/**
 * Fastmail CalDAV client factory.
 *
 * Creates a tsdav DAVClient per Fastmail credential set (one per member, per D-02).
 * The broker module owns the client lifetime — never create one per API request (Pitfall #3).
 *
 * Source: https://github.com/natelindev/tsdav
 * CalDAV principal URL pattern: https://caldav.fastmail.com/dav/principals/user/{email}/
 * (Pitfall #1: tsdav service discovery via /.well-known/caldav resolves to this principal)
 */

import { createDAVClient } from 'tsdav'

/** The resolved type of a tsdav client returned by createDAVClient. */
export type FastmailClient = Awaited<ReturnType<typeof createDAVClient>>

/**
 * Creates a tsdav DAVClient authenticated with Basic auth (app password).
 * The returned client can call fetchCalendars() and fetchCalendarObjects().
 * This call performs a service-discovery round-trip (Pitfall #3 — cache this client).
 */
export async function createFastmailClient(email: string, appPassword: string): Promise<FastmailClient> {
  return createDAVClient({
    serverUrl: 'https://caldav.fastmail.com',
    credentials: {
      username: email,
      password: appPassword,
    },
    authMethod: 'Basic',
    defaultAccountType: 'caldav',
  })
}