/*
 *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#include <algorithm>
#include <vector>

#include "testing/gtest/include/gtest/gtest.h"
#include "webrtc/modules/bitrate_controller/send_side_bandwidth_estimation.h"

namespace webrtc {

void TestProbing(bool use_delay_based) {
  SendSideBandwidthEstimation bwe;
  bwe.SetMinMaxBitrate(100000, 1500000);
  bwe.SetSendBitrate(200000);

  const int kRembBps = 1000000;
  const int kSecondRembBps = kRembBps + 500000;
  int64_t now_ms = 0;

  bwe.UpdateReceiverBlock(0, 50, 1, now_ms);

  // Initial REMB applies immediately.
  if (use_delay_based) {
    bwe.UpdateDelayBasedEstimate(now_ms, kRembBps);
  } else {
    bwe.UpdateReceiverEstimate(now_ms, kRembBps);
  }
  bwe.UpdateEstimate(now_ms);
  int bitrate;
  uint8_t fraction_loss;
  int64_t rtt;
  bwe.CurrentEstimate(&bitrate, &fraction_loss, &rtt);
  EXPECT_EQ(kRembBps, bitrate);

  // Second REMB doesn't apply immediately.
  now_ms += 2001;
  if (use_delay_based) {
    bwe.UpdateDelayBasedEstimate(now_ms, kSecondRembBps);
  } else {
    bwe.UpdateReceiverEstimate(now_ms, kSecondRembBps);
  }
  bwe.UpdateEstimate(now_ms);
  bitrate = 0;
  bwe.CurrentEstimate(&bitrate, &fraction_loss, &rtt);
  EXPECT_EQ(kRembBps, bitrate);
}

TEST(SendSideBweTest, InitialRembWithProbing) {
  TestProbing(false);
}

TEST(SendSideBweTest, InitialDelayBasedBweWithProbing) {
  TestProbing(true);
}

TEST(SendSideBweTest, DoesntReapplyBitrateDecreaseWithoutFollowingRemb) {
  SendSideBandwidthEstimation bwe;
  static const int kMinBitrateBps = 100000;
  static const int kInitialBitrateBps = 1000000;
  bwe.SetMinMaxBitrate(kMinBitrateBps, 1500000);
  bwe.SetSendBitrate(kInitialBitrateBps);

  static const uint8_t kFractionLoss = 128;
  static const int64_t kRttMs = 50;

  int64_t now_ms = 0;
  int bitrate_bps;
  uint8_t fraction_loss;
  int64_t rtt_ms;
  bwe.CurrentEstimate(&bitrate_bps, &fraction_loss, &rtt_ms);
  EXPECT_EQ(kInitialBitrateBps, bitrate_bps);
  EXPECT_EQ(0, fraction_loss);
  EXPECT_EQ(0, rtt_ms);

  // Signal heavy loss to go down in bitrate.
  bwe.UpdateReceiverBlock(kFractionLoss, kRttMs, 100, now_ms);
  // Trigger an update 2 seconds later to not be rate limited.
  now_ms += 2000;
  bwe.UpdateEstimate(now_ms);

  bwe.CurrentEstimate(&bitrate_bps, &fraction_loss, &rtt_ms);
  EXPECT_LT(bitrate_bps, kInitialBitrateBps);
  // Verify that the obtained bitrate isn't hitting the min bitrate, or this
  // test doesn't make sense. If this ever happens, update the thresholds or
  // loss rates so that it doesn't hit min bitrate after one bitrate update.
  EXPECT_GT(bitrate_bps, kMinBitrateBps);
  EXPECT_EQ(kFractionLoss, fraction_loss);
  EXPECT_EQ(kRttMs, rtt_ms);

  // Triggering an update shouldn't apply further downgrade nor upgrade since
  // there's no intermediate receiver block received indicating whether this is
  // currently good or not.
  int last_bitrate_bps = bitrate_bps;
  // Trigger an update 2 seconds later to not be rate limited (but it still
  // shouldn't update).
  now_ms += 2000;
  bwe.UpdateEstimate(now_ms);
  bwe.CurrentEstimate(&bitrate_bps, &fraction_loss, &rtt_ms);

  EXPECT_EQ(last_bitrate_bps, bitrate_bps);
  // The old loss rate should still be applied though.
  EXPECT_EQ(kFractionLoss, fraction_loss);
  EXPECT_EQ(kRttMs, rtt_ms);
}

}  // namespace webrtc