// FileChunk.m 文件切片的数据模型
@interface FileChunk : NSObject
@property (nonatomic, strong) ChunkFileModel *fileModel;	// 切片来源于哪个文件(包含文件路径、文件大小，每个分片大小，分片总数)
@property (nonatomic, assign) NSUInteger index; 	// 数据块的位置(为了中断后的重新上传时候，过滤掉已上传完成的切片)
@property (nonatomic, assign) NSUInteger offset;	// 数据块的起始位置(可能不同大小的文件，切片大小不一样，data的offset就不一样)
@property (nonatomic, strong) NSData *data; 			// 数据块内容
@property (nonatomic, strong) NSURLResponse *response; // 上传响应（会包含每片的上传状态）

// 获取文件单个切片：按指定的每个切片大小切
- (FileChunk *)initWithFileHandle(NSFileHandle *)fileHandle chunkSize:(NSUInteger)chunkSize chunkIndex:(NSUInteger)chunkIndex {
  self = [super init];
	if (self) {
    chunk.data = [fileHandle readDataOfLength:chunkSize];// 执行后文件句柄的内部偏移量会根据读取的数据长度自动向前移动
    chunk.offset = [fileHandle offsetInFile];						// 返回当前文件的偏移量，即文件句柄的当前位置
    chunk.index = chunkIndex;
  }
	return self;
}

// 要上传的切片的要设置给 HTTPHeaderField:@"Content-Range"
- (NSString *)uploadContentRangeString {
  return [NSString stringWithFormat:@"bytes %@-%@/total-size", @(chunk.offset), @(chunk.offset + chunk.data.length)];
}
@end
  


// FileChunkHelper.m
+ (void)addFinishSaveChunk:(FileChunk *)chunk forFilePath:(NSString *)filePath {
  // 以key: chunk.belongfileMD5 保存已上传完成的切片索引 [0, 1, 2, chunk.index, ...]
}
+ (void)getFinishSaveChunkForFilePath:(NSString *)filePath {
  // 以key: chunk.belongfileMD5 获取已上传完成的切片索引 [0, 1, 2, chunk.index, ...]
}

// 获取文件所有切片：按指定的每个切片大小切(中断后的重新上传时，要过滤掉已上传完成的切片)
+ (NSArray *)chunksFromFilePath:(NSString *)filePath
  										chunkSize:(NSUInteger)chunkSize 
             withoutChunkIndexs:(NSArray<NSUInteger>)chunkIndexs
{
  	NSMutableArray<FileChunk *> *chunks = [NSMutableArray array];
  
    NSFileHandle *fileHandle = [NSFileHandle fileHandleForReadingAtPath:filePath];
    [fileHandle seekFileOffset:0];	// 先定位到文件头部
    int chunkIndex = 0;
	  FileChunk *chunk = [[FileChunk alloc] initWithFileHandle:fileHandle chunkSize:chunkSize chunkIndex:chunkIndex];
    while (chunk.data) {
      	chunkIndex++;
      	if ([chunkIndexs contains chunk.index]) { // 为了中断后的重新上传时候，过滤掉已上传完成的切片
          continue;
        }
        [chunks addObject:chunk];
    }
    [fileHandle closeFile];
  
    return chunks;
}

// 单个分片的上传方法
+ (void)uploadChunk:(FileChunk *)chunk
           uploadId:(NSString *)uploadId
  completionHandler:(void (^)(BOOL success, NSError *error))completionHandler
{
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"your-upload-chunk-api-endpoint"]];
    request.HTTPMethod = @"PUT";
    request.HTTPBody = chunk.data;
    [request setValue:chunk.uploadContentRangeString forHTTPHeaderField:@"Content-Range"];

    NSURLResponse *response = nil;
    NSError *error = nil;
    [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
    if (error) {
      completionHandler(NO, error);
      return;
    }
    
    chunk.response = response;	// 如果上传成功，更新状态
    [self addFinishSaveChunk:chunk forFilePath:chunk.filePath];
    completionHandler(YES, nil);
}

