/*
 * This file is part of the SDWebImage package.
 * (c) Olivier Poitrey <rs@dailymotion.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

#import "SDWebImageDownloader.h"
#import "SDWebImageDownloaderOperation.h"

#define LOCK(lock) dispatch_semaphore_wait(lock, DISPATCH_TIME_FOREVER);
#define UNLOCK(lock) dispatch_semaphore_signal(lock);

@interface SDWebImageDownloadToken ()

@property (nonatomic, weak, nullable) NSOperation<SDWebImageDownloaderOperationInterface> *downloadOperation;

@end

@implementation SDWebImageDownloadToken

- (void)cancel {
    if (self.downloadOperation) {
        SDWebImageDownloadToken *cancelToken = self.downloadOperationCancelToken;
        if (cancelToken) {
            [self.downloadOperation cancel:cancelToken];
        }
    }
}

@end


@interface SDWebImageDownloader () <NSURLSessionTaskDelegate, NSURLSessionDataDelegate>

@property (strong, nonatomic, nonnull) NSOperationQueue *downloadQueue;
@property (weak, nonatomic, nullable) NSOperation *lastAddedOperation;
@property (assign, nonatomic, nullable) Class operationClass;
@property (strong, nonatomic, nonnull) NSMutableDictionary<NSURL *, NSOperation<SDWebImageDownloaderOperationInterface> *> *URLOperations;
@property (strong, nonatomic, nullable) SDHTTPHeadersMutableDictionary *HTTPHeaders;
@property (strong, nonatomic, nonnull) dispatch_semaphore_t operationsLock; // a lock to keep the access to `URLOperations` thread-safe
@property (strong, nonatomic, nonnull) dispatch_semaphore_t headersLock; // a lock to keep the access to `HTTPHeaders` thread-safe

// The session in which data tasks will run
@property (strong, nonatomic) NSURLSession *session;

@end

@implementation SDWebImageDownloader

+ (void)initialize {
    // Bind SDNetworkActivityIndicator if available (download it here: http://github.com/rs/SDNetworkActivityIndicator )
    // To use it, just add #import "SDNetworkActivityIndicator.h" in addition to the SDWebImage import
    if (NSClassFromString(@"SDNetworkActivityIndicator")) {

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
        id activityIndicator = [NSClassFromString(@"SDNetworkActivityIndicator") performSelector:NSSelectorFromString(@"sharedActivityIndicator")];
#pragma clang diagnostic pop

        // Remove observer in case it was previously added.
        [[NSNotificationCenter defaultCenter] removeObserver:activityIndicator name:SDWebImageDownloadStartNotification object:nil];
        [[NSNotificationCenter defaultCenter] removeObserver:activityIndicator name:SDWebImageDownloadStopNotification object:nil];

        [[NSNotificationCenter defaultCenter] addObserver:activityIndicator
                                                 selector:NSSelectorFromString(@"startActivity")
                                                     name:SDWebImageDownloadStartNotification object:nil];
        [[NSNotificationCenter defaultCenter] addObserver:activityIndicator
                                                 selector:NSSelectorFromString(@"stopActivity")
                                                     name:SDWebImageDownloadStopNotification object:nil];
    }
}

+ (nonnull instancetype)sharedDownloader {
    static dispatch_once_t once;
    static id instance;
    dispatch_once(&once, ^{
        instance = [self new];
    });
    return instance;
}

- (nonnull instancetype)init {
    return [self initWithSessionConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];
}

