// The strict DER of X.690 that spec §29.10 asks of a CMS signature, as
// der_test.go of datekeys-go at 601e6d2 (the draft of v0.12). Every error text
// is the one that the Go reference prints for the same input; the fuzz target
// is a property over seeded mutations of its seeds.

import 'dart:convert';
import 'dart:math';
import 'dart:typed_data';

import 'package:datekeys/datekeys.dart' show fromHex, toHex;
import 'package:datekeys/src/der.dart' as der;
import 'package:test/test.dart';

import 'der_support.dart';

Uint8List h(String hex) => fromHex(hex);

String zeros(int n) => '00' * n;

String hexOf(String s) => toHex(utf8.encode(s));

/// The message of the DerException that [f] throws.
String derError(void Function() f) {
  try {
    f();
  } on der.DerException catch (e) {
    return e.message;
  }
  fail('no DerException');
}

void main() {
  test('check accepts exactly the DER of the profile', () {
    // The cases of TestCheck: null for DER, and the text of the reference
    // for the rest.
    final cases = <(String, String, String?)>[
      (
        'sequence of an integer and a null',
        '3005020101'
            '0500',
        null,
      ),
      (
        'a long length',
        '04'
            '8180${zeros(128)}',
        null,
      ),
      (
        'a long form under 128',
        '0481'
            '01'
            '00',
        'der: a long form for a length under 128',
      ),
      (
        'a length with a leading zero',
        '04820001'
            '00',
        'der: a length with a leading zero',
      ),
      (
        'a length of 128 with a leading zero',
        '04820080${zeros(128)}',
        'der: a length with a leading zero',
      ),
      ('an indefinite length', '30800000', 'der: an indefinite length'),
      ('a length of 0xff', '04ff${zeros(127)}', 'der: a length of 0xff'),
      (
        'a length of five bytes',
        '0485'
            '0100000000'
            '00',
        'der: a length that does not fit',
      ),
      (
        'a length of nine bytes that wraps around to 128',
        '0489'
            '010000000000000080${zeros(128)}',
        'der: a length that does not fit',
      ),
      (
        'a length whose bytes are missing',
        '0482'
            '01',
        'der: a length that does not fit',
      ),
      ('a lone identifier octet', '04', 'der: truncated element'),
      ('nothing', '', 'der: truncated element'),
      ('a high tag number', '1f0100', 'der: a tag number of 31 or more'),
      ('truncated', '0402aa', 'der: an element longer than its container'),
      (
        'trailing bytes',
        '0500'
            '00',
        'der: 1 bytes after the element',
      ),
      ('BOOLEAN 01', '010101', 'der: a BOOLEAN that is not 00 or FF'),
      ('BOOLEAN 00', '010100', null),
      ('BOOLEAN FF', '0101ff', null),
      (
        'BOOLEAN of two bytes',
        '0102ffff',
        'der: a BOOLEAN that is not 00 or FF',
      ),
      (
        'INTEGER with a leading zero',
        '02020001',
        'der: an INTEGER that is not minimal',
      ),
      ('INTEGER 0x80 with its zero', '02020080', null),
      (
        'INTEGER with a leading FF',
        '0202ff80',
        'der: an INTEGER that is not minimal',
      ),
      (
        'INTEGER -1 in two bytes',
        '0202ffff',
        'der: an INTEGER that is not minimal',
      ),
      ('INTEGER -129', '0202ff7f', null),
      ('empty INTEGER', '0200', 'der: an empty INTEGER'),
      (
        'ENUMERATED with a leading zero',
        '0a020001',
        'der: an INTEGER that is not minimal',
      ),
      ('NULL with content', '050100', 'der: a NULL with content'),
      (
        'constructed OCTET STRING',
        '2404'
            '0402aabb',
        'der: constructed form of the universal type 4',
      ),
      (
        'constructed INTEGER',
        '2203'
            '020101',
        'der: constructed form of the universal type 2',
      ),
      (
        'BIT STRING with unused bits set',
        '03020701',
        'der: a BIT STRING with unused bits that are not zero',
      ),
      ('BIT STRING with unused bits clear', '03020780', null),
      ('BIT STRING of 4 bits', '030204f0', null),
      ('an empty BIT STRING', '030100', null),
      (
        'a BIT STRING without its first octet',
        '0300',
        'der: a malformed BIT STRING',
      ),
      (
        'a BIT STRING of eight unused bits',
        '03020800',
        'der: a malformed BIT STRING',
      ),
      (
        'a BIT STRING of no bits with unused bits',
        '030101',
        'der: a malformed BIT STRING',
      ),
      ('OID', '06032a0304', null),
      (
        'OID with 0x80 inside a subidentifier',
        '0604'
            '2a818001',
        null,
      ),
      (
        'OID with a leading 0x80',
        '06038001'
            '02',
        'der: an OBJECT IDENTIFIER with a leading 0x80 in a subidentifier',
      ),
      (
        'OID that does not end',
        '06022a83',
        'der: a malformed OBJECT IDENTIFIER',
      ),
      ('an empty OID', '0600', 'der: a malformed OBJECT IDENTIFIER'),
      ('context tag, constructed', 'a003020101', null),
      ('context tag, primitive, any content', '8003000000', null),
      (
        'SET in primitive form',
        '1100',
        'der: the universal type 17 in primitive form',
      ),
      (
        'SEQUENCE in primitive form',
        '1000',
        'der: the universal type 16 in primitive form',
      ),
      (
        'the end of contents',
        '0000',
        'der: the universal type 0, which the profile does not use',
      ),
      (
        'a reserved universal tag',
        '0e0141',
        'der: the universal type 14, which the profile does not use',
      ),
      (
        'a SEQUENCE of the end of contents',
        '30020000',
        'der: the universal type 0, which the profile does not use',
      ),
      (
        'a SEQUENCE with a bad child',
        '3003'
            '020000',
        'der: an empty INTEGER',
      ),
      (
