use crate::quantity::{Kelvins, Ohms};
use libm::{log, logf};

/// Convert thermistor resistance to a temperature using beta parameter equation
pub fn convert_beta(
    resistance: Ohms<f32>,
    beta: f32,
    reference_temp: Kelvins<f32>,
    reference_resist: Ohms<f32>,
) -> Kelvins<f32> {
    let kelvins = 1.0 / ((logf(resistance.0 / reference_resist.0) / beta) + 1.0 / reference_temp.0);
    Kelvins(kelvins)
}

/// Convert thermistor resistance to a temperature using Steinhart-Hart equation
pub fn convert_steinhart(resistance: Ohms<f64>, a: f64, b: f64, c: f64) -> Kelvins<f32> {
    let log_omhs = log(resistance.0);
    let kelvins = 1.0 / (a + b * log_omhs + c * log_omhs * log_omhs * log_omhs);
    Kelvins(kelvins as f32)
}

// ---------------------------------------------------------------------------------------------------------------------
// ----- Tests ------------------------
// ---------------------------------------------------------------------------------------------------------------------
#[cfg(test)]
mod tests {
    use float_cmp::assert_approx_eq;

    use crate::quantity::{OhmsVal, KelvinsVal};
    use super::*;

    #[test]
    fn convert_beta_test() {
        let temperature = convert_beta(1538.462.ohms(), 3950.0, 298.15.kelvins(), 100_000.0.ohms());

        assert_approx_eq!(f32, 435.31073, temperature.0);
    }
}