- (nonnull instancetype)initWithSessionConfiguration:(nullable NSURLSessionConfiguration *)sessionConfiguration {
    if ((self = [super init])) {
        _operationClass = [SDWebImageDownloaderOperation class];
        _shouldDecompressImages = YES;
        _executionOrder = SDWebImageDownloaderFIFOExecutionOrder;
        _downloadQueue = [NSOperationQueue new];
        _downloadQueue.maxConcurrentOperationCount = 6;
        _downloadQueue.name = @"com.hackemist.SDWebImageDownloader";
        _URLOperations = [NSMutableDictionary new];
        SDHTTPHeadersMutableDictionary *headerDictionary = [SDHTTPHeadersMutableDictionary dictionary];
        NSString *userAgent = nil;
#if SD_UIKIT
        // User-Agent Header; see http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.43
        userAgent = [NSString stringWithFormat:@"%@/%@ (%@; iOS %@; Scale/%0.2f)", [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleExecutableKey] ?: [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleIdentifierKey], [[NSBundle mainBundle] infoDictionary][@"CFBundleShortVersionString"] ?: [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleVersionKey], [[UIDevice currentDevice] model], [[UIDevice currentDevice] systemVersion], [[UIScreen mainScreen] scale]];
#elif SD_WATCH
        // User-Agent Header; see http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.43
        userAgent = [NSString stringWithFormat:@"%@/%@ (%@; watchOS %@; Scale/%0.2f)", [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleExecutableKey] ?: [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleIdentifierKey], [[NSBundle mainBundle] infoDictionary][@"CFBundleShortVersionString"] ?: [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleVersionKey], [[WKInterfaceDevice currentDevice] model], [[WKInterfaceDevice currentDevice] systemVersion], [[WKInterfaceDevice currentDevice] screenScale]];
#elif SD_MAC
        userAgent = [NSString stringWithFormat:@"%@/%@ (Mac OS X %@)", [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleExecutableKey] ?: [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleIdentifierKey], [[NSBundle mainBundle] infoDictionary][@"CFBundleShortVersionString"] ?: [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleVersionKey], [[NSProcessInfo processInfo] operatingSystemVersionString]];
#endif
        if (userAgent) {
            if (![userAgent canBeConvertedToEncoding:NSASCIIStringEncoding]) {
                NSMutableString *mutableUserAgent = [userAgent mutableCopy];
                if (CFStringTransform((__bridge CFMutableStringRef)(mutableUserAgent), NULL, (__bridge CFStringRef)@"Any-Latin; Latin-ASCII; [:^ASCII:] Remove", false)) {
                    userAgent = mutableUserAgent;
                }
            }
            headerDictionary[@"User-Agent"] = userAgent;
        }
#ifdef SD_WEBP
        headerDictionary[@"Accept"] = @"image/webp,image/*;q=0.8";
#else
        headerDictionary[@"Accept"] = @"image/*;q=0.8";
#endif
        _HTTPHeaders = headerDictionary;
        _operationsLock = dispatch_semaphore_create(1);
        _headersLock = dispatch_semaphore_create(1);
        _downloadTimeout = 15.0;

        [self createNewSessionWithConfiguration:sessionConfiguration];
    }
    return self;
}

- (void)createNewSessionWithConfiguration:(NSURLSessionConfiguration *)sessionConfiguration {
    [self cancelAllDownloads];

    if (self.session) {
        [self.session invalidateAndCancel];
    }

    sessionConfiguration.timeoutIntervalForRequest = self.downloadTimeout;

    /**
     *  Create the session for this task
     *  We send nil as delegate queue so that the session creates a serial operation queue for performing all delegate
     *  method calls and completion handler calls.
     */
    self.session = [NSURLSession sessionWithConfiguration:sessionConfiguration
                                                 delegate:self
                                            delegateQueue:nil];
}

- (void)invalidateSessionAndCancel:(BOOL)cancelPendingOperations {
    if (self == [SDWebImageDownloader sharedDownloader]) {
        return;
    }
    if (cancelPendingOperations) {
        [self.session invalidateAndCancel];
    } else {
        [self.session finishTasksAndInvalidate];
    }
}

- (void)dealloc {
    [self.session invalidateAndCancel];
    self.session = nil;

    [self.downloadQueue cancelAllOperations];
}

- (void)setValue:(nullable NSString *)value forHTTPHeaderField:(nullable NSString *)field {
    LOCK(self.headersLock);
    if (value) {
        self.HTTPHeaders[field] = value;
    } else {
        [self.HTTPHeaders removeObjectForKey:field];
    }
    UNLOCK(self.headersLock);
}

