using System;

using System.Collections;

using System.Collections.Generic;
using Xamarin.Forms;
using System.Threading.Tasks;


namespace PanCardView.Utility
{
    public sealed class AnimationWrapper : IEnumerable
    {
        private readonly List<AnimationWrapper> _children;

        public AnimationWrapper(Action<double> callback = null, double start = 0, double end = 1)
        {
            _children = new List<AnimationWrapper>();

            Callback = callback;

            Start = start;

            End = end;
        }

        public IEnumerator GetEnumerator() => _children.GetEnumerator();



        public double Start { get; private set; }



        public double End { get; private set; }



        public double BeginsAt { get; private set; }



        public double FinishsAt { get; private set; }



        public Action<double> Callback { get; private set; }



        public void Add(double beginAt, double finishAt, AnimationWrapper animation)

        {

            animation.BeginsAt = beginAt;

            animation.FinishsAt = finishAt;

            _children.Add(animation);

        }



        public Task Commit(View view, string name, uint rate = 16u, uint length = 250u, Easing easing = null)

        {

            if (DependencyService.Get<IAnimationsChecker>()?.AreAnimationsEnabled ?? true)

            {

                var tcs = new TaskCompletionSource<bool>();

                PrepareAnimation(this).Commit(view, name, rate, length, easing, (d, b) => tcs.SetResult(true));

                return tcs.Task;

            }



            try

            {

                view.BatchBegin();

                CommitWithoutAnimation(this);

            }

            finally

            {

                view.BatchCommit();
            }

            return Task.FromResult(true);

        }



        private void CommitWithoutAnimation(AnimationWrapper animation)

        {

            foreach (AnimationWrapper childAnimation in animation)

            {

                CommitWithoutAnimation(childAnimation);

            }

            animation.Callback?.Invoke(animation.End);

        }



        private Animation PrepareAnimation(AnimationWrapper animationWrapper)

        {

            var parentAnimation = animationWrapper.Callback != null
                ? new Animation(animationWrapper.Callback, animationWrapper.Start, animationWrapper.End)

                : new Animation();

            foreach (AnimationWrapper childAnimation in animationWrapper)

            {

                var anim = PrepareAnimation(childAnimation);

                parentAnimation.Add(childAnimation.BeginsAt, childAnimation.FinishsAt, anim);

            }

            return parentAnimation;

        }
    }
}