Simplify parsing of hull for bbox response field

Previously we used `ST_AsText` to convert the geometry of the bounding
box to WKT and then parsed that using regular expressions. We can
simplify this by converting to GeoJSON instead which is much simpler to
parse.

Author: c-w

services/features.js

@@ -42,20 +42,19 @@ function getById(query, callback) {
 }
 
 function parseBoundingBox(bbox_geo_json) {
-    const match = /^POLYGON\(\((.*)\)\)$/.exec(bbox_geo_json)
-    if (!match || match.length !== 2) {
+    const feature = JSON.parse(bbox_geo_json);
+    const coords = feature.coordinates && feature.coordinates[0];
+    if (feature.type !== 'Polygon' || coords.length !== 5) {
         return null;
     }
 
-    const coords = match[1].split(',').map(point => point.split(' '));
-    if (coords.length !== 5 || coords.some(point => point.length !== 2)) {
-        return null;
-    }
+    const xs = coords.map(point => point[0]);
+    const ys = coords.map(point => point[1]);
 
-    const minX = parseFloat(coords[0][0]);
-    const minY = parseFloat(coords[0][1]);
-    const maxX = parseFloat(coords[2][0]);
-    const maxY = parseFloat(coords[2][1]);
+    const minX = Math.min(...xs);
+    const minY = Math.min(...ys);
+    const maxX = Math.max(...xs);
+    const maxY = Math.max(...ys);
 
     return [
         maxY, // north
@@ -99,7 +98,7 @@ function buildQueryColumns(query) {
     if (query.include) {
         let includeArray = query.include.split(',');
 
-        if (includeArray.indexOf('bbox') !== -1) queryColumns += ',ST_AsText(ST_Envelope(hull)) as bbox_geo_json';
+        if (includeArray.indexOf('bbox') !== -1) queryColumns += ',ST_AsGeoJSON(ST_Envelope(hull)) as bbox_geo_json';
         if (includeArray.indexOf('hull') !== -1) queryColumns += ',ST_AsGeoJSON(hull) as hull_geo_json';
         if (includeArray.indexOf('properties') !== -1) queryColumns += ',properties';
     }