use crate::core::filter::CreateFilterSampler;
use shared::Float;
use shared::core::filter::FilterSampler;
use shared::core::geometry::{Point2f, Vector2f};
use shared::filters::MitchellFilter;

#[derive(Clone, Debug, Device)]
#[device(name = "MitchellFilter")]
pub struct MitchellFilterHost {
    pub radius: Vector2f,
    pub b: Float,
    pub c: Float,
    #[device(flatten)]
    pub sampler: FilterSampler,
}

impl MitchellFilterHost {
    pub fn new(radius: Vector2f, b: Float, c: Float) -> Self {
        let sampler = FilterSampler::new(radius, move |p: Point2f| {
            mitchell_1d(p.x() / radius.x(), b, c) * mitchell_1d(p.y() / radius.y(), b, c)
        });
        Self { radius, b, c, sampler }
    }
}

fn mitchell_1d(x: Float, b: Float, c: Float) -> Float {
    let x = (2.0 * x).abs();
    if x <= 1.0 {
        ((12.0 - 9.0 * b - 6.0 * c) * x * x * x
            + (-18.0 + 12.0 * b + 6.0 * c) * x * x
            + (6.0 - 2.0 * b))
            / 6.0
    } else if x <= 2.0 {
        ((-b - 6.0 * c) * x * x * x
            + (6.0 * b + 30.0 * c) * x * x
            + (-12.0 * b - 48.0 * c) * x
            + (8.0 * b + 24.0 * c))
            / 6.0
    } else {
        0.0
    }
}