Govor/Govor.Domain/Common/Result.cs

namespace Govor.Domain.Common;

public class Result
{
    protected Result(bool isSuccess, Error error)
    {
        if (isSuccess && error != Error.None || !isSuccess && error == Error.None)
        {
            throw new ArgumentException("Invalid error state", nameof(error));
        }

        IsSuccess = isSuccess;
        Error = error;
    }

    public bool IsSuccess { get; }
    public bool IsFailure => !IsSuccess;
    public Error Error { get; }

    public static Result Success() => new(true, Error.None);
    public static Result Failure(Error error) => new(false, error);
    
    public static Result Failure(Exception ex) => new(false, new Error(ex.GetType().Name, ex.Message));
    
    public static implicit operator Result(Error error) => Failure(error);
}

public class Result<T> : Result
{
    private readonly T? _value;
    
    private Result(T? value, bool isSuccess, Error error) : base(isSuccess, error)
    {
        _value = value;
    }

    public T Value => IsSuccess 
        ? _value! 
        : throw new InvalidOperationException("The value of a failure result cannot be accessed.");

    public static Result<T> Success(T value) => new(value, true, Error.None);
    public static new Result<T> Failure(Error error) => new(default, false, error);
    public static new Result<T> Failure(Exception ex) => new(default, false, new Error(ex.GetType().Name, ex.Message));

    public static implicit operator Result<T>(T value) =>  Success(value);

    public static implicit operator Result<T>(Error error) => Failure(error);
    public static implicit operator T(Result<T> result) => result.Value;
}