transforms 2.1.1

#[cfg(test)]
mod transform_tests {
    use crate::{
        errors::TransformError,
        geometry::{Quaternion, Transform, UNIT_NORM_TOLERANCE, Vector3},
        time::{Stamp, Timestamp},
    };
    use approx::assert_abs_diff_eq;

    #[test]
    fn new_exposes_the_components_it_was_built_from() {
        let transform = Transform::new(
            "map",
            "base",
            Vector3::new(1.0, 2.0, 3.0),
            Quaternion::identity(),
            Stamp::At(Timestamp::zero()),
        )
        .unwrap();

        assert_eq!(transform.parent(), "map");
        assert_eq!(transform.child(), "base");
        assert_eq!(transform.translation(), Vector3::new(1.0, 2.0, 3.0));
        assert_eq!(transform.rotation(), Quaternion::identity());
        assert_eq!(transform.timestamp(), Stamp::At(Timestamp::zero()));
    }

    #[test]
    fn new_rejects_transforms_that_would_corrupt_every_lookup() {
        let stamp = Stamp::At(Timestamp::zero());

        // A rotation-equivalent but non-unit quaternion scales everything it
        // is applied to — here by 2% — and would do so without any error.
        let denormalized = Transform::new(
            "map",
            "base",
            Vector3::zero(),
            Quaternion::from_wxyz(1.01, 0.0, 0.0, 0.0),
            stamp,
        );
        assert!(
            matches!(denormalized, Err(TransformError::NonUnitRotation(_))),
            "a norm-1.01 rotation must be unrepresentable, got {denormalized:?}"
        );

        // The same rejection guards the static constructor, the crate's
        // recommended way to declare a sensor mount.
        let mount = Transform::<Timestamp>::static_between(
            "base",
            "camera",
            Vector3::zero(),
            Quaternion::from_wxyz(1.01, 0.0, 0.0, 0.0),
        );
        assert!(
            matches!(mount, Err(TransformError::NonUnitRotation(_))),
            "static_between must reject a norm-1.01 rotation, got {mount:?}"
        );

        let non_finite_translation = Transform::new(
            "map",
            "base",
            Vector3::new(f64::NAN, 0.0, 0.0),
            Quaternion::identity(),
            stamp,
        );
        assert!(matches!(
            non_finite_translation,
            Err(TransformError::NonFiniteValues)
        ));

        let non_finite_rotation = Transform::new(
            "map",
            "base",
            Vector3::zero(),
            Quaternion::from_wxyz(f64::INFINITY, 0.0, 0.0, 0.0),
            stamp,
        );
        assert!(matches!(
            non_finite_rotation,
            Err(TransformError::NonFiniteValues)
        ));

        // Unit norms with f32-grade precision loss stay representable.
        let f32_grade = Transform::new(
            "map",
            "base",
            Vector3::zero(),
            Quaternion::from_wxyz(1.0 + 1e-8, 0.0, 0.0, 0.0),
            stamp,
        );
        assert!(f32_grade.is_ok(), "got {f32_grade:?}");
    }

    /// A transform whose rotation has exactly the given norm: the norm of
    /// `(w, 0, 0, 0)` is `w` itself, which the assertion here confirms
    /// rather than assumes.
    fn with_rotation_norm(norm: f64) -> Result<Transform, TransformError> {
        let rotation = Quaternion::from_wxyz(norm, 0.0, 0.0, 0.0);
        assert_eq!(rotation.norm().to_bits(), norm.to_bits());

        Transform::new(
            "a",
            "b",
            Vector3::zero(),
            rotation,
            Stamp::At(Timestamp::zero()),
        )
    }

    #[test]
    fn the_unit_norm_boundary_is_exactly_the_published_tolerance() {
        // `UNIT_NORM_TOLERANCE` is public API — downstream code sizes its own
        // rotation checks against it — so both halves are pinned here: the
        // value, and the boundary drawn around it. Bit patterns, because
        // both claims are exact ones.
        assert_eq!(UNIT_NORM_TOLERANCE.to_bits(), 1e-6_f64.to_bits());

        // Validation rejects a norm *further* than the tolerance from 1, so a
        // norm of exactly `1 + UNIT_NORM_TOLERANCE` is still accepted and the
        // very next representable norm above it is not. That step is one ulp,
        // 2.2e-16 at this magnitude, so this is the boundary itself rather
        // than a probe near it.
        let accepted = 1.0 + UNIT_NORM_TOLERANCE;
        let rejected = f64::from_bits(accepted.to_bits() + 1);
        assert!(with_rotation_norm(accepted).is_ok());
        let result = with_rotation_norm(rejected);
        assert!(
            matches!(result, Err(TransformError::NonUnitRotation(_))),
            "one ulp past the tolerance must be rejected, got {result:?}"
        );

