const crypto = require('crypto');

function normalizeClientName(value) {
  return String(value || '').trim();
}

function normalizeDeviceId(value) {
  return String(value || '').trim().replace(/[^a-zA-Z0-9_-]/g, '').slice(0, 128);
}

function collectLiveConnections(liveConnections) {
  return Array.isArray(liveConnections) ? liveConnections : [];
}

async function isClientNameAvailable(pool, clientName, excludeDeviceId, liveConnections) {
  const normalizedName = normalizeClientName(clientName);
  if (!normalizedName) {
    return false;
  }

  const normalizedDeviceId = normalizeDeviceId(excludeDeviceId);
  const live = collectLiveConnections(liveConnections);
  const lowerName = normalizedName.toLowerCase();

  try {
    if (pool) {
      const [deviceRows] = await pool.query(
        `SELECT device_id
         FROM player_onboarding_devices
         WHERE client_name IS NOT NULL
           AND TRIM(client_name) <> ''
           AND LOWER(TRIM(client_name)) = LOWER(TRIM(?))
           AND device_id <> ?
         LIMIT 1`,
        [normalizedName, normalizedDeviceId]
      );

      if (deviceRows.length) {
        return false;
      }
    }

    for (const connection of live) {
      const existingName = normalizeClientName(connection && connection.clientName ? connection.clientName : '');
      if (!existingName || existingName.toLowerCase() !== lowerName) {
        continue;
      }
      const existingDeviceId = normalizeDeviceId(connection && (connection.deviceId || connection.clientId) ? (connection.deviceId || connection.clientId) : '');
      if (normalizedDeviceId && existingDeviceId && existingDeviceId === normalizedDeviceId) {
        continue;
      }
      return false;
    }

    return true;
  } catch (_error) {
    for (const connection of live) {
      const existingName = normalizeClientName(connection && connection.clientName ? connection.clientName : '');
      if (!existingName || existingName.toLowerCase() !== lowerName) {
        continue;
      }
      const existingDeviceId = normalizeDeviceId(connection && (connection.deviceId || connection.clientId) ? (connection.deviceId || connection.clientId) : '');
      if (normalizedDeviceId && existingDeviceId && existingDeviceId === normalizedDeviceId) {
        continue;
      }
      return false;
    }

    return true;
  }
}

function buildClientNameLockName(clientName) {
  return `ps_client_name_${crypto.createHash('sha1').update(String(clientName || '').trim().toLowerCase()).digest('hex')}`;
}

async function withClientNameReservation(pool, clientName, handler) {
  if (!pool || typeof pool.getConnection !== 'function') {
    return handler();
  }

  const normalizedName = normalizeClientName(clientName);
  if (!normalizedName) {
    return handler();
  }

  const connection = await pool.getConnection();
  const lockName = buildClientNameLockName(normalizedName);
  let lockAcquired = false;

  try {
    const [lockRows] = await connection.query('SELECT GET_LOCK(?, 5) AS lock_result', [lockName]);
    const lockResult = lockRows && lockRows[0] ? Number(lockRows[0].lock_result) : 0;
    if (lockResult !== 1) {
      const error = new Error('Client name is busy. Please try again.');
      error.statusCode = 409;
      throw error;
    }

    lockAcquired = true;
    return await handler();
  } finally {
    if (lockAcquired) {
      try {
        await connection.query('SELECT RELEASE_LOCK(?)', [lockName]);
      } catch (_error) {}
    }
    connection.release();
  }
}

module.exports = {
  normalizeClientName: normalizeClientName,
  normalizeDeviceId: normalizeDeviceId,
  collectLiveConnections: collectLiveConnections,
  isClientNameAvailable: isClientNameAvailable,
  withClientNameReservation: withClientNameReservation
};