using CanonSharp.Combinator.Abstractions;

namespace CanonSharp.Combinator.Parsers.Bases;

/// <summary>
/// 恢复解析器
/// 在上游解析器失败的情况下调用指定恢复函数返回的解析器
/// </summary>
/// <param name="parser">上游解析器</param>
/// <param name="failedHandler">返回新解析器的恢复函数</param>
/// <typeparam name="TToken">输入令牌类型</typeparam>
/// <typeparam name="T">解析结果类型</typeparam>
internal sealed class ResumeParser<TToken, T>(
    IParser<TToken, T> parser,
    Func<IFailedResult<TToken, T>, IParser<TToken, T>> failedHandler) : IParser<TToken, T>
{
    public IParseResult<TToken, TResult> Run<TState, TResult>(TState state,
        Func<IParseResult<TToken, T>, IParseResult<TToken, TResult>> continuation)
        where TState : IReadState<TToken, TState>
    {
        return parser.Run(state,
            result => result.CaseOf(continuation,
                failedResult => failedHandler(failedResult).Run(state, continuation)));
    }
}