#include <mbgl/test/util.hpp>

#include <mbgl/map/transform.hpp>
#include <mbgl/util/geo.hpp>

using namespace mbgl;

TEST(Transform, InvalidScale) {
    Transform transform;

    ASSERT_DOUBLE_EQ(0, transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(0, transform.getLatLng().longitude());
    ASSERT_DOUBLE_EQ(1, transform.getScale());

    transform.setScale(2 << 0);

    ASSERT_DOUBLE_EQ(0, transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(0, transform.getLatLng().longitude());
    ASSERT_DOUBLE_EQ(2, transform.getScale());

    const double invalid = std::nan("");
    transform.setScale(invalid);

    ASSERT_DOUBLE_EQ(0, transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(0, transform.getLatLng().longitude());
    ASSERT_DOUBLE_EQ(2, transform.getScale());

    transform.scaleBy(invalid);

    ASSERT_DOUBLE_EQ(0, transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(0, transform.getLatLng().longitude());
    ASSERT_DOUBLE_EQ(2, transform.getScale());

    transform.setZoom(invalid);

    ASSERT_DOUBLE_EQ(0, transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(0, transform.getLatLng().longitude());
    ASSERT_DOUBLE_EQ(2, transform.getScale());

    transform.setLatLngZoom({ 0, 0 }, invalid);

    ASSERT_DOUBLE_EQ(0, transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(0, transform.getLatLng().longitude());
    ASSERT_DOUBLE_EQ(2, transform.getScale());
}


TEST(Transform, InvalidBearing) {
    Transform transform;

    ASSERT_DOUBLE_EQ(0, transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(0, transform.getLatLng().longitude());
    ASSERT_DOUBLE_EQ(1, transform.getScale());

    transform.setScale(2 << 0);
    transform.setAngle(2);

    ASSERT_DOUBLE_EQ(0, transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(0, transform.getLatLng().longitude());
    ASSERT_DOUBLE_EQ(2, transform.getScale());
    ASSERT_DOUBLE_EQ(2, transform.getAngle());

    const double invalid = std::nan("");
    transform.setAngle(invalid);

    ASSERT_DOUBLE_EQ(0, transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(0, transform.getLatLng().longitude());
    ASSERT_DOUBLE_EQ(2, transform.getScale());
    ASSERT_DOUBLE_EQ(2, transform.getAngle());
}

TEST(Transform, IntegerZoom) {
    Transform transform;

    auto checkIntegerZoom = [&transform](uint8_t zoomInt, double zoom) {
        double scale = transform.getState().zoomScale(zoom);
        transform.setScale(scale);
#if __ANDROID__
        // Android uses log(x) / M_LN2 instead of log2(x) because the latter
        // is _broken in ARMv5 - that approach being less precise than log2(x).
        ASSERT_NEAR(transform.getScale(), scale, 0.0001);
#else
        ASSERT_DOUBLE_EQ(transform.getScale(), scale);
#endif
        ASSERT_NEAR(transform.getZoom(), zoom, 0.0001);
        ASSERT_EQ(transform.getState().getIntegerZoom(), zoomInt);
        ASSERT_NEAR(transform.getState().getZoomFraction(), zoom - zoomInt, 0.0001);
    };

    for (uint8_t zoomInt = 0; zoomInt < 20; ++zoomInt) {
        for (uint32_t percent = 0; percent < 100; ++percent) {
            double zoom = zoomInt + (0.01 * percent);
            checkIntegerZoom(zoomInt, zoom);
        }
    }

    // Special case zoom 20.
    checkIntegerZoom(20, 20.0);
}

TEST(Transform, PerspectiveProjection) {
    LatLng loc;

    Transform transform;
    transform.resize({ 1000, 1000 });
    transform.setScale(2 << 9);
    transform.setPitch(0.9);
    transform.setLatLng(LatLng(38, -77));

    // expected values are from mapbox-gl-js

    loc = transform.getLatLng();
    ASSERT_NEAR(-77, loc.longitude(), 0.0001);
    ASSERT_NEAR(38, loc.latitude(), 0.0001);

    loc = transform.getState().screenCoordinateToLatLng({ 0, 1000 });
    ASSERT_NEAR(-77.59198961199148, loc.longitude(), 0.0002);
    ASSERT_NEAR(38.74661326302018, loc.latitude(), 0.0001);

    loc = transform.getState().screenCoordinateToLatLng({ 1000, 0 });
    ASSERT_NEAR(-76.75823239205641, loc.longitude(), 0.0001);
    ASSERT_NEAR(37.692872969426375, loc.latitude(), 0.0001);

