using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Threading;

namespace YooAsset
{
	internal abstract class VerifyCacheFilesOperation : AsyncOperationBase
	{
		public static VerifyCacheFilesOperation CreateOperation(List<VerifyCacheElement> elements)
		{
#if UNITY_WEBGL
			var operation = new VerifyCacheFilesWithoutThreadOperation(elements);
#else
			var operation = new VerifyCacheFilesWithThreadOperation(elements);
#endif
			return operation;
		}
	}

	/// <summary>
	/// 本地缓存文件验证（线程版）
	/// </summary>
	internal class VerifyCacheFilesWithThreadOperation : VerifyCacheFilesOperation
	{
		private enum ESteps
		{
			None,
			InitVerify,
			UpdateVerify,
			Done,
		}

		private readonly ThreadSyncContext _syncContext = new ThreadSyncContext();
		private List<VerifyCacheElement> _waitingList;
		private List<VerifyCacheElement> _verifyingList;
		private int _verifyMaxNum;
		private int _verifyTotalCount;
		private float _verifyStartTime;
		private int _succeedCount;
		private int _failedCount;
		private ESteps _steps = ESteps.None;

		public VerifyCacheFilesWithThreadOperation(List<VerifyCacheElement> elements)
		{
			_waitingList = elements;
		}
		internal override void Start()
		{
			_steps = ESteps.InitVerify;
			_verifyStartTime = UnityEngine.Time.realtimeSinceStartup;
		}
		internal override void Update()
		{
			if (_steps == ESteps.None || _steps == ESteps.Done)
				return;

			if (_steps == ESteps.InitVerify)
			{
				int fileCount = _waitingList.Count;

				// 设置同时验证的最大数
				ThreadPool.GetMaxThreads(out int workerThreads, out int ioThreads);
				YooLogger.Log($"Work threads : {workerThreads}, IO threads : {ioThreads}");
				_verifyMaxNum = Math.Min(workerThreads, ioThreads);
				_verifyTotalCount = fileCount;
				if (_verifyMaxNum < 1)
					_verifyMaxNum = 1;

				_verifyingList = new List<VerifyCacheElement>(_verifyMaxNum);
				_steps = ESteps.UpdateVerify;
			}

			if (_steps == ESteps.UpdateVerify)
			{
				_syncContext.Update();

				Progress = GetProgress();
				if (_waitingList.Count == 0 && _verifyingList.Count == 0)
				{
					_steps = ESteps.Done;
					Status = EOperationStatus.Succeed;
					float costTime = UnityEngine.Time.realtimeSinceStartup - _verifyStartTime;
					YooLogger.Log($"Verify cache files elapsed time {costTime:f1} seconds");
				}

				for (int i = _waitingList.Count - 1; i >= 0; i--)
				{
					if (OperationSystem.IsBusy)
						break;

					if (_verifyingList.Count >= _verifyMaxNum)
						break;

					var element = _waitingList[i];
					if (BeginVerifyFileWithThread(element))
					{
						_waitingList.RemoveAt(i);
						_verifyingList.Add(element);
					}
					else
					{
						YooLogger.Warning("The thread pool is failed queued.");
						break;
					}
				}
			}
		}

		private float GetProgress()
		{
			if (_verifyTotalCount == 0)
				return 1f;
			return (float)(_succeedCount + _failedCount) / _verifyTotalCount;
		}
		private bool BeginVerifyFileWithThread(VerifyCacheElement element)
		{
			return ThreadPool.QueueUserWorkItem(new WaitCallback(VerifyInThread), element);
		}
		private void VerifyInThread(object obj)
		{
			VerifyCacheElement element = (VerifyCacheElement)obj;
			element.Result = CacheSystem.VerifyingCacheFile(element);
			_syncContext.Post(VerifyCallback, element);
		}
		private void VerifyCallback(object obj)
		{
			VerifyCacheElement element = (VerifyCacheElement)obj;
			_verifyingList.Remove(element);

			if (element.Result == EVerifyResult.Succeed)
			{
				_succeedCount++;
				var wrapper = new PackageCache.RecordWrapper(element.InfoFilePath, element.DataFilePath, element.DataFileCRC, element.DataFileSize);
				CacheSystem.RecordFile(element.PackageName, element.CacheGUID, wrapper);
			}
			else
			{
				_failedCount++;

				YooLogger.Warning($"Failed verify file and delete files : {element.FileRootPath}");
				element.DeleteFiles();
			}
		}
	}

	/// <summary>
	/// 本地缓存文件验证（非线程版）
	/// </summary>
	internal class VerifyCacheFilesWithoutThreadOperation : VerifyCacheFilesOperation
	{
		private enum ESteps
		{
			None,
			InitVerify,
			UpdateVerify,
			Done,
		}

		private List<VerifyCacheElement> _waitingList;
		private List<VerifyCacheElement> _verifyingList;
		private int _verifyMaxNum;
		private int _verifyTotalCount;
		private float _verifyStartTime;
		private int _succeedCount;
		private int _failedCount;
		private ESteps _steps = ESteps.None;
		
		public VerifyCacheFilesWithoutThreadOperation(List<VerifyCacheElement> elements)
		{
			_waitingList = elements;
		}
		internal override void Start()
		{
			_steps = ESteps.InitVerify;
			_verifyStartTime = UnityEngine.Time.realtimeSinceStartup;
		}
		internal override void Update()
		{
			if (_steps == ESteps.None || _steps == ESteps.Done)
				return;

			if (_steps == ESteps.InitVerify)
			{
				int fileCount = _waitingList.Count;

				// 设置同时验证的最大数
				_verifyMaxNum = fileCount;
				_verifyTotalCount = fileCount;

				_verifyingList = new List<VerifyCacheElement>(_verifyMaxNum);
				_steps = ESteps.UpdateVerify;
			}

			if (_steps == ESteps.UpdateVerify)
			{
				Progress = GetProgress();
				if (_waitingList.Count == 0 && _verifyingList.Count == 0)
				{
					_steps = ESteps.Done;
					Status = EOperationStatus.Succeed;
					float costTime = UnityEngine.Time.realtimeSinceStartup - _verifyStartTime;
					YooLogger.Log($"Package verify elapsed time {costTime:f1} seconds");
				}

				for (int i = _waitingList.Count - 1; i >= 0; i--)
				{
					if (OperationSystem.IsBusy)
						break;

					if (_verifyingList.Count >= _verifyMaxNum)
						break;

					var element = _waitingList[i];
					BeginVerifyFileWithoutThread(element);
					_waitingList.RemoveAt(i);
					_verifyingList.Add(element);
				}

				// 主线程内验证，可以清空列表
				_verifyingList.Clear();
			}
		}

		private float GetProgress()
		{
			if (_verifyTotalCount == 0)
				return 1f;
			return (float)(_succeedCount + _failedCount) / _verifyTotalCount;
		}
		private void BeginVerifyFileWithoutThread(VerifyCacheElement element)
		{
			element.Result = CacheSystem.VerifyingCacheFile(element);
			if (element.Result == EVerifyResult.Succeed)
			{
				_succeedCount++;
				var wrapper = new PackageCache.RecordWrapper(element.InfoFilePath, element.DataFilePath, element.DataFileCRC, element.DataFileSize);
				CacheSystem.RecordFile(element.PackageName, element.CacheGUID, wrapper);
			}
			else
			{
				_failedCount++;

				YooLogger.Warning($"Failed verify file and delete files : {element.FileRootPath}");
				element.DeleteFiles();
			}
		}
	}
}