// 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.

import "package:expect/expect.dart";
import 'dart:convert';

String decode(List<int> inputBytes) {
  late List<int> bytes;
  var byteSink =
      new ByteConversionSink.withCallback((result) => bytes = result);
  var stringConversionSink = new Utf8Encoder().startChunkedConversion(byteSink);
  ByteConversionSink inputByteSink = stringConversionSink.asUtf8Sink(false);
  inputByteSink.add(inputBytes);
  inputByteSink.close();
  return utf8.decode(bytes);
}

String decode2(List<int> inputBytes) {
  late List<int> bytes;
  var byteSink =
      new ByteConversionSink.withCallback((result) => bytes = result);
  var stringConversionSink = new Utf8Encoder().startChunkedConversion(byteSink);
  ByteConversionSink inputByteSink = stringConversionSink.asUtf8Sink(false);
  inputBytes.forEach((b) => inputByteSink.addSlice([0, b, 1], 1, 2, false));
  inputByteSink.close();
  return utf8.decode(bytes);
}

String decodeAllowMalformed(List<int> inputBytes) {
  late List<int> bytes;
  var byteSink =
      new ByteConversionSink.withCallback((result) => bytes = result);
  var stringConversionSink = new Utf8Encoder().startChunkedConversion(byteSink);
  ByteConversionSink inputByteSink = stringConversionSink.asUtf8Sink(true);
  inputByteSink.add(inputBytes);
  inputByteSink.close();
  return utf8.decode(bytes);
}

String decodeAllowMalformed2(List<int> inputBytes) {
  late List<int> bytes;
  var byteSink =
      new ByteConversionSink.withCallback((result) => bytes = result);
  var stringConversionSink = new Utf8Encoder().startChunkedConversion(byteSink);
  ByteConversionSink inputByteSink = stringConversionSink.asUtf8Sink(true);
  inputBytes.forEach((b) => inputByteSink.addSlice([0, b, 1], 1, 2, false));
  inputByteSink.close();
  return utf8.decode(bytes);
}

final TESTS0 = [
  // Unfinished UTF-8 sequences.
  [0xc3],
  [0xE2, 0x82],
  [0xF0, 0xA4, 0xAD]
];

final TESTS1 = [
  // Overlong encoding of euro-sign.
  [0xF0, 0x82, 0x82, 0xAC],
  // Other overlong/unfinished sequences.
  [0xC0],
  [0xC1],
  [0xF5],
  [0xF6],
  [0xF7],
  [0xF8],
  [0xF9],
  [0xFA],
  [0xFB],
  [0xFC],
  [0xFD],
  [0xFE],
  [0xFF],
  [0xC0, 0x80],
  [0xC1, 0x80],
  // Outside valid range.
  [0xF4, 0xBF, 0xBF, 0xBF]
];

final TESTS2 = [
  // Test that 0xC0|1, 0x80 does not eat the next character.
  [
    [0xC0, 0x80, 0x61],
    "XXa"
  ],
  [
    [0xC1, 0x80, 0x61],
    "XXa"
  ],
  // 0xF5 .. 0xFF never appear in valid UTF-8 sequences.
  [
    [0xF5, 0x80],
    "XX"
  ],
  [
    [0xF6, 0x80],
    "XX"
  ],
  [
    [0xF7, 0x80],
    "XX"
  ],
  [
    [0xF8, 0x80],
    "XX"
  ],
  [
    [0xF9, 0x80],
    "XX"
  ],
  [
    [0xFA, 0x80],
    "XX"
  ],
  [
    [0xFB, 0x80],
    "XX"
  ],
  [
    [0xFC, 0x80],
    "XX"
  ],
  [
    [0xFD, 0x80],
    "XX"
  ],
  [
    [0xFE, 0x80],
    "XX"
  ],
  [
    [0xFF, 0x80],
    "XX"
  ],
  [
    [0xF5, 0x80, 0x61],
    "XXa"
  ],
  [
    [0xF6, 0x80, 0x61],
    "XXa"
  ],
  [
    [0xF7, 0x80, 0x61],
    "XXa"
  ],
  [
    [0xF8, 0x80, 0x61],
    "XXa"
  ],
  [
    [0xF9, 0x80, 0x61],
    "XXa"
  ],
  [
    [0xFA, 0x80, 0x61],
    "XXa"
  ],
  [
    [0xFB, 0x80, 0x61],
    "XXa"
  ],
  [
    [0xFC, 0x80, 0x61],
    "XXa"
  ],
  [
    [0xFD, 0x80, 0x61],
    "XXa"
  ],
  [
    [0xFE, 0x80, 0x61],
    "XXa"
  ],
  [
    [0xFF, 0x80, 0x61],
    "XXa"
  ],
  // Characters outside the valid range.
  [
    [0xF5, 0x80, 0x80, 0x61],
    "XXXa"
  ],
  [
    [0xF6, 0x80, 0x80, 0x61],
    "XXXa"
  ],
  [
    [0xF7, 0x80, 0x80, 0x61],
    "XXXa"
  ],
  [
    [0xF8, 0x80, 0x80, 0x61],
    "XXXa"
  ],
  [
    [0xF9, 0x80, 0x80, 0x61],
    "XXXa"
  ],
  [
    [0xFA, 0x80, 0x80, 0x61],
    "XXXa"
  ],
  [
    [0xFB, 0x80, 0x80, 0x61],
    "XXXa"
  ],
  [
    [0xFC, 0x80, 0x80, 0x61],
    "XXXa"
  ],
  [
    [0xFD, 0x80, 0x80, 0x61],
    "XXXa"
  ],
  [
    [0xFE, 0x80, 0x80, 0x61],
    "XXXa"
  ],
  [
    [0xFF, 0x80, 0x80, 0x61],
    "XXXa"
  ]
];

main() {
  var allTests = [...TESTS0, ...TESTS1].expand((test) {
    // Pairs of test and expected string output when malformed strings are
    // allowed. Replacement character: U+FFFD, one per unfinished sequence or
    // undecodable byte.
    String replacement =
        TESTS0.contains(test) ? "\u{FFFD}" : "\u{FFFD}" * test.length;
    return [
      [test, "${replacement}"],
      [
        [0x61, ...test],
        "a${replacement}"
      ],
      [
        [0x61, ...test, 0x61],
        "a${replacement}a"
      ],
      [
        [...test, 0x61],
        "${replacement}a"
      ],
      [
        [...test, ...test],
        "${replacement}${replacement}"
      ],
      [
        [...test, 0x61, ...test],
        "${replacement}a${replacement}"
      ],
      [
        [0xc3, 0xa5, ...test],
        "å${replacement}"
      ],
      [
        [0xc3, 0xa5, ...test, 0xc3, 0xa5],
        "å${replacement}å"
      ],
      [
        [...test, 0xc3, 0xa5],
        "${replacement}å"
      ],
      [
        [...test, 0xc3, 0xa5, ...test],
        "${replacement}å${replacement}"
      ]
    ];
  });

  var allTests2 = TESTS2.map((test) {
    // Pairs of test and expected string output when malformed strings are
    // allowed. Replacement character: U+FFFD
    String expected = (test[1] as String).replaceAll("X", "\u{FFFD}");
    return [test[0], expected];
  });

  for (var test in []..addAll(allTests)..addAll(allTests2)) {
    List<int> bytes = test[0];
    Expect.throwsFormatException(() => decode(bytes));
    Expect.throwsFormatException(() => decode2(bytes));

    String expected = test[1];
    Expect.equals(expected, decodeAllowMalformed(bytes));
    Expect.equals(expected, decodeAllowMalformed2(bytes));
  }
}