From 4a0ff38d0e1bbb93ab92dc9d7949918fee56d37e Mon Sep 17 00:00:00 2001
From: Rowan Winsemius <rowanwins@yahoo.com.au>
Date: Wed, 7 Jul 2021 09:18:42 +1000
Subject: [PATCH] Rework Mask module (#2130)

* rework dissolve

* make es5 friendly

* remove spread operator

* remove arrow function

* another prettier fix

Co-authored-by: mfedderly <mdfedderly@mdfedderly.com>
---
 packages/turf-mask/README.md                  |  31 +++-
 packages/turf-mask/bench.js                   |   4 +
 packages/turf-mask/index.js                   | 174 +++---------------
 packages/turf-mask/package.json               |   5 +-
 .../turf-mask/test/out/mask-outside.geojson   |   4 +-
 5 files changed, 58 insertions(+), 160 deletions(-)

diff --git a/packages/turf-mask/README.md b/packages/turf-mask/README.md
index 33f65c9a63..20033a6fe8 100644
--- a/packages/turf-mask/README.md
+++ b/packages/turf-mask/README.md
@@ -8,31 +8,44 @@ Takes any type of [polygon][1] and an optional mask and returns a [polygon][1] e
 
 **Parameters**
 
--   `polygon` **([FeatureCollection][2] \| [Feature][3]&lt;([Polygon][4] \| [MultiPolygon][5])>)** GeoJSON Polygon used as interior rings or holes.
--   `mask` **[Feature][3]&lt;[Polygon][4]>?** GeoJSON Polygon used as the exterior ring (if undefined, the world extent is used)
+- `polygon` **([FeatureCollection][2] \| [Feature][3]&lt;([Polygon][4] \| [MultiPolygon][5])>)** GeoJSON Polygon used as interior rings or holes.
+- `mask` **[Feature][3]&lt;[Polygon][4]>?** GeoJSON Polygon used as the exterior ring (if undefined, the world extent is used)
 
 **Examples**
 
 ```javascript
-var polygon = turf.polygon([[[112, -21], [116, -36], [146, -39], [153, -24], [133, -10], [112, -21]]]);
-var mask = turf.polygon([[[90, -55], [170, -55], [170, 10], [90, 10], [90, -55]]]);
+var polygon = turf.polygon([
+  [
+    [112, -21],
+    [116, -36],
+    [146, -39],
+    [153, -24],
+    [133, -10],
+    [112, -21],
+  ],
+]);
+var mask = turf.polygon([
+  [
+    [90, -55],
+    [170, -55],
+    [170, 10],
+    [90, 10],
+    [90, -55],
+  ],
+]);
 
 var masked = turf.mask(polygon, mask);
 
 //addToMap
-var addToMap = [masked]
+var addToMap = [masked];
 ```
 
 Returns **[Feature][3]&lt;[Polygon][4]>** Masked Polygon (exterior ring with holes).
 
 [1]: https://tools.ietf.org/html/rfc7946#section-3.1.6
-
 [2]: https://tools.ietf.org/html/rfc7946#section-3.3
-
 [3]: https://tools.ietf.org/html/rfc7946#section-3.2
-
 [4]: https://tools.ietf.org/html/rfc7946#section-3.1.6
-
 [5]: https://tools.ietf.org/html/rfc7946#section-3.1.7
 
 <!-- This file is automatically generated. Please don't edit it directly:
diff --git a/packages/turf-mask/bench.js b/packages/turf-mask/bench.js
index b1a59fcfbb..ffc089f366 100644
--- a/packages/turf-mask/bench.js
+++ b/packages/turf-mask/bench.js
@@ -23,6 +23,10 @@ for (const { name, geojson } of fixtures) {
   suite.add(name, () => turfMask(polygon, masking));
 }
 
