// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

part of dart.io;

// Constants used when working with native ports.
// These must match the constants in runtime/bin/dartutils.h class CObject.
const int _successResponse = 0;
const int _illegalArgumentResponse = 1;
const int _osErrorResponse = 2;
const int _fileClosedResponse = 3;

const int _errorResponseErrorType = 0;
const int _osErrorResponseErrorCode = 1;
const int _osErrorResponseMessage = 2;

// Functions used to receive exceptions from native ports.
bool _isErrorResponse(response) =>
    response is List && response[0] != _successResponse;

/// Returns an [Exception] or an [Error].
_exceptionFromResponse(response, String message, String path) {
  assert(_isErrorResponse(response));
  switch (response[_errorResponseErrorType]) {
    case _illegalArgumentResponse:
      return new ArgumentError("$message: $path");
    case _osErrorResponse:
      var err = new OSError(response[_osErrorResponseMessage],
          response[_osErrorResponseErrorCode]);
      return new FileSystemException(message, path, err);
    case _fileClosedResponse:
      return new FileSystemException("File closed", path);
    default:
      return new Exception("Unknown error");
  }
}

/// Base class for all IO related exceptions.
abstract class IOException implements Exception {
  String toString() => "IOException";
}

/// An [Exception] holding information about an error from the
/// operating system.
@pragma("vm:entry-point")
class OSError implements Exception {
  /// Constant used to indicate that no OS error code is available.
  static const int noErrorCode = -1;

  /// Error message supplied by the operating system. This will be empty if no
  /// message is associated with the error.
  final String message;

  /// Error code supplied by the operating system.
  ///
  /// Will have the value [OSError.noErrorCode] if there is no error code
  /// associated with the error.
  final int errorCode;

  /// Creates an OSError object from a message and an errorCode.
  @pragma("vm:entry-point")
  const OSError([this.message = "", this.errorCode = noErrorCode]);

  /// Converts an OSError object to a string representation.
  String toString() {
    StringBuffer sb = new StringBuffer();
    sb.write("OS Error");
    if (message.isNotEmpty) {
      sb..write(": ")..write(message);
      if (errorCode != noErrorCode) {
        sb..write(", errno = ")..write(errorCode.toString());
      }
    } else if (errorCode != noErrorCode) {
      sb..write(": errno = ")..write(errorCode.toString());
    }
    return sb.toString();
  }
}

// Object for holding a buffer and an offset.
class _BufferAndStart {
  List<int> buffer;
  int start;
  _BufferAndStart(this.buffer, this.start);
}

// Ensure that the input List can be serialized through a native port.
// Only Int8List and Uint8List Lists are serialized directly.
// All other lists are first copied into a Uint8List. This has the added
// benefit that it is faster to access from the C code as well.
_BufferAndStart _ensureFastAndSerializableByteData(
    List<int> buffer, int start, int end) {
  if (_isDirectIOCapableTypedList(buffer)) {
    return new _BufferAndStart(buffer, start);
  }
  int length = end - start;
  var newBuffer = new Uint8List(length);
  newBuffer.setRange(0, length, buffer, start);
  return new _BufferAndStart(newBuffer, 0);
}

// The VM will use ClassID to check whether buffer is Uint8List or Int8List.
external bool _isDirectIOCapableTypedList(List<int> buffer);

class _IOCrypto {
  external static Uint8List getRandomBytes(int count);
}