111 lines
3.6 KiB
JavaScript
Executable File
111 lines
3.6 KiB
JavaScript
Executable File
"use strict";
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var __importDefault = (this && this.__importDefault) || function (mod) {
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return (mod && mod.__esModule) ? mod : { "default": mod };
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};
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Object.defineProperty(exports, "__esModule", { value: true });
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var clone_1 = __importDefault(require("@turf/clone"));
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var helpers_1 = require("@turf/helpers");
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var invariant_1 = require("@turf/invariant");
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var meta_1 = require("@turf/meta");
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/**
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* Merges all connected (non-forking, non-junctioning) line strings into single lineStrings.
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* [LineString] -> LineString|MultiLineString
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*
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* @param {FeatureCollection<LineString|MultiLineString>} geojson Lines to dissolve
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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<LineString|MultiLineString>} Dissolved lines
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*/
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function lineDissolve(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 (!helpers_1.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 (invariant_1.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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if (mutate === false || mutate === undefined) {
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geojson = clone_1.default(geojson);
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}
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var result = [];
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var lastLine = meta_1.lineReduce(geojson, function (previousLine, currentLine) {
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// Attempt to merge this LineString with the other LineStrings, updating
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// the reference as it is merged with others and grows.
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var merged = mergeLineStrings(previousLine, currentLine);
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// Accumulate the merged LineString
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if (merged) {
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return merged;
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// Put the unmerged LineString back into the list
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}
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else {
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result.push(previousLine);
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return currentLine;
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}
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});
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// Append the last line
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if (lastLine) {
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result.push(lastLine);
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}
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// Return null if no lines were dissolved
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if (!result.length) {
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return null;
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// Return LineString if only 1 line was dissolved
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}
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else if (result.length === 1) {
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return result[0];
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// Return MultiLineString if multiple lines were dissolved with gaps
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}
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else {
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return helpers_1.multiLineString(result.map(function (line) {
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return line.coordinates;
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}));
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}
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}
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// [Number, Number] -> String
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function coordId(coord) {
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return coord[0].toString() + "," + coord[1].toString();
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}
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/**
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* LineString, LineString -> LineString
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*
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* @private
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* @param {Feature<LineString>} a line1
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* @param {Feature<LineString>} b line2
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* @returns {Feature<LineString>|null} Merged LineString
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*/
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function mergeLineStrings(a, b) {
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var coords1 = a.geometry.coordinates;
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var coords2 = b.geometry.coordinates;
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var s1 = coordId(coords1[0]);
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var e1 = coordId(coords1[coords1.length - 1]);
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var s2 = coordId(coords2[0]);
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var e2 = coordId(coords2[coords2.length - 1]);
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// TODO: handle case where more than one of these is true!
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var coords;
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if (s1 === e2) {
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coords = coords2.concat(coords1.slice(1));
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}
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else if (s2 === e1) {
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coords = coords1.concat(coords2.slice(1));
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}
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else if (s1 === s2) {
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coords = coords1.slice(1).reverse().concat(coords2);
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}
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else if (e1 === e2) {
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coords = coords1.concat(coords2.reverse().slice(1));
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}
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else {
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return null;
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}
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return helpers_1.lineString(coords);
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}
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exports.default = lineDissolve;
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