        // Below 1 the exponent is one lower and the spacing half as wide, so
        // `1 - UNIT_NORM_TOLERANCE` rounds to slightly *more* than the
        // tolerance away from 1 and is rejected, while the next norm back
        // toward 1 is accepted. The boundary is symmetric in intent, not in
        // bits, and a fixture that assumed otherwise would be testing the
        // rounding rather than the rule.
        let rejected = 1.0 - UNIT_NORM_TOLERANCE;
        let accepted = f64::from_bits(rejected.to_bits() + 1);
        let result = with_rotation_norm(rejected);
        assert!(
            matches!(result, Err(TransformError::NonUnitRotation(_))),
            "one ulp past the tolerance must be rejected, got {result:?}"
        );
        assert!(with_rotation_norm(accepted).is_ok());
    }

    #[test]
    fn inverse_renormalizes_a_rotation_that_drifted_off_the_unit_sphere() {
        // The constructors accept every norm within UNIT_NORM_TOLERANCE, so a
        // rotation that was transmitted as `f32` and widened back reaches
        // storage a whisker off the unit sphere. `inverse` is the only
        // renormalization point on a lookup: without it the drift scales
        // every value the inverted transform is applied to, with no error to
        // notice it by.
        let drifted = Quaternion::from_wxyz(1.0 - 9e-7, 0.0, 0.0, 0.0);
        let transform = Transform::new(
            "a",
            "b",
            Vector3::new(1.0, 2.0, 3.0),
            drifted,
            Stamp::At(Timestamp::zero()),
        )
        .unwrap();
        assert!(
            (transform.rotation().norm() - 1.0).abs() > 8e-7,
            "the fixture must actually sit off the unit sphere"
        );

        let inverted = transform.inverse().unwrap();

        assert_abs_diff_eq!(inverted.rotation().norm(), 1.0, epsilon = 1e-15);
        // The drift would otherwise have scaled the inverted translation by
        // the squared norm — here by 1.8e-6, 1.8 metres per thousand
        // kilometres.
        assert_abs_diff_eq!(
            inverted.translation(),
            Vector3::new(-1.0, -2.0, -3.0),
            epsilon = 1e-12
        );
    }

    #[test]
    fn inverse_reports_a_non_finite_translation() {
        // Constructors cannot produce this, but `*` does not re-validate, so
        // a composition of extreme operands can. Inverting it must report the
        // problem rather than hand back a NaN pose.
        let broken = Transform::unvalidated(
            "a".into(),
            "b".into(),
            Vector3::new(f64::NAN, 0.0, 0.0),
            Quaternion::identity(),
            Stamp::At(Timestamp::zero()),
        );

        let result = broken.inverse();
        assert!(
            matches!(result, Err(TransformError::NonFiniteValues)),
            "a NaN translation must not survive inversion, got {result:?}"
        );
    }

    #[test]
    fn mul_translation() {
        let t = Timestamp::zero();

        let t_a_b = Transform::new(
            "a",
            "b",
            Vector3::new(1.0, 0.0, 0.0),
            Quaternion::identity(),
            Stamp::At(t),
        )
        .unwrap();

        let t_b_c = Transform::new(
            "b",
            "c",
            Vector3::new(0.0, 2.0, 0.0),
            Quaternion::identity(),
            Stamp::At(t),
        )
        .unwrap();

        let result = (t_a_b * t_b_c).unwrap();

        assert_eq!(result.translation(), Vector3::new(1.0, 2.0, 0.0));
        assert_eq!(result.parent(), "a");
        assert_eq!(result.child(), "c");
    }

    #[test]
    fn mul_with_rotation() {
        let t = Timestamp::zero();
        let theta = core::f64::consts::PI / 2.0;

        let t_a_b = Transform::new(
            "a",
            "b",
            Vector3::zero(),
            Quaternion::from_wxyz((theta / 2.0).cos(), 0.0, 0.0, (theta / 2.0).sin()),
            Stamp::At(t),
        )
        .unwrap();

        let t_b_c = Transform::new(
            "b",
            "c",
            Vector3::new(1.0, 0.0, 0.0),
            Quaternion::identity(),
            Stamp::At(t),
        )
        .unwrap();

        let result = (t_a_b * t_b_c).unwrap();

        assert!((result.translation().x - 0.0).abs() < 1e-10);
        assert!((result.translation().y - 1.0).abs() < 1e-10);
    }