    ScreenCoordinate point = transform.getState().latLngToScreenCoordinate({38.74661326302018, -77.59198961199148});
    ASSERT_NEAR(point.x, 0, 0.01);
    ASSERT_NEAR(point.y, 1000, 0.01);

    point = transform.getState().latLngToScreenCoordinate({37.692872969426375, -76.75823239205641});
    ASSERT_NEAR(point.x, 1000, 0.02);
    ASSERT_NEAR(point.y, 0, 0.02);
}

TEST(Transform, UnwrappedLatLng) {
    Transform transform;
    transform.resize({ 1000, 1000 });
    transform.setScale(2 << 9);
    transform.setPitch(0.9);
    transform.setLatLng(LatLng(38, -77));

    const TransformState& state = transform.getState();

    LatLng fromGetLatLng = state.getLatLng();
    ASSERT_DOUBLE_EQ(fromGetLatLng.latitude(), 38);
    ASSERT_DOUBLE_EQ(fromGetLatLng.longitude(), -77);

    LatLng fromScreenCoordinate = state.screenCoordinateToLatLng({ 500, 500 });
    ASSERT_NEAR(fromScreenCoordinate.latitude(),   37.999999999999829, 0.0001); // 1.71E-13
    ASSERT_NEAR(fromScreenCoordinate.longitude(), -76.999999999999773, 0.0001); // 2.27E-13

    LatLng wrappedForwards = state.screenCoordinateToLatLng(state.latLngToScreenCoordinate({ 38, 283 }));
    ASSERT_NEAR(wrappedForwards.latitude(), 37.999999999999716, 0.0001); // 2.84E-13
    ASSERT_NEAR(wrappedForwards.longitude(), 282.99999999988751, 0.0001); // 1.1249E-11
    wrappedForwards.wrap();
    ASSERT_NEAR(wrappedForwards.longitude(), -77.000000000112493, 0.001); // 1.1249E-11

    LatLng wrappedBackwards = state.screenCoordinateToLatLng(state.latLngToScreenCoordinate({ 38, -437 }));
    ASSERT_NEAR(wrappedBackwards.latitude(), wrappedForwards.latitude(), 0.001);
    ASSERT_NEAR(wrappedBackwards.longitude(), -436.99999999988728, 0.001); // 1.1272E-11
    wrappedBackwards.wrap();
    ASSERT_NEAR(wrappedBackwards.longitude(), -76.99999999988728, 0.001); // 1.1272E-11
}

TEST(Transform, ConstrainHeightOnly) {
    LatLng loc;

    Transform transform;
    transform.resize({ 1000, 1000 });
    transform.setScale(std::pow(2, util::MAX_ZOOM));

    transform.setLatLng(LatLngBounds::world().southwest());
    loc = transform.getLatLng();
    ASSERT_NEAR(-util::LATITUDE_MAX, loc.latitude(), 0.001);
    ASSERT_NEAR(util::LONGITUDE_MAX, std::abs(loc.longitude()), 0.001);

    transform.setLatLng(LatLngBounds::world().northeast());
    loc = transform.getLatLng();
    ASSERT_NEAR(util::LATITUDE_MAX, loc.latitude(), 0.001);
    ASSERT_NEAR(util::LONGITUDE_MAX, std::abs(loc.longitude()), 0.001);
}

TEST(Transform, ConstrainWidthAndHeight) {
    LatLng loc;

    Transform transform(MapObserver::nullObserver(), ConstrainMode::WidthAndHeight);
    transform.resize({ 1000, 1000 });
    transform.setScale(std::pow(2, util::MAX_ZOOM));

    transform.setLatLng(LatLngBounds::world().southwest());
    loc = transform.getLatLng();
    ASSERT_NEAR(-util::LATITUDE_MAX, loc.latitude(), 0.001);
    ASSERT_NEAR(-util::LONGITUDE_MAX, loc.longitude(), 0.001);

    transform.setLatLng(LatLngBounds::world().northeast());
    loc = transform.getLatLng();
    ASSERT_NEAR(util::LATITUDE_MAX, loc.latitude(), 0.001);
    ASSERT_NEAR(util::LONGITUDE_MAX, std::abs(loc.longitude()), 0.001);
}

TEST(Transform, Anchor) {
    Transform transform;
    transform.resize({ 1000, 1000 });

    const LatLng latLng { 10, -100 };
    transform.setLatLngZoom(latLng, 10);

