jtr/DevDisciples.Parsing/ParserContext.cs

namespace DevDisciples.Parsing;

public class ParserContext<TToken> : ParsableStream<Lexer<TToken>.Token> where TToken : Enum
{
    protected readonly TToken _endOfSource;

    public ParserContext(Memory<Lexer<TToken>.Token> tokens, TToken endOfSource) : base(tokens)
    {
        _endOfSource = endOfSource;
    }

    public bool Check(TToken type, int offset = 0)
    {
        if (Ended()) return false;
        if (Equals(Peek(offset).Type, _endOfSource)) return false;
        return Equals(Peek(offset).Type, type);
    }

    /// <summary>
    /// Checks whether the passed sequence can be matched against the current parsing context.
    /// </summary>
    /// <param name="sequence"></param>
    /// <returns></returns>
    public bool CheckSequence(params TToken[] sequence)
    {
        for (var i = 0; i < sequence.Length; i++)
        {
            if (!Check(sequence[i], i))
            {
                return false;
            }
        }

        return true;
    }

    public override bool Ended()
    {
        return base.Ended() || Equals(Current.Type, _endOfSource);
    }

    public bool Match(TToken token)
    {
        var matched = Check(token);
        if (matched) Advance();
        return matched;
    }

    public bool MatchAny(params TToken[] types)
    {
        for (var i = 0; i < types.Length; i++)
        {
            if (Check(types[i]))
            {
                Advance();
                return true;
            }
        }

        return false;
    }

    public bool MatchSequence(params TToken[] sequence)
    {
        for (var i = 0; i < sequence.Length; i++)
        {
            if (!Check(sequence[i], i))
            {
                return false;
            }
        }

        for (var i = 0; i < sequence.Length; i++)
        {
            Advance();
        }

        return true;
    }

    public Lexer<TToken>.Token Previous()
    {
        return Peek(-1);
    }

    public Lexer<TToken>.Token Consume(TToken type, string message)
    {
        if (Check(type)) return Advance();
        throw Error(message);
    }

    public Exception Error(string message)
    {
        return new ParsingException(Report.FormatMessage(Current, message));
    }

    public Exception Error(Lexer<TToken>.Token token, string message)
    {
        return new ParsingException(Report.FormatMessage(token, message));
    }

    public void Halt(Lexer<TToken>.Token token, string message)
    {
        throw new ParsingException(Report.FormatMessage(token, message));
    }
}