using Numbers.NumberString;

namespace Numbers.Test.NumberString;

public sealed class DigitEnumeratorTests
{
    [Fact]
    public void MoveNext_NoMoreDigits()
    {
        var enumerator = new DigitEnumerator("abc");

        enumerator.MoveNext().Should().BeFalse();
    }

    [Fact]
    public void MoveNext_MoreDigits()
    {
        var enumerator = new DigitEnumerator("abc123");

        enumerator.MoveNext().Should().BeTrue();
    }

    [Theory]
    [MemberData(nameof(EnumeratorTestData))]
    public void Current_CorrectDigit(string input, int moveSteps, int expectedDigit)
    {
        var enumerator = new DigitEnumerator(input);

        enumerator.Current.Should().Be(-1, "enumerator not moved yet");
        for (var i = 0; i < moveSteps; i++)
        {
            enumerator.MoveNext();
        }

        enumerator.Current.Should().Be(expectedDigit);
    }

    [Fact]
    public void Reset()
    {
        var enumerator = new DigitEnumerator("abc123");
        enumerator.MoveNext();
        enumerator.MoveNext();

        enumerator.Reset();
        enumerator.MoveNext();

        enumerator.Current.Should().Be(1);
    }

    [Fact]
    public void Interface()
    {
        var enumerator = new DigitEnumerator("abc123");

        enumerator.Should().BeAssignableTo<IEnumerator<int>>();
    }

    public static TheoryData<string, int, int> EnumeratorTestData() =>
        new()
        {
            { "abc132", 1, 1 },
            { "abc132", 2, 3 },
            { "abc132", 3, 2 },
            { "1abc23", 1, 1 },
            { "1abc23", 2, 2 },
            { "1abc23", 3, 3 },
            { "a1b2c3", 1, 1 },
            { "a1b2c3", 2, 2 },
            { "a1b2c3", 3, 3 },
            { "123abc", 1, 1 },
            { "123abc", 2, 2 },
            { "123abc", 3, 3 },
            { "2def456", 1, 2 },
            { "2def456", 2, 4 },
            { "2def456", 3, 5 },
            { "d4ef56", 1, 4 },
            { "d4ef56", 2, 5 },
            { "d4ef56", 3, 6 }
        };
}