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planar_graph.rs
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planar_graph.rs
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use std::collections::{HashMap, HashSet};
use geo::{Coord, LineString, Point};
use geojson::{Feature, FeatureCollection, Geometry};
use utils::Mercator;
#[derive(Clone, Copy, PartialEq, Eq, Hash)]
struct HashedPoint(isize, isize);
impl HashedPoint {
fn new(pt: Coord) -> Self {
// cm precision
Self((pt.x * 100.0) as isize, (pt.y * 100.0) as isize)
}
fn to_geo(self) -> Coord {
Coord {
x: self.0 as f64 / 100.0,
y: self.1 as f64 / 100.0,
}
}
}
pub fn get_faces(mercator: &Mercator, input: &Vec<LineString>) -> String {
// Repeat every edge in both directions
let mut linestrings = Vec::new();
for ls in input {
linestrings.push(ls.clone());
let mut rev = ls.clone();
rev.0.reverse();
linestrings.push(rev);
}
// Build a graph from these. Edges are identified by index.
let mut edges_per_node: HashMap<HashedPoint, Vec<usize>> = HashMap::new();
for (idx, linestring) in linestrings.iter().enumerate() {
let i1 = HashedPoint::new(*linestring.0.first().unwrap());
let i2 = HashedPoint::new(*linestring.0.last().unwrap());
edges_per_node.entry(i1).or_insert_with(Vec::new).push(idx);
edges_per_node.entry(i2).or_insert_with(Vec::new).push(idx);
}
// Sort the list of edges at each node so that they're in counter-clockwise order
for (pt, edges) in &mut edges_per_node {
sort_edges_ccw(*pt, edges, &linestrings);
}
let mut features = Vec::new();
for (idx, ls) in linestrings.iter().enumerate() {
let mut f = Feature::from(Geometry::from(&mercator.to_wgs84(ls)));
f.set_property("idx", idx);
f.set_property("forwards", idx % 2 == 0);
features.push(f);
}
for (pt, edges) in &edges_per_node {
let mut f = Feature::from(Geometry::from(&Point::from(
mercator.pt_to_wgs84(pt.to_geo()),
)));
f.set_property("edges", format!("{edges:?}"));
f.set_property(
"angles",
format!(
"{:?}",
edges
.iter()
.map(|idx| {
(100.0 * angle_from_endpoint(*pt, &linestrings[*idx])).round() / 100.0
})
.collect::<Vec<_>>()
),
);
features.push(f);
}
serde_json::to_string(&FeatureCollection {
features,
bbox: None,
foreign_members: None,
})
.unwrap()
/*let mut results = Vec::new();
let mut visited_edges: HashSet<usize> = HashSet::new();
for start_idx in 0..linestrings.len() {
if visited_edges.contains(&start_idx) {
continue;
}
// Look for a cycle starting here
let mut points = Vec::new();
let mut current = start_idx;
loop {
log::info!("from {start_idx}, at {current}");
if visited_edges.contains(¤t) {
log::info!(" bug! hit a loop in the wrong way");
points.dedup();
results.push(LineString::new(points));
break;
}
visited_edges.insert(current);
points.extend(linestrings[current].0.clone());
current = pick_next_ccw_edge(current, &edges_per_node, &linestrings);
if current == start_idx {
points.dedup();
results.push(LineString::new(points));
break;
}
}
// TODO Only work on one right now
break;
}
results*/
}
fn sort_edges_ccw(endpoint: HashedPoint, edges: &mut Vec<usize>, linestrings: &Vec<LineString>) {
edges.sort_by_key(|idx| {
// Make the angle sortable
(angle_from_endpoint(endpoint, &linestrings[*idx]) * 1000.0) as isize
});
}
fn angle_from_endpoint(endpoint: HashedPoint, linestring: &LineString) -> f64 {
let points = &linestring.0;
// Which end of the linestring starts here?
let starts_at_endpoint = endpoint == HashedPoint::new(points[0]);
// Find the angle in degrees from the endpoint to the next point in this line
let next_pt = if starts_at_endpoint {
points[1]
} else {
points[points.len() - 2]
};
let endpoint_geo = endpoint.to_geo();
let angle_degrees = (next_pt.y - endpoint_geo.y)
.atan2(next_pt.x - endpoint_geo.x)
.to_degrees();
let flip = if starts_at_endpoint { 0.0 } else { 180.0 };
// Normalize to [0, 360)
(angle_degrees + flip + 360.0) % 360.0
}
fn pick_next_ccw_edge(
current: usize,
edges_per_node: &HashMap<HashedPoint, Vec<usize>>,
linestrings: &Vec<LineString>,
) -> usize {
// We always trace forwards on the edges
let endpoint = HashedPoint::new(*linestrings[current].0.last().unwrap());
// TODO We don't need to the filter out the edges_per_node for edges originating at this
// endpoint. If we trust the sorting process, then it'll just happen.
let edges = &edges_per_node[&endpoint];
let pos = edges.iter().position(|e| *e == current).unwrap();
if pos == edges.len() - 1 {
edges[0]
} else {
edges[pos + 1]
}
/*if pos == 0 {
edges[edges.len() - 1]
} else {
edges[pos - 1]
}*/
}