// Copyright (c) 2014, 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:string_scanner/src/charcode.dart';
import 'package:string_scanner/string_scanner.dart';
import 'package:test/test.dart';

void main() {
  group('with an empty string', () {
    late StringScanner scanner;
    setUp(() {
      scanner = StringScanner('');
    });

    test('is done', () {
      expect(scanner.isDone, isTrue);
      expect(scanner.expectDone, isNot(throwsFormatException));
    });

    test('rest is empty', () {
      expect(scanner.rest, isEmpty);
    });

    test('lastMatch is null', () {
      expect(scanner.lastMatch, isNull);
    });

    test('position is zero', () {
      expect(scanner.position, equals(0));
    });

    test("readChar fails and doesn't change the state", () {
      expect(scanner.readChar, throwsFormatException);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
    });

    test("readCodePoint fails and doesn't change the state", () {
      expect(scanner.readCodePoint, throwsFormatException);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
    });

    test("peekChar returns null and doesn't change the state", () {
      expect(scanner.peekChar(), isNull);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
    });

    test("peekCodePoint returns null and doesn't change the state", () {
      expect(scanner.peekCodePoint(), isNull);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
    });

    test("scanChar returns false and doesn't change the state", () {
      expect(scanner.scanChar($f), isFalse);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
    });

    test("expectChar fails and doesn't change the state", () {
      expect(() => scanner.expectChar($f), throwsFormatException);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
    });

    test("scan returns false and doesn't change the state", () {
      expect(scanner.scan(RegExp('.')), isFalse);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
    });

    test("expect throws a FormatException and doesn't change the state", () {
      expect(() => scanner.expect(RegExp('.')), throwsFormatException);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
    });

    test("matches returns false and doesn't change the state", () {
      expect(scanner.matches(RegExp('.')), isFalse);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
    });

    test('substring returns the empty string', () {
      expect(scanner.substring(0), isEmpty);
    });

    test('setting position to 1 throws an ArgumentError', () {
      expect(() {
        scanner.position = 1;
      }, throwsArgumentError);
    });

    test('setting position to -1 throws an ArgumentError', () {
      expect(() {
        scanner.position = -1;
      }, throwsArgumentError);
    });
  });

  group('at the beginning of a string', () {
    late StringScanner scanner;
    setUp(() {
      scanner = StringScanner('foo bar');
    });

    test('is not done', () {
      expect(scanner.isDone, isFalse);
      expect(scanner.expectDone, throwsFormatException);
    });

    test('rest is the whole string', () {
      expect(scanner.rest, equals('foo bar'));
    });

    test('lastMatch is null', () {
      expect(scanner.lastMatch, isNull);
    });

    test('position is zero', () {
      expect(scanner.position, equals(0));
    });

    test('readChar returns the first character and moves forward', () {
      expect(scanner.readChar(), equals(0x66));
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(1));
    });

    test('readCodePoint returns the first character and moves forward', () {
      expect(scanner.readCodePoint(), equals(0x66));
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(1));
    });

    test('peekChar returns the first character', () {
      expect(scanner.peekChar(), equals(0x66));
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
    });

    test('peekChar with an argument returns the nth character', () {
      expect(scanner.peekChar(4), equals(0x62));
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
    });

    test('peekCodePoint returns the first character', () {
      expect(scanner.peekCodePoint(), equals(0x66));
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
    });

    test('a matching scanChar returns true moves forward', () {
      expect(scanner.scanChar($f), isTrue);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(1));
    });

    test('a non-matching scanChar returns false and does nothing', () {
      expect(scanner.scanChar($x), isFalse);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
    });

    test('a matching expectChar moves forward', () {
      scanner.expectChar($f);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(1));
    });

    test('a non-matching expectChar fails', () {
      expect(() => scanner.expectChar($x), throwsFormatException);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
    });

    test('a matching scan returns true and changes the state', () {
      expect(scanner.scan(RegExp('f(..)')), isTrue);
      expect(scanner.lastMatch![1], equals('oo'));
      expect(scanner.position, equals(3));
      expect(scanner.rest, equals(' bar'));
    });

