use super::funejson::Value;
use super::math_pow::pow;
use super::math_round_float::round_float;

fn check_range(name: &str, value: f64, low: f64, high: f64, unit: &str) {
    if !value.is_finite() || value < low || value > high {
        panic!("{} must be a number from {} to {} {}, received {}", name, low, high, unit, value);
    }
}

/// Body surface area by both published formulas. They differ by up to a few
/// per cent, and a dose protocol names one, so both are returned rather than a
/// silent default. Powers go through math.pow, never `powf` or `sqrt`, so the
/// three languages agree to the bit before rounding.
///
/// # Panics
/// Panics when the weight or height is outside its range.
pub fn body_surface_area(weight_kg: f64, height_cm: f64) -> BodySurfaceArea {
    check_range("weightKg", weight_kg, 1.0, 650.0, "kg");
    // Height in metres (1.75) is the commonest unit slip.
    check_range("heightCm", height_cm, 30.0, 272.0, "cm");
    // Mosteller (1987): BSA (m²) = ([height (cm) × weight (kg)] / 3600)^½.
    let mosteller = pow((height_cm * weight_kg) / 3600.0, 0.5);
    // DuBois & DuBois (1916): A = W^0.425 × H^0.725 × 71.84, A in cm².
    let du_bois = (pow(weight_kg, 0.425) * pow(height_cm, 0.725) * 71.84) / 10000.0;
    BodySurfaceArea { mosteller: round_float(mosteller, 2), du_bois: round_float(du_bois, 2) }
}

pub fn body_surface_area_to_value(result: &BodySurfaceArea) -> Value {
    Value::obj(vec![("mosteller", Value::Float(result.mosteller)), ("duBois", Value::Float(result.du_bois))])
}

fn number_arg(value: &Value, name: &str, low: f64, high: f64, unit: &str) -> f64 {
    match value {
        Value::Int(_) | Value::Float(_) => value.as_f64(),
        _ => panic!("{} must be a number from {} to {} {}, received {:?}", name, low, high, unit, value),
    }
}

pub fn fune_vector(args: &[Value]) -> Value {
    body_surface_area_to_value(&body_surface_area(
        number_arg(&args[0], "weightKg", 1.0, 650.0, "kg"),
        number_arg(&args[1], "heightCm", 30.0, 272.0, "cm"),
    ))
}