- (nullable NSString *)valueForHTTPHeaderField:(nullable NSString *)field {
    if (!field) {
        return nil;
    }
    return [[self allHTTPHeaderFields] objectForKey:field];
}

- (nonnull SDHTTPHeadersDictionary *)allHTTPHeaderFields {
    LOCK(self.headersLock);
    SDHTTPHeadersDictionary *allHTTPHeaderFields = [self.HTTPHeaders copy];
    UNLOCK(self.headersLock);
    return allHTTPHeaderFields;
}

- (void)setMaxConcurrentDownloads:(NSInteger)maxConcurrentDownloads {
    _downloadQueue.maxConcurrentOperationCount = maxConcurrentDownloads;
}

- (NSUInteger)currentDownloadCount {
    return _downloadQueue.operationCount;
}

- (NSInteger)maxConcurrentDownloads {
    return _downloadQueue.maxConcurrentOperationCount;
}

- (NSURLSessionConfiguration *)sessionConfiguration {
    return self.session.configuration;
}

- (void)setOperationClass:(nullable Class)operationClass {
    if (operationClass && [operationClass isSubclassOfClass:[NSOperation class]] && [operationClass conformsToProtocol:@protocol(SDWebImageDownloaderOperationInterface)]) {
        _operationClass = operationClass;
    } else {
        _operationClass = [SDWebImageDownloaderOperation class];
    }
}

- (NSOperation<SDWebImageDownloaderOperationInterface> *)createDownloaderOperationWithUrl:(nullable NSURL *)url
                                                                                  options:(SDWebImageDownloaderOptions)options {
    NSTimeInterval timeoutInterval = self.downloadTimeout;
    if (timeoutInterval == 0.0) {
        timeoutInterval = 15.0;
    }

    // In order to prevent from potential duplicate caching (NSURLCache + SDImageCache) we disable the cache for image requests if told otherwise
    NSURLRequestCachePolicy cachePolicy = options & SDWebImageDownloaderUseNSURLCache ? NSURLRequestUseProtocolCachePolicy : NSURLRequestReloadIgnoringLocalCacheData;
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url
                                                                cachePolicy:cachePolicy
                                                            timeoutInterval:timeoutInterval];
    
    request.HTTPShouldHandleCookies = (options & SDWebImageDownloaderHandleCookies);
    request.HTTPShouldUsePipelining = YES;
    if (self.headersFilter) {
        request.allHTTPHeaderFields = self.headersFilter(url, [self allHTTPHeaderFields]);
    }
    else {
        request.allHTTPHeaderFields = [self allHTTPHeaderFields];
    }
    NSOperation<SDWebImageDownloaderOperationInterface> *operation = [[self.operationClass alloc] initWithRequest:request inSession:self.session options:options];
    operation.shouldDecompressImages = self.shouldDecompressImages;
    
    if (self.urlCredential) {
        operation.credential = self.urlCredential;
    } else if (self.username && self.password) {
        operation.credential = [NSURLCredential credentialWithUser:self.username password:self.password persistence:NSURLCredentialPersistenceForSession];
    }
    
    if (options & SDWebImageDownloaderHighPriority) {
        operation.queuePriority = NSOperationQueuePriorityHigh;
    } else if (options & SDWebImageDownloaderLowPriority) {
        operation.queuePriority = NSOperationQueuePriorityLow;
    }
    
    if (self.executionOrder == SDWebImageDownloaderLIFOExecutionOrder) {
        // Emulate LIFO execution order by systematically adding new operations as last operation's dependency
        [self.lastAddedOperation addDependency:operation];
        self.lastAddedOperation = operation;
    }

    return operation;
}

- (void)cancel:(nullable SDWebImageDownloadToken *)token {
    NSURL *url = token.url;
    if (!url) {
        return;
    }
    LOCK(self.operationsLock);
    NSOperation<SDWebImageDownloaderOperationInterface> *operation = [self.URLOperations objectForKey:url];
    if (operation) {
        BOOL canceled = [operation cancel:token.downloadOperationCancelToken];
        if (canceled) {
            [self.URLOperations removeObjectForKey:url];
        }
    }
    UNLOCK(self.operationsLock);
}