+ (void)uploadChunks:(NSArray<FileChunk *> *)chunks
      	withUploadId:(NSString *)uploadId
   completionHandler:(void (^)())completionHandler
{
    dispatch_group_t group = dispatch_group_create();
    NSMutableArray *uploadTasks = [NSMutableArray array];
    for (FileChunk *chunk in chunks) {
      dispatch_group_enter(group);
      [FileChunkHelper uploadChunk:chunk uploadId:uploadId completionHandler:^(BOOL success,NSError *error) {
        completionHandler(success, error);
        dispatch_group_leave(group);
      }];

      [uploadTasks addObject:@{@"task": @"uploadChunk", @"chunk": chunk}];
    }

    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        completionHandler();
    });
}

// 请求文件是否上传过。（未上传过：返回用于上传的upload；正在上传中：返回upload；已上传过：返回url)
- (void)requestUploadInfoForFilePath:(NSString *)filePath
{
  NSDictionary *parameters = @{
      @"file_name": @"filename.txt", // 替换为实际文件名
      @"file_size": @([FileChunkHelper getFileSize:filePath]), // 调用方法获取文件大小
      @"part_size": @(partSize)
  };
  if (resultModel.uploadFinish) {
    NSString *url = resultModel.url;
    return;
  }
  
	NSString *uploadId = resultModel.uploadId;
  //NSArray<NSInteger> finishChunkIndexs = resultModel.finishChunkIndexs; // 个人感觉不需要后台返回未完成的
	// 1、获取文件所有切片：按指定的每个切片大小切(中断后的重新上传时，要过滤掉已上传完成的切片)
  NSUInteger chunkSize = 1024 * 1024; // 1M
  NSArray<NSUInteger> chunkIndexs = [FileChunkHelper getFinishSaveChunkForFilePath:filePath];
	NSArray<FileChunk *> *chunks = [FileChunkHelper chunksFromFilePath:filePath chunkSize:chunkSize withoutChunkIndexs:chunkIndexs];
  // 2、上传分片：提交时除了文件data，同时传入、总片数、当前是第几片
  [FileChunksUpload uploadChunks:chunks withUploadId:uploadId completionHandler:^(void){
    // 3、上传所有分片后，有时候这里会额外调用服务器API告诉后台已完成全部上传。实际上后台自己也可以根据上传个数是否等于总数判断
  }];
}

NSURL *url = [NSURL URLWithString:@"http://example.com/resource"];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60];

// 检查并设置If-Modified-Since和If-None-Match头部
NSString *cachedLastModified = // 从本地获取Last-Modified值
NSString *cachedETag = // 从本地获取ETag值
if (cachedLastModified) {
    [request setValue:cachedLastModified forHTTPHeaderField:@"If-Modified-Since"];
}
if (cachedETag) {
    [request setValue:cachedETag forHTTPHeaderField:@"If-None-Match"];
}

NSString *storageKey = "LastModified_url和已去除timestamp等无关参数的参数 组成的key"
NSURLSession *session = [NSURLSession sharedSession];
NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
    NSString *newLastModified = httpResponse.allHeaderFields[@"Last-Modified"];
    NSString *newETag = httpResponse.allHeaderFields[@"ETag"];
    if (httpResponse.statusCode == 200) {
     	// 资源有更新，保存新数据和新的Last-Modified、ETag
      [self saveData:data LastModified:newLastModified ETag:newETag forKey:storageKey]
      callback(data, isCacheData:false);
    } else if (httpResponse.statusCode == 304) {
      // 资源未更新，使用本地缓存数据(从本地再次加载缓存数据)
      cacheData = [self loadCachedDataForKey:storageKey];
      callback(data, isCacheData:true);
    }
    
    // 处理数据...
}];

[dataTask resume];

