import 'dart:io';
import 'package:intl/intl.dart';
import 'package:path_provider/path_provider.dart';
import 'package:share_plus/share_plus.dart'; // Ensure share_plus is in dependencies or use printing/share mechanism
import '../models/cycle_entry.dart';

// Since we might not have share_plus in the pubspec explicitly seen earlier (user plan said adding dependencies),
// keeping it safe. The pubspec had 'pdf', 'printing', 'path_provider', 'universal_html'.
// 'share_plus' was not explicitly in the list I viewed in Step 258, but 'printing' can share PDF.
// For ICS, we need a way to share the file. 'printing' relies on pdf.
// Wait, Step 258 pubspec content lines 9-48...
// I don't see `share_plus`.
// I'll check `pubspec.yaml` again to be absolutely sure or add it via `flutter pub add`.
// Actually, `printing` has a share method but it's specific to PDF bytes usually? No, `Printing.sharePdf`.
// I should use `share_plus` if I want to share a text/ics file. 
// Or I can just write to file and open it with `open_filex`.

import 'package:open_filex/open_filex.dart';

class IcsService {
  static Future<void> generateCycleCalendar(List<CycleEntry> entries) async {
    final buffer = StringBuffer();
    buffer.writeln('BEGIN:VCALENDAR');
    buffer.writeln('VERSION:2.0');
    buffer.writeln('PRODID:-//Christian Period Tracker//Cycle Calendar//EN');
    
    // Sort entries
    entries.sort((a, b) => a.date.compareTo(b.date));

    for (var entry in entries) {
      if (entry.isPeriodDay) {
        final dateStr = DateFormat('yyyyMMdd').format(entry.date);
        buffer.writeln('BEGIN:VEVENT');
        buffer.writeln('UID:${entry.id}');
        buffer.writeln('DTSTAMP:${DateFormat('yyyyMMddTHHmmss').format(DateTime.now())}Z');
        buffer.writeln('DTSTART;VALUE=DATE:$dateStr'); // All day event
        buffer.writeln('DTEND;VALUE=DATE:${DateFormat('yyyyMMdd').format(entry.date.add(const Duration(days: 1)))}');
        buffer.writeln('SUMMARY:Period');
        buffer.writeln('DESCRIPTION:Logged period day.');
        buffer.writeln('END:VEVENT');
      }
    }

    buffer.writeln('END:VCALENDAR');

    // Save to file
    final directory = await getApplicationDocumentsDirectory();
    final file = File('${directory.path}/cycle_calendar.ics');
    await file.writeAsString(buffer.toString());

    // Open/Share file
    final result = await OpenFilex.open(file.path);
    if (result.type != ResultType.done) {
      throw 'Could not open file: ${result.message}';
    }
  }
}