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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * by Oracle in the LICENSE file that accompanied this code.
 *
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * accompanied this code).
 *
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package jdk.internal.net.quic;

import java.util.Collection;
import java.util.Comparator;
import java.util.Objects;
import java.util.Optional;

/**
 * Represents the Quic versions defined in their corresponding RFCs
 */
public enum QuicVersion {
    // the version numbers are defined in their respective RFCs
    QUIC_V1(1), // RFC-9000
    QUIC_V2(0x6b3343cf); // RFC 9369

    // 32 bits unsigned integer representing the version as
    // defined in RFC. This is the version number as sent
    // in long headers packets (see RFC 9000).
    private final int versionNumber;

    private QuicVersion(final int versionNumber) {
        this.versionNumber = versionNumber;
    }

    /**
     * {@return the version number}
     */
    public int versionNumber() {
        return this.versionNumber;
    }

    /**
     * {@return the QuicVersion corresponding to the {@code versionNumber} or
     * {@link Optional#empty() an empty Optional} if the {@code versionNumber}
     * doesn't correspond to a Quic version}
     *
     * @param versionNumber The version number
     */
    public static Optional<QuicVersion> of(int versionNumber) {
        for (QuicVersion qv : QuicVersion.values()) {
            if (qv.versionNumber == versionNumber) {
                return Optional.of(qv);
            }
        }
        return Optional.empty();
    }

    /**
     * From among the {@code quicVersions}, selects a {@code QuicVersion} to be used in the
     * first packet during connection initiation.
     *
     * @param quicVersions the available QUIC versions
     * @return the QUIC version to use in the first packet
     * @throws NullPointerException     if {@code quicVersions} is null or any element
     *                                  in it is null
     * @throws IllegalArgumentException if {@code quicVersions} is empty
     */
    public static QuicVersion firstFlightVersion(final Collection<QuicVersion> quicVersions) {
        Objects.requireNonNull(quicVersions);
        if (quicVersions.isEmpty()) {
            throw new IllegalArgumentException("Empty quic versions");
        }
        if (quicVersions.size() == 1) {
            return quicVersions.iterator().next();
        }
        for (final QuicVersion version : quicVersions) {
            if (version == QUIC_V1) {
                // we always prefer QUIC v1 for first flight version
                return QUIC_V1;
            }
        }
        // the given versions did not have QUIC v1, which implies the
        // only available first flight version is QUIC v2
        return QUIC_V2;
    }
}