//
//  RQDownloadManager.m
//  TEST
//
//  Created by 张嵘 on 2018/10/22.
//  Copyright © 2018 张嵘. All rights reserved.
//

#import "RQDownloadManager.h"
#import "AppDelegate.h"

@interface RQDownloadManager () <NSURLSessionDelegate, NSURLSessionDownloadDelegate>
@property (nonatomic, strong) NSURLSession *session;             // NSURLSession
@property (nonatomic, strong) NSMutableDictionary *dataTaskDic;  // 同时下载多个文件，需要创建多个NSURLSessionDownloadTask，用该字典来存储
@property (nonatomic, assign) NSInteger currentCount;            // 当前正在下载的个数
@property (nonatomic, assign) NSInteger maxConcurrentCount;      // 最大同时下载数量
@property (nonatomic, assign) BOOL allowsCellularAccess;         // 是否允许蜂窝网络下载

@end

@implementation RQDownloadManager


#pragma mark - 单例相关
static id instace = nil;
+ (id)allocWithZone:(struct _NSZone *)zone {
	if (instace == nil) {
		static dispatch_once_t onceToken;
		dispatch_once(&onceToken, ^{
			instace = [super allocWithZone:zone];
			// 初始化
			[instace initBase];
			// 添加未捕获异常的监听
			[instace handleUncaughtExreption];
			// 添加监听
			[instace addObservers];
			// 开启网络监听
			[[RQNetworkReachabilityManager shareManager] monitorNetworkStatus];
		});
	}
	return instace;
}

- (instancetype)init {
	return instace;
}

+ (instancetype)sharedManager {
	return [[self alloc] init];
}

- (id)copyWithZone:(struct _NSZone *)zone {
	return instace;
}

- (id)mutableCopyWithZone:(struct _NSZone *)zone {
	return instace;
}


#pragma mark - 单例初始化调用
- (void)initBase {
	// 初始化
	_currentCount = 0;
	_maxConcurrentCount = [[NSUserDefaults standardUserDefaults] integerForKey:RQDownloadMaxConcurrentCountKey];
	_allowsCellularAccess = [[NSUserDefaults standardUserDefaults] boolForKey:RQDownloadAllowsCellularAccessKey];
	_dataTaskDic = [NSMutableDictionary dictionary];
	
	// 单线程代理队列
	NSOperationQueue *queue = [[NSOperationQueue alloc] init];
	queue.maxConcurrentOperationCount = 1;
	
	// 后台下载标识
	NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:@"RQDownloadBackgroundSessionIdentifier"];
	// 允许蜂窝网络下载，默认为YES，这里开启，我们添加了一个变量去控制用户切换选择
	configuration.allowsCellularAccess = YES;
	
	// 创建NSURLSession，配置信息、代理、代理线程
	_session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:queue];
}

/**
 *  添加监听
 */
- (void)addObservers {
	[[NSNotificationCenter defaultCenter] addObserver:instace selector:@selector(openDownloadTask) name:UIApplicationDidFinishLaunchingNotification object:nil];
	
	[[NSNotificationCenter defaultCenter] addObserver:instace selector:@selector(applicationWillTerminate) name:UIApplicationWillTerminateNotification object:nil];
	
	[[NSNotificationCenter defaultCenter] addObserver:instace selector:@selector(applicationWillTerminate) name:kNotificationUncaughtException object:nil];
	
	// 最大下载并发数变更通知
	[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(downloadMaxConcurrentCountChange:) name:RQDownloadMaxConcurrentCountChangeNotification object:nil];
	
	// 是否允许蜂窝网络下载改变通知
	[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(downloadAllowsCellularAccessChange:) name:RQDownloadAllowsCellularAccessChangeNotification object:nil];
	
	// 网路改变通知
	[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(networkingReachabilityDidChange:) name:RQNetworkingReachabilityDidChangeNotification object:nil];
}

/**
 *  添加未捕获异常的监听
 */
- (void)handleUncaughtExreption {
	[RQUncaughtExceptionHandler setDefaultHandler];
}


#pragma mark - Private Method
// 加入准备下载任务
- (void)startDownloadTask:(RQDownloadModel *)model {
	// 取出数据库中模型数据，如果不存在，添加到数据空中
	RQDownloadModel *downloadModel = [[RQDataBaseManager shareManager] getModelWithUrl:model.urlString];
	if (!downloadModel) {
		downloadModel = model;
		[[RQDataBaseManager shareManager] insertModel:downloadModel];
	}
	