    #[test]
    fn interpolate_rejects_static_endpoints() {
        // A static transform is valid for all time — it is never an
        // interpolation endpoint. The rejection is explicit and fires for
        // either operand, before any other check.
        let dynamic = Transform::new(
            "a",
            "b",
            Vector3::zero(),
            Quaternion::identity(),
            Stamp::At(Timestamp::from_nanos(1_000_000_000)),
        )
        .unwrap();
        let fixed = Transform::static_between(
            "a",
            "b",
            Vector3::new(1.0, 0.0, 0.0),
            Quaternion::identity(),
        )
        .unwrap();
        let query = Timestamp::from_nanos(1_000_000_000);

        for (from, to) in [(&fixed, &dynamic), (&dynamic, &fixed), (&fixed, &fixed)] {
            let result = Transform::interpolate(from, to, query);
            assert!(
                matches!(result, Err(TransformError::StaticInterpolation)),
                "a static endpoint must be rejected, got {result:?}"
            );
        }
    }

    #[test]
    fn inverse() {
        let t_a_b = Transform::new(
            "a",
            "b",
            Vector3::new(1.0, 2.0, 3.0),
            Quaternion::identity(),
            Stamp::At(Timestamp::zero()),
        )
        .unwrap();

        let t_b_a = t_a_b.inverse().unwrap();

        assert_eq!(t_b_a.translation(), Vector3::new(-1.0, -2.0, -3.0));
        assert_eq!(t_b_a.parent(), "b");
        assert_eq!(t_b_a.child(), "a");
    }

    #[test]
    fn mul_inverse_identity() {
        let t_a_b = Transform::new(
            "a",
            "b",
            Vector3::new(1.0, 2.0, 3.0),
            Quaternion::from_wxyz(0.707, 0.707, 0.0, 0.0)
                .normalize()
                .unwrap(),
            Stamp::At(Timestamp::zero()),
        )
        .unwrap();

        let t_b_a = t_a_b.clone().inverse().unwrap();
        let result = (t_a_b * t_b_a).unwrap();

        assert!(result.translation().x.abs() < 1e-10);
        assert!(result.translation().y.abs() < 1e-10);
        assert!(result.translation().z.abs() < 1e-10);
        assert!((result.rotation().w - Quaternion::identity().w).abs() < 1e-10);
    }

    #[test]
    fn mul_static_to_timestamped() {
        let t_a_b = Transform::new(
            "a",
            "b",
            Vector3::new(1.0, 0.0, 0.0),
            Quaternion::identity(),
            Stamp::Static,
        )
        .unwrap();

        let t_now = Timestamp::from_nanos(1_000_000_000);

        let t_b_c = Transform::new(
            "b",
            "c",
            Vector3::new(0.0, 1.0, 0.0),
            Quaternion::identity(),
            Stamp::At(t_now),
        )
        .unwrap();

        let t_a_c_expected = Transform::new(
            "a",
            "c",
            Vector3::new(1.0, 1.0, 0.0),
            Quaternion::identity(),
            Stamp::At(t_now),
        )
        .unwrap();

        let result = (t_a_b * t_b_c).expect("multiplication should succeed");

        assert_eq!(
            result, t_a_c_expected,
            "Static * Timestamped should produce timestamped result"
        );
    }

    #[test]
    fn mul_timestamped_to_static() {
        let t_now = Timestamp::from_nanos(1_000_000_000);

        let t_a_b = Transform::new(
            "a",
            "b",
            Vector3::new(1.0, 0.0, 0.0),
            Quaternion::identity(),
            Stamp::At(t_now),
        )
        .unwrap();

        let t_b_c = Transform::new(
            "b",
            "c",
            Vector3::new(0.0, 1.0, 0.0),
            Quaternion::identity(),
            Stamp::Static,
        )
        .unwrap();

        let t_a_c_expected = Transform::new(
            "a",
            "c",
            Vector3::new(1.0, 1.0, 0.0),
            Quaternion::identity(),
            Stamp::At(t_now),
        )
        .unwrap();

        let result = (t_a_b * t_b_c).expect("multiplication should succeed");

        assert_eq!(
            result, t_a_c_expected,
            "Timestamped * Static should produce timestamped result"
        );
    }

    fn transform_at(
        parent: &str,
        child: &str,
        t: Timestamp,
    ) -> Transform {
        Transform::new(
            parent,
            child,
            Vector3::new(1.0, 0.0, 0.0),
            Quaternion::identity(),
            Stamp::At(t),
        )
        .unwrap()
    }