    test('a non-matching scan returns false and sets lastMatch to null', () {
      expect(scanner.matches(RegExp('f(..)')), isTrue);
      expect(scanner.lastMatch, isNotNull);

      expect(scanner.scan(RegExp('b(..)')), isFalse);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
      expect(scanner.rest, equals('foo bar'));
    });

    test('a matching expect changes the state', () {
      scanner.expect(RegExp('f(..)'));
      expect(scanner.lastMatch![1], equals('oo'));
      expect(scanner.position, equals(3));
      expect(scanner.rest, equals(' bar'));
    });

    test(
        'a non-matching expect throws a FormatException and sets lastMatch to '
        'null', () {
      expect(scanner.matches(RegExp('f(..)')), isTrue);
      expect(scanner.lastMatch, isNotNull);

      expect(() => scanner.expect(RegExp('b(..)')), throwsFormatException);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
      expect(scanner.rest, equals('foo bar'));
    });

    test('a matching matches returns true and only changes lastMatch', () {
      expect(scanner.matches(RegExp('f(..)')), isTrue);
      expect(scanner.lastMatch![1], equals('oo'));
      expect(scanner.position, equals(0));
      expect(scanner.rest, equals('foo bar'));
    });

    test("a non-matching matches returns false and doesn't change the state",
        () {
      expect(scanner.matches(RegExp('b(..)')), isFalse);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(0));
      expect(scanner.rest, equals('foo bar'));
    });

    test('substring from the beginning returns the empty string', () {
      expect(scanner.substring(0), isEmpty);
    });

    test('substring with a custom end returns the substring', () {
      expect(scanner.substring(0, 3), equals('foo'));
    });

    test('substring with the string length returns the whole string', () {
      expect(scanner.substring(0, 7), equals('foo bar'));
    });

    test('setting position to 1 moves the cursor forward', () {
      scanner.position = 1;
      expect(scanner.position, equals(1));
      expect(scanner.rest, equals('oo bar'));

      expect(scanner.scan(RegExp('oo.')), isTrue);
      expect(scanner.lastMatch![0], equals('oo '));
      expect(scanner.position, equals(4));
      expect(scanner.rest, equals('bar'));
    });

    test('setting position beyond the string throws an ArgumentError', () {
      expect(() {
        scanner.position = 8;
      }, throwsArgumentError);
    });

    test('setting position to -1 throws an ArgumentError', () {
      expect(() {
        scanner.position = -1;
      }, throwsArgumentError);
    });

    test('scan accepts any Pattern', () {
      expect(scanner.scan('foo'), isTrue);
      expect(scanner.lastMatch![0], equals('foo'));
      expect(scanner.position, equals(3));
      expect(scanner.rest, equals(' bar'));
    });

    test('scans multiple times', () {
      expect(scanner.scan(RegExp('f(..)')), isTrue);
      expect(scanner.lastMatch![1], equals('oo'));
      expect(scanner.position, equals(3));
      expect(scanner.rest, equals(' bar'));

      expect(scanner.scan(RegExp(' b(..)')), isTrue);
      expect(scanner.lastMatch![1], equals('ar'));
      expect(scanner.position, equals(7));
      expect(scanner.rest, equals(''));
      expect(scanner.isDone, isTrue);
      expect(scanner.expectDone, isNot(throwsFormatException));
    });
  });

  group('after a scan', () {
    late StringScanner scanner;
    setUp(() {
      scanner = StringScanner('foo bar');
      expect(scanner.scan('foo'), isTrue);
    });

    test('readChar returns the first character and unsets the last match', () {
      expect(scanner.readChar(), equals($space));
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(4));
    });

    test('readCodePoint returns the first character and unsets the last match',
        () {
      expect(scanner.readCodePoint(), equals($space));
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(4));
    });

