isCleanClose static method

Implementation

static bool isCleanClose(int closeCode, String? closeReason) {
  // Normalize closeReason to handle null and case insensitivity
  final normalizedReason = closeReason?.toLowerCase() ?? '';

  // --- 1. Explicitly Unclean Close Codes (Protocol-defined errors) ---
  // These codes explicitly indicate an error or an abnormal termination.
  switch (closeCode) {
    case 1006: // Abnormal closure (no close frame, e.g., network error)
    case 1007: // Invalid frame payload data
    case 1008: // Policy Violation
    case 1009: // Message too big
    case 1010: // Missing a required extension
    case 1011: // Internal Error
    case 1015: // TLS Handshake (failure to complete TLS handshake)
      return false;
  }

  // --- 2. Lower-level/Network-related Unclean Closures ---
  // These often indicate a connection failure before or during the handshake,
  // or a system-level error.
  if (closeCode ==
          500 || // Custom/Non-standard HTTP-like error, treat as unclean
      normalizedReason.contains('failed host lookup') ||
      normalizedReason.contains('socketexception') ||
      normalizedReason.contains('connection refused') ||
      normalizedReason.contains(
        'connection reset by peer',
      ) || // Common network error
      normalizedReason.contains('network is unreachable')) {
    return false;
  }

  // --- 3. Standard Clean Close Codes ---
  // These are standard WebSocket codes that typically indicate a graceful or expected closure.
  // We've excluded the error codes handled above.
  if (closeCode == 1000 || // Normal Closure
      closeCode ==
          1001 || // Going Away (e.g., server shutting down, browser navigating)
      closeCode ==
          1002 || // Protocol error (could be clean if client understands/expects it, but safer to treat as potentially unclean if not explicit) - DECISION: For this version, keeping it here for simplicity of standard codes.
      closeCode == 1003 ||
      closeCode ==
          1005) // No status provided, generally sent when manually disconnected
  {
    // Unacceptable Data
    return true;
  }

  // --- 4. Application-Defined Close Codes (3000-4999) ---
  // These codes are application-specific. By default, we treat them as UNCLEAN
  // unless you have a specific list of "clean" application codes.
  // Example: if (closeCode == 3001 && normalizedReason == 'user logged out') return true;
  if (closeCode >= 3000 && closeCode <= 4999) {
    // You would need to add specific logic here if you define custom CLEAN codes.
    // For now, by default, we'll assume they're NOT clean unless explicitly handled.
    return false;
  }

  // --- 5. Fallback / Everything Else ---
  // Any other close code not explicitly handled, or a non-standard code,
  // is generally treated as an unclean closure. This includes:
  // - Reserved codes (1016-2999)
  // - Codes outside the standard WebSocket range that aren't specifically handled (e.g., 5000+)
  // - Custom codes not explicitly marked as clean.
  return false;
}