// 1. 为 NSURLSessionConfiguration 配置一个 NSURLCache 实例(设置合适的内存和磁盘缓存容量)。
NSUInteger memoryCapacity = 4 * 1024 * 1024;	// 内存缓存大小（如4MB）
NSUInteger diskCapacity = 20 * 1024 * 1024;		// 磁盘缓存大小（如20MB）
NSURLCache *urlCache = [[NSURLCache alloc] initWithMemoryCapacity:memoryCapacity diskCapacity:diskCapacity diskPath:nil];
NSURLSessionConfiguration *sessionConfig = [NSURLSessionConfiguration defaultSessionConfiguration];
sessionConfig.URLCache = urlCache;

// 2. 使用配置好的 NSURLSessionConfiguration 创建 NSURLSession。
NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfig];

// 3. 创建并发送请求。如果之前有缓存，并且缓存包含了 Last-Modified 或 ETag，则 NSURLCache 会根据这些信息自动处理条件请求。
NSURL *url = [NSURL URLWithString:@"http://example.com/resource"];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
	if (error != nil) {
 		......
    return;
 	}
  
  NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
  switch (httpResponse.statusCode) {
    case 200:
      // 资源有更新，NSURLCache 会自动更新缓存
     	callback(data, isCacheData:false);
  		break;
 		case 304:
     	// 资源未修改，从 NSURLCache 获取缓存的数据
  		NSCachedURLResponse *cachedResponse = [[NSURLCache sharedURLCache] cachedResponseForRequest:request];				if (cachedResponse) {
				NSData *cachedData = cachedResponse.data;
				callback(cachedData, isCacheData:true);	// 由于是缓存的数据，通常不需要更新UI，除非有特殊需求
			}
			break;
  	default:
			// 处理其他HTTP状态码
    	break;
 		}
}];

[dataTask resume];

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didFinishCollectingMetrics:(NSURLSessionTaskMetrics *)metrics API_AVAILABLE(macosx(10.12), ios(10.0), watchos(3.0), tvos(10.0)) 
{
  // 首先检查是否是iOS 10.0或更高版本，如果不是，则退出方法
  if (!@available(iOS 10.0, *)) {
    return; // 退出方法
  }
    
  // 由于使用了@available注解，下面的代码默认只在iOS 10.0或更高版本上执行
  for (NSURLSessionTaskTransactionMetrics *sMetric in metrics.transactionMetrics) {
    NSInteger dom = timeDiff(sMetric.domainLookupStartDate, sMetric.domainLookupEndDate);	// 域名解析
    NSInteger sec = timeDiff(sMetric.secureConnectionStartDate, sMetric.secureConnectionEndDate);// TLS
    NSInteger con = timeDiff(sMetric.connectStartDate, sMetric.connectEndDate);		// 连接耗时(包括TLS)
    NSInteger req = timeDiff(sMetric.requestStartDate, sMetric.requestEndDate);		// 请求
    NSInteger res = timeDiff(sMetric.responseStartDate, sMetric.responseEndDate);	// 回调
    NSInteger tot = timeDiff(sMetric.fetchStartDate, sMetric.responseEndDate); 		// 总耗时

    NSString *locip = @"";
    NSString *remip = @"";
    if (@available(iOS 13.0, *)) {
      locip = [NSString stringWithFormat:@"%@", sMetric.localAddress];
      remip = [NSString stringWithFormat:@"%@", sMetric.remoteAddress];
    }

    NSLog(@"metric path:%@ 总耗时:%ldms, 域名解析:%ldms, 连接耗时:%ldms(包括TLS:%ldms), 请求:%ldms, 回调:%ldms l:%@ r:%@", sessionMetric.request.URL.lastPathComponent, (long)tot, (long)dom, (long)con, (long)sec, (long)req, (long)res, locip, remip);
  }
}

// 辅助方法，计算两个NSDate之间的时间差，单位为毫秒
- (NSInteger)timeDifferenceInMilliseconds:(NSDate *)start to:(NSDate *)end {
    return (NSInteger)((end.timeIntervalSince1970 - start.timeIntervalSince1970) * 1000);
}