- (nullable SDWebImageDownloadToken *)downloadImageWithURL:(NSURL *)url
                                                 completed:(SDWebImageDownloaderCompletedBlock)completedBlock {
  return [self downloadImageWithURL:url options:0 progress:nil completed:completedBlock];
}

- (nullable SDWebImageDownloadToken *)downloadImageWithURL:(nullable NSURL *)url
                                                   options:(SDWebImageDownloaderOptions)options
                                                  progress:(nullable SDWebImageDownloaderProgressBlock)progressBlock
                                                 completed:(nullable SDWebImageDownloaderCompletedBlock)completedBlock {
    // The URL will be used as the key to the callbacks dictionary so it cannot be nil. If it is nil immediately call the completed block with no image or data.
    if (url == nil) {
        if (completedBlock != nil) {
            completedBlock(nil, nil, nil, NO);
        }
        return nil;
    }
    
    LOCK(self.operationsLock);
    id downloadOperationCancelToken;
    NSOperation<SDWebImageDownloaderOperationInterface> *operation = [self.URLOperations objectForKey:url];
    // There is a case that the operation may be marked as finished or cancelled, but not been removed from `self.URLOperations`.
    if (!operation || operation.isFinished || operation.isCancelled) {
        operation = [self createDownloaderOperationWithUrl:url options:options];
        __weak typeof(self) wself = self;
        operation.completionBlock = ^{
            __strong typeof(wself) sself = wself;
            if (!sself) {
                return;
            }
            LOCK(sself.operationsLock);
            [sself.URLOperations removeObjectForKey:url];
            UNLOCK(sself.operationsLock);
        };
        [self.URLOperations setObject:operation forKey:url];
        // Add the handlers before submitting to operation queue, avoid the race condition that operation finished before setting handlers.
        downloadOperationCancelToken = [operation addHandlersForProgress:progressBlock completed:completedBlock];
        // Add operation to operation queue only after all configuration done according to Apple's doc.
        // `addOperation:` does not synchronously execute the `operation.completionBlock` so this will not cause deadlock.
        [self.downloadQueue addOperation:operation];
    } else {
        // When we reuse the download operation to attach more callbacks, there may be thread safe issue because the getter of callbacks may in another queue (decoding queue or delegate queue)
        // So we lock the operation here, and in `SDWebImageDownloaderOperation`, we use `@synchonzied (self)`, to ensure the thread safe between these two classes.
        @synchronized (operation) {
            downloadOperationCancelToken = [operation addHandlersForProgress:progressBlock completed:completedBlock];
        }
        if (!operation.isExecuting) {
            if (options & SDWebImageDownloaderHighPriority) {
                operation.queuePriority = NSOperationQueuePriorityHigh;
            } else if (options & SDWebImageDownloaderLowPriority) {
                operation.queuePriority = NSOperationQueuePriorityLow;
            } else {
                operation.queuePriority = NSOperationQueuePriorityNormal;
            }
        }
    }
    UNLOCK(self.operationsLock);
    
    SDWebImageDownloadToken *token = [SDWebImageDownloadToken new];
    token.downloadOperation = operation;
    token.url = url;
    token.downloadOperationCancelToken = downloadOperationCancelToken;

    return token;
}

- (void)setSuspended:(BOOL)suspended {
    self.downloadQueue.suspended = suspended;
}

- (void)cancelAllDownloads {
    [self.downloadQueue cancelAllOperations];
}

#pragma mark Helper methods

- (NSOperation<SDWebImageDownloaderOperationInterface> *)operationWithTask:(NSURLSessionTask *)task {
    NSOperation<SDWebImageDownloaderOperationInterface> *returnOperation = nil;
    for (NSOperation<SDWebImageDownloaderOperationInterface> *operation in self.downloadQueue.operations) {
        if ([operation respondsToSelector:@selector(dataTask)]) {
            // So we lock the operation here, and in `SDWebImageDownloaderOperation`, we use `@synchonzied (self)`, to ensure the thread safe between these two classes.
            NSURLSessionTask *operationTask;
            @synchronized (operation) {
                operationTask = operation.dataTask;
            }
            if (operationTask.taskIdentifier == task.taskIdentifier) {
                returnOperation = operation;
                break;
            }
        }
    }
    return returnOperation;
}

