// Copyright (c) The Geekeey Authors
// SPDX-License-Identifier: EUPL-1.2

#pragma warning disable CA1716

namespace Geekeey.Request.Result;

/// <summary>
/// An error containing a simple message. Makes up the other half of a <see cref="Result{T}"/> which might be an error.
/// </summary>
/// <remarks>
/// An error is conceptually very similar to an exception but without the ability to be thrown, meant to be a more
/// lightweight type meant to be wrapped in a <see cref="Result{T}"/>.
/// An error fundamentally only contains a single string message, however other more concrete types such as
/// <see cref="ExceptionError"/> or <see cref="AggregateError"/> may define other properties.
/// Errors are meant to be small, specific, and descriptive, such that they are easy to match over and provide specific
/// handling for specific kinds of errors.
/// </remarks>
public abstract class Error
{
	/// <summary>
	/// A statically accessible default "Result has no value." error.
	/// </summary>
	internal static Error DefaultValueError { get; } = new StringError("The result has no value.");

	/// <summary>
	/// The message used to display the error.
	/// </summary>
	public abstract string Message { get; }

	/// <summary>
	/// Gets a string representation of the error. Returns <see cref="Message"/> by default.
	/// </summary>
	public override string ToString()
	{
		return Message;
	}

	/// <summary>
	/// Implicitly converts a string into a <see cref="StringError"/>.
	/// </summary>
	/// <param name="message">The message of the error.</param>
	public static implicit operator Error(string message)
	{
		return new StringError(message);
	}

	/// <summary>
	/// Implicitly converts an exception into an <see cref="ExceptionError"/>.
	/// </summary>
	/// <param name="exception">The exception to convert.</param>
	public static implicit operator Error(Exception exception)
	{
		return new ExceptionError(exception);
	}
}