using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using UnityEngine;

namespace AibisDream.FrameAnimation
{
    public sealed class FrameAnimationPlaybackHandle : CustomYieldInstruction
    {
        private readonly TaskCompletionSource<FrameAnimationPlaybackResult> completionSource =
            new TaskCompletionSource<FrameAnimationPlaybackResult>(TaskCreationOptions.RunContinuationsAsynchronously);
        private readonly List<Action<FrameAnimationPlaybackResult>> callbacks =
            new List<Action<FrameAnimationPlaybackResult>>();

        private bool isCompleted;
        private FrameAnimationPlaybackResult result;

        public long RequestId { get; }
        public bool IsCompleted => isCompleted;
        public override bool keepWaiting => !isCompleted;

        public FrameAnimationPlaybackResult Result
        {
            get
            {
                if (!isCompleted)
                {
                    throw new InvalidOperationException("播放请求尚未完成，不能读取 Result。");
                }

                return result;
            }
        }

        internal FrameAnimationPlaybackHandle(long requestId)
        {
            RequestId = requestId;
        }

        public Task<FrameAnimationPlaybackResult> WaitAsync()
        {
            return completionSource.Task;
        }

        public void RegisterCompleted(Action<FrameAnimationPlaybackResult> callback)
        {
            if (callback == null)
            {
                throw new ArgumentNullException(nameof(callback));
            }

            if (isCompleted)
            {
                InvokeCallback(callback, result);
                return;
            }

            callbacks.Add(callback);
        }

        internal bool TryComplete(FrameAnimationPlaybackResult completionResult)
        {
            if (isCompleted)
            {
                return false;
            }

            isCompleted = true;
            result = completionResult;
            completionSource.TrySetResult(completionResult);

            var callbacksToInvoke = callbacks.ToArray();
            callbacks.Clear();
            foreach (var callback in callbacksToInvoke)
            {
                InvokeCallback(callback, completionResult);
            }

            return true;
        }

        private static void InvokeCallback(
            Action<FrameAnimationPlaybackResult> callback,
            FrameAnimationPlaybackResult completionResult)
        {
            try
            {
                callback(completionResult);
            }
            catch (Exception exception)
            {
                Debug.LogException(exception);
            }
        }
    }
}