    ASSERT_DOUBLE_EQ(latLng.latitude(), transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(latLng.longitude(), transform.getLatLng().longitude());
    ASSERT_DOUBLE_EQ(10, transform.getZoom());
    ASSERT_DOUBLE_EQ(0, transform.getAngle());

    const optional<ScreenCoordinate> invalidAnchorPoint {};
    const ScreenCoordinate anchorPoint = { 150, 150 };

    const LatLng anchorLatLng = transform.getState().screenCoordinateToLatLng(anchorPoint);
    ASSERT_NE(latLng.latitude(), anchorLatLng.latitude());
    ASSERT_NE(latLng.longitude(), anchorLatLng.longitude());

    transform.setLatLngZoom(latLng, 2);
    transform.scaleBy(1);
    ASSERT_DOUBLE_EQ(4, transform.getScale());
    ASSERT_DOUBLE_EQ(latLng.latitude(), transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(latLng.longitude(), transform.getLatLng().longitude());

    transform.scaleBy(1.5, invalidAnchorPoint);
    ASSERT_DOUBLE_EQ(6, transform.getScale());
    ASSERT_DOUBLE_EQ(latLng.latitude(), transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(latLng.longitude(), transform.getLatLng().longitude());

    transform.scaleBy(2, anchorPoint);
    ASSERT_DOUBLE_EQ(12, transform.getScale());
    ASSERT_NE(latLng.latitude(), transform.getLatLng().latitude());
    ASSERT_NE(latLng.longitude(), transform.getLatLng().longitude());

    transform.setLatLngZoom(latLng, 10);
    transform.setScale(2 << 2);
    ASSERT_DOUBLE_EQ(2 << 2, transform.getScale());
    ASSERT_NEAR(latLng.latitude(), transform.getLatLng().latitude(), 0.000001);
    ASSERT_NEAR(latLng.longitude(), transform.getLatLng().longitude(), 0.000001);

    transform.setScale(2 << 4, invalidAnchorPoint);
    ASSERT_DOUBLE_EQ(2 << 4, transform.getScale());
    ASSERT_NEAR(latLng.latitude(), transform.getLatLng().latitude(), 0.000001);
    ASSERT_NEAR(latLng.longitude(), transform.getLatLng().longitude(), 0.000001);

    transform.setScale(2 << 6, anchorPoint);
    ASSERT_DOUBLE_EQ(2 << 6, transform.getScale());
    ASSERT_NE(latLng.latitude(), transform.getLatLng().latitude());
    ASSERT_NE(latLng.longitude(), transform.getLatLng().longitude());

    transform.setLatLngZoom(latLng, 10);
    transform.setZoom(2);
    ASSERT_DOUBLE_EQ(2, transform.getZoom());
    ASSERT_NEAR(latLng.latitude(), transform.getLatLng().latitude(), 0.000001);
    ASSERT_NEAR(latLng.longitude(), transform.getLatLng().longitude(), 0.000001);

    transform.setZoom(4, invalidAnchorPoint);
    ASSERT_DOUBLE_EQ(4, transform.getZoom());
    ASSERT_NEAR(latLng.latitude(), transform.getLatLng().latitude(), 0.000001);
    ASSERT_NEAR(latLng.longitude(), transform.getLatLng().longitude(), 0.000001);

    transform.setZoom(8, anchorPoint);
    ASSERT_DOUBLE_EQ(8, transform.getZoom());
    ASSERT_NE(latLng.latitude(), transform.getLatLng().latitude());
    ASSERT_NE(latLng.longitude(), transform.getLatLng().longitude());

    transform.setLatLngZoom(latLng, 10);
    transform.setAngle(M_PI_4);
    ASSERT_NEAR(M_PI_4, transform.getAngle(), 0.000001);
    ASSERT_DOUBLE_EQ(latLng.latitude(), transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(latLng.longitude(), transform.getLatLng().longitude());

    transform.setAngle(0, invalidAnchorPoint);
    ASSERT_DOUBLE_EQ(0, transform.getAngle());
    ASSERT_DOUBLE_EQ(latLng.latitude(), transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(latLng.longitude(), transform.getLatLng().longitude());

    transform.setAngle(45 * util::DEG2RAD, anchorPoint);
    ASSERT_NEAR(45 / util::RAD2DEG, transform.getAngle(), 0.000001);
    ASSERT_NEAR(anchorLatLng.latitude(), transform.getLatLng().latitude(), 1);
    ASSERT_NEAR(anchorLatLng.longitude(), transform.getLatLng().longitude(), 1);