+// basic x 4,627 ops/sec ±25.23% (21 runs sampled)
+// mask-outside x 3,892 ops/sec ±34.80% (15 runs sampled)
+// multi-polygon x 5,837 ops/sec ±3.03% (91 runs sampled)
+// overlapping x 22,326 ops/sec ±1.34% (90 runs sampled)
 suite
   .on("cycle", (event) => {
     console.log(String(event.target));
diff --git a/packages/turf-mask/index.js b/packages/turf-mask/index.js
index 0e4fe901c1..1c8fb89cbc 100644
--- a/packages/turf-mask/index.js
+++ b/packages/turf-mask/index.js
@@ -1,8 +1,5 @@
-import rbush from "rbush";
-import union from "@turf/union";
-import { polygon, featureCollection } from "@turf/helpers";
-import turfBBox from "@turf/bbox";
-import { flattenEach } from "@turf/meta";
+import { polygon as createPolygon, multiPolygon } from "@turf/helpers";
+import polygonClipping from "polygon-clipping";
 
 /**
  * Takes any type of {@link Polygon|polygon} and an optional mask and returns a {@link Polygon|polygon} exterior ring with holes.
@@ -24,63 +21,38 @@ function mask(polygon, mask) {
   // Define mask
   var maskPolygon = createMask(mask);
 
-  // Define polygon
-  var separated = separatePolygons(polygon);
-  var polygonOuters = separated[0];
-  var polygonInners = separated[1];
+  var polygonOuters = null;
+  if (polygon.type === "FeatureCollection") polygonOuters = unionFc(polygon);
+  else
+    polygonOuters = createGeomFromPolygonClippingOutput(
+      polygonClipping.union(polygon.geometry.coordinates)
+    );
 
-  // Union Outers & Inners
-  polygonOuters = unionPolygons(polygonOuters);
-  polygonInners = unionPolygons(polygonInners);
+  polygonOuters.geometry.coordinates.forEach(function (contour) {
+    maskPolygon.geometry.coordinates.push(contour[0]);
+  });
 
-  // Create masked area
-  var masked = buildMask(maskPolygon, polygonOuters, polygonInners);
-  return masked;
+  return maskPolygon;
 }
 
-/**
- * Build Mask
- *
- * @private
- * @param {Feature<Polygon>} maskPolygon Mask Outer
- * @param {FeatureCollection<Polygon>} polygonOuters Polygon Outers
- * @param {FeatureCollection<Polygon>} polygonInners Polygon Inners
- * @returns {Feature<Polygon>} Feature Polygon
- */
-function buildMask(maskPolygon, polygonOuters, polygonInners) {
-  var coordinates = [];
-  coordinates.push(maskPolygon.geometry.coordinates[0]);
-
-  flattenEach(polygonOuters, function (feature) {
-    coordinates.push(feature.geometry.coordinates[0]);
-  });
-
-  flattenEach(polygonInners, function (feature) {
-    coordinates.push(feature.geometry.coordinates[0]);
-  });
-  return polygon(coordinates);
+function unionFc(fc) {
+  var unioned =
+    fc.features.length === 2
+      ? polygonClipping.union(
+          fc.features[0].geometry.coordinates,
+          fc.features[1].geometry.coordinates
+        )
+      : polygonClipping.union.apply(
+          polygonClipping,
+          fc.features.map(function (f) {
+            return f.geometry.coordinates;
+          })
+        );
+  return createGeomFromPolygonClippingOutput(unioned);
 }
 
-/**
- * Separate Polygons to inners & outers
- *
- * @private
- * @param {FeatureCollection|Feature<Polygon|MultiPolygon>} poly GeoJSON Feature
- * @returns {Array<FeatureCollection<Polygon>, FeatureCollection<Polygon>>} Outer & Inner lines
- */
-function separatePolygons(poly) {
-  var outers = [];
-  var inners = [];
-  flattenEach(poly, function (feature) {
-    var coordinates = feature.geometry.coordinates;
-    var featureOuter = coordinates[0];
-    var featureInner = coordinates.slice(1);
-    outers.push(polygon([featureOuter]));
-    featureInner.forEach(function (inner) {
-      inners.push(polygon([inner]));
-    });
-  });
-  return [featureCollection(outers), featureCollection(inners)];
+function createGeomFromPolygonClippingOutput(unioned) {
+  return multiPolygon(unioned);
 }
 
