GhostEngine/Ghost.Core/Result.cs

using System.Runtime.CompilerServices;

namespace Ghost.Core;

public readonly struct Result
{
    private readonly bool _isSuccess;
    private readonly string? _message;

    public readonly bool IsSuccess => _isSuccess;
    public readonly bool IsFailure => !_isSuccess;

    public readonly string? Message => _message;

    public Result(bool success, string? message = null)
    {
        _isSuccess = success;
        _message = message;
    }

    public static Result Success()
    {
        return new Result(true);
    }

    public static Result Failure(string? message = null)
    {
        return new Result(false, message);
    }

    public static Result<T> Success<T>(T value)
    {
        return Result<T>.Success(value);
    }

    public static Result<T> Failure<T>(string? message = null)
    {
        return Result<T>.Failure(message);
    }

    public static Result<T, S> Create<T, S>(T value, S status)
        where S : Enum
    {
        return new Result<T, S>(value, status);
    }

    public static RefResult<T, S> CreateRef<T, S>(ref T value, S status)
        where S : Enum
    {
        return new RefResult<T, S>(ref value, status);
    }

    public override string ToString() => IsSuccess ? "OK" : $"Error: {Message}";

    public static implicit operator bool(Result result) => result.IsSuccess;
}

public readonly struct Result<T>
{
    private readonly bool _isSuccess;
    private readonly T _value;
    private readonly string? _message;

    public readonly bool IsSuccess => _isSuccess;
    public readonly bool IsFailure => !_isSuccess;

    public readonly T Value => _value;
    public readonly string? Message => _message;

    public Result(bool success, T value, string? message = null)
    {
        _isSuccess = success;
        _value = value;
        _message = message;
    }

    public static Result<T> Success(T value)
    {
        return new Result<T>(true, value);
    }

    public static Result<T> Failure(string? message = null)
    {
        return new Result<T>(false, default!, message);
    }

    public override string ToString() => IsSuccess ? $"OK: {Value}" : $"Error: {Message}";

    public static implicit operator Result<T>(T? data) => data is not null ? Success(data) : Failure(null);
    public static implicit operator Result<T>(Result result) => result.IsSuccess ? Success(default!) : Failure(result.Message);
    public static implicit operator bool(Result<T> result) => result.IsSuccess;
}

public enum ResultStatus : byte
{
    Success,
    NotFound,
    InvalidArgument,
    InvalidState,
    InternalError,
    PermissionDenied,
    NotSupported,
    OutOfMemory,
    Timeout,
    Cancelled,
    UnknownError
}

public readonly struct Result<T, S>
    where S : Enum
{
    private readonly T _value;
    private readonly S _status;

    public T Value => _value;
    public S Status => _status;

    public Result(T value, S status)
    {
        _value = value;
        _status = status;
    }

    public static Result<T, S> Create(T value, S status)
    {
        return new Result<T, S>(value, status);
    }

    public override string ToString() => $"Value: {_value}, Status: {_status}";
}

public readonly ref struct RefResult<T, S>
    where S : Enum
{
    private readonly ref T _value;
    private readonly S _status;

    public ref T Value => ref _value;
    public S Status => _status;

    public RefResult(ref T value, S status)
    {
        _value = ref value;
        _status = status;
    }

    public static RefResult<T, S> Create(ref T value, S status)
    {
        return new RefResult<T, S>(ref value, status);
    }

    public override string ToString() => $"Value: {_value}, Status: {_status}";
}

public static class ResultExtensions
{
    public static void ThrowIfFailed(this ResultStatus result, [CallerArgumentExpression(nameof(result))] string? op = null)
    {
        if (result != ResultStatus.Success)
        {
            throw new InvalidOperationException($"{op} failed: {result}");
        }
    }

    public static void ThrowIfFailed(this Result result, [CallerArgumentExpression(nameof(result))] string? op = null)
    {
        if (!result.IsSuccess)
        {
            throw new InvalidOperationException($"{op} failed: {result.Message}");
        }
    }

    public static T GetValueOrThrow<T>(this Result<T> result, [CallerArgumentExpression(nameof(result))] string? op = null)
    {
        if (!result.IsSuccess)
        {
            throw new InvalidOperationException($"{op} failed: {result.Message}");
        }

        return result.Value;
    }

    public static T GetValueOrThrow<T, S>(this Result<T, S> result, S expect, [CallerArgumentExpression(nameof(result))] string? op = null)
        where S : Enum
    {
        if (!EqualityComparer<S>.Default.Equals(result.Status, expect))
        {
            throw new InvalidOperationException($"{op} failed: expected status {expect}, but got {result.Status}");
        }

        return result.Value;
    }

    public static T? GetValueOrDefault<T>(this Result<T> result, T? defaultValue = default)
    {
        return result.IsSuccess ? result.Value : defaultValue;
    }

    public static T? GetValueOrDefault<T, S>(this Result<T, S> result, S expect, T? defaultValue = default)
        where S : Enum
    {
        return (result.Status?.Equals(expect) ?? false) ? defaultValue : result.Value;
    }

    public static bool TryGetValue<T>(this Result<T> result, out T value)
    {
        if (result.IsSuccess)
        {
            value = result.Value;
            return true;
        }

        value = default!;
        return false;
    }

    public static bool TryGetValue<T, S>(this Result<T, S> result, S expect, out T value)
        where S : Enum
    {
        if (EqualityComparer<S>.Default.Equals(result.Status, expect))
        {
            value = result.Value;
            return true;
        }

        value = default!;
        return false;
    }

    public static Result OnSuccess(this Result result, Action action)
    {
        if (result.IsSuccess)
        {
            action();
        }

        return result;
    }

    public static Result<T> OnSuccess<T>(this Result<T> result, Action<T> action)
    {
        if (result.IsSuccess)
        {
            action(result.Value);
        }

        return result;
    }

    public static Result OnFailed(this Result result, Action<string?> action)
    {
        if (result.IsFailure)
        {
            action(result.Message);
        }

        return result;
    }

    public static Result<T> OnFailed<T>(this Result<T> result, Action<string?> action)
    {
        if (result.IsFailure)
        {
            action(result.Message);
        }

        return result;
    }
}