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use core::ops::{Mul, Sub};

use cast_trait::Cast;
use num_traits::{FromPrimitive, One, Zero};
use vec2;

#[inline]
pub fn cubic<'out, T, F>(
    out: &'out mut [T; 2],
    p0: &[T; 2],
    p1: &[T; 2],
    p2: &[T; 2],
    t: &F,
) -> &'out mut [T; 2]
where
    T: Clone + Cast<F>,
    F: Clone + One + Zero + FromPrimitive + PartialOrd + Cast<T>,
    for<'a, 'b> &'a F: Sub<&'b F, Output = F> + Mul<&'b F, Output = F>,
{
    if t <= &F::zero() {
        *out = p0.clone();
        out
    } else if t >= &F::one() {
        *out = p2.clone();
        out
    } else {
        let two = F::from_usize(2).unwrap();
        let one_min_t = &F::one() - t;
        let one_min_t_sq = &one_min_t * &one_min_t;
        let t_sq = t * t;

        let p0x = p0[0].clone().cast();
        let p0y = p0[1].clone().cast();
        let p1x = p1[0].clone().cast();
        let p1y = p1[1].clone().cast();
        let p2x = p2[0].clone().cast();
        let p2y = p2[1].clone().cast();

        vec2::set(
            out,
            (one_min_t_sq.clone() * p0x
                + two.clone() * one_min_t.clone() * t.clone() * p1x
                + t_sq.clone() * p2x)
                .cast(),
            (one_min_t_sq * p0y + two * one_min_t * t.clone() * p1y + t_sq * p2y).cast(),
        )
    }
}
#[test]
fn test_cubic() {
    assert_eq!(
        cubic(&mut [0, 0], &[0, 0], &[100, 200], &[200, 0], &0.25),
        &[50, 75]
    );
    assert_eq!(
        cubic(&mut [0, 0], &[0, 0], &[100, 200], &[200, 0], &0.5),
        &[100, 100]
    );
    assert_eq!(
        cubic(&mut [0, 0], &[0, 0], &[100, 200], &[200, 0], &0.75),
        &[150, 75]
    );
}