    #[test]
    fn mul_rejects_reversed_composition() {
        // Only `t_a_b * t_b_c` (lhs child == rhs parent) is a valid
        // composition. The reversed order composes the underlying math in the
        // wrong order and must be rejected.
        let t = Timestamp::from_nanos(1_000_000_000);
        let t_a_b = transform_at("a", "b", t);
        let t_b_c = transform_at("b", "c", t);

        let result = t_b_c * t_a_b;
        assert!(
            matches!(result, Err(TransformError::IncompatibleFrames { .. })),
            "reversed composition must be rejected, got {result:?}"
        );
    }

    #[test]
    fn mul_rejects_unrelated_frames() {
        let t = Timestamp::from_nanos(1_000_000_000);
        let t_a_b = transform_at("a", "b", t);
        let t_c_d = transform_at("c", "d", t);

        let result = t_a_b * t_c_d;
        assert!(
            matches!(result, Err(TransformError::IncompatibleFrames { .. })),
            "unrelated frames must be rejected, got {result:?}"
        );
    }

    #[test]
    fn mul_rejects_mismatched_timestamps() {
        let t_a_b = transform_at("a", "b", Timestamp::from_nanos(1_000_000_000));
        let t_b_c = transform_at("b", "c", Timestamp::from_nanos(2_000_000_000));

        let result = t_a_b * t_b_c;
        assert!(
            matches!(result, Err(TransformError::TimestampMismatch { .. })),
            "dynamic transforms with different timestamps must be rejected, got {result:?}"
        );
    }

    #[test]
    fn interpolate_rejects_out_of_range_timestamps() {
        let from = transform_at("a", "b", Timestamp::from_nanos(1_000_000_000));
        let to = transform_at("a", "b", Timestamp::from_nanos(2_000_000_000));

        // Before the covered range: extrapolation must be rejected.
        let result = Transform::interpolate(&from, &to, Timestamp::from_nanos(500_000_000));
        assert!(
            matches!(result, Err(TransformError::TimestampOutOfRange { .. })),
            "interpolation before the range must fail, got {result:?}"
        );

        // After the covered range: extrapolation must be rejected.
        let result = Transform::interpolate(&from, &to, Timestamp::from_nanos(3_000_000_000));
        assert!(
            matches!(result, Err(TransformError::TimestampOutOfRange { .. })),
            "interpolation after the range must fail, got {result:?}"
        );

        // Swapped endpoints must be rejected.
        let result = Transform::interpolate(&to, &from, Timestamp::from_nanos(1_500_000_000));
        assert!(
            matches!(result, Err(TransformError::TimestampMismatch { .. })),
            "swapped endpoints must fail, got {result:?}"
        );
    }

    #[test]
    fn errors_survive_wall_clock_timestamps() {
        // Realistic wall-clock nanosecond values cannot be converted to
        // seconds exactly; error reporting previously failed with
        // AccuracyLoss instead of diagnosing the actual problem.
        let t1 = Timestamp::from_nanos(1_783_400_000_123_456_789);
        let t2 = Timestamp::from_nanos(1_783_400_001_123_456_789);

        let t_a_b = transform_at("a", "b", t1);
        let t_b_c = transform_at("b", "c", t2);
        let result = t_a_b * t_b_c;
        assert!(
            matches!(result, Err(TransformError::TimestampMismatch { .. })),
            "expected TimestampMismatch, got {result:?}"
        );

        let from = transform_at("a", "b", t1);
        let to = transform_at("a", "b", t2);
        let result =
            Transform::interpolate(&from, &to, Timestamp::from_nanos(1_783_400_002_000_000_000));
        assert!(
            matches!(result, Err(TransformError::TimestampOutOfRange { .. })),
            "expected TimestampOutOfRange, got {result:?}"
        );
    }

    #[test]
    fn interpolate_over_a_zero_span_returns_the_earlier_endpoint() {
        // Two endpoints stamped at the same instant leave no span to
        // interpolate over, and the earlier one answers. Returning `to`
        // instead would swap which of two same-stamp samples a lookup
        // reports — the ratio is undefined either way, so nothing downstream
        // would flag it.
        let t = Timestamp::from_nanos(1_000_000_000);
        let from = Transform::new(
            "a",
            "b",
            Vector3::new(1.0, 0.0, 0.0),
            Quaternion::identity(),
            Stamp::At(t),
        )
        .unwrap();
        let to = Transform::new(
            "a",
            "b",
            Vector3::new(2.0, 0.0, 0.0),
            Quaternion::identity(),
            Stamp::At(t),
        )
        .unwrap();

        let result = Transform::interpolate(&from, &to, t).unwrap();

        assert_eq!(result, from);
        assert_ne!(result, to);
    }

    #[test]
    fn interpolate_rejects_mismatched_frames() {
        let from = transform_at("a", "b", Timestamp::from_nanos(1_000_000_000));
        let to = transform_at("a", "c", Timestamp::from_nanos(2_000_000_000));

        let result = Transform::interpolate(&from, &to, Timestamp::from_nanos(1_500_000_000));
        assert!(
            matches!(result, Err(TransformError::IncompatibleFrames { .. })),
            "interpolating between different frame pairs must fail, got {result:?}"
        );
    }