	// 更新状态为等待下载
	downloadModel.status = RQDownloadStatus_Waiting;
	[[RQDataBaseManager shareManager] updateWithModel:downloadModel option:RQDBUpdateOptionAllParam];
	
	// 下载
	if (_currentCount < self.maxConcurrentCount && [self networkingAllowsDownloadTask]) [self downloadwithModel:downloadModel];
}

// 开始下载
- (void)downloadwithModel:(RQDownloadModel *)model {
	// 更新状态为开始
	model.status = RQDownloadStatus_Running;
	[[RQDataBaseManager shareManager] updateWithModel:model option:RQDBUpdateOptionAllParam];
	_currentCount++;
	
	// 创建NSURLSessionDownloadTask
	NSURLSessionDownloadTask *downloadTask;
	if (model.resumeData) {
		CGFloat version = [[[UIDevice currentDevice] systemVersion] floatValue];
		if (version >= 10.0 && version < 10.2) {
			downloadTask = [_session downloadTaskWithCorrectResumeData:model.resumeData];
		}else {
			downloadTask = [_session downloadTaskWithResumeData:model.resumeData];
		}
		
	}else {
		downloadTask = [_session downloadTaskWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:model.urlString]]];
	}
	
	// 添加描述标签
	downloadTask.taskDescription = model.urlString;
	
	// 更新存储的NSURLSessionDownloadTask对象
	[_dataTaskDic setValue:downloadTask forKey:model.urlString];
	
	// 启动（继续下载）
	[downloadTask resume];
}

// 暂停下载
- (void)pauseDownloadTask:(RQDownloadModel *)model {
	// 取最新数据
	RQDownloadModel *downloadModel = [[RQDataBaseManager shareManager] getModelWithUrl:model.urlString];
	
	// 取消任务
	[self cancelTaskWithModel:downloadModel delete:NO];
	
	// 更新数据库状态为暂停
	downloadModel.status = RQDownloadStatus_Suspended;
	[[RQDataBaseManager shareManager] updateWithModel:downloadModel option:RQDBUpdateOptionAllParam];
}

// 删除下载任务及本地缓存
- (void)deleteTaskAndCache:(RQDownloadModel *)model {
	// 删除本地缓存、数据库数据
	dispatch_async(dispatch_get_global_queue(0, 0), ^{
		[[NSFileManager defaultManager] removeItemAtPath:model.destinationPath error:nil];
		model.status = RQDownloadStatus_None;
		model.statusText = nil;
		[[RQDataBaseManager shareManager] updateWithModel:model option:RQDBUpdateOptionAllParam];
		[[RQDataBaseManager shareManager] deleteModelWithUrl:model.urlString];
		[self clearTmpDirectory];
	});
	
	// 如果正在下载，取消任务
	[self cancelTaskWithModel:model delete:YES];
}

// 清除沙盒临时文件
- (void)clearTmpDirectory
{
    NSArray* tmpDirectory = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:NSTemporaryDirectory() error:NULL];
    for (NSString *file in tmpDirectory) {
        [[NSFileManager defaultManager] removeItemAtPath:[NSString stringWithFormat:@"%@%@", NSTemporaryDirectory(), file] error:NULL];
    }
}

// 取消任务
- (void)cancelTaskWithModel:(RQDownloadModel *)model delete:(BOOL)delete {
	if (model.status == RQDownloadStatus_Running) {
		// 获取NSURLSessionDownloadTask
		NSURLSessionDownloadTask *downloadTask = [_dataTaskDic valueForKey:model.urlString];
		
		// 取消任务
		[downloadTask cancelByProducingResumeData:^(NSData * _Nullable resumeData) {
			// 更新下载数据
			model.resumeData = delete? nil : resumeData;
			[[RQDataBaseManager shareManager] updateWithModel:model option:RQDBUpdateOptionResumeData];
			
			// 更新当前正在下载的个数
			if (_currentCount > 0) _currentCount--;
			
			// 开启等待下载任务
			[self startDownloadWaitingTask];
		}];
		
		// 移除字典存储的对象
		if (delete)  {
			[_dataTaskDic removeObjectForKey:model.urlString];
		}
	}
}

// 开启等待下载任务
- (void)startDownloadWaitingTask {
	if (_currentCount < self.maxConcurrentCount && [self networkingAllowsDownloadTask]) {
		// 获取下一条等待的数据
		RQDownloadModel *model = [[RQDataBaseManager shareManager] getWaitingModel];
		
		if (model) {
			// 下载
			[self downloadwithModel:model];
			
