MARTe-Integrated-Components/Client/udpscope/tests/FrameDecoderTest.cpp

#include "FrameDecoder.h"

#include <gtest/gtest.h>

#include <vector>

using namespace udpscope;

namespace {

/** Builds a FrameView over vectors the test owns. */
struct FrameBuilder {
    std::vector<std::vector<double>> storage;
    std::vector<const double*>       ptrs;
    std::vector<uint32_t>            counts;
    FrameView                        view;

    void addSignal(std::vector<double> vals) {
        storage.push_back(std::move(vals));
    }

    /* Real frames carry a per-update counter; leaving it at zero would hide
     * whichever rules depend on it, so it must be passed explicitly. */
    const FrameView& build(uint64_t hrt, double recvTime, uint32_t numSamples = 1,
                           uint32_t counter = 0) {
        ptrs.clear();
        counts.clear();
        for (const auto& s : storage) {
            ptrs.push_back(s.data());
            counts.push_back(static_cast<uint32_t>(s.size()));
        }
        view.counter    = counter;
        view.hrt        = hrt;
        view.recvTime   = recvTime;
        view.numSamples = numSamples;
        view.numSignals = static_cast<uint32_t>(storage.size());
        view.values     = ptrs.data();
        view.counts     = counts.data();
        return view;
    }
};

SignalMeta burst(const char* name, uint8_t timeMode, double rate,
                 uint32_t elems, uint32_t timeIdx) {
    SignalMeta m;
    m.name          = name;
    m.typeCode      = 8;              /* float32 */
    m.numRows       = elems;
    m.numCols       = 1;
    m.timeMode      = timeMode;
    m.samplingRate  = rate;
    m.timeSignalIdx = timeIdx;
    return m;
}

SignalMeta timeSignal(const char* name, uint32_t elems) {
    SignalMeta m;
    m.name     = name;
    m.typeCode = 6;                   /* uint64 -> nanoseconds */
    m.numRows  = elems;
    m.numCols  = 1;
    return m;
}

} /* namespace */

TEST(FrameDecoder, FullArrayTakesOneStampPerElementFromTheTimeSignal) {
    FrameDecoder dec;
    dec.setSignals({burst("Sine", kTimeFullArray, 1000.0, 4, 1),
                    timeSignal("Time", 4)});

    FrameBuilder fb;
    fb.addSignal({1.0, 2.0, 3.0, 4.0});
    /* Nanoseconds: 5.000, 5.001, 5.002, 5.003 s of producer time. */
    fb.addSignal({5.0e9, 5.001e9, 5.002e9, 5.003e9});
    const FrameView& f = fb.build(0, 1000.0);

    dec.beginFrame(f);
    std::vector<double> ts;
    ASSERT_TRUE(dec.timestamps(f, 0, ts));
    ASSERT_EQ(ts.size(), 4u);

    /* Element 0 lands on the arrival time; the rest keep the producer spacing. */
    EXPECT_NEAR(ts[0], 1000.000, 1e-9);
    EXPECT_NEAR(ts[1], 1000.001, 1e-9);
    EXPECT_NEAR(ts[2], 1000.002, 1e-9);
    EXPECT_NEAR(ts[3], 1000.003, 1e-9);
}

TEST(FrameDecoder, FirstSampleAnchorsElementZeroAndCountsForward) {
    FrameDecoder dec;
    dec.setSignals({burst("Sine", kTimeFirstSample, 1000.0, 4, 1),
                    timeSignal("Time", 1)});

    FrameBuilder fb;
    fb.addSignal({1.0, 2.0, 3.0, 4.0});
    fb.addSignal({7.0e9});
    const FrameView& f = fb.build(0, 2000.0);

    dec.beginFrame(f);
    std::vector<double> ts;
    ASSERT_TRUE(dec.timestamps(f, 0, ts));
    ASSERT_EQ(ts.size(), 4u);
    EXPECT_NEAR(ts[0], 2000.000, 1e-9);
    EXPECT_NEAR(ts[3], 2000.003, 1e-9);
}

TEST(FrameDecoder, LastSampleAnchorsTheFinalElementAndCountsBackward) {
    FrameDecoder dec;
    dec.setSignals({burst("Sine", kTimeLastSample, 1000.0, 4, 1),
                    timeSignal("Time", 1)});

