feat: client-side ICS download with tests

README.md

@@ -15,25 +15,18 @@ A Vietnamese lunar calendar ([Âm Lịch](https://amlich.demen.org)) web app bui
 - Solar/Lunar focus toggle
 - Dark (celestial) and Light theme
 - Swipe gestures for day and month navigation
+- Download .ics calendar file for any decade
 
-## Add Vietnamese Lunar Calendar to Google Calendar
+## Download Lunar Calendar (.ics)
 
-You can subscribe to the Vietnamese lunar calendar to see lunar dates directly in your Google Calendar:
+You can download the Vietnamese lunar calendar as an `.ics` file and import it into Google Calendar, Apple Calendar, Outlook, or any calendar app:
 
-1. Open [Google Calendar](https://calendar.google.com)
-2. Click **+** next to "Other calendars" in the left sidebar
-3. Select **From URL**
-4. Paste this URL:
+1. Open [amlich.demen.org](https://amlich.demen.org)
+2. Navigate to the year/decade you want
+3. Click **"Tải Âm Lịch 2020s"** (or whichever decade is shown) at the bottom
+4. Import the downloaded `.ics` file into your calendar app
 
-```
-https://calendar.google.com/calendar/ical/demen.org_4jc7p02lkoire319rabglmfifo%40group.calendar.google.com/public/basic.ics
-```
-
-5. Click **Add calendar**
-
-Or click this link to add it directly:
-
-[Add to Google Calendar](https://calendar.google.com/calendar/r?cid=demen.org_4jc7p02lkoire319rabglmfifo@group.calendar.google.com)
+The file is generated client-side from the app's lunar conversion algorithm and covers a full decade (e.g. 2020-2029). Each day includes the lunar date, Can Chi, and moon phase info.
 
 ## URL Parameters
 

lib/ics_generator.dart

@@ -0,0 +1,77 @@
+import 'package:licham/lunar_converter.dart';
+import 'package:licham/widget/moon_phase.dart';
+
+String generateIcs(int startYear, int endYear) {
+  final buf = StringBuffer()
+    ..writeln('BEGIN:VCALENDAR')
+    ..writeln('VERSION:2.0')
+    ..writeln('PRODID:-//Am Lich//amlich.demen.org//VI')
+    ..writeln('X-WR-CALNAME:Âm Lịch')
+    ..writeln('X-WR-TIMEZONE:Asia/Ho_Chi_Minh');
+
+  for (var year = startYear; year <= endYear; year++) {
+    for (var month = 1; month <= 12; month++) {
+      final daysInMonth = DateTime(year, month + 1, 0).day;
+      for (var day = 1; day <= daysInMonth; day++) {
+        _writeEvent(buf, year, month, day);
+      }
+    }
+  }
+
+  buf.writeln('END:VCALENDAR');
+  return buf.toString();
+}
+
+void _writeEvent(StringBuffer buf, int year, int month, int day) {
+  final lunar = LunarConverter.solarToLunar(day, month, year);
+  final lunarDay = lunar[0];
+  final lunarMonth = lunar[1];
+  final lunarYear = lunar[2];
+  final isLeap = lunar[3] != 0;
+
+  final monthName =
+      LunarConverter.getLunarMonthName(lunarMonth, isLeap: isLeap);
+  final summary = _buildSummary(lunarDay, lunarMonth, lunarYear, monthName);
+
+  final jd = LunarConverter.julianDay(day, month, year);
+  final canChiDay = LunarConverter.getCanChiDay(jd);
+  final phase = moonPhaseFromLunarDay(lunarDay);
+  final phaseLabel = moonPhaseLabel(phase).replaceAll('\n', ' ');
+
+  final desc = StringBuffer('Ngày $canChiDay');
+  if (phaseLabel.isNotEmpty) desc.write(' ($phaseLabel)');
+
+  final dtStart = _formatDate(year, month, day);
+  final next = DateTime(year, month, day + 1);
+  final dtEnd = _formatDate(next.year, next.month, next.day);
+
+  buf
+    ..writeln('BEGIN:VEVENT')
+    ..writeln('DTSTART;VALUE=DATE:$dtStart')
+    ..writeln('DTEND;VALUE=DATE:$dtEnd')
+    ..writeln('SUMMARY:$summary')
+    ..writeln('DESCRIPTION:$desc')
+    ..writeln('END:VEVENT');
+}
+
+String _buildSummary(
+  int lunarDay,
+  int lunarMonth,
+  int lunarYear,
+  String monthName,
+) {
+  if (lunarDay == 1 && lunarMonth == 1) {
+    return 'Tết Nguyên Đán ${LunarConverter.getCanChiYear(lunarYear)}'
+        ' - Mùng 1 $monthName';
+  }
+  if (lunarDay == 1) return 'Mùng 1 $monthName';
+  if (lunarDay == 15) return 'Rằm $monthName';
+  return 'Ngày $lunarDay $monthName';
+}
+
+String _formatDate(int y, int m, int d) {
+  final yy = y.toString().padLeft(4, '0');
+  final mm = m.toString().padLeft(2, '0');
+  final dd = d.toString().padLeft(2, '0');
+  return '$yy$mm$dd';
+}