			// 递归，开启下一个等待任务
			[self startDownloadWaitingTask];
		}
	}
}

// 下载时，杀死进程，更新所有正在下载的任务为等待
- (void)updateDownloadingTaskState {
	NSArray *downloadingData = [[RQDataBaseManager shareManager] getAllDownloadingData];
	for (RQDownloadModel *model in downloadingData) {
		model.status = RQDownloadStatus_Waiting;
		[[RQDataBaseManager shareManager] updateWithModel:model option:RQDBUpdateOptionState];
	}
}

// 重启时开启等待下载的任务
- (void)openDownloadTask {
	dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.f * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
		[self startDownloadWaitingTask];
	});
}

// 停止正在下载任务为等待状态
- (void)pauseDownloadingTaskWithAll:(BOOL)all {
	// 获取正在下载的数据
	NSArray *downloadingData = [[RQDataBaseManager shareManager] getAllDownloadingData];
	NSInteger count = all ? downloadingData.count : downloadingData.count - self.maxConcurrentCount;
	for (NSInteger i = 0; i < count; i++) {
		// 取消任务
		RQDownloadModel *model = downloadingData[i];
		[self cancelTaskWithModel:model delete:NO];
		
		// 更新状态为等待
		model.status = RQDownloadStatus_Waiting;
		[[RQDataBaseManager shareManager] updateWithModel:model option:RQDBUpdateOptionAllParam];
	}
}

- (void)applicationWillTerminate {
	[self updateDownloadingTaskState];
}

#pragma mark - NSURLSessionDownloadDelegate
// 接收到服务器返回数据，会被调用多次
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite
{
	// 获取模型
	RQDownloadModel *model = [[RQDataBaseManager shareManager] getModelWithUrl:downloadTask.taskDescription];
	
	// 更新当前下载大小
	model.fileDownloadSize = totalBytesWritten;
	model.fileTotalSize = totalBytesExpectedToWrite;
	
	// 计算速度时间内下载文件的大小
	model.intervalFileSize += bytesWritten;
	
	// 获取上次计算时间与当前时间间隔
	NSInteger intervals = [RQ_SHARE_FUNCTION getIntervalsWithTimeStamp:model.lastSpeedTime];
	if (intervals >= 1) {
		// 计算速度
		model.speed = model.intervalFileSize / intervals;
		
		// 重置变量
		model.intervalFileSize = 0;
		model.lastSpeedTime = [RQ_SHARE_FUNCTION getTimeStampWithDate:[NSDate date]];
	}
	
	// 计算进度
	double byts = totalBytesWritten * 1.0 / 1024 /1024;
	double total = totalBytesExpectedToWrite * 1.0 / 1024 /1024;
	NSString *text = [NSString stringWithFormat:@"%.1lfMB/%.1lfMB",byts,total];
	CGFloat progress = 1.0 * byts / total;
	model.statusText = text;
	model.progress = progress;
	NSLog(@"%@",text);
	
	// 更新数据库中数据
	[[RQDataBaseManager shareManager] updateWithModel:model option:RQDBUpdateOptionAllParam];
	
	// 进度通知
	[[NSNotificationCenter defaultCenter] postNotificationName:RQDownloadProgressNotification object:model];
}

// 下载完成
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location
{
	// 获取模型
	RQDownloadModel *model = [[RQDataBaseManager shareManager] getModelWithUrl:downloadTask.taskDescription];
	
	// 移动文件，原路径文件由系统自动删除
	NSError *error = nil;
	if (model) {
		[[NSFileManager defaultManager] moveItemAtPath:[location path] toPath:model.destinationPath error:&error];
		if (error) NSLog(@"下载完成，移动文件发生错误：%@", error);
	}
}

#pragma mark - NSURLSessionTaskDelegate
// 请求完成
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
{
	// 调用cancel方法直接返回，在相应操作是直接进行处理
	if (error && [error.localizedDescription isEqualToString:@"cancelled"]) return;
	
	// 获取模型
	RQDownloadModel *model = [[RQDataBaseManager shareManager] getModelWithUrl:task.taskDescription];
	
	// 下载时，进程杀死，重新启动，回调错误
	if (error && [error.userInfo objectForKey:NSURLErrorBackgroundTaskCancelledReasonKey]) {
		model.status = RQDownloadStatus_Waiting;
		model.resumeData = [error.userInfo objectForKey:NSURLSessionDownloadTaskResumeData];
		[[RQDataBaseManager shareManager] updateWithModel:model option:RQDBUpdateOptionAllParam];
		return;
	}
	