        'a SEQUENCE whose child does not fit',
        '3003'
            '040500',
        'der: an element longer than its container',
      ),
      ('UTF8String', '0c026162', null),
      ('UTF8String that is not UTF-8', '0c01ff', null),
      ('PrintableString with an underscore', '13015f', null),
      ('TeletexString', '1401e9', null),
      ('IA5String', '160161', null),
      ('VisibleString', '1a0161', null),
      ('UniversalString', '1c0400000061', null),
      ('BMPString', '1e020061', null),
      // The other string types are DER too, whatever their content: a name
      // may hold a NumericString, as the INN of a Russian certificate.
      ('NumericString', '1204${hexOf('1234')}', null),
      ('NumericString with a letter', '1201${hexOf('A')}', null),
      ('VideotexString', '150141', null),
      ('GraphicString', '190141', null),
      ('GeneralString', '1b0141', null),
      ('ObjectDescriptor', '070141', null),
      (
        'NumericString in constructed form',
        '3203'
            '120131',
        'der: constructed form of the universal type 18',
      ),
      (
        'REAL',
        '0900',
        'der: the universal type 9, which the profile does not use',
      ),
      (
        'RELATIVE-OID',
        '0d0101',
        'der: the universal type 13, which the profile does not use',
      ),
      // Times in the forms of DER (X.690 11.7, 11.8).
      ('UTCTime', '170d${hexOf('250101120000Z')}', null),
      (
        'an empty UTCTime',
        '1700',
        'der: a time that is not in the form of DER',
      ),
      (
        'UTCTime without seconds',
        '170b${hexOf('2501011200Z')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'UTCTime with a digit more',
        '170e${hexOf('2501011200001Z')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'UTCTime with an offset',
        '1711${hexOf('250101120000+0100')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'UTCTime of 30 February',
        '170d${hexOf('250230120000Z')}',
        'der: a date or a time that does not exist',
      ),
      (
        'UTCTime with second 60',
        '170d${hexOf('250101235960Z')}',
        'der: a date or a time that does not exist',
      ),
      (
        'a UTCTime that is not a time',
        '170a${hexOf('not a time')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'UTCTime with a slash in its seconds',
        '170d${hexOf('2501011200/0Z')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'UTCTime with a colon in its day',
        '170d${hexOf('25010:120000Z')}',
        'der: a time that is not in the form of DER',
      ),
      ('GeneralizedTime', '180f${hexOf('20250101120000Z')}', null),
      (
        'GeneralizedTime with a fraction',
        '1812${hexOf('20250101120000.25Z')}',
        null,
      ),
      (
        'GeneralizedTime with a trailing zero',
        '1813${hexOf('20250101120000.250Z')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'GeneralizedTime with an empty fraction',
        '1810${hexOf('20250101120000.Z')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'GeneralizedTime with a letter in its fraction',
        '1812${hexOf('20250101120000.2aZ')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'GeneralizedTime without Z',
        '180e${hexOf('20250101120000')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'GeneralizedTime with a comma',
        '1812${hexOf('20250101120000,25Z')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'GeneralizedTime without seconds',
        '180d${hexOf('202501011200Z')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'GeneralizedTime with a slash in its seconds',
        '180f${hexOf('202501011200/0Z')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'GeneralizedTime of month 0',
        '180f${hexOf('20250001120000Z')}',
        'der: a date or a time that does not exist',
      ),
      (
        'GeneralizedTime of month 13',
        '180f${hexOf('20251301120000Z')}',
        'der: a date or a time that does not exist',
      ),
      (
        'GeneralizedTime of day 0',
        '180f${hexOf('20250100120000Z')}',
        'der: a date or a time that does not exist',
      ),
      (
        'GeneralizedTime of 31 April',
        '180f${hexOf('20250431120000Z')}',
        'der: a date or a time that does not exist',
      ),
      (
        'GeneralizedTime of hour 24',
        '180f${hexOf('20250101240000Z')}',
        'der: a date or a time that does not exist',
      ),
      (
        'GeneralizedTime of minute 60',
        '180f${hexOf('20250101126000Z')}',
        'der: a date or a time that does not exist',
      ),
      (
        'GeneralizedTime of 29 February 2024',
        '180f${hexOf('20240229235959Z')}',
        null,
      ),
      // What a check that is missing would let through: the last byte read
      // as Z, a colon read as the digit 10, a slash read as a year, a tag of
      // a high number read as one byte, and an indefinite length read as a
      // long form.
      (
        'UTCTime that ends in another letter',
        '170d${hexOf('250101120000X')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'GeneralizedTime with a digit in the place of Z',
        '180f${hexOf('202501011200000')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'GeneralizedTime with a colon in its day',
        '180f${hexOf('2025010:120000Z')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'GeneralizedTime with a slash in its year',
        '180f${hexOf('/0250101120000Z')}',
        'der: a time that is not in the form of DER',
      ),
      (
        'a context tag of a high number',
        '9f0100',
        'der: a tag number of 31 or more',
      ),
      (
        'an indefinite length and nothing after it',
        '3080',
        'der: an indefinite length',
      ),
    ];
    for (final (name, hex, text) in cases) {
      final b = h(hex);
      if (text == null) {
        expect(() => der.check(b), returnsNormally, reason: name);
      } else {
        expect(derError(() => der.check(b)), text, reason: name);
      }
    }
  });

