splinefit 0.1.0

use super::Result;
use csv::ReaderBuilder;
use serde::Serialize;
use spliny::SplineCurve;

/// Serialisable snapshot of a spline's knot vector and B-spline coefficients.
///
/// Useful for saving a fitted spline to JSON or another serde-compatible format.
#[derive(Serialize)]
pub struct SplineCurveData<'a> {
    /// Spline degree.
    pub k: usize,
    /// Number of dimensions of the curve's output space.
    pub n: usize,
    /// Knot vector.
    pub t: &'a [f64],
    /// B-spline coefficients.
    pub c: &'a [f64],
}

impl<'a, const K: usize, const N: usize> From<&'a SplineCurve<K, N>> for SplineCurveData<'a> {
    fn from(s: &'a SplineCurve<K, N>) -> Self {
        Self { k: K, n: N, t: &s.t, c: &s.c }
    }
}

/// Read `(x, y)` pairs from a two-column CSV file (with header row).
///
/// Returns `(x_values, y_values)`.
pub fn read_csv_xy(csv_file: &str) -> Result<(Vec<f64>, Vec<f64>)> {
    let mut rdr = csv::Reader::from_path(csv_file)?;
    let mut x = Vec::<f64>::new();
    let mut y = Vec::<f64>::new();
    for r in rdr.records() {
        if let Ok(r) = r {
            x.push(r[0].parse::<f64>().unwrap());
            y.push(r[1].parse::<f64>().unwrap());
        } else {
            break
        }
    }
    Ok((x, y))
}

/// Read `(u, x, y)` triples from a three-column CSV file (no header, `#` comments allowed).
///
/// Returns `(u_values, x_values, y_values)`.
pub fn read_csv_uxy(csv_file: &str) -> Result<(Vec<f64>, Vec<f64>, Vec<f64>)> {
    let mut rdr = ReaderBuilder::new()
        .has_headers(false)
        .comment(Some(b'#'))
        .trim(csv::Trim::All)
        .from_path(csv_file)?;
    let mut u = Vec::<f64>::new();
    let mut x = Vec::<f64>::new();
    let mut y = Vec::<f64>::new();
    for r in rdr.records() {
        if let Ok(r) = r {
            u.push(r[0].parse::<f64>().unwrap());
            x.push(r[1].parse::<f64>().unwrap());
            y.push(r[2].parse::<f64>().unwrap());
        } else {
            break
        }
    }
    Ok((u, x, y))
}

/// Write `(x, y)` pairs to a two-column CSV file with a `wl[nm],spd[-]` header.
pub fn write_csv_xy(csv_file: &str, x: &[f64], y: &[f64]) -> Result<()> {
    let mut wtr = csv::Writer::from_path(csv_file)?;
    wtr.write_record(&["wl[nm]", "spd[-]"])?;
    for (&x, &y) in x.iter().zip(y.iter()) {
        wtr.write_record(&[format!("{:.2}", x), format!("{:.4}", y)])?
    }
    wtr.flush()?;
    Ok(())
}