/**
 * Calendar API client functions.
 * Consumes the calendar backend built in 05-03.
 * All calls use credentials: 'include' for cookie-based auth.
 *
 * Anti-pattern (RESEARCH): The browser NEVER fetches external calendars directly.
 * All event data flows through /api/calendar/events which proxies via the backend.
 */

const API_URL = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:3001';

// --- Types mirroring the 05-03 backend contract ---

/**
 * Calendar source as returned by GET /calendar/sources.
 * Note: encryptedPassword is NEVER returned (T-05-09).
 */
export interface CalendarSource {
  id: string;
  userId: string;
  tenantId: string;
  name: string;
  type: 'caldav' | 'ics' | 'exchange';
  exchangeMode?: string | null;
  domain?: string | null;
  url: string;
  username?: string | null;
  color?: string | null;
  isVisible: boolean;
  syncIntervalMin: number;
  lastSyncAt?: string | null;
  lastSyncError?: string | null;
  createdAt: string;
  updatedAt: string;
}

/**
 * Normalized calendar event from GET /calendar/events.
 * Mirrors CalendarEvent from calendar.service.ts.
 */
export interface CalendarEvent {
  id: string;
  sourceId: string;
  title: string;
  start: string;
  end: string;
  allDay: boolean;
  location?: string;
  description?: string;
  color?: string;
}

/**
 * Payload for creating a new calendar source.
 */
export interface CreateSourcePayload {
  name: string;
  type: 'caldav' | 'ics' | 'exchange';
  url: string;
  username?: string;
  password?: string;
  exchangeMode?: string;
  domain?: string;
  color?: string;
}

/**
 * Payload for updating an existing calendar source.
 * All fields are optional.
 */
export interface UpdateSourcePayload {
  name?: string;
  type?: 'caldav' | 'ics' | 'exchange';
  url?: string;
  username?: string;
  password?: string;
  exchangeMode?: string;
  domain?: string;
  color?: string;
  isVisible?: boolean;
}

// --- API functions ---

/**
 * Fetch all calendar sources for the current user.
 * GET /calendar/sources
 */
export async function fetchSources(): Promise<CalendarSource[]> {
  const res = await fetch(`${API_URL}/calendar/sources`, {
    credentials: 'include',
  });
  if (!res.ok) throw new Error('Failed to fetch calendar sources');
  return res.json();
}

/**
 * Add a new calendar source.
 * POST /calendar/sources
 */
export async function addSource(
  payload: CreateSourcePayload,
): Promise<CalendarSource> {
  const res = await fetch(`${API_URL}/calendar/sources`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    credentials: 'include',
    body: JSON.stringify(payload),
  });
  if (!res.ok) throw new Error('Failed to add calendar source');
  return res.json();
}

/**
 * Update an existing calendar source (including isVisible toggle for CAL-02).
 * PATCH /calendar/sources/:id
 */
export async function updateSource(
  id: string,
  payload: UpdateSourcePayload,
): Promise<CalendarSource> {
  const res = await fetch(`${API_URL}/calendar/sources/${id}`, {
    method: 'PATCH',
    headers: { 'Content-Type': 'application/json' },
    credentials: 'include',
    body: JSON.stringify(payload),
  });
  if (!res.ok) throw new Error('Failed to update calendar source');
  return res.json();
}

/**
 * Delete a calendar source.
 * DELETE /calendar/sources/:id
 */
export async function deleteSource(id: string): Promise<void> {
  const res = await fetch(`${API_URL}/calendar/sources/${id}`, {
    method: 'DELETE',
    credentials: 'include',
  });
  if (!res.ok) throw new Error('Failed to delete calendar source');
}

/**
 * Test a calendar configuration without saving it.
 * POST /calendar/sources/test-config
 */
export async function testSourceConfig(config: {
  type: string;
  url: string;
  username?: string;
  password?: string;
  exchangeMode?: string;
  domain?: string;
}): Promise<{ success: boolean; error?: string }> {
  const res = await fetch(`${API_URL}/calendar/sources/test-config`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    credentials: 'include',
    body: JSON.stringify(config),
  });
  if (!res.ok) throw new Error('Test request failed');
  return res.json();
}

/**
 * Test connection to a calendar source.
 * POST /calendar/sources/:id/test
 * Returns { success: boolean } from the backend.
 */
export async function testSource(
  id: string,
): Promise<{ success: boolean; error?: string }> {
  const res = await fetch(`${API_URL}/calendar/sources/${id}/test`, {
    method: 'POST',
    credentials: 'include',
  });
  if (!res.ok) throw new Error('Failed to test calendar source');
  return res.json();
}

/**
 * Fetch aggregated events from all visible sources.
 * GET /calendar/events?from=...&to=...
 * Default window: now to now + 30 days (backend default).
 */
export async function fetchEvents(
  from?: string,
  to?: string,
): Promise<CalendarEvent[]> {
  const params = new URLSearchParams();
  if (from) params.set('from', from);
  if (to) params.set('to', to);

  const queryStr = params.toString();
  const url = `${API_URL}/calendar/events${queryStr ? `?${queryStr}` : ''}`;

  const res = await fetch(url, {
    credentials: 'include',
  });
  if (!res.ok) throw new Error('Failed to fetch calendar events');
  return res.json();
}