add TZID property to date-time if available

it's not clear if that actually leads to a better user experience than
floating time that we are currently using

Google Calendar seems to work OK with floating time - it is using the
event location to properly display the time if the default timezone of
the calendar is different from that of the event

if we do set TZID Google Calendar will also use it, but it might make
incorrect assumptions about DST (for example America/New York tends to
result in Eastern Time - and not EDT or EST depending on the specific
date)

.jshintrc

@@ -10,5 +10,5 @@
   "sub": true,
   "undef": true,
   "unused": true,
-  "esversion": 10
+  "esversion": 11
 }

lib/ical.js

@@ -20,7 +20,11 @@ function ts2date(ts) {
   return new Date(ts).toISOString().replace(/[-:]/g, '').slice(0, -5);
 }
 
-function* ical({ metadata, routes }) {
+function tzid(property, tz) {
+  return tz ? `${property};TZID=${tz}` : property;
+}
+
+function* ical({ metadata, routes, options = {} }) {
   const dtstamp = ts2date(Date.now());
 
   yield* property('BEGIN', 'VCALENDAR');
@@ -41,8 +45,9 @@ function* ical({ metadata, routes }) {
     yield* property('URL', step.url);
     yield* property('LOCATION', step.address);
     yield* property('GEO', [step.coordinates.lat, step.coordinates.lon], formatArray);
-    yield* property('DTSTART', ts2date(step.arrival_time));
-    yield* property('DTEND', ts2date(step.departure_time));
+    const tz = options.tzid && step.timezone?.name;
+    yield* property(tzid('DTSTART', tz), ts2date(step.arrival_time));
+    yield* property(tzid('DTEND', tz), ts2date(step.departure_time));
     yield* property('END', 'VEVENT');
   }
   yield* property('END', 'VCALENDAR');

test/fixtures/simple-trip.json

@@ -34,7 +34,10 @@
           "visit_duration": 0,
           "nights": 0,
           "arrival_time": 1373274000000,
-          "departure_time": 1373274000000
+          "departure_time": 1373274000000,
+          "timezone": {
+            "name": "America/Los_Angeles"
+          }
         },
         {
           "id": "5144f7cbd6e4d26079000009",
@@ -58,7 +61,10 @@
           "driving": 11580,
           "nights": 0,
           "arrival_time": 1373285580000,
-          "departure_time": 1373286480000
+          "departure_time": 1373286480000,
+          "timezone": {
+            "name": "America/Los_Angeles"
+          }
         },
         {
           "id": "5144f7dfd6e4d2607900000a",
@@ -84,6 +90,9 @@
           "nights": 0,
           "arrival_time": 1373304660000,
           "departure_time": 1373305560000,
+          "timezone": {
+            "name": "America/Los_Angeles"
+          },
           "symbol": "Gas Station"
         },
         {
@@ -108,10 +117,13 @@
           "driving": 6595,
           "nights": 0,
           "arrival_time": 1373312155000,
-          "departure_time": 1373312155000
+          "departure_time": 1373312155000,
+          "timezone": {
+            "name": "America/Los_Angeles"
+          }
         }
       ],
       "name": ""
     }
   ]
-}
+}

test/fixtures/simple_tz.ics

@@ -0,0 +1,41 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//code42day//Furkot - road trip planner//EN
+BEGIN:VEVENT
+DTSTAMP:20220529T071758
+UID:[email protected]
+SUMMARY:San Francisco
+LOCATION:San Francisco\, CA
+GEO:37.7749295;-122.41941550000001
+DTSTART;TZID=America/Los_Angeles:20130708T090000
+DTEND;TZID=America/Los_Angeles:20130708T090000
+END:VEVENT
+BEGIN:VEVENT
+DTSTAMP:20220529T071758
+UID:[email protected]
+SUMMARY:Redding
+LOCATION:1510 Gordon Lane\, Redding\, CA 96002\, USA
+GEO:40.54720023441049;-122.34375
+DTSTART;TZID=America/Los_Angeles:20130708T121300
+DTEND;TZID=America/Los_Angeles:20130708T122800
+END:VEVENT
+BEGIN:VEVENT
+DTSTAMP:20220529T071758
+UID:[email protected]
+SUMMARY:Lane
+LOCATION:51-559 Walnut Place\, Springfield\, OR 97477\, USA
+GEO:44.04811573082351;-123.046875
+DTSTART;TZID=America/Los_Angeles:20130708T173100
+DTEND;TZID=America/Los_Angeles:20130708T174600
+END:VEVENT
+BEGIN:VEVENT
+DTSTAMP:20220529T071758
+UID:[email protected]
+SUMMARY:Portland
+DESCRIPTION:Trip notes for first stop
+LOCATION:Portland\, OR
+GEO:45.5234515;-122.6762071
+DTSTART;TZID=America/Los_Angeles:20130708T193555
+DTEND;TZID=America/Los_Angeles:20130708T193555
+END:VEVENT
+END:VCALENDAR

test/ical.js

@@ -45,6 +45,14 @@ describe('ical', function () {
     compareLines(generated, expected);
   });
 
+  it('simple trip with TZID', function () {
+    const t = require('./fixtures/simple-trip.json');
+    const generated = ical({ ...t, options: { tzid: true } });
+    const expected = readFileSync('fixtures/simple_tz.ics');
+
+    compareLines(generated, expected);
+  });
+
   it('multi trip', function () {
     const t = require('./fixtures/multi-trip.json');
     const generated = ical(t);