using System;
using System.Collections.Generic;
using UnityEngine;

namespace TyphoonUI
{
    /// <summary>
    /// UI活动队列
    /// </summary>
    internal class UIOperationQueue : MonoBehaviour, IOperationQueue
    {
        private readonly Queue<UIOperationHandler> _queue = new Queue<UIOperationHandler>();

        private UIOperationQueue()
        {
        }

        /// <summary>
        /// 是否在处理中
        /// </summary>
        private bool _isHandling = false;

        /// <summary>
        /// 初始化
        /// </summary>
        public void Initialize()
        {
            DontDestroyOnLoad(gameObject);
            UIOperation.OnStateChanged += OnOperationStatusChanged;
        }

        /// <summary>
        /// 加入队列
        /// </summary>
        public IOperationQueue Enqueue(Action handler)
        {
            var operationHandler = UIOperation.Create((h) =>
            {
                handler?.Invoke();
                //默认执行完后完成
                h.ToFinishStatus();
            });
            //加入队列
            _queue.Enqueue(operationHandler);
            return this;
        }

        /// <summary>
        /// 加入队列
        /// </summary>
        public IOperationQueue Enqueue(Action<UIOperationHandler> handler)
        {
            var operation = UIOperation.Create(handler);
            _queue.Enqueue(operation);
            return this;
        }

        /// <summary>
        /// 中断
        /// </summary>
        public void Interrupt()
        {
            while (_queue.Count > 0)
            {
                var operation = _queue.Dequeue();
                operation.Release();
            }

            if (!_isHandling)
            {
                HandleOperation();
            }
        }

        /// <summary>
        /// 执行队列
        /// </summary>
        public void Run()
        {
            if (!_isHandling)
            {
                HandleOperation();
            }
        }

        //处理活动队列
        private void HandleOperation()
        {
            _isHandling = true;
            if (_queue.Count <= 0)
            {
                _isHandling = false;
                return;
            }

            while (_queue.Count > 0)
            {
                var peek = _queue.Peek();
                if (peek.IsValid())
                {
                    _queue.Dequeue();
                    continue;
                }

                switch (peek.GetStatus())
                {
                    case OperationStatus.Ready:
                        //执行行为
                        peek.Run();
                        break;
                    case OperationStatus.Running:
                        //执行中，暂时退出
                        _isHandling = false;
                        return;
                    case OperationStatus.Finish:
                        var operation = _queue.Dequeue();
                        operation.Release();
                        break;
                }
            }

            if (_queue.Count <= 0)
            {
                _isHandling = false;
            }
        }


        private void OnOperationStatusChanged(long operationId)
        {
            if (_isHandling)
            {
                return;
            }

            //继续执行
            if (_queue.Count > 0 && _queue.Peek().Id == operationId)
            {
                HandleOperation();
            }
        }
    }
}