    FrameBuilder fb;
    fb.addSignal({1.0, 2.0, 3.0, 4.0});
    fb.addSignal({7.0e9});
    const FrameView& f = fb.build(0, 3000.0);

    dec.beginFrame(f);
    std::vector<double> ts;
    ASSERT_TRUE(dec.timestamps(f, 0, ts));
    ASSERT_EQ(ts.size(), 4u);
    EXPECT_NEAR(ts[3], 3000.000, 1e-9);
    EXPECT_NEAR(ts[0], 3000.000 - 0.003, 1e-9);
}

TEST(FrameDecoder, PlainScalarUsesArrivalTime) {
    FrameDecoder dec;
    SignalMeta m;
    m.name = "Level";
    m.typeCode = 9;
    dec.setSignals({m});

    FrameBuilder fb;
    fb.addSignal({42.0});
    const FrameView& f = fb.build(0, 1234.5);

    dec.beginFrame(f);
    std::vector<double> ts;
    ASSERT_TRUE(dec.timestamps(f, 0, ts));
    ASSERT_EQ(ts.size(), 1u);
    EXPECT_DOUBLE_EQ(ts[0], 1234.5);
}

// This is the failure UDPSourceSession.cpp:560 documents. The kernel delivers
// two queued datagrams microseconds apart even though each carries 10 ms of
// signal. Dating from arrival crams the second packet's samples into that gap
// and the trace becomes a sawtooth; dating from the producer hrt does not.
TEST(FrameDecoder, AccumulatedScalarSurvivesBurstyDelivery) {
    FrameDecoder dec;
    SignalMeta m;
    m.name         = "Acc";
    m.typeCode     = 9;
    m.numRows      = 1;
    m.samplingRate = 1000.0;          /* 1 kHz, 10 samples = 10 ms per packet */
    dec.setSignals({m});

    const double ticks = 1.0e9;
    std::vector<double> all;

    for (int p = 0; p < 40; p++) {
        FrameBuilder fb;
        fb.addSignal(std::vector<double>(10, static_cast<double>(p)));
        const double producerSec = 100.0 + p * 0.010;
        /* Packets 20+ arrive in a burst, all within 50 us of each other. */
        const double arrival = (p < 20) ? (500.0 + p * 0.010)
                                        : (500.2 + (p - 20) * 0.00005);
        const FrameView& f = fb.build(static_cast<uint64_t>(producerSec * ticks),
                                      arrival, 10, static_cast<uint32_t>(p + 1));
        dec.beginFrame(f);
        std::vector<double> ts;
        if (dec.timestamps(f, 0, ts)) {
            all.insert(all.end(), ts.begin(), ts.end());
        }
    }

    ASSERT_GT(all.size(), 300u);
    for (size_t i = 1; i < all.size(); i++) {
        EXPECT_GT(all[i], all[i - 1]) << "non-monotonic at " << i;
        EXPECT_NEAR(all[i] - all[i - 1], 0.001, 2e-4)
            << "spacing collapsed at " << i << " (sawtooth)";
    }
}

namespace {

/** Ten contiguous 10-sample bursts at 1 kHz, counters 1..10, ending at 500.090. */
SignalMeta accSignal() {
    SignalMeta m;
    m.name         = "Acc";
    m.typeCode     = 9;
    m.numRows      = 1;
    m.samplingRate = 1000.0;          /* 10 samples = 10 ms per packet */
    return m;
}

void primeTenBursts(FrameDecoder& dec, std::vector<double>& ts, bool withCounter) {
    for (int p = 0; p < 10; p++) {
        FrameBuilder fb;
        fb.addSignal(std::vector<double>(10, 1.0));
        const FrameView& f = fb.build(0, 500.0 + p * 0.010, 10,
                                      withCounter ? static_cast<uint32_t>(p + 1) : 0u);
        dec.beginFrame(f);
        ASSERT_TRUE(dec.timestamps(f, 0, ts));
    }
    ASSERT_NEAR(ts[9], 500.090, 1e-9);
}