  test(
    'the elements of a SET OF go in ascending order, equal ones may repeat',
    () {
      final a = [0x02, 0x01, 0x01];
      final b = [0x02, 0x01, 0x02];
      expect(der.setOfSorted([a, b]), isTrue);
      expect(der.setOfSorted([b, a]), isFalse);
      expect(der.setOfSorted([a, a, b]), isTrue);
      expect(der.setOfSorted([a, b, a]), isFalse);
      expect(der.setOfSorted([]), isTrue);
    },
  );

  test('elements nested 32 levels below the outer one are DER, 33 are not', () {
    Uint8List nested(int n) {
      var b = [0x05, 0x00];
      for (var i = 0; i < n; i++) {
        b = [0x30, b.length, ...b];
      }
      return Uint8List.fromList(b);
    }

    der.check(nested(32));
    expect(derError(() => der.check(nested(33))), 'der: nested too deep');
  });

  test('parseTime reads the times of DER exactly to the nanosecond', () {
    // Seconds since the epoch, nanoseconds and the form of RFC 3339, as Go's
    // Time.Unix, Time.Nanosecond and RFC3339Nano print them.
    final cases = <(String, int, int, bool, String)>[
      (
        '\x17\x0d'
            '491231235959Z',
        2524607999,
        0,
        false,
        '2049-12-31T23:59:59Z',
      ),
      (
        '\x17\x0d'
            '500101000000Z',
        -631152000,
        0,
        false,
        '1950-01-01T00:00:00Z',
      ),
      (
        '\x18\x13'
            '20240229120000.125Z',
        1709208000,
        125000000,
        true,
        '2024-02-29T12:00:00.125Z',
      ),
      (
        '\x18\x19'
            '20240229120000.123456789Z',
        1709208000,
        123456789,
        true,
        '2024-02-29T12:00:00.123456789Z',
      ),
      (
        '\x18\x0f'
            '19490101000000Z',
        -662688000,
        0,
        false,
        '1949-01-01T00:00:00Z',
      ),
      // Digits beyond the nanosecond are dropped, as Go drops them.
      (
        '\x18\x1b'
            '20240229120000.12345678912Z',
        1709208000,
        123456789,
        true,
        '2024-02-29T12:00:00.123456789Z',
      ),
      // The proleptic Gregorian calendar of Go: the year 0 is a leap year.
      (
        '\x18\x0f'
            '00000229120000Z',
        -62162078400,
        0,
        false,
        '0000-02-29T12:00:00Z',
      ),
      (
        '\x18\x0f'
            '99991231235959Z',
        253402300799,
        0,
        false,
        '9999-12-31T23:59:59Z',
      ),
    ];
    for (final (el, seconds, nanos, fraction, text) in cases) {
      final t = der.parseTime(Uint8List.fromList(el.codeUnits));
      expect(t.time.unixSeconds, seconds, reason: text);
      expect(t.time.nanosecond, nanos, reason: text);
      expect(t.fraction, fraction, reason: text);
      expect('${t.time}', text);
    }
    final bad = <(String, String)>[
      (
        '\x18\x0f'
            '20230229120000Z',
        'der: a date or a time that does not exist',
      ),
      (
        '\x04\x0d'
            '491231235959Z',
        'der: not a UTCTime or a GeneralizedTime',
      ),
      // A GeneralizedTime in an OCTET STRING, a UTCTime in a UTF8String.
      (
        '\x04\x0f'
            '20230228120000Z',
        'der: not a UTCTime or a GeneralizedTime',
      ),
      (
        '\x0c\x0d'
            '491231235959Z',
        'der: not a UTCTime or a GeneralizedTime',
      ),
      ('\x17', 'der: not a UTCTime or a GeneralizedTime'),
      // Its content does not fit.
      (
        '\x17\x0d'
            '4912',
        'der: an element longer than its container',
      ),
      ('', 'der: not a UTCTime or a GeneralizedTime'),
    ];
    for (final (el, text) in bad) {
      expect(
        derError(() => der.parseTime(Uint8List.fromList(el.codeUnits))),
        text,
      );
    }
  });

