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use ndarray::*;
use ::utils;

pub fn default() -> GradientFilter {
    let horizontal_edge_filter = Array1::<f32>::from(
        vec![
            -1., 0., 1.,
            -2., 0., 2.,
            -1., 0., 1.,
        ]
    ).into_shape((3,3)).unwrap();
    let vertical_edge_filter = Array1::<f32>::from(
        vec![
            -1.,-2.,-1.,
            0. , 0., 0.,
            1. , 2., 1.,
        ]
    ).into_shape((3,3)).unwrap();

    GradientFilter{
        horizontal_edge_filter: horizontal_edge_filter,
        vertical_edge_filter: vertical_edge_filter
    }
}

pub struct GradientFilter {
    pub horizontal_edge_filter: Array2<f32>,
    pub vertical_edge_filter: Array2<f32>
}

impl GradientFilter {
    pub fn run (&self, img: Array2<f32>) -> Array2<f32> {
        return self.gradient_abs(img)
    }

    fn gradient_abs(&self, img: Array2<f32>) -> Array2<f32> {
        let vertical_gradient = utils::convolve2d(&img, &(self.vertical_edge_filter));
        let horizontal_gradient = utils::convolve2d(&img, &(self.horizontal_edge_filter));
        let mut result = Array2::<f32>::zeros((horizontal_gradient.shape()[0], horizontal_gradient.shape()[1]));
        Zip::from(&mut result).and(&horizontal_gradient)
                              .and(&vertical_gradient)
                              .apply(|r, h, v| *r = f32::sqrt(h*h + v*v));
        return result;
    }
}