Sanitize filenames of downloads.

Some routes have characters like ":" in them which can be illegal on
certain filesystems. Remove the known common ones and replace them with
an underscore.

README.md

@@ -1,23 +1,28 @@
 # SAC Route Portal GPX Downloader
+
 The [Swiss Alpine Club](https://www.sac-cas.ch/en/) has a great
-[route portal](https://www.sac-cas.ch/en/huts-and-tours/sac-route-portal/)
-for finding interesting hiking routes.
+[route portal](https://www.sac-cas.ch/en/huts-and-tours/sac-route-portal/) for
+finding interesting hiking routes.
 
-However you can not download the tracks as gpx files, as they argue that the exact
-paths are subject to change and it could be dangerous to adhere too closely to them. 
+However you can not download the tracks as gpx files, as they argue that the
+exact paths are subject to change and it could be dangerous to adhere too
+closely to them.
 
-I do agree with that, but you can draw your own routes
-and download those, mainly taking some time to draw after the route they are 
-already showing on the map.
+I do agree with that, but you can draw your own routes and download those,
+mainly taking some time to draw after the route they are already showing on the
+map.
 
 With this extension you can select any track and then download it as a gpx file
 (an active subscription is needed).
 
 ## Be Cautious!
+
 Heed their warning and do not blindly follow the gps track! Use your brain and
 plan your route beforehand to be aware of dangerous parts and alternatives.
 
-Take a look at their [safety instructions](https://www.sac-cas.ch/en/training-and-safety/safety/).
+Take a look at their
+[safety instructions](https://www.sac-cas.ch/en/training-and-safety/safety/).
 
 ## Contributors
+
 - wizche

background.js

@@ -21,14 +21,16 @@ function toWGS84(point) {
   const x_aux = (point[1] - 1200000) / 1000000;
 
   // calculate longitude and latitude in the unit 10000"
-  let lat = 16.9023892 +
+  let lat =
+    16.9023892 +
     3.238272 * x_aux -
     0.270978 * Math.pow(y_aux, 2) -
     0.002528 * Math.pow(x_aux, 2) -
     0.0447 * Math.pow(y_aux, 2) * x_aux -
     0.014 * Math.pow(x_aux, 3);
 
-  let lon = 2.6779094 +
+  let lon =
+    2.6779094 +
     4.728982 * y_aux +
     0.791484 * y_aux * x_aux +
     0.1306 * y_aux * Math.pow(x_aux, 2) -
@@ -179,6 +181,41 @@ function checkTrack(tab) {
   return tab.url.match("https://www.sac-cas.ch/.*") && gpxTrack;
 }
 
+/**
+ * Remove characters that lead to problems in common filesystems.
+ *
+ * Windows (NTFS) seems to have the most restrictions, so it is mostly sourced from there.
+ *
+ * Reserved names on windows: https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file
+ *
+ * Code comes from https://github.com/parshap/node-sanitize-filename/blob/master/index.js
+ */
+function sanitizeFilename(input) {
+  const illegal = /[\/\?<>\\:\*\|"]/g;
+  // deno-lint-ignore no-control-regex
+  const control = /[\x00-\x1f\x80-\x9f]/g;
+  const reserved = /^\.+$/;
+  const windowsReserved = /^(con|prn|aux|nul|com[0-9]|lpt[0-9])(\..*)?$/i;
+  const windowsTrailing = /[\. ]+$/;
+  const replacement = "_";
+
+  const sanitized = input
+    .replace(illegal, replacement)
+    .replace(control, replacement)
+    .replace(reserved, replacement)
+    .replace(windowsReserved, replacement)
+    .replace(windowsTrailing, replacement);
+
+  if (sanitized.length === 0) {
+    sanitized = "unnamed";
+  }
+
+  const maxLength = 250;
+  const uint8Array = new TextEncoder().encode(sanitized);
+  const truncated = uint8Array.slice(0, maxLength);
+  return new TextDecoder().decode(truncated);
+}
+
 /**
  * If a valid tack was selected, download it as a gpx file.
  */
@@ -191,9 +228,10 @@ function handleClick(tab) {
   const blob = new Blob([gpxTrack.data], { type: "application/gpx+xml" });
   const objectURL = URL.createObjectURL(blob);
 
+  const filename = sanitizeFilename(gpxTrack.title);
   const downloading = browser.downloads.download({
     url: objectURL,
-    filename: `${gpxTrack.title}.gpx`,
+    filename: `${filename}.gpx`,
     saveAs: true,
     conflictAction: "uniquify",
   });

manifest.json

@@ -1,7 +1,7 @@
 {
     "manifest_version": 2,
     "name": "SAC Route Portal GPX Downloader",
-    "version": "0.8",
+    "version": "0.9",
     "developer": {
         "name": "Sebastian Hugentobler",
         "url": "https://code.vanwa.ch/sebastian/sac-route-portal-gpx-fx"