From 72c51bc28350d65ae2f037f2f76146a945dbe073 Mon Sep 17 00:00:00 2001
From: Bryan Housel <bryan@mapbox.com>
Date: Wed, 14 Dec 2016 17:21:32 -0500
Subject: [PATCH] Add getSmallestSurroundingRectangle

---
 modules/actions/reflect.js    | 97 ++++++++++++++++++++++++++++++-----
 modules/operations/reflect.js |  8 +--
 2 files changed, 87 insertions(+), 18 deletions(-)

diff --git a/modules/actions/reflect.js b/modules/actions/reflect.js
index 394948c35..aa02b4dd2 100644
--- a/modules/actions/reflect.js
+++ b/modules/actions/reflect.js
@@ -1,26 +1,95 @@
 import _ from 'lodash';
-/* Flip the provided way horizontally 
-Only operates on "area" ways
-*/
+import {
+    polygonHull as d3polygonHull,
+    polygonCentroid as d3polygonCentroid
+} from 'd3';
 
-export function actionReflect(wayId) {
+import { geoExtent } from '../geo/extent';
 
-    return function (graph) {        
-        const targetWay = graph.entity(wayId);
 
-        // If the way is not an area, we will not process it
+/* Flip the provided way horizontally. Only operates on "area" ways */
+export function actionReflect(wayId, projection) {
+
+    function rotatePolygon(polygon, angle, centroid) {
+        return polygon.map(function(point) {
+            var radial = [point[0] - centroid[0], point[1] - centroid[1]];
+            return [
+                radial[0] * Math.cos(angle) - radial[1] * Math.sin(angle) + centroid[0],
+                radial[0] * Math.sin(angle) + radial[1] * Math.cos(angle) + centroid[1]
+            ];
+        });
+    }
+
+    // http://gis.stackexchange.com/questions/22895/finding-minimum-area-rectangle-for-given-points
+    // http://gis.stackexchange.com/questions/3739/generalisation-strategies-for-building-outlines/3756#3756
+    function getSmallestSurroundingRectangle(graph, way) {
+        var nodes = _.uniq(graph.childNodes(way)),
+            points = nodes.map(function(n) { return projection(n.loc); }),
+            hull = d3polygonHull(points),
+            centroid = d3polygonCentroid(hull),
+            minArea = Infinity,
+            ssrExtent = [],
+            ssrAngle = 0,
+            c1 = hull[0];
+
+        for (var i = 0; i < hull.length - 1; i++) {
+            var c2 = hull[i + 1],
+                angle = Math.atan2(c2[1] - c1[1], c2[0] - c1[0]),
+                poly = rotatePolygon(hull, -angle, centroid),
+                extent = poly.reduce(function(extent, point) {
+                        return extent.extend(geoExtent(point));
+                    }, geoExtent()),
+                area = extent.area();
+
+            if (area < minArea) {
+                minArea = area;
+                ssrExtent = extent;
+                ssrAngle = angle;
+            }
+            c1 = c2;
+        }
+
+        return {
+            poly: rotatePolygon(ssrExtent.polygon(), ssrAngle, centroid),
+            angle: ssrAngle
+        };
+    }
+
+
+    return function (graph) {
+        var targetWay = graph.entity(wayId);
         if (!targetWay.isArea()) {
-            // return input graph without changes
             return graph;
         }
+
+
+// lol hacky debug
+        var ssr = getSmallestSurroundingRectangle(graph, targetWay);
+        var nodes = targetWay.nodes;
+        for (var d = 0; d < nodes.length - 1; d++) {
+            var node = graph.entity(nodes[d]);
+            if (d < 4) {
+                node = node.move(projection.invert(ssr.poly[d]));
+                graph = graph.replace(node);
+            } else {
+                graph = graph.remove(node);
+            }
+        }
+        graph = graph.replace(targetWay.update(
+            { nodes: [nodes[0], nodes[1], nodes[2], nodes[3], nodes[0]] })
+        );
+
+        return graph;
+// end debug
+
         // Get the bounding rectangle of the area
-        const boundingRect = targetWay.extent(graph).rectangle();
+        var boundingRect = targetWay.extent(graph).rectangle();
         // rectangle returned as [ lon (x) top left, lat (y) top left, lon (x) bottom right, lat (y) bottom right]
         // Obtain the left and right lonlat's
-        const left = boundingRect[0];
-        const right = boundingRect[2];
+        var left = boundingRect[0];
+        var right = boundingRect[2];
         // Determine the mid-point that we will flip on
-        const midPoint = left + ((right - left) / 2);
+        var midPoint = left + ((right - left) / 2);
 
         // Obtain all of the nodes on the way, iterate over them to translate then aggreate up
         return _(targetWay.nodes)
@@ -31,7 +100,7 @@ export function actionReflect(wayId) {
             .uniqBy(function (node) { return node.id; })
             // Get distance from midPoint and produce a translated node
             .map(function (node) {
-                const delta = node.loc[0] - midPoint;
+                var delta = node.loc[0] - midPoint;
                 return node.move([node.loc[0]-(2*delta), node.loc[1]]);
             })
             // Chain together consecutive updates to the graph for each updated node and return
@@ -40,4 +109,4 @@ export function actionReflect(wayId) {
             }, graph);
 
     };
-}
\ No newline at end of file
+}
diff --git a/modules/operations/reflect.js b/modules/operations/reflect.js
index 42b267df2..3ef5ed60f 100644
--- a/modules/operations/reflect.js
+++ b/modules/operations/reflect.js
@@ -2,10 +2,10 @@ import { t } from '../util/locale';
 import { actionReflect } from '../actions/index';
 
 export function operationReflect(selectedIDs, context) {
-    const entityId = selectedIDs[0];
-    const entity = context.entity(entityId);
-    const extent = entity.extent(context.graph());
-    const action = actionReflect(entityId);
+    var entityId = selectedIDs[0];
+    var entity = context.entity(entityId);
+    var extent = entity.extent(context.graph());
+    var action = actionReflect(entityId, context.projection);
 
     var operation = function() {
         context.perform(