From 0aa3be04882dc00c1079bac2f677a6ec20153e44 Mon Sep 17 00:00:00 2001
From: "jeremy@jermolene.com" <jeremy@jermolene.com>
Date: Fri, 6 Jan 2023 10:38:12 +0000
Subject: [PATCH] Add new geounion/geointersect/geodifference operators

---
 .../geospatial/operators/transformation.js    | 88 +++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 plugins/tiddlywiki/geospatial/operators/transformation.js

diff --git a/plugins/tiddlywiki/geospatial/operators/transformation.js b/plugins/tiddlywiki/geospatial/operators/transformation.js
new file mode 100644
index 000000000..2947780c5
--- /dev/null
+++ b/plugins/tiddlywiki/geospatial/operators/transformation.js
@@ -0,0 +1,88 @@
+/*\
+title: $:/plugins/tiddlywiki/geospatial/operators/transformation.js
+type: application/javascript
+module-type: filteroperator
+
+Filter operators for geospatial transformation
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+var turf = require("$:/plugins/tiddlywiki/geospatial/turf.js"),
+	geotools = require("$:/plugins/tiddlywiki/geospatial/geotools.js");
+
+exports.geounion = makeTransformation("union");
+
+exports.geointersect = makeTransformation("intersect");
+
+exports.geodifference = makeTransformation("difference");
+
+function makeTransformation(methodName) {
+	return function(source,operator,options) {
+		// Collect the input
+		var jsonObjects = [];
+		source(function(tiddler,title) {
+			var jsonObject = $tw.utils.parseJSONSafe(title,null);
+			if(jsonObject) {
+				jsonObjects.push(jsonObject)
+			}
+		});
+		// Perform the transformation
+		var result = geojsonOp(jsonObjects,methodName);
+		return [JSON.stringify(result)];
+	};
+}
+
+function geojsonOp(geojsonObjects, op) {
+	var resultFeatures = [];
+	$tw.utils.each(geojsonObjects,function (geojson1) {
+		if(geojson1.type === "FeatureCollection") {
+			resultFeatures = resultFeatures.length ? resultFeatures : geojson1.features;
+		} else if(geojson1.type === "Feature") {
+			resultFeatures = resultFeatures.length ? resultFeatures : [geojson1];
+		}
+		$tw.utils.each(geojsonObjects,function (geojson2) {
+			if(geojson1 !== geojson2) {
+				var newResultFeatures = [];
+				$tw.utils.each(resultFeatures,function (feature1) {
+					if(geojson2.type === "FeatureCollection") {
+						$tw.utils.each(geojson2.features,function (feature2) {
+							var result;
+							if(op === "union") {
+								result = turf.union(feature1, feature2);
+							} else if(op === "intersect") {
+								result = turf.intersect(feature1, feature2);
+							} else if(op === "difference") {
+								result = turf.difference(feature1, feature2);
+							}
+							if(result) {
+								newResultFeatures.push(result);
+							}
+						});
+					} else if(geojson2.type === "Feature") {
+						var result;
+						if(op === "union") {
+							result = turf.union(feature1, geojson2);
+						} else if(op === "intersect") {
+							result = turf.intersect(feature1, geojson2);
+						} else if(op === "difference") {
+							result = turf.difference(feature1, geojson2);
+						}
+						if(result) {
+							newResultFeatures.push(result);
+						}
+					}
+				});
+				resultFeatures = newResultFeatures;
+			}
+		});
+	});
+	return turf.featureCollection(resultFeatures);
+}
+
+
+})();