astrokit/tests/reference_format.rs

//! The reference-trajectory format: that it round trips, and that it refuses a fixture
//! which would otherwise produce a number looking like a result.
//!
//! No fixture files are committed yet — generating them needs a JVM, which this machine
//! does not have. What is tested here is the format itself, which a generator has to
//! conform to.

mod common;

use common::{FixtureError, ReferenceArc, ReferenceSetup, ReferenceState};

fn setup() -> ReferenceSetup {
    ReferenceSetup {
        tool: "orekit".to_string(),
        version: "13.1.8".to_string(),
        generated: "2026-10-02".to_string(),
        forces: vec!["HolmesFeatherstoneAttractionModel(EGM96, 70, 70)".to_string()],
        integrator: "DormandPrince853, abs 1e-12, rel 1e-12".to_string(),
        notes: vec!["EOP: none applied".to_string()],
    }
}

fn arc(states: Vec<ReferenceState>) -> ReferenceArc {
    ReferenceArc {
        name: "low-earth-one-day".to_string(),
        setup: setup(),
        epoch: "2026-01-01T00:00:00 UTC".to_string(),
        frame: "EME2000".to_string(),
        states,
    }
}

fn state(elapsed: f64) -> ReferenceState {
    ReferenceState {
        elapsed,
        position: [6.978e6, 0.0, 0.0],
        velocity: [0.0, 7.56e3, 0.0],
    }
}

fn write(arc: &ReferenceArc) -> tempfile_path::Written {
    tempfile_path::write(&serde_json::to_string_pretty(arc).unwrap())
}

/// A minimal stand-in for a temporary file, so the test needs no extra dependency.
mod tempfile_path {
    use std::path::{Path, PathBuf};
    use std::sync::atomic::{AtomicUsize, Ordering};

    pub struct Written(PathBuf);

    impl Written {
        pub fn path(&self) -> &Path {
            &self.0
        }
    }

    impl Drop for Written {
        fn drop(&mut self) {
            let _ = std::fs::remove_file(&self.0);
        }
    }

    pub fn write(text: &str) -> Written {
        static COUNT: AtomicUsize = AtomicUsize::new(0);
        let path = std::env::temp_dir().join(format!(
            "astrokit-fixture-{}-{}.json",
            std::process::id(),
            COUNT.fetch_add(1, Ordering::Relaxed)
        ));
        std::fs::write(&path, text).expect("the temporary directory is writable");
        Written(path)
    }
}

#[test]
fn test_an_arc_round_trips_through_the_format() {
    let original = arc(vec![state(0.0), state(60.0), state(120.0)]);
    let written = write(&original);
    assert_eq!(ReferenceArc::load(written.path()).unwrap(), original);
}

#[test]
fn test_the_setup_is_carried_verbatim() {
    // The point of the block: it records what the *other* tool was told, in that tool's
    // own words, so a mismatch is visible rather than translated away.
    let original = arc(vec![state(0.0), state(60.0)]);
    let written = write(&original);
    let loaded = ReferenceArc::load(written.path()).unwrap();

    assert_eq!(loaded.setup.tool, "orekit");
    assert_eq!(loaded.setup.version, "13.1.8");
    assert!(loaded.setup.forces[0].contains("EGM96"));
    assert!(loaded.setup.integrator.contains("1e-12"));
    assert_eq!(loaded.duration(), 60.0);
}

#[test]
fn test_a_fixture_that_would_mislead_is_refused() {
    let unusable = |arc: ReferenceArc, expected: &str| {
        let written = write(&arc);
        match ReferenceArc::load(written.path()) {
            Err(FixtureError::Invalid(why)) => {
                assert!(why.contains(expected), "expected {expected:?} in {why:?}")
            }
            other => panic!("should have been refused: {other:?}"),
        }
    };

    // One state is not an arc.
    unusable(arc(vec![state(0.0)]), "1 states");

    // Not starting at its own epoch means every comparison is offset by an unknown.
    unusable(
        arc(vec![state(30.0), state(60.0)]),
        "rather than at its own epoch",
    );

    // Times that do not advance mean the states cannot be matched to anything.
    unusable(
        arc(vec![state(0.0), state(60.0), state(60.0)]),
        "not increasing",
    );

    // An arc with no recorded force model cannot be matched, so it cannot be compared.
    let mut no_forces = arc(vec![state(0.0), state(60.0)]);
    no_forces.setup.forces.clear();
    unusable(no_forces, "records no force model");
}

/// A non-finite state cannot survive the format at all: JSON has no NaN, so it is written
/// as `null` and refused on the way back in.
#[test]
fn test_a_non_finite_state_cannot_round_trip() {
    let mut broken = arc(vec![state(0.0), state(60.0)]);
    broken.states[1].position[0] = f64::NAN;
    let written = write(&broken);
    assert!(matches!(
        ReferenceArc::load(written.path()),
        Err(FixtureError::Malformed(_))
    ));
}

#[test]
fn test_a_malformed_file_is_told_apart_from_an_unusable_one() {
    let written = tempfile_path::write("{\"name\": \"half a fixture\"}");
    assert!(matches!(
        ReferenceArc::load(written.path()),
        Err(FixtureError::Malformed(_))
    ));

    let missing = std::path::Path::new("tests/fixtures/orekit/not-generated-yet.json");
    assert!(matches!(
        ReferenceArc::load(missing),
        Err(FixtureError::Unreadable(_))
    ));
}