    test('a matching scanChar returns true and unsets the last match', () {
      expect(scanner.scanChar($space), isTrue);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(4));
    });

    test('a matching expectChar returns true and unsets the last match', () {
      scanner.expectChar($space);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(4));
    });
  });

  group('at the end of a string', () {
    late StringScanner scanner;
    setUp(() {
      scanner = StringScanner('foo bar');
      expect(scanner.scan('foo bar'), isTrue);
    });

    test('is done', () {
      expect(scanner.isDone, isTrue);
      expect(scanner.expectDone, isNot(throwsFormatException));
    });

    test('rest is empty', () {
      expect(scanner.rest, isEmpty);
    });

    test('position is zero', () {
      expect(scanner.position, equals(7));
    });

    test("readChar fails and doesn't change the state", () {
      expect(scanner.readChar, throwsFormatException);
      expect(scanner.lastMatch, isNotNull);
      expect(scanner.position, equals(7));
    });

    test("readCodePoint fails and doesn't change the state", () {
      expect(scanner.readCodePoint, throwsFormatException);
      expect(scanner.lastMatch, isNotNull);
      expect(scanner.position, equals(7));
    });

    test("peekChar returns null and doesn't change the state", () {
      expect(scanner.peekChar(), isNull);
      expect(scanner.lastMatch, isNotNull);
      expect(scanner.position, equals(7));
    });

    test("peekCodePoint returns null and doesn't change the state", () {
      expect(scanner.peekCodePoint(), isNull);
      expect(scanner.lastMatch, isNotNull);
      expect(scanner.position, equals(7));
    });

    test("scanChar returns false and doesn't change the state", () {
      expect(scanner.scanChar($f), isFalse);
      expect(scanner.lastMatch, isNotNull);
      expect(scanner.position, equals(7));
    });

    test("expectChar fails and doesn't change the state", () {
      expect(() => scanner.expectChar($f), throwsFormatException);
      expect(scanner.lastMatch, isNotNull);
      expect(scanner.position, equals(7));
    });

    test('scan returns false and sets lastMatch to null', () {
      expect(scanner.scan(RegExp('.')), isFalse);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(7));
    });

    test('expect throws a FormatException and sets lastMatch to null', () {
      expect(() => scanner.expect(RegExp('.')), throwsFormatException);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(7));
    });

    test('matches returns false sets lastMatch to null', () {
      expect(scanner.matches(RegExp('.')), isFalse);
      expect(scanner.lastMatch, isNull);
      expect(scanner.position, equals(7));
    });

    test('substring from the beginning returns the whole string', () {
      expect(scanner.substring(0), equals('foo bar'));
    });

    test('substring with a custom start returns a substring from there', () {
      expect(scanner.substring(4), equals('bar'));
    });

    test('substring with a custom start and end returns that substring', () {
      expect(scanner.substring(3, 5), equals(' b'));
    });

    test('setting position to 1 moves the cursor backward', () {
      scanner.position = 1;
      expect(scanner.position, equals(1));
      expect(scanner.rest, equals('oo bar'));

      expect(scanner.scan(RegExp('oo.')), isTrue);
      expect(scanner.lastMatch![0], equals('oo '));
      expect(scanner.position, equals(4));
      expect(scanner.rest, equals('bar'));
    });

    test('setting and resetting position clears lastMatch', () {
      final oldPosition = scanner.position;
      scanner.position = 1;
      scanner.position = oldPosition;
      expect(scanner.lastMatch, isNull);
    });

    test('setting position beyond the string throws an ArgumentError', () {
      expect(() {
        scanner.position = 8;
      }, throwsArgumentError);
    });

    test('setting position to -1 throws an ArgumentError', () {
      expect(() {
        scanner.position = -1;
      }, throwsArgumentError);
    });
  });

  group('before a surrogate pair', () {
    final codePoint = '\uD83D\uDC6D'.runes.first;
    const highSurrogate = 0xD83D;

    late StringScanner scanner;
    setUp(() {
      scanner = StringScanner('foo: \uD83D\uDC6D');
      expect(scanner.scan('foo: '), isTrue);
    });

