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/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch 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.
 */

/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.search.aggregations.metrics;

import org.opensearch.core.ParseField;
import org.opensearch.core.common.io.stream.StreamInput;
import org.opensearch.core.common.io.stream.StreamOutput;
import org.opensearch.core.common.io.stream.Writeable;
import org.opensearch.core.xcontent.ObjectParser;

import java.io.IOException;

/**
 * An enum representing the methods for calculating percentiles
 *
 * @opensearch.internal
 */
public enum PercentilesMethod implements Writeable {
    /**
     * The TDigest method for calculating percentiles
     */
    TDIGEST("tdigest", "TDigest", "TDIGEST") {
        @Override
        PercentilesConfig configFromStream(StreamInput in) throws IOException {
            return new PercentilesConfig.TDigest(in);
        }
    },
    /**
     * The HDRHistogram method of calculating percentiles
     */
    HDR("hdr", "HDR") {
        @Override
        PercentilesConfig configFromStream(StreamInput in) throws IOException {
            return new PercentilesConfig.Hdr(in);
        }
    };

    public static final ParseField COMPRESSION_FIELD = new ParseField("compression");
    public static final ParseField NUMBER_SIGNIFICANT_DIGITS_FIELD = new ParseField("number_of_significant_value_digits");

    public static final ObjectParser TDIGEST_PARSER;
    static {
        TDIGEST_PARSER = new ObjectParser<>(PercentilesMethod.TDIGEST.getParseField().getPreferredName(), PercentilesConfig.TDigest::new);
        TDIGEST_PARSER.declareDouble(PercentilesConfig.TDigest::setCompression, COMPRESSION_FIELD);
    }

    public static final ObjectParser HDR_PARSER;
    static {
        HDR_PARSER = new ObjectParser<>(PercentilesMethod.HDR.getParseField().getPreferredName(), PercentilesConfig.Hdr::new);
        HDR_PARSER.declareInt(PercentilesConfig.Hdr::setNumberOfSignificantValueDigits, NUMBER_SIGNIFICANT_DIGITS_FIELD);
    }

    private final ParseField parseField;

    PercentilesMethod(String name, String... deprecatedNames) {
        this.parseField = new ParseField(name, deprecatedNames);
    }

    abstract PercentilesConfig configFromStream(StreamInput in) throws IOException;

    /**
     * @return the name of the method
     */
    public ParseField getParseField() {
        return parseField;
    }

    public static PercentilesMethod readFromStream(StreamInput in) throws IOException {
        return in.readEnum(PercentilesMethod.class);
    }

    @Override
    public void writeTo(StreamOutput out) throws IOException {
        out.writeEnum(this);
    }

    @Override
    public String toString() {
        return parseField.getPreferredName();
    }

}