//! This crate's propagator against Orekit's, on the fixtures in `tests/fixtures/orekit`.
//!
//! Generated by `scripts/generate-orekit-fixtures.sh`. Each fixture records the setup
//! Orekit was given, so a disagreement can be attributed to the models rather than left
//! as a mystery; see `tests/common/mod.rs` for what has to match and why.
//!
//! The only fixture so far is a point mass. That is deliberate as a first step: with no
//! field, no third body, no atmosphere and an inertial frame, there is nothing left to
//! mismatch, so the figure it produces measures the comparison itself — frames, time
//! scale, units and `mu` — rather than any model. Anything added after this is measured
//! against a harness already known to be sound.

mod common;

use astrokit::prelude::*;
use common::ReferenceArc;
use nalgebra::Vector3;
use std::path::Path;

/// Propagates the fixture's initial state with this crate and returns the worst position
/// and velocity disagreement over the arc.
fn compare(arc: &ReferenceArc, forces: &[Dynamics]) -> (f64, f64) {
    let start = &arc.states[0];
    let epoch = Epoch::from_gregorian_utc_hms(2026, 1, 1, 0, 0, 0);
    let mut propagation = Propagation::new(
        epoch,
        Orbit
            .with_position(Vector3::from_column_slice(&start.position))
            .with_velocity(Vector3::from_column_slice(&start.velocity)),
        forces,
    )
    .frame(Frame::EARTH_J2000)
    .duration(Duration::from_seconds(arc.duration()))
    .accuracy(Accuracy::High);

    let solution = propagation.run();
    let (mut worst_position, mut worst_velocity) = (0.0_f64, 0.0_f64);
    for state in &arc.states {
        let ours = Orbit.state(solution.interpolate(state.elapsed));
        worst_position = worst_position
            .max((ours.position() - Vector3::from_column_slice(&state.position)).norm());
        worst_velocity = worst_velocity
            .max((ours.velocity() - Vector3::from_column_slice(&state.velocity)).norm());
    }
    (worst_position, worst_velocity)
}

#[test]
fn test_a_point_mass_arc_agrees_with_orekit() {
    let path = Path::new("tests/fixtures/orekit/two-body-low-earth.json");
    let arc = ReferenceArc::load(path).expect("the fixture is committed");

    assert_eq!(arc.setup.tool, "orekit");
    assert_eq!(arc.duration(), 86400.0);
    assert_eq!(arc.states.len(), 1441);

    let (position, velocity) = compare(&arc, &[TwoBody { body: Body::EARTH }]);

    // Sub-millimeter over a day. Nothing in this case can disagree except the two
    // integrators and the arithmetic, so this is the floor the comparison can measure to:
    // a later fixture that disagrees by more than this is disagreeing about physics.
    assert!(
        position < 1.0e-3,
        "worst position disagreement {position:.3e} m over the day"
    );
    assert!(
        velocity < 1.0e-6,
        "worst velocity disagreement {velocity:.3e} m/s over the day"
    );
    println!("point mass: {position:.3e} m, {velocity:.3e} m/s");
}