} /* namespace */

// The counterweight to the test above. Chaining bursts to suppress arrival
// jitter is only safe if loss is accounted for: a bare chain closes the hole a
// dropped datagram left and dates every later sample early for the rest of the
// run. The wire says exactly how much is missing, so no estimate is needed —
// and this test deliberately makes arrival time a LIAR (200 ms off) to prove
// the reconstruction comes from the counter and not from when the packet landed.
TEST(FrameDecoder, AccumulatedScalarReinstatesLostPacketsFromTheCounterGap) {
    FrameDecoder dec;
    dec.setSignals({accSignal()});
    std::vector<double> ts;
    primeTenBursts(dec, ts, /*withCounter=*/true);

    /* Counter 111 after 10: 100 packets lost, 1000 samples, exactly 1 s. The
     * packet lands 200 ms later than that truth would predict. */
    FrameBuilder fb;
    fb.addSignal(std::vector<double>(10, 1.0));
    const FrameView& f = fb.build(0, 501.300, 10, 111u);
    dec.beginFrame(f);
    ASSERT_TRUE(dec.timestamps(f, 0, ts));

    /* Chaining blindly gives 500.091; anchoring on arrival gives 501.291. */
    EXPECT_NEAR(ts[0], 501.091, 1e-9);
    EXPECT_NEAR(ts[9], 501.100, 1e-9);
}

// A producer that never advances the counter, or restarts it, leaves nothing to
// reconstruct from. Arrival time is then the better of two bad answers, and the
// chain has to be abandoned rather than left to drift forever.
TEST(FrameDecoder, AccumulatedScalarResyncsOnArrivalWhenTheCounterSaysNothing) {
    FrameDecoder dec;
    dec.setSignals({accSignal()});
    std::vector<double> ts;
    primeTenBursts(dec, ts, /*withCounter=*/false);

    FrameBuilder fb;
    fb.addSignal(std::vector<double>(10, 1.0));
    const FrameView& f = fb.build(0, 501.100, 10, 0u);
    dec.beginFrame(f);
    ASSERT_TRUE(dec.timestamps(f, 0, ts));

    EXPECT_NEAR(ts[0], 501.091, 1e-9);
    EXPECT_NEAR(ts[9], 501.100, 1e-9);
}

// Re-anchoring must never move a signal's timestamps backwards: the ring, the
// trigger and the exporter all assume they increase, and a backward step is
// indistinguishable from corruption downstream. Here the counter claims a
// 20 s hole while the packet arrives 10 ms after the last one, so the
// prediction and arrival disagree wildly and arrival points into the past.
TEST(FrameDecoder, AccumulatedScalarNeverStepsBackwardsWhenResyncing) {
    FrameDecoder dec;
    dec.setSignals({accSignal()});
    std::vector<double> ts;
    primeTenBursts(dec, ts, /*withCounter=*/true);
    const double prevEnd = ts[9];

    FrameBuilder fb;
    fb.addSignal(std::vector<double>(10, 1.0));
    const FrameView& f = fb.build(0, 500.000, 10, 2010u);
    dec.beginFrame(f);
    ASSERT_TRUE(dec.timestamps(f, 0, ts));

    /* Arrival (500.000) is behind our timeline, so there is nothing to spread
     * into; the burst is drawn narrower instead, which starts to bleed the lead
     * off while still moving strictly forwards. */
    EXPECT_NEAR(ts[0], 500.0909, 1e-9);
    EXPECT_GT(ts[0], prevEnd) << "resync stepped backwards over the previous burst";
    for (size_t i = 1; i < ts.size(); i++) {
        EXPECT_GT(ts[i], ts[i - 1]);
    }
}

// When the chain has to be abandoned but arrival lies just ahead of where the
// last burst ended, the correction is made by COMPRESSING this one burst rather
// than by stepping back. Rejecting the correction instead would be one-directional
// — `predicted` is never below lastEmittedEnd + dt — and a timeline running fast
// could then never be pulled back.
TEST(FrameDecoder, AccumulatedScalarCompressesOneBurstRatherThanStepBack) {
    FrameDecoder dec;
    dec.setSignals({accSignal()});
    std::vector<double> ts;
    primeTenBursts(dec, ts, /*withCounter=*/true);

    /* A counter gap far beyond any real outage: the prediction is unusable, and
     * the arrival anchor (500.086) sits behind the previous burst end. */
    FrameBuilder fb;
    fb.addSignal(std::vector<double>(10, 1.0));
    const FrameView& f = fb.build(0, 500.095, 10, 900011u);
    dec.beginFrame(f);
    ASSERT_TRUE(dec.timestamps(f, 0, ts));

