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package jdk.internal.net.http.quic;

import jdk.internal.net.http.common.Deadline;
import jdk.internal.net.http.common.Log;

/**
 * Implementation of QUIC congestion controller based on RFC 9002.
 * This is a QUIC variant of New Reno algorithm.
 *
 * @spec https://www.rfc-editor.org/info/rfc9000
 *      RFC 9000: QUIC: A UDP-Based Multiplexed and Secure Transport
 * @spec https://www.rfc-editor.org/info/rfc9002
 *      RFC 9002: QUIC Loss Detection and Congestion Control
 */
final class QuicRenoCongestionController extends QuicBaseCongestionController {
    public QuicRenoCongestionController(String dbgTag, QuicRttEstimator rttEstimator) {
        super(dbgTag, rttEstimator);
    }

    boolean congestionAvoidanceAcked(int packetBytes, Deadline sentTime) {
        boolean isAppLimited = congestionWindow > maxBytesInFlight + 2L * maxDatagramSize;
        if (!isAppLimited) {
            congestionWindow += Math.max((long) maxDatagramSize * packetBytes / congestionWindow, 1L);
        }
        return isAppLimited;
    }

    void onCongestionEvent(Deadline sentTime) {
        if (inCongestionRecovery(sentTime)) {
            return;
        }
        congestionRecoveryStartTime = timeSource.instant();
        ssThresh = congestionWindow / 2;
        congestionWindow = Math.max(minimumWindow, ssThresh);
        maxBytesInFlight = 0;
        if (Log.quicCC()) {
            Log.logQuic(dbgTag + " Congestion: ssThresh: " + ssThresh +
                    ", in flight: " + bytesInFlight +
                    ", cwnd:" + congestionWindow);
        }
    }
}