    #[test]
    fn validate_checks_a_transform_of_unknown_provenance() {
        // `validate` exists for values the constructors did not vet: results
        // of composition, and transforms a third-party `Transformable` impl
        // receives from elsewhere. The unchecked constructor stands in for
        // those here.
        let t = Timestamp::from_nanos(1_000_000_000);
        let with_rotation = |rotation| {
            Transform::unvalidated(
                "a".into(),
                "b".into(),
                Vector3::new(1.0, 0.0, 0.0),
                rotation,
                Stamp::At(t),
            )
        };

        assert!(transform_at("a", "b", t).validate().is_ok());

        // f32-grade precision loss on a unit rotation is accepted.
        let f32_grade = with_rotation(Quaternion::from_wxyz(1.0 + 1e-8, 0.0, 0.0, 0.0));
        assert!(f32_grade.validate().is_ok());

        // A genuinely denormalized rotation is rejected with its norm.
        let denormalized = with_rotation(Quaternion::from_wxyz(1.001, 0.0, 0.0, 0.0));
        assert!(matches!(
            denormalized.validate(),
            Err(TransformError::NonUnitRotation(_))
        ));

        let non_finite = with_rotation(Quaternion::from_wxyz(f64::NAN, 0.0, 0.0, 0.0));
        assert!(matches!(
            non_finite.validate(),
            Err(TransformError::NonFiniteValues)
        ));

        let inf_translation = Transform::unvalidated(
            "a".into(),
            "b".into(),
            Vector3::new(f64::INFINITY, 0.0, 0.0),
            Quaternion::identity(),
            Stamp::At(t),
        );
        assert!(matches!(
            inf_translation.validate(),
            Err(TransformError::NonFiniteValues)
        ));
    }

    #[test]
    fn same_child_multiplication_is_rejected_with_the_frame_named() {
        let t = Timestamp::from_nanos(1_000_000_000);
        let t_a_b = transform_at("a", "b", t);
        let t_c_b = transform_at("c", "b", t);

        // Same child frame on both sides. This check runs BEFORE the
        // parent/child pairing check, so it wins over IncompatibleFrames.
        match t_a_b * t_c_b {
            Err(TransformError::SameFrameMultiplication { frame }) => {
                assert_eq!(frame, "b");
            }
            other => panic!("expected SameFrameMultiplication, got {other:?}"),
        }
    }

    #[test]
    fn self_multiplication_is_same_frame_multiplication() {
        let t = Timestamp::from_nanos(1_000_000_000);
        let t_a_b = transform_at("a", "b", t);
        assert!(matches!(
            t_a_b.clone() * t_a_b,
            Err(TransformError::SameFrameMultiplication { .. })
        ));
    }

    #[test]
    fn unrelated_frames_multiplication_names_both_sides() {
        // Control for the check ordering: distinct children with no
        // parent/child match is IncompatibleFrames, carrying what the
        // composition required and what it found.
        let t = Timestamp::from_nanos(1_000_000_000);
        let t_a_b = transform_at("a", "b", t);
        let t_c_d = transform_at("c", "d", t);

        match t_a_b * t_c_d {
            Err(TransformError::IncompatibleFrames { expected, found }) => {
                assert_eq!(expected, "b");
                assert_eq!(found, "c");
            }
            other => panic!("expected IncompatibleFrames, got {other:?}"),
        }
    }

    #[test]
    // The compared values are exactly representable; the assertion is on
    // reported payloads, not on float arithmetic.
    #[allow(clippy::float_cmp)]
    fn timestamp_mismatch_payload_carries_both_times_in_seconds() {
        let t_a_b = transform_at("a", "b", Timestamp::from_nanos(1_000_000_000));
        let t_b_c = transform_at("b", "c", Timestamp::from_nanos(2_000_000_000));

        match t_a_b * t_b_c {
            Err(TransformError::TimestampMismatch { lhs, rhs }) => {
                assert_eq!(lhs, 1.0);
                assert_eq!(rhs, 2.0);
            }
            other => panic!("expected TimestampMismatch, got {other:?}"),
        }
    }
}