    transform.setLatLngZoom(latLng, 10);
    transform.setPitch(10 * util::DEG2RAD);
    ASSERT_DOUBLE_EQ(10 / util::RAD2DEG, transform.getPitch());
    ASSERT_DOUBLE_EQ(latLng.latitude(), transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(latLng.longitude(), transform.getLatLng().longitude());

    transform.setPitch(15 * util::DEG2RAD, invalidAnchorPoint);
    ASSERT_DOUBLE_EQ(15 / util::RAD2DEG, transform.getPitch());
    ASSERT_DOUBLE_EQ(latLng.latitude(), transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(latLng.longitude(), transform.getLatLng().longitude());

    transform.setPitch(20 * util::DEG2RAD, anchorPoint);
    ASSERT_DOUBLE_EQ(20 / util::RAD2DEG, transform.getPitch());
    ASSERT_NEAR(anchorLatLng.latitude(), transform.getLatLng().latitude(), 1);
    ASSERT_NEAR(anchorLatLng.longitude(), transform.getLatLng().longitude(), 1);
}

TEST(Transform, Padding) {
    Transform transform;
    transform.resize({ 1000, 1000 });

    ASSERT_DOUBLE_EQ(0, transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(0, transform.getLatLng().longitude());

    transform.setLatLngZoom({ 10, -100 }, 10);

    const LatLng trueCenter = transform.getLatLng();
    ASSERT_DOUBLE_EQ(10, trueCenter.latitude());
    ASSERT_DOUBLE_EQ(-100, trueCenter.longitude());
    ASSERT_DOUBLE_EQ(10, transform.getZoom());

    const LatLng manualShiftedCenter = transform.getState().screenCoordinateToLatLng({
        1000.0 / 2.0,
        1000.0 / 4.0,
    });

    EdgeInsets padding(1000.0 / 2.0, 0, 0, 0);
    const LatLng shiftedCenter = transform.getLatLng(padding);
    ASSERT_NE(trueCenter.latitude(), shiftedCenter.latitude());
    ASSERT_NEAR(trueCenter.longitude(), shiftedCenter.longitude(), 1e-9);
    ASSERT_DOUBLE_EQ(manualShiftedCenter.latitude(), shiftedCenter.latitude());
    ASSERT_DOUBLE_EQ(manualShiftedCenter.longitude(), shiftedCenter.longitude());
}

TEST(Transform, MoveBy) {
    Transform transform;
    transform.resize({ 1000, 1000 });
    transform.setLatLngZoom({ 0, 0 }, 10);

    LatLng trueCenter = transform.getLatLng();
    ASSERT_DOUBLE_EQ(0, trueCenter.latitude());
    ASSERT_DOUBLE_EQ(0, trueCenter.longitude());
    ASSERT_DOUBLE_EQ(10, transform.getZoom());

    for (uint8_t x = 0; x < 20; ++x) {
        bool odd = x % 2;
        bool forward = x % 10;

        LatLng coordinate = transform.screenCoordinateToLatLng({ odd ? 400. : 600., forward ? 400. : 600 });
        transform.moveBy({ odd ? 100. : -100., forward ? 100. : -100 });

        trueCenter = transform.getLatLng();
        ASSERT_NEAR(coordinate.latitude(), trueCenter.latitude(), 0.0001);
        ASSERT_NEAR(coordinate.longitude(), trueCenter.longitude(), 0.0001);
    }

    // We have ~1.1 precision loss for each coordinate for 20 rounds of moveBy.
    ASSERT_NEAR(0, trueCenter.latitude(), 1.1);
    ASSERT_NEAR(0, trueCenter.longitude(), 1.1);
}