lib/js/window.dart

@@ -1,6 +1,21 @@
 import 'dart:js_interop';
 
+import 'package:web/web.dart' as web;
+
 @JS('open')
 external void _open(JSString url);
 
 void open(String url) => _open(url.toJS);
+
+void download(String filename, String content) {
+  final blob = web.Blob(
+    [content.toJS].toJS,
+    web.BlobPropertyBag(type: 'text/calendar;charset=utf-8'),
+  );
+  final url = web.URL.createObjectURL(blob);
+  (web.document.createElement('a') as web.HTMLAnchorElement
+        ..href = url
+        ..download = filename)
+      .click();
+  web.URL.revokeObjectURL(url);
+}

lib/main_view.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:licham/ics_generator.dart';
 import 'package:licham/js/window.dart';
 import 'package:licham/lunar.dart';
 import 'package:licham/lunar_converter.dart';
@@ -91,7 +92,7 @@ class _MainViewState extends State<MainView> {
                     const SizedBox(height: 12),
                     _InfoPanel(lunar: lunar),
                     const SizedBox(height: 12),
-                    _Footer(),
+                    _Footer(selectedYear: solar.year),
                     const SizedBox(height: 24),
                   ],
                 ),
@@ -857,17 +858,26 @@ class _InfoPanel extends StatelessWidget {
 // Footer
 // ---------------------------------------------------------------------------
 class _Footer extends StatelessWidget {
+  const _Footer({required this.selectedYear});
+
+  final int selectedYear;
+
   @override
   Widget build(BuildContext context) {
+    final decadeStart = selectedYear ~/ 10 * 10;
+    final decadeEnd = decadeStart + 9;
+    final label = '${decadeStart}s';
+
     return Row(
       mainAxisAlignment: MainAxisAlignment.center,
       children: [
         TextButton.icon(
-          icon: const Icon(CustomIcons.calendarPlusO, size: 16),
-          label: const Text('Google Calendar'),
-          onPressed: () => open(
-            'https://calendar.google.com/calendar/r?cid=demen.org_4jc7p02lkoire319rabglmfifo@group.calendar.google.com',
-          ),
+          icon: const Icon(Icons.download, size: 16),
+          label: Text('Tải Âm Lịch $label'),
+          onPressed: () {
+            final ics = generateIcs(decadeStart, decadeEnd);
+            download('amlich-$label.ics', ics);
+          },
         ),
         const SizedBox(width: 8),
         TextButton.icon(

pubspec.yaml

@@ -13,6 +13,7 @@ dependencies:
     sdk: flutter
   flutter_bloc: ^9.1.1
   intl: ^0.20.2
+  web: ^1.1.1
 
