import { Injectable } from '@nestjs/common';
import { v4 as uuidv4 } from 'uuid';
import * as moment from 'moment';

@Injectable()
export class IcsMeetingService {
  private formatUtc(dateIso: string | Date): string {
    return moment.utc(dateIso).format('YYYYMMDDTHHmmss[Z]');
  }

  async generateIcs(dto: any, configJson?: any): Promise<string> {
    const uid = `${uuidv4()}@etherapp.in`;
    const now = this.formatUtc(new Date());

    const dtStart = this.formatUtc(dto.startTime);
    const dtEnd = this.formatUtc(new Date(dto.endTime));

    const organizerEmail = (configJson.email || configJson.fromEmail) ?? 'yash.joshi@rezolut.in';
    const organizerName = dto.organizerName ?? 'Organizer';
    const organizer = `ORGANIZER;CN=${organizerName}:mailto:${organizerEmail}`;

    const attendees = dto.attendees
      ?.map(
        (a) => `ATTENDEE;CUTYPE=INDIVIDUAL;ROLE=REQ-PARTICIPANT;PARTSTAT=NEEDS-ACTION;CN=${a.name ?? a.email};X-NUM-GUESTS=0:mailto:${a.email}`,
      )
      .join('\r\n');

    const icsContent = [
      'BEGIN:VCALENDAR',
      'PRODID:-//Google Inc//Google Calendar 70.9054//EN',
      'VERSION:2.0',
      'CALSCALE:GREGORIAN',
      'METHOD:REQUEST',
      'BEGIN:VEVENT',
      `DTSTART:${dtStart}`,
      `DTEND:${dtEnd}`,
      `DTSTAMP:${now}`,
      organizer,
      `UID:${uid}`,
      attendees ?? '',
      `CREATED:${now}`,
      `DESCRIPTION:${dto.description ?? ''}`,
      `LAST-MODIFIED:${now}`,
      `LOCATION:${dto.location ?? 'Google Meet'}`,
      'SEQUENCE:0',
      'STATUS:CONFIRMED',
      `SUMMARY:${dto.title}`,
      'TRANSP:OPAQUE',
      'END:VEVENT',
      'END:VCALENDAR',
    ]
      .filter(Boolean)
      .join('\r\n');

    return Buffer.from(icsContent, 'utf-8').toString('base64');
  }
}