  test('times compare in order, to the nanosecond', () {
    der.DerTime t(String s) => der
        .parseTime(Uint8List.fromList([0x18, s.length, ...s.codeUnits]))
        .time;
    final a = t('20240229120000.1Z');
    final b = t('20240229120000.100000001Z');
    final c = t('20240229120001Z');
    expect(a.isBefore(b), isTrue);
    expect(b.isBefore(c), isTrue);
    expect(c.isAfter(a), isTrue);
    expect(a.compareTo(a), 0);
    expect(a, t('20240229120000.1Z'));
    expect(a, isNot(b));
    // A UTCTime and a GeneralizedTime of the same instant are the same time.
    final utc = der.parseTime(h('170d${hexOf('491231235959Z')}')).time;
    expect(utc, t('20491231235959Z'));
    expect(utc.hashCode, t('20491231235959Z').hashCode);
  });

  test('split and content read the children and the content', () {
    final b = h('30050201010500');
    der.check(b);
    final s = der.split(b);
    expect(s.id, 0x30);
    expect(s.children.map(toHex), ['020101', '0500']);
    expect(toHex(der.content(b)), '0201010500');
    // Nothing, a primitive element, and constructed ones whose content, or a
    // child, does not fit.
    final bad = <(String, String)>[
      ('', 'der: not a constructed element'),
      ('0400', 'der: not a constructed element'),
      ('3005', 'der: an element longer than its container'),
      ('a005', 'der: an element longer than its container'),
      ('300304050000', 'der: an element longer than its container'),
    ];
    for (final (hex, text) in bad) {
      expect(derError(() => der.split(h(hex))), text, reason: hex);
    }
    expect(
      derError(() => der.content(h('040500'))),
      'der: an element longer than its container',
    );
    expect(derError(() => der.content(h('04'))), 'der: truncated element');
  });

  test('a child that does not fit is an error of split, which returns', () {
    // The loop over the children advances by each header: a child that does
    // not fit must end it, or it would never end.
    expect(
      derError(() => der.split(h('3003040500'))),
      'der: an element longer than its container',
    );
  });

  test('what check accepts, split, content and parseTime read', () {
    // FuzzDERCheck over seeded mutations of its seeds: the children of a
    // constructed element are its content exactly, a primitive one is not
    // split, and a time of the universal class is read by parseTime.
    final seeds = [
      for (final s in [
        '30050201010500',
        'a003020101',
        '0603'
            '2a0304',
        '170d${hexOf('250101120000Z')}',
        '1812${hexOf('20250101120000.25Z')}',
        '30800000',
        '0489'
            '010000000000000080',
        '3010'
            '170d${hexOf('491231235959Z')}'
            '0101ff',
      ])
        h(s),
    ];
    final r = Random(7);
    var accepted = 0;
    for (var i = 0; i < 20000; i++) {
      final b = mutateDer(r, seeds[r.nextInt(seeds.length)]);
      try {
        der.check(b);
      } on der.DerException {
        continue;
      }
      accepted++;
      walkAccepted(b);
    }
    expect(accepted, greaterThan(100));
  });
}