TEST(Transform, Antimeridian) {
    Transform transform;
    transform.resize({ 1000, 1000 });
    transform.setLatLngZoom({ 0, 0 }, 1);

    const LatLng coordinateSanFrancisco { 37.7833, -122.4167 };
    ScreenCoordinate pixelSF = transform.latLngToScreenCoordinate(coordinateSanFrancisco);
    ASSERT_NEAR(151.79409149185352, pixelSF.x, 1e-2);
    ASSERT_NEAR(383.76774094913071, pixelSF.y, 1e-2);

    transform.setLatLng({ 0, -181 });
    ScreenCoordinate pixelSFBackwards = transform.latLngToScreenCoordinate(coordinateSanFrancisco);
    ASSERT_NEAR(666.63617954008976, pixelSFBackwards.x, 1e-2);
    ASSERT_DOUBLE_EQ(pixelSF.y, pixelSFBackwards.y);

    transform.setLatLng({ 0, 179 });
    ScreenCoordinate pixelSFForwards = transform.latLngToScreenCoordinate(coordinateSanFrancisco);
    ASSERT_DOUBLE_EQ(pixelSFBackwards.x, pixelSFForwards.x);
    ASSERT_DOUBLE_EQ(pixelSFBackwards.y, pixelSFForwards.y);

    const LatLng coordinateWaikiri{ -16.9310, 179.9787 };
    transform.setLatLngZoom(coordinateWaikiri, 10);
    ScreenCoordinate pixelWaikiri = transform.latLngToScreenCoordinate(coordinateWaikiri);
    ASSERT_NEAR(500, pixelWaikiri.x, 1e-2);
    ASSERT_NEAR(500, pixelWaikiri.y, 1e-2);

    transform.setLatLng({ coordinateWaikiri.latitude(), 180.0213 });
    ScreenCoordinate pixelWaikiriForwards = transform.latLngToScreenCoordinate(coordinateWaikiri);
    ASSERT_NEAR(437.95953728819512, pixelWaikiriForwards.x, 1e-2);
    ASSERT_DOUBLE_EQ(pixelWaikiri.y, pixelWaikiriForwards.y);
    LatLng coordinateFromPixel = transform.screenCoordinateToLatLng(pixelWaikiriForwards);
    ASSERT_NEAR(coordinateWaikiri.latitude(), coordinateFromPixel.latitude(), 0.000001);
    ASSERT_NEAR(coordinateWaikiri.longitude(), coordinateFromPixel.longitude(), 0.000001);

    transform.setLatLng({ coordinateWaikiri.latitude(), -179.9787 });
    ScreenCoordinate pixelWaikiriBackwards = transform.latLngToScreenCoordinate(coordinateWaikiri);
    ASSERT_DOUBLE_EQ(pixelWaikiriForwards.x, pixelWaikiriBackwards.x);
    ASSERT_DOUBLE_EQ(pixelWaikiriForwards.y, pixelWaikiriBackwards.y);
    coordinateFromPixel = transform.screenCoordinateToLatLng(pixelWaikiriBackwards);
    ASSERT_NEAR(coordinateWaikiri.latitude(), coordinateFromPixel.latitude(), 0.000001);
    ASSERT_NEAR(coordinateWaikiri.longitude(), coordinateFromPixel.longitude(), 0.000001);
}

TEST(Transform, Camera) {
    Transform transform;
    transform.resize({ 1000, 1000 });

    const LatLng latLng1 { 45, 135 };
    CameraOptions cameraOptions1;
    cameraOptions1.zoom = 20;
    cameraOptions1.center = latLng1;
    transform.jumpTo(cameraOptions1);

    ASSERT_DOUBLE_EQ(latLng1.latitude(), transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(latLng1.longitude(), transform.getLatLng().longitude());
    ASSERT_DOUBLE_EQ(20, transform.getZoom());

    const LatLng latLng2 { -45, -135 };
    CameraOptions cameraOptions2;
    cameraOptions2.zoom = 10;
    cameraOptions2.center = latLng2;

    transform.jumpTo(cameraOptions2);
    ASSERT_DOUBLE_EQ(latLng2.latitude(), transform.getLatLng().latitude());
    ASSERT_DOUBLE_EQ(latLng2.longitude(), transform.getLatLng().longitude());
    ASSERT_DOUBLE_EQ(10, transform.getZoom());

    AnimationOptions easeOptions(Seconds(1));
    easeOptions.transitionFrameFn = [&](double t) {
        ASSERT_TRUE(t >= 0 && t <= 1);
        ASSERT_GE(latLng1.latitude(), transform.getLatLng().latitude());
        ASSERT_LE(latLng1.longitude(), transform.getLatLng().longitude());
    };
    easeOptions.transitionFinishFn = [&]() {
        ASSERT_NEAR(latLng1.latitude(), transform.getLatLng().latitude(), 0.000001);
        ASSERT_NEAR(latLng1.longitude(), transform.getLatLng().longitude(), 0.000001);
        ASSERT_NEAR(20, transform.getZoom(), 0.000001);
    };

    transform.easeTo(cameraOptions1, easeOptions);
    ASSERT_TRUE(transform.inTransition());
    transform.updateTransitions(transform.getTransitionStart() + Milliseconds(250));
    transform.updateTransitions(transform.getTransitionStart() + Milliseconds(500));
    transform.updateTransitions(transform.getTransitionStart() + Milliseconds(750));
    transform.updateTransitions(transform.getTransitionStart() + transform.getTransitionDuration());
    ASSERT_FALSE(transform.inTransition());