#pragma mark NSURLSessionDataDelegate

- (void)URLSession:(NSURLSession *)session
          dataTask:(NSURLSessionDataTask *)dataTask
didReceiveResponse:(NSURLResponse *)response
 completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler {

    // Identify the operation that runs this task and pass it the delegate method
    NSOperation<SDWebImageDownloaderOperationInterface> *dataOperation = [self operationWithTask:dataTask];
    if ([dataOperation respondsToSelector:@selector(URLSession:dataTask:didReceiveResponse:completionHandler:)]) {
        [dataOperation URLSession:session dataTask:dataTask didReceiveResponse:response completionHandler:completionHandler];
    } else {
        if (completionHandler) {
            completionHandler(NSURLSessionResponseAllow);
        }
    }
}

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data {

    // Identify the operation that runs this task and pass it the delegate method
    NSOperation<SDWebImageDownloaderOperationInterface> *dataOperation = [self operationWithTask:dataTask];
    if ([dataOperation respondsToSelector:@selector(URLSession:dataTask:didReceiveData:)]) {
        [dataOperation URLSession:session dataTask:dataTask didReceiveData:data];
    }
}

- (void)URLSession:(NSURLSession *)session
          dataTask:(NSURLSessionDataTask *)dataTask
 willCacheResponse:(NSCachedURLResponse *)proposedResponse
 completionHandler:(void (^)(NSCachedURLResponse *cachedResponse))completionHandler {

    // Identify the operation that runs this task and pass it the delegate method
    NSOperation<SDWebImageDownloaderOperationInterface> *dataOperation = [self operationWithTask:dataTask];
    if ([dataOperation respondsToSelector:@selector(URLSession:dataTask:willCacheResponse:completionHandler:)]) {
        [dataOperation URLSession:session dataTask:dataTask willCacheResponse:proposedResponse completionHandler:completionHandler];
    } else {
        if (completionHandler) {
            completionHandler(proposedResponse);
        }
    }
}

#pragma mark NSURLSessionTaskDelegate

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {
    
    // Identify the operation that runs this task and pass it the delegate method
    NSOperation<SDWebImageDownloaderOperationInterface> *dataOperation = [self operationWithTask:task];
    if ([dataOperation respondsToSelector:@selector(URLSession:task:didCompleteWithError:)]) {
        [dataOperation URLSession:session task:task didCompleteWithError:error];
    }
}

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task willPerformHTTPRedirection:(NSHTTPURLResponse *)response newRequest:(NSURLRequest *)request completionHandler:(void (^)(NSURLRequest * _Nullable))completionHandler {
    
    // Identify the operation that runs this task and pass it the delegate method
    NSOperation<SDWebImageDownloaderOperationInterface> *dataOperation = [self operationWithTask:task];
    if ([dataOperation respondsToSelector:@selector(URLSession:task:willPerformHTTPRedirection:newRequest:completionHandler:)]) {
        [dataOperation URLSession:session task:task willPerformHTTPRedirection:response newRequest:request completionHandler:completionHandler];
    } else {
        if (completionHandler) {
            completionHandler(request);
        }
    }
}

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didReceiveChallenge:(NSURLAuthenticationChallenge *)challenge completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition disposition, NSURLCredential *credential))completionHandler {

    // Identify the operation that runs this task and pass it the delegate method
    NSOperation<SDWebImageDownloaderOperationInterface> *dataOperation = [self operationWithTask:task];
    if ([dataOperation respondsToSelector:@selector(URLSession:task:didReceiveChallenge:completionHandler:)]) {
        [dataOperation URLSession:session task:task didReceiveChallenge:challenge completionHandler:completionHandler];
    } else {
        if (completionHandler) {
            completionHandler(NSURLSessionAuthChallengePerformDefaultHandling, nil);
        }
    }
}

@end