    EXPECT_GT(ts[0], 500.090) << "compressed burst must still start after the last one";
    EXPECT_NEAR(ts[9], 500.095, 1e-9) << "and end exactly on arrival";
    EXPECT_NEAR(ts[1] - ts[0], 0.0005, 1e-9) << "spread over the available room";
}

// The whole point of compressing: a declared SamplingRate is a hand-written
// config value, and even a correct one is measured against the producer host's
// crystal, not ours. Tens of ppm of difference is certain over a long session,
// so the reconstructed timeline WILL run away from the wall clock. It has to be
// pulled back, and it has to stay monotonic while that happens.
TEST(FrameDecoder, AccumulatedScalarDoesNotDriftAwayFromTheWallClockForever) {
    FrameDecoder dec;
    dec.setSignals({accSignal()});   /* declares 1 kHz */

    /* The producer really runs 1 % fast: 10 samples take 9.9 ms of wall time,
     * so a chain stepping the declared 10 ms per packet gains 0.1 ms every
     * packet. This is the direction re-anchoring alone cannot fix: arrival is
     * always BEHIND the chain, so anchoring on it would step backwards and is
     * refused. Only compression pulls the timeline back. */
    double worstLead = 0.0;
    double lastEnd   = 0.0;
    for (int p = 0; p < 20000; p++) {
        FrameBuilder fb;
        fb.addSignal(std::vector<double>(10, 1.0));
        const double arrival = 500.0 + p * 0.0099;
        const FrameView& f =
            fb.build(0, arrival, 10, static_cast<uint32_t>(p + 1));
        dec.beginFrame(f);
        std::vector<double> ts;
        ASSERT_TRUE(dec.timestamps(f, 0, ts));

        for (size_t i = 0; i < ts.size(); i++) {
            ASSERT_GT(ts[i], lastEnd) << "timeline went backwards at packet " << p;
            lastEnd = ts[i];
        }
        worstLead = std::max(worstLead, ts[9] - arrival);
    }

    /* Unchecked, 20000 packets at 0.1 ms each would put the trace 2 s ahead. */
    EXPECT_LT(worstLead, 0.6) << "timeline drifted " << worstLead << " s ahead";
}

// The C client de-duplicates fragments but not whole unfragmented updates, so a
// host subscribed on two interfaces sees each datagram twice. Emitting the
// repeat would double the values and advance time by a burst that never was.
TEST(FrameDecoder, AccumulatedScalarDropsADuplicatedDatagram) {
    FrameDecoder dec;
    dec.setSignals({accSignal()});
    std::vector<double> ts;
    primeTenBursts(dec, ts, /*withCounter=*/true);
    const double endBefore = ts[9];

    FrameBuilder fb;
    fb.addSignal(std::vector<double>(10, 1.0));
    const FrameView& dup = fb.build(0, 500.1001, 10, 10u);   /* counter 10 again */
    dec.beginFrame(dup);
    EXPECT_FALSE(dec.timestamps(dup, 0, ts));

    /* And the drop must not have disturbed the chain: the genuine next packet
     * still lands one period after burst 10 ended. */
    const FrameView& next = fb.build(0, 500.109, 10, 11u);
    dec.beginFrame(next);
    ASSERT_TRUE(dec.timestamps(next, 0, ts));
    EXPECT_NEAR(ts[0], endBefore + 0.001, 1e-9);
}

TEST(FrameDecoder, AccumulatedScalarDerivesDtFromTheHrtGapWhenNoRateIsDeclared) {
    FrameDecoder dec;
    SignalMeta m;
    m.name         = "Acc";
    m.typeCode     = 9;
    m.samplingRate = 0.0;             /* undeclared */
    dec.setSignals({m});

    const double ticks = 1.0e9;
    std::vector<double> last;
    for (int p = 0; p < 40; p++) {
        FrameBuilder fb;
        fb.addSignal(std::vector<double>(10, 1.0));
        /* 25 ms per packet, deliberately NOT 10: at 10 the expected 1 ms period
         * equals kDefaultDt, so a decoder that never derived anything and just
         * returned the default would pass a test named for the derivation. */
        const double producerSec = 100.0 + p * 0.025;
        /* Zero-mean arrival jitter, so the rate fit still converges but no
         * single arrival GAP is right. Without it, uniform arrivals make
         * packetBurst and the hrt path return the same number by construction
         * and the test cannot tell which branch answered. */
        const double jitter[4] = {0.0, 0.003, 0.0, -0.003};
        const FrameView& f = fb.build(static_cast<uint64_t>(producerSec * ticks),
                                      700.0 + p * 0.025 + jitter[p % 4], 10,
                                      static_cast<uint32_t>(p + 1));
        dec.beginFrame(f);
        std::vector<double> ts;
        if (dec.timestamps(f, 0, ts)) { last = ts; }
    }

