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extern crate geojson;
use geojson::Feature;
use std::f64::consts::PI;
const WGS84_RADIUS: f64 = 6378137.0;
pub fn rewind(feat: &mut Feature, outer: bool) {
let geom = match &mut feat.geometry {
None => { return },
Some(geom) => geom
};
match &mut geom.value {
geojson::Value::Polygon(poly) => {
correct_rings(poly, outer)
},
geojson::Value::MultiPolygon(mpoly) => {
for poly in mpoly {
correct_rings(poly, outer)
}
},
_ => { return }
}
}
fn correct_rings(coords: &mut Vec<Vec<geojson::Position>>, outer: bool) {
wind(&mut coords[0], outer);
let mut i = 1;
while i < coords.len() {
wind(&mut coords[i], !outer);
i = i + 1;
}
}
fn wind(coords: &mut Vec<geojson::Position>, outer: bool) {
let coords_len = coords.len() as u32;
if coords_len <= 2 { return }
let mut area: f64 = 0.0;
for i in 0..coords_len {
let mut lower_index: u32;
let mut middle_index: u32;
let mut upper_index: u32;
if i == coords_len - 2 {
lower_index = coords_len - 2;
middle_index = coords_len - 1;
upper_index = 0;
} else if i == coords_len - 1 {
lower_index = coords_len - 1;
middle_index = 0;
upper_index = 1;
} else {
lower_index = i;
middle_index = i + 1;
upper_index = i + 2;
}
let mut p1 = &coords[lower_index as usize];
let mut p2 = &coords[middle_index as usize];
let mut p3 = &coords[upper_index as usize];
area = area + ((p3[0] * PI / 180.0) - (p1[0] * PI / 180.0)) * (p2[1] * PI / 180.0).sin();
}
area = area * WGS84_RADIUS * WGS84_RADIUS / 2.0;
if (area > 0.0) == !outer {
coords.reverse();
}
}