 dev_dependencies:
   build_runner: ^2.4.0

test/ics_generator_test.dart

@@ -0,0 +1,108 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:licham/ics_generator.dart';
+
+void main() {
+  group('generateIcs', () {
+    late String ics;
+
+    setUpAll(() {
+      ics = generateIcs(2024, 2024);
+    });
+
+    test('produces valid iCalendar wrapper', () {
+      expect(ics, startsWith('BEGIN:VCALENDAR'));
+      expect(ics, contains('VERSION:2.0'));
+      expect(ics, contains('PRODID:-//Am Lich//amlich.demen.org//VI'));
+      expect(ics, contains('X-WR-CALNAME:Âm Lịch'));
+      expect(ics.trimRight(), endsWith('END:VCALENDAR'));
+    });
+
+    test('contains one event per day for a full year', () {
+      final eventCount = 'BEGIN:VEVENT'.allMatches(ics).length;
+      expect(eventCount, 366); // 2024 is a leap year
+    });
+
+    test('events have required fields', () {
+      expect(ics, contains('DTSTART;VALUE=DATE:'));
+      expect(ics, contains('DTEND;VALUE=DATE:'));
+      expect(ics, contains('SUMMARY:'));
+      expect(ics, contains('DESCRIPTION:'));
+    });
+
+    test('Tết 2024 event has correct summary', () {
+      expect(
+        ics,
+        contains(
+          'SUMMARY:Tết Nguyên Đán Giáp Thìn - Mùng 1 Tháng Giêng',
+        ),
+      );
+    });
+
+    test('Tết 2024 is on Feb 10', () {
+      final lines = ics.split('\n');
+      final tetIndex = lines.indexWhere(
+        (l) => l.contains('Tết Nguyên Đán Giáp Thìn'),
+      );
+      final dtStart = lines[tetIndex - 2];
+      expect(dtStart, contains('20240210'));
+    });
+
+    test('Rằm Trung Thu 2024 event exists', () {
+      expect(ics, contains('SUMMARY:Rằm Tháng Tám'));
+    });
+
+    test('Rằm Trung Thu 2024 is on Sep 17', () {
+      final lines = ics.split('\n');
+      final ramIndex = lines.indexWhere(
+        (l) => l.contains('Rằm Tháng Tám'),
+      );
+      final dtStart = lines[ramIndex - 2];
+      expect(dtStart, contains('20240917'));
+    });
+
+    test('Mùng 1 events for each lunar month', () {
+      final mung1Count = 'SUMMARY:Mùng 1'.allMatches(ics).length;
+      // 12 or 13 months (leap year may have extra), minus the Tết one
+      expect(mung1Count, greaterThanOrEqualTo(11));
+    });
+
+    test('description includes Can Chi', () {
+      expect(ics, contains('DESCRIPTION:Ngày'));
+    });
+
+    test('description includes moon phase for key days', () {
+      expect(ics, contains('(Sóc)'));
+      expect(ics, contains('(Vọng)'));
+    });
+
+    test('date format is YYYYMMDD', () {
+      expect(ics, contains('DTSTART;VALUE=DATE:20240101'));
+      expect(ics, contains('DTEND;VALUE=DATE:20240102'));
+      expect(ics, contains('DTSTART;VALUE=DATE:20241231'));
+      expect(ics, contains('DTEND;VALUE=DATE:20250101'));
+    });
+  });
+
+  group('multi-year generation', () {
+    test('decade covers all years', () {
+      final ics = generateIcs(2020, 2029);
+      for (var year = 2020; year <= 2029; year++) {
+        expect(
+          ics,
+          contains('DTSTART;VALUE=DATE:${year}0101'),
+          reason: 'Missing Jan 1 of $year',
+        );
+      }
+    });
+
+    test('decade event count matches total days', () {
+      final ics = generateIcs(2020, 2029);
+      final eventCount = 'BEGIN:VEVENT'.allMatches(ics).length;
+      var totalDays = 0;
+      for (var y = 2020; y <= 2029; y++) {
+        totalDays += DateTime(y + 1).difference(DateTime(y)).inDays;
+      }
+      expect(eventCount, totalDays);
+    });
+  });
+}