using CanonSharp.Combinator.Abstractions;
using CanonSharp.Combinator.Extensions;

namespace CanonSharp.Combinator.Parsers.Primitives;

/// <summary>
/// 跳过指定数量的输入令牌
/// </summary>
/// <param name="count">需要跳过的令牌数量</param>
/// <typeparam name="TToken">输入流类型</typeparam>
internal sealed class SkipParser<TToken>(int count) : PrimitiveParser<TToken, Unit>
{
    protected override IParseResult<TToken, Unit> Run<TState>(TState state)
    {
        List<TState> result = state.AsEnumerable<TToken, TState>().Take(count).ToList();

        return result.Count == count
            ? ParseResultBuilder.Succeed<TToken, TState, Unit>(Unit.Instance,
                result.Count == 0 ? state : result.Last().Next)
            : ParseResultBuilder.Fail<TToken, TState, Unit>("An input does not have required length.", state);
    }
}