CanonSharp/CanonSharp.Combinator/Abstractions/IFailedResult.cs

namespace CanonSharp.Combinator.Abstractions;

/// <summary>
/// 失败解析结果基类
/// </summary>
/// <typeparam name="TToken">输入流类型</typeparam>
/// <typeparam name="T">解析结果类型</typeparam>
public interface IFailedResult<TToken, out T> : IParseResult<TToken, T>
{
    T IParseResult<TToken, T>.Value => throw Exception;

    /// <summary>
    /// 当前读取到的状态
    /// </summary>
    public IReadState<TToken> State { get; }

    /// <summary>
    /// 解析失败的消息
    /// </summary>
    public string Message { get; }

    /// <summary>
    /// 解析失败的异常
    /// </summary>
    public ParseException Exception => new(Message);

    /// <summary>
    /// 转换该失败结果的类型
    /// </summary>
    /// <typeparam name="TNext">转换之后的结果类型</typeparam>
    /// <returns>转换之后的失败解析类型</returns>
    public IFailedResult<TToken, TNext> Convert<TNext>();

    IParseResult<TToken, TResult> IParseResult<TToken, T>.Next<TNext, TResult>(
        Func<T, IParser<TToken, TNext>> nextParser,
        Func<IParseResult<TToken, TNext>, IParseResult<TToken, TResult>> continuation)
        => continuation(Convert<TNext>());

    IParseResult<TToken, TResult> IParseResult<TToken, T>.Map<TResult>(Func<T, TResult> map)
        => Convert<TResult>();

    TResult IParseResult<TToken, T>.CaseOf<TResult>(Func<ISuccessfulResult<TToken, T>, TResult> successfulHandler,
        Func<IFailedResult<TToken, T>, TResult> failedHandler)
        => failedHandler(this);
}