From 73a597c9ffdf4b43545975c27f858cbb60cf587a Mon Sep 17 00:00:00 2001
From: Michael Stenta <mike@mstenta.net>
Date: Fri, 5 May 2023 21:04:40 -0400
Subject: [PATCH] Expose methods for reading features from GeoJSON and WKT.
 #194

---
 CHANGELOG.md                     |  1 +
 README.md                        | 30 +++++++++++++++++++++++++++++
 src/instance/instance.js         |  2 ++
 src/instance/methods/features.js | 33 ++++++++++++++++++++++++++++++++
 src/instance/methods/layer.js    | 15 ++++-----------
 5 files changed, 70 insertions(+), 11 deletions(-)
 create mode 100644 src/instance/methods/features.js

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4a149e4..ffe11c8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Save dist folder to an artifact in run-build.yml workflow. #193
+- Expose methods for reading features from GeoJSON and WKT. #194
 
 ## [v2.1.0] - 2022-11-15
 
diff --git a/README.md b/README.md
index fab93df..18785dd 100644
--- a/README.md
+++ b/README.md
@@ -320,6 +320,36 @@ const xyzOpts = {
 const xyzLayer = myMap.addLayer('xyz', xyzOpts);
 ```
 
+### Reading Features
+
+A `readFeatures` method is provided to enable reading geometry features from
+various formats like GeoJSON and WKT. It takes a format as its first parameter,
+and the input data as its second parameter.
+
+For example:
+
+```js
+// Reading features from GeoJSON.
+const geojson = {
+  type: "Feature",
+  geometry: {
+    type: "Polygon",
+    coordinates: [
+      [[30, 10], [40, 40], [20, 40], [10, 20], [30, 10]]
+    ]
+  },
+  properties: {
+    name: "Property Boundary"
+  }
+};
+const features = myMap.readFeatures('geojson', geojson);
+features[0].get('name') === 'Property Boundary'
+
+// Reading features from Well-Known Text (WKT).
+const wkt = "POLYGON ((-75.53643733263014 42.54424760416683, -75.5360350012779 42.54427527000766, -75.53589016199109 42.54412508386721, -75.53588747978209 42.54302634269183, -75.53643733263014 42.54424760416683))";
+const features = myMap.readFeatures('wkt', wkt);
+```
+
 ### Controlling the zoom level
 
 There are two methods for controlling the zoom level. The first, `zoomToVectors`,
diff --git a/src/instance/instance.js b/src/instance/instance.js
index 11c90b1..b09fbf1 100644
--- a/src/instance/instance.js
+++ b/src/instance/instance.js
@@ -7,6 +7,7 @@ import defaults from './defaults';
 
 // Import instance methods.
 import addLayer, { getLayerByName } from './methods/layer';
+import readFeatures from './methods/features';
 import addPopup from './methods/popup';
 import { zoomToVectors, zoomToLayer } from './methods/zoom';
 import { addBehavior, attachBehavior, attachBehaviorsByWeight } from './methods/behavior';
@@ -51,6 +52,7 @@ const createInstance = ({ target, options = {} }) => {
     addLayer,
     addPopup,
     getLayerByName,
+    readFeatures,
     zoomToVectors,
     zoomToLayer,
     addBehavior,
diff --git a/src/instance/methods/features.js b/src/instance/methods/features.js
new file mode 100644
index 0000000..54e9df6
--- /dev/null
+++ b/src/instance/methods/features.js
@@ -0,0 +1,33 @@
+// Import formats.
+import GeoJSON from 'ol/format/GeoJSON';
+import WKT from 'ol/format/WKT';
+
+// Import the default projection configuration
+import projection from '../../projection';
+
+// Read features from Well Known Text (WKT).
+function readFeaturesWKT(wkt) {
+  const isMultipart = wkt.includes('MULTIPOINT')
+    || wkt.includes('MULTILINESTRING')
+    || wkt.includes('MULTIPOLYGON')
+    || wkt.includes('GEOMETRYCOLLECTION');
+  return isMultipart
+    ? new WKT({ splitCollection: true }).readFeatures(wkt, projection)
+    : [new WKT().readFeature(wkt, projection)];
+}
+
+// Read features from GeoJSON.
+function readFeaturesGeoJSON(geojson) {
+  return (new GeoJSON()).readFeatures(geojson, projection);
+}
+
+// Read features from various formats.
+export default function readFeatures(type, input) {
+  if (type.toLowerCase() === 'geojson') {
+    return readFeaturesGeoJSON(input);
+  }
+  if (type.toLowerCase() === 'wkt') {
+    return readFeaturesWKT(input);
+  }
+  return undefined;
+}
diff --git a/src/instance/methods/layer.js b/src/instance/methods/layer.js
index 0cc9bfb..f13c057 100644
--- a/src/instance/methods/layer.js
+++ b/src/instance/methods/layer.js
@@ -8,7 +8,6 @@ import LayerGroup from 'ol/layer/Group';
 import VectorLayer from 'ol/layer/Vector';
 import TileLayer from 'ol/layer/Tile';
 import GeoJSON from 'ol/format/GeoJSON';
-import WKT from 'ol/format/WKT';
 
 // Import setWithCredentials function.
 import { setWithCredentials } from 'ol/featureloader';
@@ -17,8 +16,8 @@ import { setWithCredentials } from 'ol/featureloader';
 import * as Style from 'ol/style';
 import colorStyles, { clusterStyle } from '../../styles';
 
-// Import the default projection configuration
-import projection from '../../projection';
+// Import readFeatures function.
+import readFeatures from './features';
 
 // Set withCredentials to true for all XHR requests made via OpenLayers'
 // feature loader. Typically farmOS requires authentication in order to
@@ -90,7 +89,7 @@ function addGeoJSONLayer({
     });
   } else {
     source = new VectorSource({
-      features: (new GeoJSON()).readFeatures(geojson, projection),
+      features: readFeatures('geojson', geojson),
       format,
       attributions,
     });
@@ -130,13 +129,7 @@ function addWKTLayer({
   const style = styleFunction
     ? (feature, resolution) => styleFunction(feature, resolution, Style)
     : colorStyles(color);
-  const isMultipart = wkt.includes('MULTIPOINT')
-    || wkt.includes('MULTILINESTRING')
-    || wkt.includes('MULTIPOLYGON')
-    || wkt.includes('GEOMETRYCOLLECTION');
-  const features = isMultipart
-    ? new WKT({ splitCollection: true }).readFeatures(wkt, projection)
-    : [new WKT().readFeature(wkt, projection)];
+  const features = readFeatures('wkt', wkt);
   const attributions = [attribution];
   const source = new VectorSource({
     features,