spectre.console/src/Spectre.Console/Extensions/AnsiConsoleExtensions.Async.cs

namespace Spectre.Console.Extensions;

/// <summary>
/// Provides extension methods for running tasks with a spinner animation.
/// </summary>
public static class SpinnerExtensions
{
    /// <summary>
    /// Runs a task with a spinner animation.
    /// </summary>
    /// <param name="task">The task to run.</param>
    /// <param name="spinner">The spinner to use.</param>
    /// <param name="style">The style to apply to the spinner.</param>
    /// <param name="ansiConsole">The console to write to.</param>
    /// <returns>The result of the task.</returns>
    public static async Task Spinner(this Task task, Spinner? spinner = null, Style? style = null, IAnsiConsole? ansiConsole = null)
    {
        await SpinnerInternal<object>(task, spinner ?? Console.Spinner.Known.Default, style, ansiConsole);
    }

    /// <summary>
    /// Runs a task with a spinner animation.
    /// </summary>
    /// <typeparam name="T">The type of the task result.</typeparam>
    /// <param name="task">The task to run.</param>
    /// <param name="spinner">The spinner to use.</param>
    /// <param name="style">The style to apply to the spinner.</param>
    /// <param name="ansiConsole">The console to write to.</param>
    /// <returns>The result of the task.</returns>
    public static async Task<T> Spinner<T>(this Task<T> task, Spinner? spinner = null, Style? style = null, IAnsiConsole? ansiConsole = null)
    {
        return (await SpinnerInternal<T>(task, spinner ?? Console.Spinner.Known.Default, style, ansiConsole))!;
    }

    private static async Task<T?> SpinnerInternal<T>(Task task, Spinner spinner, Style? style = null, IAnsiConsole? ansiConsole = null)
    {
        ansiConsole ??= AnsiConsole.Console;

        style ??= Style.Plain;
        var currentFrame = 0;
        var cancellationTokenSource = new CancellationTokenSource();

        // Start spinner animation in background
        var spinnerTask = Task.Run(
            async () =>
        {
            while (!cancellationTokenSource.Token.IsCancellationRequested)
            {
                ansiConsole.Cursor.Show(false);

                var spinnerFrame = spinner.Frames[currentFrame];

                // Write the spinner frame
                ansiConsole.Write(new Text(spinnerFrame, style));
                ansiConsole.Write(new ControlCode(AnsiSequences.CUB(spinnerFrame.Length)));

                currentFrame = (currentFrame + 1) % spinner.Frames.Count;
                await Task.Delay(spinner.Interval, cancellationTokenSource.Token);
            }
        }, cancellationTokenSource.Token);

        try
        {
            // Wait for the actual task to complete
            if (task is Task<T> taskWithResult)
            {
                var result = await taskWithResult;
                await cancellationTokenSource.CancelAsync();
                await spinnerTask.ContinueWith(_ => { }, TaskContinuationOptions.OnlyOnCanceled);

                return result;
            }
            else
            {
                await task;
                await cancellationTokenSource.CancelAsync();
                await spinnerTask.ContinueWith(_ => { }, TaskContinuationOptions.OnlyOnCanceled);

                return default;
            }
        }
        finally
        {
            var spinnerFrame = spinner.Frames[currentFrame];

            ansiConsole.Write(new string(' ', spinnerFrame.Length));
            ansiConsole.Write(new ControlCode(AnsiSequences.CUB(spinnerFrame.Length)));
            ansiConsole.Cursor.Show();
            await cancellationTokenSource.CancelAsync();
        }
    }
}