72 lines
2.2 KiB
JavaScript
Executable File
72 lines
2.2 KiB
JavaScript
Executable File
import clone from "@turf/clone";
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import { isObject } from "@turf/helpers";
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import { getType } from "@turf/invariant";
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import { flattenEach } from "@turf/meta";
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import lineDissolve from "./turf-line-dissolve.js";
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import polygonDissolve from "./turf-polygon-dissolve.js";
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/**
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* Transform function: attempts to dissolve geojson objects where possible
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* [GeoJSON] -> GeoJSON geometry
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*
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* @private
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* @param {FeatureCollection<LineString|MultiLineString|Polygon|MultiPolygon>} geojson Features to dissolved
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* @param {Object} [options={}] Optional parameters
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* @param {boolean} [options.mutate=false] Prevent input mutation
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* @returns {Feature<MultiLineString|MultiPolygon>} Dissolved Features
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*/
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function dissolve(geojson, options) {
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if (options === void 0) { options = {}; }
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// Optional parameters
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options = options || {};
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if (!isObject(options)) {
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throw new Error("options is invalid");
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}
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var mutate = options.mutate;
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// Validation
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if (getType(geojson) !== "FeatureCollection") {
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throw new Error("geojson must be a FeatureCollection");
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}
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if (!geojson.features.length) {
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throw new Error("geojson is empty");
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}
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// Clone geojson to avoid side effects
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// Topojson modifies in place, so we need to deep clone first
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if (mutate === false || mutate === undefined) {
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geojson = clone(geojson);
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}
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// Assert homogenity
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var type = getHomogenousType(geojson);
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if (!type) {
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throw new Error("geojson must be homogenous");
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}
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// Data => Typescript hack
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var data = geojson;
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switch (type) {
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case "LineString":
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return lineDissolve(data, options);
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case "Polygon":
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return polygonDissolve(data, options);
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default:
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throw new Error(type + " is not supported");
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}
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}
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/**
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* Checks if GeoJSON is Homogenous
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*
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* @private
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* @param {GeoJSON} geojson GeoJSON
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* @returns {string|null} Homogenous type or null if multiple types
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*/
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function getHomogenousType(geojson) {
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var types = {};
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flattenEach(geojson, function (feature) {
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types[feature.geometry.type] = true;
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});
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var keys = Object.keys(types);
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if (keys.length === 1) {
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return keys[0];
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}
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return null;
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}
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export default dissolve;
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