Objects.deepEquals(innerIntervals, other.innerIntervals)
                && Objects.equals(dateTimeUnit, other.dateTimeUnit);
        }

        @Override
        public String toString() {
            return "RoundingInfo[" + rounding + " " + Arrays.toString(innerIntervals) + "]";
        }
    }

    @Override
    protected void validateSequentiallyOrdered(String type, String name, Consumer<String> addValidationError) {}

    @Override
    protected void validateSequentiallyOrderedWithoutGaps(String type, String name, Consumer<String> addValidationError) {
        // auto_date_histogram never has gaps
    }
}
