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/*
Copyright 2018 Martin Buck

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation the
rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the Software
is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall
be included all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE
OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

//! Douglas Peucker algorithm for 2D https://en.wikipedia.org/wiki/Ramer%E2%80%93Douglas%E2%80%93Peucker_algorithm

use crate::*;

//------------------------------------------------------------------------------

/// Douglas Peucker algorithm for 2D https://en.wikipedia.org/wiki/Ramer%E2%80%93Douglas%E2%80%93Peucker_algorithm
pub fn douglas_peucker_2d<P>(mut pc: PointCloud2D<P>, epsilon: f64) -> PointCloud2D<P>
where
    P: Is2D + Clone,
{
    if pc.len() < 1 {
        return pc;
    }

    let mut dmax = 0.0;
    let mut index = 0;
    let end = pc.len() - 1;

    for i in 1..end {
        let d = distance_point_line(&pc.data[i], &pc.data[0], &pc.data[end]);
        if d > dmax {
            index = i;
            dmax = d;
        }
    }

    if dmax > epsilon {
        let mut pc1 = pc.clone();
        let mut pc2 = pc.clone();

        pc1.data = pc.data.iter().cloned().take(index).collect();
        pc1 = douglas_peucker_2d(pc1, epsilon);

        pc2.data = pc.data.into_iter().skip(index).collect();
        pc2 = douglas_peucker_2d(pc2, epsilon);

        let n_take = pc1.data.len() - 1;
        pc1.data = pc1.data.into_iter().take(n_take).collect();
        pc = pc1.combine(&pc2);
    } else {
        let p1 = pc.data[0].clone();
        let p2 = pc.data[end].clone();
        pc.data.clear();
        pc.data.push(p1);
        pc.data.push(p2);
    }

    pc
}

//------------------------------------------------------------------------------

fn distance_point_line<P, Q, R>(p: &P, l1: &Q, l2: &R) -> f64
where
    P: Is2D,
    Q: Is2D,
    R: Is2D,
{
    let a1 = l1.x();
    let a2 = l1.y();

    let b1 = l2.x();
    let b2 = l2.y();

    let c1 = p.x();
    let c2 = p.y();

    let x = (a1 * a1 * c1 - a1 * a2 * b2 + a1 * a2 * c2 - 2.0 * a1 * b1 * c1 + a1 * b2 * b2
        - a1 * b2 * c2
        + a2 * a2 * b1
        - a2 * b1 * b2
        - a2 * b1 * c2
        + b1 * b1 * c1
        + b1 * b2 * c2)
        / (a1 * a1 - 2.0 * a1 * b1 + a2 * a2 - 2.0 * a2 * b2 + b1 * b1 + b2 * b2);

    let y = ((a2 - b2) * x + a1 * b2 - a2 * b1) / (a1 - b1);

    ((x - p.x()).powi(2) + (y - p.y()).powi(2)).sqrt()
}