/**
 * Modul: Generic CalDAV Sync
 * Zweck: Multi-Account CalDAV synchronization with calendar selection
 * Abhängigkeiten: tsdav, server/db.js, server/services/ics-parser.js
 */

import { createLogger } from '../logger.js';
const log = createLogger('CalDAV');

import * as db from '../db.js';

// Reused functions from apple-calendar.js
import {
  parseICS,
  formatICSDate,
  tzLocalToUTC,
  applyDuration
} from './ics-parser.js';

// --------------------------------------------------------
// Helper Functions
// --------------------------------------------------------

function normalizeCalColor(c) {
  if (!c) return null;
  if (/^#[0-9a-fA-F]{8}$/.test(c)) return c.slice(0, 7); // strip alpha
  if (/^#[0-9a-fA-F]{6}$/.test(c)) return c;
  return null;
}

function upsertExternalCalendar(source, externalId, name, color) {
  const row = db.get().prepare(`
    INSERT INTO external_calendars (source, external_id, name, color)
    VALUES (?, ?, ?, ?)
    ON CONFLICT(source, external_id) DO UPDATE SET
      name  = excluded.name,
      color = excluded.color
    RETURNING id
  `).get(source, externalId, name, color);
  return row.id;
}

// --------------------------------------------------------
// Credentials Helpers
// --------------------------------------------------------

function getAccountById(accountId) {
  return db.get().prepare('SELECT * FROM caldav_accounts WHERE id = ?').get(accountId);
}

function getAllAccounts() {
  return db.get().prepare('SELECT * FROM caldav_accounts').all();
}

// --------------------------------------------------------
// Connection Testing
// --------------------------------------------------------

async function testConnection(caldavUrl, username, password) {
  try {
    const { createDAVClient } = await import('tsdav');
    const client = await createDAVClient({
      serverUrl:          caldavUrl,
      credentials:        { username, password },
      authMethod:         'Basic',
      defaultAccountType: 'caldav',
    });

    const calendars = await client.fetchCalendars();
    if (!calendars.length) {
      throw new Error('Connected, but no calendars found.');
    }

    return { ok: true, calendars };
  } catch (err) {
    log.error('Connection test failed:', err.message);
    throw new Error(`CalDAV connection failed: ${err.message}`);
  }
}

// --------------------------------------------------------
// Account Management
// --------------------------------------------------------

async function addAccount(name, caldavUrl, username, password) {
  // Validate inputs
  if (!name || !caldavUrl || !username || !password) {
    throw new Error('All fields required: name, caldavUrl, username, password');
  }

  // Test connection first
  const { calendars } = await testConnection(caldavUrl, username, password);

  // Check for duplicate
  const existing = db.get().prepare(
    'SELECT id FROM caldav_accounts WHERE caldav_url = ? AND username = ?'
  ).get(caldavUrl, username);

  if (existing) {
    throw new Error('Account with this URL and username already exists.');
  }

  // Warn if DB_ENCRYPTION_KEY not set
  if (!process.env.DB_ENCRYPTION_KEY) {
    log.warn('WARNING: DB_ENCRYPTION_KEY is not set - CalDAV credentials will be stored unencrypted.');
  }

  // Insert account
  const result = db.get().prepare(`
    INSERT INTO caldav_accounts (name, caldav_url, username, password)
    VALUES (?, ?, ?, ?)
  `).run(name, caldavUrl, username, password);

  const accountId = result.lastInsertRowid;

  // Insert calendar selections (all enabled by default)
  const calendarData = [];
  for (const cal of calendars) {
    const calColor = normalizeCalColor(cal.calendarColor) || '#4A90E2';
    const calName = cal.displayName || 'Unnamed Calendar';

    db.get().prepare(`
      INSERT INTO caldav_calendar_selection (account_id, calendar_url, calendar_name, calendar_color, enabled)
      VALUES (?, ?, ?, ?, 1)
    `).run(accountId, cal.url, calName, calColor);

    calendarData.push({ url: cal.url, name: calName, color: calColor, enabled: true });
  }

  log.info(`Added CalDAV account "${name}" with ${calendars.length} calendars.`);

  return { accountId, calendars: calendarData };
}

function listAccounts() {
  const accounts = db.get().prepare(`
    SELECT id, name, caldav_url, username, created_at, last_sync
    FROM caldav_accounts
    ORDER BY created_at DESC
  `).all();

  // Do NOT return password (security)
  return accounts.map(acc => ({
    id: acc.id,
    name: acc.name,
    caldavUrl: acc.caldav_url,
    username: acc.username,
    createdAt: acc.created_at,
    lastSync: acc.last_sync,
  }));
}

async function updateAccount(accountId, { name, caldavUrl, username, password }) {
  const account = getAccountById(accountId);
  if (!account) {
    throw new Error(`Account ${accountId} not found.`);
  }

  // If credentials changed, test connection
  const credentialsChanged =
    (caldavUrl && caldavUrl !== account.caldav_url) ||
    (username && username !== account.username) ||
    (password && password !== account.password);

  if (credentialsChanged) {
    const testUrl = caldavUrl || account.caldav_url;
    const testUser = username || account.username;
    const testPwd = password || account.password;

    const { calendars } = await testConnection(testUrl, testUser, testPwd);

    // If credentials changed, refresh calendar list
    if (calendars) {
      // Delete old selections
      db.get().prepare('DELETE FROM caldav_calendar_selection WHERE account_id = ?').run(accountId);

      // Insert new selections
      for (const cal of calendars) {
        const calColor = normalizeCalColor(cal.calendarColor) || '#4A90E2';
        const calName = cal.displayName || 'Unnamed Calendar';

        db.get().prepare(`
          INSERT INTO caldav_calendar_selection (account_id, calendar_url, calendar_name, calendar_color, enabled)
          VALUES (?, ?, ?, ?, 1)
        `).run(accountId, cal.url, calName, calColor);
      }
    }
  }

  // Update account
  const updates = [];
  const values = [];

  if (name) { updates.push('name = ?'); values.push(name); }
  if (caldavUrl) { updates.push('caldav_url = ?'); values.push(caldavUrl); }
  if (username) { updates.push('username = ?'); values.push(username); }
  if (password) { updates.push('password = ?'); values.push(password); }

  if (updates.length === 0) {
    throw new Error('No fields to update.');
  }

  values.push(accountId);

  db.get().prepare(`
    UPDATE caldav_accounts SET ${updates.join(', ')} WHERE id = ?
  `).run(...values);

  log.info(`Updated CalDAV account ${accountId}.`);

  return { success: true };
}

function deleteAccount(accountId) {
  const account = getAccountById(accountId);
  if (!account) {
    throw new Error(`Account ${accountId} not found.`);
  }

  // CASCADE will delete caldav_calendar_selection entries
  db.get().prepare('DELETE FROM caldav_accounts WHERE id = ?').run(accountId);

  // Events with calendar_ref_id to deleted account remain (orphaned but visible)

  log.info(`Deleted CalDAV account ${accountId} ("${account.name}").`);

  return { success: true };
}

// --------------------------------------------------------
// Exports
// --------------------------------------------------------

export {
  addAccount,
  listAccounts,
  updateAccount,
  deleteAccount
};