use super::funejson::Value;
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 mass index for an adult: weight over height squared, to one decimal
/// place, and the band it falls in. The bands are published to one decimal
/// place (18.5-24.9, 25-29.9, ...), so the category is read from the rounded
/// index: 24.97 is reported as 25.0 and is overweight, not healthy.
///
/// # Panics
/// Panics when the weight or height is outside its range.
pub fn bmi(weight_kg: f64, height_cm: f64) -> Bmi {
    check_range("weightKg", weight_kg, 10.0, 650.0, "kg");
    // Height in metres (1.75) is the commonest unit slip; 50 cm is the floor.
    check_range("heightCm", height_cm, 50.0, 272.0, "cm");
    let metres = height_cm / 100.0;
    let value = round_float(weight_kg / (metres * metres), 1);
    let category = if value < 18.5 {
        "underweight"
    } else if value <= 24.9 {
        "healthy-weight"
    } else if value <= 29.9 {
        "overweight"
    } else if value <= 34.9 {
        "obesity-class-1"
    } else if value <= 39.9 {
        "obesity-class-2"
    } else {
        "obesity-class-3"
    };
    Bmi { value, category: category.to_string() }
}

pub fn bmi_to_value(result: &Bmi) -> Value {
    Value::obj(vec![("value", Value::Float(result.value)), ("category", Value::str(&result.category))])
}

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 {
    bmi_to_value(&bmi(
        number_arg(&args[0], "weightKg", 10.0, 650.0, "kg"),
        number_arg(&args[1], "heightCm", 50.0, 272.0, "cm"),
    ))
}