	// 更新下载数据、任务状态
	if (error) {
		model.status = RQDownloadStatus_Failed;
		model.resumeData = [error.userInfo objectForKey:NSURLSessionDownloadTaskResumeData];
		[[RQDataBaseManager shareManager] updateWithModel:model option:RQDBUpdateOptionAllParam];
		
	}else {
		model.status = RQDownloadStatus_Completed;
	}
	
	// 更新数据
	if (_currentCount > 0) _currentCount--;
	if (model.urlString) {
		[_dataTaskDic removeObjectForKey:model.urlString];
	}	
	// 更新数据库状态
	[[RQDataBaseManager shareManager] updateWithModel:model option:RQDBUpdateOptionAllParam];
	
	// 开启等待下载任务
	[self startDownloadWaitingTask];
	NSLog(@"\n    文件：%@，下载完成 \n    本地路径：%@ \n    错误：%@ \n", model.fileName, model.destinationPath, error);
}

#pragma mark - NSURLSessionDelegate
// 应用处于后台，所有下载任务完成及NSURLSession协议调用之后调用
- (void)URLSessionDidFinishEventsForBackgroundURLSession:(NSURLSession *)session
{
	dispatch_async(dispatch_get_main_queue(), ^{
		AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
		if (appDelegate.backgroundSessionCompletionHandler) {
			void (^completionHandler)(void) = appDelegate.backgroundSessionCompletionHandler;
			appDelegate.backgroundSessionCompletionHandler = nil;
			
			// 执行block，系统后台生成快照，释放阻止应用挂起的断言
			completionHandler();
		}
	});
}

#pragma mark - RQDownloadMaxConcurrentCountChangeNotification
- (void)downloadMaxConcurrentCountChange:(NSNotification *)notification {
	self.maxConcurrentCount = [notification.object integerValue];
	
	if (_currentCount < self.maxConcurrentCount) {
		// 当前下载数小于并发数，开启等待下载任务
		[self startDownloadWaitingTask];
		
	}else if (_currentCount > self.maxConcurrentCount) {
		// 变更正在下载任务为等待下载
		[self pauseDownloadingTaskWithAll:NO];
	}
}

#pragma mark - RQDownloadAllowsCellularAccessChangeNotification
- (void)downloadAllowsCellularAccessChange:(NSNotification *)notification {
	_allowsCellularAccess = [notification.object boolValue];
	
	[self allowsCellularAccessOrNetworkingReachabilityDidChangeAction];
}

#pragma mark - RQNetworkingReachabilityDidChangeNotification
- (void)networkingReachabilityDidChange:(NSNotification *)notification
{
	[self allowsCellularAccessOrNetworkingReachabilityDidChangeAction];
}

// 是否允许蜂窝网络下载或网络状态变更事件
- (void)allowsCellularAccessOrNetworkingReachabilityDidChangeAction {
	if ([[RQNetworkReachabilityManager shareManager] networkReachabilityStatus] == AFNetworkReachabilityStatusNotReachable) {
		// 无网络，暂停正在下载任务
		[self pauseDownloadingTaskWithAll:YES];
		
	}else {
		if ([self networkingAllowsDownloadTask]) {
			// 开启等待任务
			[self startDownloadWaitingTask];
			
		}else {
			// 增加一个友善的提示，蜂窝网络情况下如果有正在下载，提示已暂停
			if ([kRQDownloadDataBaseManager getLastDownloadingModel]) {
				ShowMsg(@"当前为蜂窝网络，已停止下载任务，可在设置中开启");
			}
			
			// 当前为蜂窝网络，不允许下载，暂停正在下载任务
			[self pauseDownloadingTaskWithAll:YES];
		}
	}
}

// 是否允许下载任务
- (BOOL)networkingAllowsDownloadTask {
	// 当前网络状态
	AFNetworkReachabilityStatus status = [[RQNetworkReachabilityManager shareManager] networkReachabilityStatus];
	
	// 无网络 或 （当前为蜂窝网络，且不允许蜂窝网络下载）
//	if (status == AFNetworkReachabilityStatusNotReachable || (status == AFNetworkReachabilityStatusReachableViaWWAN && !_allowsCellularAccess)) {
//		return NO;
//	}
	
	if (status == AFNetworkReachabilityStatusNotReachable) {
		return NO;
	}
	
	return YES;
}

- (void)dealloc {
	[_session invalidateAndCancel];
	[[NSNotificationCenter defaultCenter] removeObserver:self];
}

#pragma mark - LazyLoad

@end