 /**
@@ -101,95 +73,7 @@ function createMask(mask) {
     ],
   ];
   var coordinates = (mask && mask.geometry.coordinates) || world;
-  return polygon(coordinates);
-}
-
-/**
- * Union Polygons
- *
- * @private
- * @param {FeatureCollection<Polygon>} polygons collection of polygons
- * @returns {FeatureCollection<Polygon>} polygons only apply union if they collide
- */
-function unionPolygons(polygons) {
-  if (polygons.features.length <= 1) return polygons;
-
-  var tree = createIndex(polygons);
-  var results = [];
-  var removed = {};
-
-  flattenEach(polygons, function (currentFeature, currentIndex) {
-    // Exclude any removed features
-    if (removed[currentIndex]) return true;
-
-    // Don't search for itself
-    tree.remove({ index: currentIndex }, filterByIndex);
-    removed[currentIndex] = true;
-
-    // Keep applying the union operation until no more overlapping features
-    while (true) {
-      var bbox = turfBBox(currentFeature);
-      var search = tree.search({
-        minX: bbox[0],
-        minY: bbox[1],
-        maxX: bbox[2],
-        maxY: bbox[3],
-      });
-      if (search.length > 0) {
-        var polys = search.map(function (item) {
-          removed[item.index] = true;
-          tree.remove({ index: item.index }, filterByIndex);
-          return item.geojson;
-        });
-
-        for (var i = 0, l = polys.length; i < l; i++) {
-          currentFeature = union(currentFeature, polys[i]);
-        }
-      }
-      // Done
-      if (search.length === 0) break;
-    }
-    results.push(currentFeature);
-  });
-
-  return featureCollection(results);
-}
-
-/**
- * Filter by Index - RBush helper function
- *
- * @private
- * @param {Object} a remove item
- * @param {Object} b search item
- * @returns {boolean} true if matches
- */
-function filterByIndex(a, b) {
-  return a.index === b.index;
-}
-
-/**
- * Create RBush Tree Index
- *
- * @private
- * @param {FeatureCollection<any>} features GeoJSON FeatureCollection
- * @returns {RBush} RBush Tree
- */
-function createIndex(features) {
-  var tree = rbush();
-  var load = [];
-  flattenEach(features, function (feature, index) {
-    var bbox = turfBBox(feature);
-    load.push({
-      minX: bbox[0],
-      minY: bbox[1],
-      maxX: bbox[2],
-      maxY: bbox[3],
-      geojson: feature,
-      index: index,
-    });
-  });
-  tree.load(load);
-  return tree;
+  return createPolygon(coordinates);
 }
 
 export default mask;
diff --git a/packages/turf-mask/package.json b/packages/turf-mask/package.json
index 565f6e570c..58c1e67bfd 100644
--- a/packages/turf-mask/package.json
+++ b/packages/turf-mask/package.json
@@ -54,10 +54,7 @@
     "write-json-file": "*"
   },
   "dependencies": {
-    "@turf/bbox": "^6.4.0",
     "@turf/helpers": "^6.4.0",
-    "@turf/meta": "^6.4.0",
-    "@turf/union": "^6.4.0",
-    "rbush": "^2.0.1"
+    "polygon-clipping": "^0.15.3"
   }
 }
diff --git a/packages/turf-mask/test/out/mask-outside.geojson b/packages/turf-mask/test/out/mask-outside.geojson
index 313025cc08..2e698006e5 100644
--- a/packages/turf-mask/test/out/mask-outside.geojson
+++ b/packages/turf-mask/test/out/mask-outside.geojson
@@ -12,7 +12,6 @@
         [119.53125, -39.77476948529546]
       ],
       [
-        [113.115234375, -22.105998799750566],
         [112.587890625, -24.766784522874428],
         [113.73046875, -29.382175075145277],
         [114.78515624999999, -32.916485347314385],
@@ -25,7 +24,8 @@
         [127.44140625, -17.560246503294888],
         [122.431640625, -17.308687886770024],
         [116.806640625, -17.978733095556155],
-        [113.115234375, -22.105998799750566]
+        [113.115234375, -22.105998799750566],
+        [112.587890625, -24.766784522874428]
       ]
     ]
   }