Polygons

use polygons.qweruse polygon_contains, polygon_find from polygons      // Quillo 0.6: only these

geo = "0.28"geojson = "0.24"

// Delivery zones drawn on a map (GeoJSON from geojson.io or QGIS): the fee for an address,// and how big each zone is.////   quillo run polygons.qwe      then open http://localhost:8080/fee?lat=52.373&lon=4.892use "polygons.qwer"let ZONES = json.parse(read_file("polygons_sample.geojson")?)route GET /fee ? { lat: float, lon: float } {    let z = polygon_find(ZONES, lat, lon)?    if z == null { return { delivers: false } }    { delivers: true, zone: z.zone, fee: z.fee, minutes: z.minutes }}route GET /zones = ZONES.features | map((f) => merge({ zone: f.properties.zone }, polygon_measure(f)?))route GET /inside = { centre: polygon_contains(ZONES.features[0], 52.373, 4.892)?, ring_hole: polygon_contains(ZONES.features[1], 52.373, 4.892)? }

//! Points and areas from GeoJSON: is a point inside a polygon (a delivery zone, a city, a store's catchment), which zone holds it, and an area's size in km², perimeter, centre and bounding box.//! version: 1.0.0//!//! [dependencies]//! geo = "0.28"//! geojson = "0.24"use geo::{BoundingRect, Centroid, Contains, GeodesicArea};use serde_json::{json, Value};const MAX_FEATURES: usize = 100_000;/// GeoJSON as given: a map, or its JSON text.fn read(gj: &Value) -> Result<geojson::GeoJson, String> {    let v = match gj {        Value::String(s) => serde_json::from_str(s).map_err(|e| format!("not JSON: {}", e))?,        other => other.clone(),    };    geojson::GeoJson::from_json_value(v).map_err(|e| format!("not GeoJSON: {}", e))}fn geometry(gj: &geojson::GeoJson) -> Result<geo::GeometryCollection<f64>, String> {    geojson::quick_collection(gj).map_err(|e| e.to_string())}fn point(lat: f64, lon: f64) -> Result<geo::Point<f64>, String> {    if !(-90.0..=90.0).contains(&lat) || !(-180.0..=180.0).contains(&lon) {        return Err(format!("{}, {} is not a place", lat, lon));    }    Ok(geo::Point::new(lon, lat))}/// Whether the point is inside any polygon of the GeoJSON (a Polygon, MultiPolygon, Feature or FeatureCollection). A point on the edge is not inside.pub fn polygon_contains(geojson: serde_json::Value, lat: f64, lon: f64) -> Result<bool, String> {    let p = point(lat, lon)?;    Ok(geometry(&read(&geojson)?)?.iter().any(|g| g.contains(&p)))}/// The `properties` of the first feature of a FeatureCollection whose geometry holds the point (`{ zone: "A", fee: 2.5 }`), or null when none does.pub fn polygon_find(geojson: serde_json::Value, lat: f64, lon: f64) -> Result<Value, String> {    let p = point(lat, lon)?;    let geojson::GeoJson::FeatureCollection(fc) = read(&geojson)? else { return Err("polygon_find takes a FeatureCollection".into()) };    if fc.features.len() > MAX_FEATURES {        return Err("at most 100,000 features".into());    }    for f in fc.features {        let Some(g) = f.geometry else { continue };        let g: geo::Geometry<f64> = g.try_into().map_err(|e: geojson::Error| e.to_string())?;        if g.contains(&p) {            return Ok(f.properties.map(Value::Object).unwrap_or(json!({})));        }    }    Ok(Value::Null)}/// An area's measures on the Earth (geodesic, WGS 84): `{ area_km2, perimeter_km, centroid: { lat, lon }, bbox: { min_lat, min_lon, max_lat, max_lon } }`, all polygons of the GeoJSON together.pub fn polygon_measure(geojson: serde_json::Value) -> Result<Value, String> {    let gc = geometry(&read(&geojson)?)?;    let mut area = 0.0;    let mut perim = 0.0;    for g in gc.iter() {        let polys: Vec<geo::Polygon<f64>> = match g {            geo::Geometry::Polygon(p) => vec![p.clone()],            geo::Geometry::MultiPolygon(mp) => mp.0.clone(),            _ => vec![],        };        for p in polys {            let (pe, a) = p.geodesic_perimeter_area_unsigned();            area += a;            perim += pe;        }    }    let c = gc.centroid();    let b = gc.bounding_rect();    let r = |x: f64, d: f64| (x * d).round() / d;    Ok(json!({        "area_km2": r(area / 1e6, 1e4), "perimeter_km": r(perim / 1e3, 1e4),        "centroid": c.map(|c| json!({ "lat": r(c.y(), 1e6), "lon": r(c.x(), 1e6) })),        "bbox": b.map(|b| json!({ "min_lat": b.min().y, "min_lon": b.min().x, "max_lat": b.max().y, "max_lon": b.max().x })),    }))}