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lib/models/printer_port_handle.dart

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+/// Close callback type for [PrinterPortHandle].
+typedef ClosePortCallback = Future<bool> Function(int handle);
+
+/// Represents an open printer port handle.
+///
+/// Wraps an integer handle and provides a [close] method to release
+/// the underlying native port resource. Once closed, the handle
+/// becomes invalid.
+class PrinterPortHandle {
+  /// The integer handle returned by the native layer.
+  final int handle;
+
+  /// Callback to close the port. If null, close() is a no-op.
+  final ClosePortCallback? _closeCallback;
+
+  /// Whether the port is still valid (not closed).
+  bool _isValid;
+
+  /// Creates a [PrinterPortHandle] with the given [handle] and optional [closeCallback].
+  PrinterPortHandle({
+    required this.handle,
+    ClosePortCallback? closeCallback,
+  })  : _closeCallback = closeCallback,
+        _isValid = true;
+
+  /// Returns true if the port is still open and not closed.
+  bool get isValid => _isValid;
+
+  /// Closes the port and marks the handle as invalid.
+  ///
+  /// Subsequent calls to [close] are no-ops if the port is already closed.
+  Future<void> close() async {
+    if (!_isValid) {
+      return;
+    }
+    _isValid = false;
+    if (_closeCallback != null) {
+      await _closeCallback(handle);
+    }
+  }
+
+  @override
+  String toString() => 'PrinterPortHandle(handle: $handle, valid: $_isValid)';
+}