Kill jsts

index.js

@@ -1,5 +1,4 @@
-// depend on jsts for now https://github.com/bjornharrtell/jsts/blob/master/examples/overlay.html
-var jsts = require('jsts');
+var gh = require('gh-clipping-algorithm');
 
 /**
  * Finds the difference between two {@link Polygon|polygons} by clipping the second
@@ -57,40 +56,39 @@ var jsts = require('jsts');
  * //=differenced
  */
 
-module.exports = function(p1, p2) {
-  var poly1 = JSON.parse(JSON.stringify(p1));
-  var poly2 = JSON.parse(JSON.stringify(p2));
-  if(poly1.type !== 'Feature') {
-    poly1 = {
-      type: 'Feature',
-      properties: {},
-      geometry: poly1
-    };
-  }
-  if(poly2.type !== 'Feature') {
-    poly2 = {
-      type: 'Feature',
-      properties: {},
-      geometry: poly2
-    };
-  }
-
-  var reader = new jsts.io.GeoJSONReader();
-  var a = reader.read(JSON.stringify(poly1.geometry));
-  var b = reader.read(JSON.stringify(poly2.geometry));
-  var differenced = a.difference(b);
-  var parser = new jsts.io.GeoJSONParser();
-  differenced = parser.write(differenced);
+module.exports = function(poly1, poly2) {
+  // console.log(poly1);
+  var a = poly1.coordinates ? poly1.coordinates : poly1.geometry.coordinates;
+  var b = poly2.coordinates ? poly2.coordinates : poly2.geometry.coordinates;
+  var u = gh.subtract(a, b);
 
-  poly1.geometry = differenced;
+  var feature = {
+    "type": "Feature",
+    "properties": {},
+    "geometry": {}
+  };
 
-  if (poly1.geometry.type === 'GeometryCollection' && poly1.geometry.geometries.length === 0) {
+  if (!u || u.length == 0) {
     return undefined;
-  } else {
-    return {
-      type: 'Feature',
-      properties: poly1.properties,
-      geometry: differenced
-    };
   }
+
+  if (gh.utils.isMultiPolygon(u)) {
+    if (u.length > 1) {
+      feature.geometry.type = "MultiPolygon";
+      feature.geometry.coordinates = u;
+    } else {
+      feature.geometry.type = "Polygon";
+      feature.geometry.coordinates = u[0];
+    }
+  } else if (gh.utils.isPolygon(u)) {
+    feature.geometry.type = "Polygon";
+    feature.geometry.coordinates = u;
+  }
+
+  if (poly1.properties) {
+    feature.properties = poly1.properties;
+  }
+
+  return feature;
 };
+

package.json

@@ -26,10 +26,11 @@
     "glob": "~5.0.5",
     "tape": "~4.0.0",
     "dox": "^0.7.1",
-    "doxme": "^1.8.2"
+    "doxme": "^1.8.2",
+    "geojson-equality": "^0.1.4"
   },
   "dependencies": {
-    "jsts": "~0.15.0",
+    "gh-clipping-algorithm": "^0.*",
     "turf-featurecollection": "^1.0.1"
   }
 }

test/test.js

@@ -1,7 +1,8 @@
 var difference = require('../'),
   test = require('tape'),
   glob = require('glob'),
-  fs = require('fs');
+  fs = require('fs')
+  equal = new(require('geojson-equality'));
 
 var REGEN = process.env.REGEN;
 
@@ -12,7 +13,7 @@ test('difference', function(t){
       var output = difference(features[0], features[1]);
       if (REGEN) fs.writeFileSync(input.replace('/in/', '/out/'), JSON.stringify(output));
       t.deepEqual(before, features, 'does not mutate data');
-      t.deepEqual(output, JSON.parse(fs.readFileSync(input.replace('/in/', '/out/'))), input);
+      t.ok(equal.compare(output, JSON.parse(fs.readFileSync(input.replace('/in/', '/out/')))), input);
   });
   t.end();
 });
@@ -24,7 +25,7 @@ test('difference -- geometries', function(t){
       var output = difference(fcs[0].geometry, fcs[1].geometry);
       if (REGEN) fs.writeFileSync(input.replace('/in/', '/out/'), JSON.stringify(output));
       t.deepEqual(before, fcs, 'does not mutate data');
-      t.deepEqual(output, JSON.parse(fs.readFileSync(input.replace('/in/', '/out/'))), input);
+      t.ok(equal.compare(output, JSON.parse(fs.readFileSync(input.replace('/in/', '/out/')))), input);
   });
   t.end();
 });
@@ -36,7 +37,7 @@ test('difference -- geometries', function(t){
       var output = difference(fcs[0].geometry, fcs[1].geometry);
       if (REGEN) fs.writeFileSync(input.replace('/in/', '/out/'), JSON.stringify(output));
       t.deepEqual(before, fcs, 'does not mutate data');
-      t.deepEqual(output, JSON.parse(fs.readFileSync(input.replace('/in/', '/out/'))), input);
+      t.ok(equal.compare(output, JSON.parse(fs.readFileSync(input.replace('/in/', '/out/')))), input);
   });
   t.end();
 });