namespace Umbraco.Cms.Core;

/// <summary>
///     Represents the result of an operation attempt.
/// </summary>
/// <typeparam name="TResult">The type of the attempted operation result.</typeparam>
[Serializable]
public struct Attempt<TResult>
{
    // optimize, use a singleton failed attempt
    private static readonly Attempt<TResult> Failed = new(false, default, null);

    // private - use Succeed() or Fail() methods to create attempts
    private Attempt(bool success, TResult? result, Exception? exception)
    {
        Success = success;
        Result = result;
        Exception = exception;
    }

    /// <summary>
    ///     Gets a value indicating whether this <see cref="Attempt{TResult}" /> was successful.
    /// </summary>
    public bool Success { get; }

    /// <summary>
    ///     Gets the exception associated with an unsuccessful attempt.
    /// </summary>
    public Exception? Exception { get; }

    /// <summary>
    ///     Gets the attempt result.
    /// </summary>
    public TResult? Result { get; }

    /// <summary>
    ///     Implicitly operator to check if the attempt was successful without having to access the 'success' property
    /// </summary>
    /// <param name="a"></param>
    /// <returns></returns>
    public static implicit operator bool(Attempt<TResult> a) => a.Success;

    /// <summary>
    ///     Gets the attempt result, if successful, else a default value.
    /// </summary>
    public TResult ResultOr(TResult value)
    {
        if (Success && Result is not null)
        {
            return Result;
        }

        return value;
    }

    /// <summary>
    ///     Creates a successful attempt.
    /// </summary>
    /// <returns>The successful attempt.</returns>
    public static Attempt<TResult> Succeed() => new(true, default, null);

    /// <summary>
    ///     Creates a successful attempt with a result.
    /// </summary>
    /// <param name="result">The result of the attempt.</param>
    /// <returns>The successful attempt.</returns>
    public static Attempt<TResult> Succeed(TResult? result) => new(true, result, null);

    /// <summary>
    ///     Creates a failed attempt.
    /// </summary>
    /// <returns>The failed attempt.</returns>
    public static Attempt<TResult> Fail() => Failed;

    /// <summary>
    ///     Creates a failed attempt with an exception.
    /// </summary>
    /// <param name="exception">The exception causing the failure of the attempt.</param>
    /// <returns>The failed attempt.</returns>
    public static Attempt<TResult> Fail(Exception? exception) => new(false, default, exception);

    /// <summary>
    ///     Creates a failed attempt with a result.
    /// </summary>
    /// <param name="result">The result of the attempt.</param>
    /// <returns>The failed attempt.</returns>
    public static Attempt<TResult> Fail(TResult result) => new(false, result, null);

    /// <summary>
    ///     Creates a failed attempt with a result and an exception.
    /// </summary>
    /// <param name="result">The result of the attempt.</param>
    /// <param name="exception">The exception causing the failure of the attempt.</param>
    /// <returns>The failed attempt.</returns>
    public static Attempt<TResult?> Fail(TResult result, Exception exception) => new(false, result, exception);

    /// <summary>
    ///     Creates a successful or a failed attempt.
    /// </summary>
    /// <param name="condition">A value indicating whether the attempt is successful.</param>
    /// <returns>The attempt.</returns>
    public static Attempt<TResult> If(bool condition) => condition ? new Attempt<TResult>(true, default, null) : Failed;

    /// <summary>
    ///     Creates a successful or a failed attempt, with a result.
    /// </summary>
    /// <param name="condition">A value indicating whether the attempt is successful.</param>
    /// <param name="result">The result of the attempt.</param>
    /// <returns>The attempt.</returns>
    public static Attempt<TResult> If(bool condition, TResult? result) => new(condition, result, null);
}