YooAsset/Assets/YooAsset/Runtime/AssetSystem/Provider/ProviderBase.cs

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

namespace YooAsset
{
	internal abstract class ProviderBase
	{
		public enum EStatus
		{
			None = 0,
			CheckBundle,
			Loading,
			Checking,
			Success,
			Fail,
		}

		/// <summary>
		/// 资源路径
		/// </summary>
		public string AssetPath { private set; get; }

		/// <summary>
		/// 资源对象的名称
		/// </summary>
		public string AssetName { private set; get; }

		/// <summary>
		/// 资源对象的类型
		/// </summary>
		public System.Type AssetType { private set; get; }

		/// <summary>
		/// 获取的资源对象
		/// </summary>
		public UnityEngine.Object AssetObject { protected set; get; }

		/// <summary>
		/// 获取的资源对象集合
		/// </summary>
		public UnityEngine.Object[] AllAssetObjects { protected set; get; }

		/// <summary>
		/// 获取的场景对象
		/// </summary>
		public UnityEngine.SceneManagement.Scene SceneObject { protected set; get; }


		/// <summary>
		/// 当前的加载状态
		/// </summary>
		public EStatus Status { protected set; get; } = EStatus.None;

		/// <summary>
		/// 引用计数
		/// </summary>
		public int RefCount { private set; get; } = 0;

		/// <summary>
		/// 是否已经销毁
		/// </summary>
		public bool IsDestroyed { private set; get; } = false;

		/// <summary>
		/// 是否完毕（成功或失败）
		/// </summary>
		public bool IsDone
		{
			get
			{
				return Status == EStatus.Success || Status == EStatus.Fail;
			}
		}

		/// <summary>
		/// 加载进度
		/// </summary>
		public virtual float Progress
		{
			get
			{
				return 0;
			}
		}


		protected bool IsWaitForAsyncComplete { private set; get; } = false;
		private readonly List<OperationHandleBase> _handles = new List<OperationHandleBase>();


		public ProviderBase(string assetPath, System.Type assetType)
		{
			AssetPath = assetPath;
			AssetName = System.IO.Path.GetFileName(assetPath);
			AssetType = assetType;
		}

		/// <summary>
		/// 轮询更新方法
		/// </summary>
		public abstract void Update();

		/// <summary>
		/// 销毁资源对象
		/// </summary>
		public virtual void Destory()
		{
			IsDestroyed = true;
			_taskCompletionSource = null;
		}

		/// <summary>
		/// 是否可以销毁
		/// </summary>
		public bool CanDestroy()
		{
			if (IsDone == false)
				return false;

			return RefCount <= 0;
		}

		/// <summary>
		/// 创建操作句柄
		/// </summary>
		/// <returns></returns>
		public OperationHandleBase CreateHandle()
		{
			// 引用计数增加
			RefCount++;

			OperationHandleBase handle;
			if (IsSceneProvider())
				handle = new SceneOperationHandle(this);
			else if (IsSubAssetsProvider())
				handle = new SubAssetsOperationHandle(this);
			else
				handle = new AssetOperationHandle(this);

			_handles.Add(handle);
			return handle;
		}

		/// <summary>
		/// 释放操作句柄
		/// </summary>
		public void ReleaseHandle(OperationHandleBase handle)
		{
			if (RefCount <= 0)
				YooLogger.Warning("Asset provider reference count is already zero. There may be resource leaks !");

			if (_handles.Remove(handle) == false)
				throw new System.Exception("Should never get here !");

			// 引用计数减少
			RefCount--;
		}

		/// <summary>
		/// 是否为场景提供者
		/// </summary>
		public bool IsSceneProvider()
		{
			if (this is BundledSceneProvider || this is DatabaseSceneProvider)
				return true;
			else
				return false;
		}

		/// <summary>
		/// 是否为子资源对象提供者
		/// </summary>
		public bool IsSubAssetsProvider()
		{
			if (this is BundledSubAssetsProvider || this is DatabaseSubAssetsProvider)
				return true;
			else
				return false;
		}

		/// <summary>
		/// 等待异步执行完毕
		/// </summary>
		public void WaitForAsyncComplete()
		{
			IsWaitForAsyncComplete = true;

			// 注意：主动轮询更新完成同步加载
			Update();

			// 验证结果
			if (IsDone == false)
			{
				YooLogger.Warning($"WaitForAsyncComplete failed to loading : {AssetPath}");
			}
		}

		/// <summary>
		/// 异步操作任务
		/// </summary>
		public Task<object> Task
		{
			get
			{
				if(_taskCompletionSource == null)
				{
					_taskCompletionSource = new TaskCompletionSource<object>();
					if (IsDone)
						_taskCompletionSource.SetResult(this);
				}
				return _taskCompletionSource.Task;
			}
		}

		#region 异步编程相关
		private TaskCompletionSource<object> _taskCompletionSource;
		protected void InvokeCompletion()
		{
			// 注意：创建临时列表是为了防止外部逻辑在回调函数内创建或者释放资源句柄。
			List<OperationHandleBase> tempers = new List<OperationHandleBase>(_handles);
			foreach (var hande in tempers)
			{
				if (hande.IsValid)
				{
					hande.InvokeCallback();
				}
			}

			if(_taskCompletionSource != null)
				_taskCompletionSource.TrySetResult(this);
		}
		#endregion
	}
}