TransitionAnimation.cs

using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Maui.Controls;
 
namespace NeuroAccessMaui.Animations
{
    public sealed class TransitionAnimation : ITransitionAnimation
    {
        private readonly IViewAnimation? enterAnimation;
        private readonly IViewAnimation? exitAnimation;
        private readonly IViewAnimation? overlayAnimation;
 
        public TransitionAnimation(IViewAnimation? EnterAnimation, IViewAnimation? ExitAnimation, IViewAnimation? OverlayAnimation = null)
        {
            this.enterAnimation = EnterAnimation;
            this.exitAnimation = ExitAnimation;
            this.overlayAnimation = OverlayAnimation;
        }
 
        public async Task RunAsync(VisualElement? Entering, VisualElement? Exiting, IAnimationContext Context, AnimationOptions? Options, CancellationToken Token)
        {
            ArgumentNullException.ThrowIfNull(Context);
            List<Task> Tasks = new List<Task>(3);
 
            if (this.enterAnimation is not null && Entering is not null)
                Tasks.Add(this.enterAnimation.RunAsync(Entering, Context, Options, Token));
 
            if (this.exitAnimation is not null && Exiting is not null)
                Tasks.Add(this.exitAnimation.RunAsync(Exiting, Context, Options, Token));
 
            if (this.overlayAnimation is not null)
            {
                VisualElement Anchor = Entering ?? Exiting ?? throw new InvalidOperationException("Overlay animations require at least one visual element.");
                Tasks.Add(this.overlayAnimation.RunAsync(Anchor, Context, Options, Token));
            }
 
            if (Tasks.Count == 0)
                return;
 
            await Task.WhenAll(Tasks);
        }
    }
}