feat: Add parsing of GPX extensions speed, course, hAcc, vAcc (#18)

* Add parsing of GPX extensions speed, course, hAcc, vAcc

Apple Watches track additional values that weren't being parsed
these are:

speed - speed in meters
course - bearing
hAcc - horizontal accuracy
vAcc - vertical accuracy

Add support for parsing and storing these values.

* Suggestions from PR review

lib/gpx.js

@@ -1,5 +1,13 @@
 import { nodeVal } from "./shared";
 
+const attributeNames = [
+  ["speed", "speeds"],
+  ["course", "courses"],
+  ["hAcc", "hAccs"],
+  ["vAcc", "vAccs"],
+  ["heartRate", "heartRates"]
+];
+
 function getLineStyle(extensions) {
   const style = {};
   if (extensions) {
@@ -72,11 +80,28 @@ function coordPair(x) {
       ll.push(e);
     }
   }
-  return {
+  const result = {
     coordinates: ll,
     time: time ? nodeVal(time) : null,
     heartRate: heartRate ? parseFloat(nodeVal(heartRate)) : null
   };
+
+  const extensions = get1(x, "extensions");
+  if (extensions !== null) {
+    attributeNames
+      .map(r => r[0])
+      .filter(n => n !== "heartrate")
+      .forEach(name => {
+        const raw = get1(extensions, name);
+        if (raw !== null) {
+          const v = parseFloat(nodeVal(raw));
+          if (!isNaN(v)) {
+            result[name] = v;
+          }
+        }
+      });
+  }
+  return result;
 }
 function getRoute(node) {
   const line = getPoints(node, "rtept");
@@ -98,46 +123,70 @@ function getPoints(node, pointname) {
   const line = [];
   const times = [];
   const l = pts.length;
-  let heartRates = undefined;
+  const extendedValues = {};
   if (l < 2) return {}; // Invalid line in GeoJSON
   for (let i = 0; i < l; i++) {
     const c = coordPair(pts[i]);
     line.push(c.coordinates);
     if (c.time) times.push(c.time);
-    if (c.heartRate || heartRates) {
-      if (!heartRates) heartRates = Array(i).fill(null);
-      heartRates.push(c.heartRate || null);
-    }
+    attributeNames
+      .map(r => r[0])
+      .forEach(name => {
+        if (c[name] || extendedValues[name]) {
+          if (!extendedValues[name]) {
+            extendedValues[name] = Array(i).fill(null);
+          }
+          extendedValues[name].push(c[name] || null);
+        }
+      });
   }
-  return {
+  const result = {
     line: line,
-    times: times,
-    heartRates: heartRates || []
+    times: times
   };
+  attributeNames.forEach(n => {
+    if (extendedValues[n[0]]) {
+      result[n[1]] = extendedValues[n[0]] || [];
+    }
+  });
+  return result;
 }
 function getTrack(node) {
   const segments = node.getElementsByTagName("trkseg");
   const track = [];
   const times = [];
-  const heartRates = [];
+  const extendedValues = {};
   let line;
   for (let i = 0; i < segments.length; i++) {
     line = getPoints(segments[i], "trkpt");
     if (line) {
       if (line.line) track.push(line.line);
       if (line.times && line.times.length) times.push(line.times);
-      if (heartRates.length || (line.heartRates && line.heartRates.length)) {
-        if (!heartRates.length) {
-          for (let s = 0; s < i; s++) {
-            heartRates.push(Array(track[s].length).fill(null));
+
+      attributeNames
+        .map(r => r[1])
+        .forEach(name => {
+          if (
+            (extendedValues[name] && extendedValues[name].length) ||
+            (line[name] && line[name].length)
+          ) {
+            if (!extendedValues[name]) {
+              extendedValues[name] = [];
+            }
+            if (!extendedValues[name].length) {
+              for (let s = 0; s < i; s++) {
+                extendedValues[name].push(Array(track[s].length).fill(null));
+              }
+            }
+            if (line[name] && line[name].length) {
+              extendedValues[name].push(line[name]);
+            } else {
+              extendedValues[name].push(
+                Array(line.line.length || 0).fill(null)
+              );
+            }
           }
-        }
-        if (line.heartRates && line.heartRates.length) {
-          heartRates.push(line.heartRates);
-        } else {
-          heartRates.push(Array(line.line.length || 0).fill(null));
-        }
-      }
+        });
     }
   }
   if (track.length === 0) return;
@@ -147,8 +196,13 @@ function getTrack(node) {
   );
   if (times.length)
     properties.coordTimes = track.length === 1 ? times[0] : times;
-  if (heartRates.length)
-    properties.heartRates = track.length === 1 ? heartRates[0] : heartRates;
+  attributeNames.forEach(n => {
+    if (extendedValues[n[1]] && extendedValues[n[1]].length) {
+      properties[n[1]] =
+        track.length === 1 ? extendedValues[n[1]][0] : extendedValues[n[1]];
+    }
+  });
+
   return {
     type: "Feature",
     properties: properties,