    test('readChar returns the high surrogate and moves into the pair', () {
      expect(scanner.readChar(), equals(highSurrogate));
      expect(scanner.position, equals(6));
    });

    test('readCodePoint returns the code unit and moves past the pair', () {
      expect(scanner.readCodePoint(), equals(codePoint));
      expect(scanner.position, equals(7));
    });

    test('peekChar returns the high surrogate', () {
      expect(scanner.peekChar(), equals(highSurrogate));
      expect(scanner.position, equals(5));
    });

    test('peekCodePoint returns the code unit', () {
      expect(scanner.peekCodePoint(), equals(codePoint));
      expect(scanner.position, equals(5));
    });

    test('scanChar with the high surrogate moves into the pair', () {
      expect(scanner.scanChar(highSurrogate), isTrue);
      expect(scanner.position, equals(6));
    });

    test('scanChar with the code point moves past the pair', () {
      expect(scanner.scanChar(codePoint), isTrue);
      expect(scanner.position, equals(7));
    });

    test('expectChar with the high surrogate moves into the pair', () {
      scanner.expectChar(highSurrogate);
      expect(scanner.position, equals(6));
    });

    test('expectChar with the code point moves past the pair', () {
      scanner.expectChar(codePoint);
      expect(scanner.position, equals(7));
    });
  });

  group('before an invalid surrogate pair', () {
    // This surrogate pair is invalid because U+E000 is just outside the range
    // of low surrogates. If it were interpreted as a surrogate pair anyway, the
    // value would be U+110000, which is outside of the Unicode gamut.
    const codePoint = 0x110000;
    const highSurrogate = 0xD800;

    late StringScanner scanner;
    setUp(() {
      scanner = StringScanner('foo: \uD800\uE000');
      expect(scanner.scan('foo: '), isTrue);
    });

    test('readChar returns the high surrogate and moves into the pair', () {
      expect(scanner.readChar(), equals(highSurrogate));
      expect(scanner.position, equals(6));
    });

    test('readCodePoint returns the high surrogate and moves past the pair',
        () {
      expect(scanner.readCodePoint(), equals(highSurrogate));
      expect(scanner.position, equals(6));
    });

    test('peekChar returns the high surrogate', () {
      expect(scanner.peekChar(), equals(highSurrogate));
      expect(scanner.position, equals(5));
    });

    test('peekCodePoint returns the high surrogate', () {
      expect(scanner.peekCodePoint(), equals(highSurrogate));
      expect(scanner.position, equals(5));
    });

    test('scanChar with the high surrogate moves into the pair', () {
      expect(scanner.scanChar(highSurrogate), isTrue);
      expect(scanner.position, equals(6));
    });

    test('scanChar with the fake code point returns false', () {
      expect(scanner.scanChar(codePoint), isFalse);
      expect(scanner.position, equals(5));
    });

    test('expectChar with the high surrogate moves into the pair', () {
      scanner.expectChar(highSurrogate);
      expect(scanner.position, equals(6));
    });

    test('expectChar with the fake code point fails', () {
      expect(() => scanner.expectChar(codePoint), throwsRangeError);
    });
  });

  group('a scanner constructed with a custom position', () {
    test('starts scanning from that position', () {
      final scanner = StringScanner('foo bar', position: 1);
      expect(scanner.position, equals(1));
      expect(scanner.rest, equals('oo bar'));

      expect(scanner.scan(RegExp('oo.')), isTrue);
      expect(scanner.lastMatch![0], equals('oo '));
      expect(scanner.position, equals(4));
      expect(scanner.rest, equals('bar'));
    });

    test('throws an ArgumentError if the position is -1', () {
      expect(() => StringScanner('foo bar', position: -1), throwsArgumentError);
    });

    test('throws an ArgumentError if the position is beyond the string', () {
      expect(() => StringScanner('foo bar', position: 8), throwsArgumentError);
    });
  });
}