using CanonSharp.Combinator.Abstractions;

namespace CanonSharp.Combinator.Parsers.Bases;

/// <summary>
/// 映射解析器
/// 提供一个函数修改上游解析器返回的结果
/// </summary>
/// <param name="parser">上游解析器</param>
/// <param name="func">修改上游解析器返回结果的</param>
/// <typeparam name="TToken"></typeparam>
/// <typeparam name="TIntermediate"></typeparam>
/// <typeparam name="T"></typeparam>
internal sealed class MapParser<TToken, TIntermediate, T>(
    Parser<TToken, TIntermediate> parser,
    Func<TIntermediate, T> func) : Parser<TToken, T>
{
    internal override ParseResult<TToken, TResult> Run<TState, TResult>(TState state,
        Func<ParseResult<TToken, T>, ParseResult<TToken, TResult>> continuation)
        => parser.Run(state, result => continuation(result.Map(func)));
}