    ASSERT_EQ(last.size(), 10u);
    /* 25 ms of producer time across 10 samples is a 2.5 ms period, whatever the
     * datagrams did on the way over. Arrival-spanning the last gap (22 ms)
     * would give 2.2 ms; defaulting would give 1 ms. */
    EXPECT_NEAR(last[1] - last[0], 0.0025, 2e-5);
}

// A PACKET burst has no per-element time at all. Elements span
// (lastPacket, thisPacket] — backwards from arrival, because the samples were
// acquired before the packet landed. Forward extrapolation would let a jittered
// packet overlap the next one and break ring monotonicity.
TEST(FrameDecoder, PacketBurstDropsTheFirstFrameThenSpansBackwards) {
    FrameDecoder dec;
    dec.setSignals({burst("Raw", kTimePacket, 0.0, 5, kNoTimeSignal)});

    FrameBuilder fb1;
    fb1.addSignal({1.0, 2.0, 3.0, 4.0, 5.0});
    const FrameView& f1 = fb1.build(0, 10.0);
    dec.beginFrame(f1);
    std::vector<double> ts;
    EXPECT_FALSE(dec.timestamps(f1, 0, ts))
        << "the first packet has no previous arrival to span from";

    FrameBuilder fb2;
    fb2.addSignal({6.0, 7.0, 8.0, 9.0, 10.0});
    const FrameView& f2 = fb2.build(0, 10.05);
    dec.beginFrame(f2);
    ASSERT_TRUE(dec.timestamps(f2, 0, ts));
    ASSERT_EQ(ts.size(), 5u);
    EXPECT_GT(ts[0], 10.0);
    EXPECT_NEAR(ts[4], 10.05, 1e-12);
    EXPECT_NEAR(ts[1] - ts[0], 0.01, 1e-12);
}

TEST(FrameDecoder, PacketBurstStaysMonotonicUnderJitteredArrivals) {
    FrameDecoder dec;
    dec.setSignals({burst("Raw", kTimePacket, 0.0, 8, kNoTimeSignal)});

    const double jitter[] = {0.0, 0.004, -0.003, 0.006, -0.002, 0.0, 0.005, -0.004};
    std::vector<double> all;
    for (int p = 0; p < 8; p++) {
        FrameBuilder fb;
        fb.addSignal(std::vector<double>(8, 1.0));
        const FrameView& f = fb.build(0, 20.0 + p * 0.05 + jitter[p]);
        dec.beginFrame(f);
        std::vector<double> ts;
        if (dec.timestamps(f, 0, ts)) {
            all.insert(all.end(), ts.begin(), ts.end());
        }
    }

    ASSERT_GT(all.size(), 8u);
    for (size_t i = 1; i < all.size(); i++) {
        EXPECT_GT(all[i], all[i - 1]) << "packets overlapped at " << i;
    }
}

TEST(FrameDecoder, ResetForgetsPerSignalHistory) {
    FrameDecoder dec;
    dec.setSignals({burst("Raw", kTimePacket, 0.0, 4, kNoTimeSignal)});

    FrameBuilder fb;
    fb.addSignal({1.0, 2.0, 3.0, 4.0});
    const FrameView& f = fb.build(0, 5.0);
    dec.beginFrame(f);
    std::vector<double> ts;
    EXPECT_FALSE(dec.timestamps(f, 0, ts));

    const FrameView& f2 = fb.build(0, 5.1);
    dec.beginFrame(f2);
    EXPECT_TRUE(dec.timestamps(f2, 0, ts));

    dec.reset();
    const FrameView& f3 = fb.build(0, 5.2);
    dec.beginFrame(f3);
    EXPECT_FALSE(dec.timestamps(f3, 0, ts))
        << "after reset the next packet is again the first one";
}