    AnimationOptions flyOptions(Seconds(1));
    flyOptions.transitionFrameFn = [&](double t) {
        ASSERT_TRUE(t >= 0 && t <= 1);
        ASSERT_LE(latLng2.latitude(), transform.getLatLng().latitude());
        ASSERT_GE(latLng2.longitude(), transform.getLatLng().longitude());
    };
    flyOptions.transitionFinishFn = [&]() {
        // XXX Fix precision loss in flyTo:
        // https://github.com/mapbox/mapbox-gl-native/issues/4298
        ASSERT_NEAR(latLng2.latitude(), transform.getLatLng().latitude(), 0.001);
        ASSERT_NEAR(latLng2.longitude(), transform.getLatLng().longitude(), 0.001);
        ASSERT_NEAR(10, transform.getZoom(), 0.00001);
    };

    transform.flyTo(cameraOptions2, flyOptions);
    ASSERT_TRUE(transform.inTransition());
    transform.updateTransitions(transform.getTransitionStart() + Milliseconds(250));
    transform.updateTransitions(transform.getTransitionStart() + Milliseconds(500));
    transform.updateTransitions(transform.getTransitionStart() + Milliseconds(750));
    transform.updateTransitions(transform.getTransitionStart() + transform.getTransitionDuration());
    ASSERT_FALSE(transform.inTransition());
}

TEST(Transform, DefaultTransform) {
    struct TransformObserver : public mbgl::MapObserver {
        void onCameraWillChange(MapObserver::CameraChangeMode) final {
            cameraWillChangeCallback();
        };

        void onCameraDidChange(MapObserver::CameraChangeMode) final {
            cameraDidChangeCallback();
        };

        std::function<void()> cameraWillChangeCallback;
        std::function<void()> cameraDidChangeCallback;
    };

    uint32_t cameraWillChangeCount = 0;
    uint32_t cameraDidChangeCount = 0;

    TransformObserver observer;
    observer.cameraWillChangeCallback = [&cameraWillChangeCount]() { cameraWillChangeCount++; };
    observer.cameraDidChangeCallback = [&cameraDidChangeCount]() { cameraDidChangeCount++; };

    Transform transform(observer);
    const TransformState& state = transform.getState();
    ASSERT_FALSE(state.valid());

    LatLng nullIsland, latLng = {};
    ScreenCoordinate center, point = {};
    const uint32_t min = 0;
    const uint32_t max = 65535;

    // Cannot assign invalid sizes.
    std::vector<Size> invalidSizes = { {}, { min, max }, { max, min } };
    for (const Size& size : invalidSizes) {
        ASSERT_TRUE(size.isEmpty());
        bool pass = false;
        try {
            transform.resize(size);
        } catch (...) {
            pass = true;
        }
        ASSERT_TRUE(pass) << "Expected to throw";
    }

    Size validSize { max, max };
    ASSERT_FALSE(validSize.isEmpty());

    try {
        transform.resize(validSize);
        ASSERT_EQ(cameraWillChangeCount, 1u);
        ASSERT_EQ(cameraDidChangeCount, 1u);
    } catch (...) {
        ASSERT_TRUE(false) << "Should not throw";
    }

    ASSERT_TRUE(state.valid());

    // Double resize
    try {
        transform.resize(validSize);
        ASSERT_EQ(cameraWillChangeCount, 1u);
        ASSERT_EQ(cameraDidChangeCount, 1u);
    } catch (...) {
        ASSERT_TRUE(false) << "Should not throw";
    }

    center = { max / 2., max / 2. };
    latLng = state.screenCoordinateToLatLng(center);
    ASSERT_NEAR(latLng.latitude(), nullIsland.latitude(), 1e-5);
    ASSERT_NEAR(latLng.longitude(), nullIsland.longitude(), 1e-5);

    point = state.latLngToScreenCoordinate(nullIsland);
    ASSERT_DOUBLE_EQ(point.x, center.x);
    ASSERT_DOUBLE_EQ(point.y, center.y);
}