using FluentResults;
using pgLabII.PgUtils.ConnectionStrings;
using OneOf;

namespace pgLabII.PgUtils.Tests.ConnectionStrings;

using Elem = OneOf<PqToken, string, IError>;

internal class UnitTestTokenizer : IPqConnectionStringTokenizer
{
    private readonly List<Elem> _tokens = new();
    private int _position = 0;

    public UnitTestTokenizer AddString(string output)
    {
        _tokens.Add(output);
        return this;
    }

    public UnitTestTokenizer AddError(Error error)
    {
        _tokens.Add(error);
        return this;
    }

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

    public void AddEof()
    {
        _tokens.Add(PqToken.Eof);
    }

    // note we do no whitespace at end tests here
    public bool IsEof
    {
        get
        {
            EnsureNotEol();
            return _tokens[_position].IsT0 && _tokens[_position].AsT0 == PqToken.Eof;
        }
    }

    public Result<string> GetKeyword()
    {
        EnsureNotEol();
        var elem = Consume();
        return elem.Match<Result<string>>(
            token => throw new Exception("Unexpected call to GetKeyword"),
            str => str,
            error => Result.Fail(error));
    }

    public Result ConsumeEquals()
    {
        EnsureNotEol();
        var elem = Consume();

        return elem.Match<Result>(
            token =>
            {
                if (token != PqToken.Equals)
                    throw new Exception("Unexpected call to GetKeyword");
                return Result.Ok();
            },
            str => throw new Exception("Unexpected call to ConsumeEquals"),
            error => Result.Fail(error));
    }

    public Result<string> GetValue()
    {
        EnsureNotEol();
        var elem = Consume();
        return elem.Match<Result<string>>(
            token => throw new Exception("Unexpected call to GetValue"),
            str => str,
            error => Result.Fail(error));
    }

    private Elem Consume()
    {
        return _tokens[_position++];
    }

    private void EnsureNotEol()
    {
        if (_position >= _tokens.Count)
            throw new Exception("unexpected end of list in test, wrong parser call?");
    }
}