From 1f860bc34f01d25f95310ea8cb7e2f27fff3283b Mon Sep 17 00:00:00 2001
From: Martin Fischer <martin@push-f.com>
Date: Fri, 14 Mar 2025 06:32:43 +0100
Subject: refactor: introduce route and parseLatLon functions

---
 script.js | 56 +++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 39 insertions(+), 17 deletions(-)

diff --git a/script.js b/script.js
index d9086b8..ec32e6e 100644
--- a/script.js
+++ b/script.js
@@ -17,27 +17,49 @@ const LINKS = [
     },
 ];
 
-const latlon = location.hash.substring(1);
-const [lat, lon] = latlon.split(',');
-
 const heading = document.getElementById('heading');
 
-// TODO: listen on hashChange
+route();
+// TODO: route on hashChange
+
+function route() {
+    const latLon = parseLatLon(location.hash.slice(1));
+
+    if (!latLon) {
+        heading.textContent = 'not yet implemented';
+    } else {
+        const linkList = document.getElementById('links');
+        document.getElementById('instructions').hidden = false;
 
-if (isNaN(lat) || isNaN(lon)) {
-    heading.textContent = 'not yet implemented';
-} else {
-    const linkList = document.getElementById('links');
-    document.getElementById('instructions').hidden = false;
+        document.title = 'Open location';
+        heading.textContent = '';
 
-    document.title = 'Open location';
+        const [lat, lon] = latLon;
 
-    for (const link of LINKS) {
-        const li = document.createElement('li');
-        const a = document.createElement('a');
-        a.href = link.url.replace('{lat}', lat).replace('{lon}', lon);
-        a.textContent = link.label;
-        li.appendChild(a);
-        linkList.appendChild(li);
+        for (const link of LINKS) {
+            const li = document.createElement('li');
+            const a = document.createElement('a');
+            a.href = link.url.replace('{lat}', lat).replace('{lon}', lon);
+            a.textContent = link.label;
+            li.appendChild(a);
+            linkList.appendChild(li);
+        }
+    }
+}
+
+function parseLatLon(text) {
+    if (text == '') {
+        return null;
+    }
+
+    let [lat, lon] = text.split(',');
+    lat = parseFloat(lat);
+    lon = parseFloat(lon);
+    if (Number.isNaN(lat) || Number.isNaN(lon)) {
+        throw Error('failed to parse latitude or longitude');
+    }
+    if (lat < -180 || lat > 180 || lon < -90 || lon > 90) {
+        throw Error('latitude or longitude are out of range');
     }
+    return [lat, lon];
 }
-- 
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