use std::cmp::{PartialOrd};
use std::ops::{Add, Sub, Mul, Div, Rem};
use ::num_traits::{Trig, Float};

// generic number type, but realistically it's only useful for
// floats. Maybe also complex<float>

pub struct Sinusoid<T> {
    amplitude: T,
    frequency: T,
    phase: T
}

impl<T> Sinusoid<T> {
    pub fn new(amplitude:T, frequency: T, phase: T) -> Sinusoid<T> {
        Sinusoid {
            amplitude: amplitude,
            frequency: frequency,
            phase: phase
        }
    }
}
impl<T> Sinusoid<T> where T: Float + Copy {
    pub fn period(&self) -> T {
        self.frequency.recip()
    }
}
impl<T> Sinusoid<T> where T: Float + Add<Output=T> + Sub<Output=T> + Mul<Output=T> + Div<Output=T> + From<u16> + Trig + Copy + PartialOrd + Rem<Output=T> {
    pub fn radial_frequency(&self) -> T {
        (T::from(2))*T::pi()*self.frequency
    }
    pub fn sample(&self, t: T) -> T {
        (self.radial_frequency()*(t%self.period()) + self.phase).cos() * self.amplitude
    }
    //inclusive of start, exclusive of end
    pub fn sample_range(&self, start: T, end: T, sample_rate: T) -> Vec<T> {
        let sample_resolution = T::from(1) / sample_rate;
        let mut result = Vec::new();
        let mut i: u16 = 0;
        loop {
            let t = start + T::from(i)/sample_rate;
            if t >= end {
                break;
            }
            result.push(self.sample(t));
            i += 1;
        }
        
        result
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::f32;

    #[test]
    fn period() {
        let sinusoid = Sinusoid::new(1.0 as f32, 0.5, 0.0);
        assert!((sinusoid.period()-2.0) < f32::EPSILON);
    }
    #[test]
    fn radial_f() {
        let sinusoid = Sinusoid::new(1.0 as f32, 1.0, 0.0);
        assert!((sinusoid.radial_frequency()-2.0*f32::consts::PI) < f32::EPSILON);
    }

    #[test]
    fn sample() {
        let sinusoid = Sinusoid::new(1.0 as f32, 1.0, -f32::consts::PI/2.0); //AKA sin

        assert!((sinusoid.sample(0.0)-0.0) < f32::EPSILON);
        assert!((sinusoid.sample(0.25)-1.0) < f32::EPSILON);
        assert!((sinusoid.sample(0.5)-0.0) < f32::EPSILON);
        assert!((sinusoid.sample(0.75)+1.0) < f32::EPSILON);
        assert!((sinusoid.sample(1.0)-0.0) < f32::EPSILON);
    }

    #[test]
    fn sample_range() {
        let sinusoid = Sinusoid::new(1.0 as f32, 1.0, -f32::consts::PI/2.0); //AKA sin
        let samples = sinusoid.sample_range(0.0, 100.0, 4.0);
        println!("Epsilon is {}", f32::EPSILON);
        assert_eq!(samples.len(), 400);
        for i in (0..100).map(|i| i*4) {
            assert!((samples[i+0]-0.0) < f32::EPSILON, "Sample {} was {}", i+0, samples[i+0]);
            assert!((samples[i+1]-1.0) < f32::EPSILON, "Sample {} was {}", i+1, samples[i+1]);
            assert!((samples[i+2]-0.0) < f32::EPSILON, "Sample {} was {}", i+2, samples[i+2]);
            assert!((samples[i+3]+1.0) < f32::EPSILON, "Sample {} was {}", i+3, samples[i+3]);
        }
    }
}