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

namespace CanonSharp.Combinator.Parsers.Primitives;

/// <summary>
/// 解析指定数量的解析器
/// </summary>
/// <param name="count">需要解析的数量</param>
/// <typeparam name="TToken">输入流类型</typeparam>
internal sealed class TakeParser<TToken>(int count) : PrimitiveParser<TToken, IEnumerable<TToken>>
{
    protected override IParseResult<TToken, IEnumerable<TToken>> Run<TState>(TState state)
    {
        List<TState> result = state.AsEnumerable<TToken, TState>().Take(count).ToList();

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