using pgLabII.PgUtils.ConnectionStrings;

namespace pgLabII.PgUtils.Tests.ConnectionStrings;

internal class UnitTestTokenizer : IPqConnectionStringTokenizer
{
    private readonly struct Elem(PqToken result, object? output)
    {
        public readonly PqToken Result = result;
        public readonly object? Output = output;
    }

    private readonly List<Elem> _tokens = [];
    private int _position = 0;


    public UnitTestTokenizer AddString(string? output)
    {
        _tokens.Add(new(PqToken.String, output));
        return this;
    }

    public UnitTestTokenizer AddException(Exception? output)
    {
        _tokens.Add(new(PqToken.Exception, output));
        return this;
    }

    public UnitTestTokenizer AddEquals()
    {
        _tokens.Add(new(PqToken.Equals, null));
        return this;
    }

    // note we do no whitespace at end tests here
    public bool Eof => _position >= _tokens.Count;

    public string GetKeyword()
    {
        EnsureNotEof();
        var elem = Consume();
        if (elem.Result == PqToken.String)
            return (string)elem.Output!;

        throw new Exception("Unexpected call to GetKeyword");
    }


    public void ConsumeEquals()
    {
        EnsureNotEof();
        var elem = Consume();
        if (elem.Result == PqToken.Equals)
            return;

        throw new Exception("Unexpected call to ConsumeEquals");
    }

    public string GetValue()
    {
        EnsureNotEof();
        var elem = Consume();
        if (elem.Result == PqToken.String)
            return (string)elem.Output!;

        throw new Exception("Unexpected call to GetValue");
    }

    private Elem Consume()
    {
        var elem = _tokens[_position++];
        if (elem.Result == PqToken.Exception)
        {
            throw (Exception)elem.Output!;
        }
        return elem;
    }

    private void EnsureNotEof()
    {
        if (Eof)
            throw new Exception("unexpected eof in test, wrong parser call?");
    }
}