import { Injectable, Logger } from '@nestjs/common';
import { DAVClient } from 'tsdav';
import * as ical from 'node-ical';
import { CalendarEvent, CalendarProvider } from '../calendar.service';

/**
 * CalDAV calendar provider — uses tsdav for protocol handling.
 *
 * Connects via Basic auth (username + decrypted password), fetches calendars,
 * then fetchCalendarObjects with time-range filter (A2).
 * Parses returned iCal data with node-ical and maps to CalendarEvent.
 */
@Injectable()
export class CalDAVProvider implements CalendarProvider {
  private readonly logger = new Logger(CalDAVProvider.name);

  /**
   * Fetches events from a CalDAV server within the specified date range.
   * Uses tsdav's time-range filter to only fetch relevant events (A2).
   */
  async fetchEvents(
    source: { url: string; username?: string; password?: string; id: string; color?: string | null },
    from: Date,
    to: Date,
  ): Promise<CalendarEvent[]> {
    const events: CalendarEvent[] = [];

    try {
      const client = await this.createClient(source);
      const calendars = await client.fetchCalendars();

      for (const calendar of calendars) {
        const objects = await client.fetchCalendarObjects({
          calendar,
          timeRange: {
            start: from.toISOString(),
            end: to.toISOString(),
          },
          expand: true,
        });

        for (const obj of objects) {
          if (!obj.data) continue;

          try {
            const parsed = ical.sync.parseICS(obj.data);

            for (const key of Object.keys(parsed)) {
              const component = parsed[key];
              if (component?.type !== 'VEVENT') continue;

              const vevent = component as ical.VEvent;
              const start = new Date(vevent.start);
              const end = vevent.end
                ? new Date(vevent.end)
                : new Date(start.getTime() + 3600000);

              events.push({
                id: `${source.id}-${vevent.uid || key}`,
                sourceId: source.id,
                title: extractString(vevent.summary),
                start,
                end,
                allDay: vevent.datetype === 'date',
                location: vevent.location
                  ? extractString(vevent.location)
                  : undefined,
                description: vevent.description
                  ? extractString(vevent.description)
                  : undefined,
                color: source.color ?? undefined,
              });
            }
          } catch (parseErr) {
            this.logger.warn(
              `Failed to parse CalDAV object: ${(parseErr as Error).message}`,
            );
          }
        }
      }
    } catch (error) {
      this.logger.error(
        `Failed to fetch CalDAV events from ${source.url}: ${(error as Error).message}`,
      );
      throw error;
    }

    return events;
  }

  /**
   * Tests connection by attempting login and listing calendars.
   */
  async testConnection(
    source: { url: string; username?: string; password?: string; id: string },
  ): Promise<boolean> {
    try {
      const client = await this.createClient(source);
      const calendars = await client.fetchCalendars();
      return calendars.length > 0;
    } catch {
      return false;
    }
  }

  /**
   * Creates a tsdav DAVClient with Basic auth and logs in.
   */
  private async createClient(
    source: { url: string; username?: string; password?: string },
  ): Promise<DAVClient> {
    const client = new DAVClient({
      serverUrl: source.url,
      credentials: {
        username: source.username || '',
        password: source.password || '',
      },
      authMethod: 'Basic',
      defaultAccountType: 'caldav',
    });

    await client.login();
    return client;
  }
}

/**
 * Extracts a plain string from a node-ical ParameterValue.
 */
function extractString(
  value: ical.ParameterValue | string | undefined,
): string {
  if (!value) return '';
  if (typeof value === 'string') return value;
  if (typeof value === 'object' && 'val' in value) return String(value.val);
  return String(value);
}