const { parse, validate } = require('@telegram-apps/init-data-node');
const crypto = require('crypto');
const config = require('../config');

const MAX_AUTH_AGE_SECONDS = 5 * 60;

/**
 * Manual validation with base64 padding fix
 * Based on: https://docs.telegram-mini-apps.com/platform/init-data
 */
function manualValidateInitData(initDataRaw, botToken) {
  const params = new URLSearchParams(initDataRaw);
  const hash = params.get('hash');
  
  if (!hash) {
    throw new Error('Отсутствует hash в initData');
  }

  // Remove hash from params
  params.delete('hash');

  // Create data check string
  const dataCheckArr = Array.from(params.entries())
    .sort(([a], [b]) => a.localeCompare(b))
    .map(([key, value]) => `${key}=${value}`);

  const dataCheckString = dataCheckArr.join('\n');

  // Create secret key
  const secretKey = crypto
    .createHmac('sha256', 'WebAppData')
    .update(botToken)
    .digest();

  // Create signature
  const signature = crypto
    .createHmac('sha256', secretKey)
    .update(dataCheckString)
    .digest('hex');

  // Compare signatures
  return signature === hash;
}

function validateAndParseInitData(initDataRaw) {
  console.log('[Telegram] validateAndParseInitData called:', {
    hasInitData: !!initDataRaw,
    type: typeof initDataRaw,
    length: initDataRaw?.length || 0,
    preview: initDataRaw?.substring(0, 100) + '...'
  });

  if (!config.telegramBotToken) {
    throw new Error('TELEGRAM_BOT_TOKEN не настроен');
  }

  if (!initDataRaw || typeof initDataRaw !== 'string') {
    throw new Error('initData не передан');
  }

  const trimmed = initDataRaw.trim();

  if (!trimmed.length) {
    throw new Error('initData пуст');
  }

  console.log('[Telegram] Validating initData with bot token...');

  // Try library validation first
  let valid = false;
  try {
    validate(trimmed, config.telegramBotToken);
    valid = true;
    console.log('[Telegram] Library validation successful');
  } catch (libError) {
    console.log('[Telegram] Library validation failed, trying manual validation:', libError.message);
    
    // Fallback to manual validation with base64 padding fix
    try {
      valid = manualValidateInitData(trimmed, config.telegramBotToken);
      if (valid) {
        console.log('[Telegram] Manual validation successful');
      }
    } catch (manualError) {
      console.error('[Telegram] Manual validation also failed:', manualError.message);
    }
  }

  if (!valid) {
    console.error('[Telegram] All validation attempts failed');
    throw new Error('Неверная подпись initData');
  }

  console.log('[Telegram] initData validation successful, parsing...');

  const payload = parse(trimmed);

  console.log('[Telegram] Parsed payload:', {
    hasUser: !!payload?.user,
    userId: payload?.user?.id,
    authDate: payload?.auth_date
  });

  if (!payload || !payload.user) {
    throw new Error('Отсутствует пользователь в initData');
  }

  const authDate = Number(payload.auth_date);

  if (!authDate) {
    throw new Error('Отсутствует auth_date в initData');
  }

  const now = Math.floor(Date.now() / 1000);

  if (Math.abs(now - authDate) > MAX_AUTH_AGE_SECONDS) {
    throw new Error('Данные авторизации устарели');
  }

  console.log('[Telegram] initData validation complete');

  return payload;
}

module.exports = {
  validateAndParseInitData
};