Synnefo » Pithos iOS Client

//

//  ASIDownloadCache.m

//  Part of ASIHTTPRequest -> http://allseeing-i.com/ASIHTTPRequest

//

//  Created by Ben Copsey on 01/05/2010.

//  Copyright 2010 All-Seeing Interactive. All rights reserved.

//

#import "ASIDownloadCache.h"

#import "ASIHTTPRequest.h"

#import <CommonCrypto/CommonHMAC.h>

static ASIDownloadCache *sharedCache = nil;

static NSString *sessionCacheFolder = @"SessionStore";

static NSString *permanentCacheFolder = @"PermanentStore";

@interface ASIDownloadCache ()

+ (NSString *)keyForURL:(NSURL *)url;

@end

@implementation ASIDownloadCache

- (id)init

{

	self = [super init];

	[self setShouldRespectCacheControlHeaders:YES];

	[self setDefaultCachePolicy:ASIUseDefaultCachePolicy];

	[self setAccessLock:[[[NSRecursiveLock alloc] init] autorelease]];

	return self;

}

+ (id)sharedCache

{

	if (!sharedCache) {

		sharedCache = [[self alloc] init];

		[sharedCache setStoragePath:[[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0] stringByAppendingPathComponent:@"ASIHTTPRequestCache"]];

	}

	return sharedCache;

}

- (void)dealloc

{

	[storagePath release];

	[accessLock release];

	[super dealloc];

}

- (NSString *)storagePath

{

	[[self accessLock] lock];

	NSString *p = [[storagePath retain] autorelease];

	[[self accessLock] unlock];

	return p;

}

- (void)setStoragePath:(NSString *)path

{

	[[self accessLock] lock];

	[self clearCachedResponsesForStoragePolicy:ASICacheForSessionDurationCacheStoragePolicy];

	[storagePath release];

	storagePath = [path retain];

	BOOL isDirectory = NO;

	NSArray *directories = [NSArray arrayWithObjects:path,[path stringByAppendingPathComponent:sessionCacheFolder],[path stringByAppendingPathComponent:permanentCacheFolder],nil];

	for (NSString *directory in directories) {

		BOOL exists = [[NSFileManager defaultManager] fileExistsAtPath:directory isDirectory:&isDirectory];

		if (exists && !isDirectory) {

			[[self accessLock] unlock];

			[NSException raise:@"FileExistsAtCachePath" format:@"Cannot create a directory for the cache at '%@', because a file already exists",directory];

		} else if (!exists) {

			[[NSFileManager defaultManager] createDirectoryAtPath:directory withIntermediateDirectories:NO attributes:nil error:nil];

			if (![[NSFileManager defaultManager] fileExistsAtPath:directory]) {

				[[self accessLock] unlock];

				[NSException raise:@"FailedToCreateCacheDirectory" format:@"Failed to create a directory for the cache at '%@'",directory];

			}

		}

	}

	[self clearCachedResponsesForStoragePolicy:ASICacheForSessionDurationCacheStoragePolicy];

	[[self accessLock] unlock];

}

- (void)storeResponseForRequest:(ASIHTTPRequest *)request maxAge:(NSTimeInterval)maxAge

{

	[[self accessLock] lock];

	if ([request error] || ![request responseHeaders] || ([request responseStatusCode] != 200) || ([request cachePolicy] & ASIDoNotWriteToCacheCachePolicy)) {

		[[self accessLock] unlock];

		return;

	}

	if ([self shouldRespectCacheControlHeaders] && ![[self class] serverAllowsResponseCachingForRequest:request]) {

		[[self accessLock] unlock];

		return;

	}

	NSString *headerPath = [self pathToStoreCachedResponseHeadersForRequest:request];

	NSString *dataPath = [self pathToStoreCachedResponseDataForRequest:request];

	NSMutableDictionary *responseHeaders = [NSMutableDictionary dictionaryWithDictionary:[request responseHeaders]];

	if ([request isResponseCompressed]) {

		[responseHeaders removeObjectForKey:@"Content-Encoding"];

	}

	if (maxAge != 0) {

		[responseHeaders removeObjectForKey:@"Expires"];

		[responseHeaders setObject:[NSString stringWithFormat:@"max-age=%i",(int)maxAge] forKey:@"Cache-Control"];

	}

	// We use this special key to help expire the request when we get a max-age header

	[responseHeaders setObject:[[[self class] rfc1123DateFormatter] stringFromDate:[NSDate date]] forKey:@"X-ASIHTTPRequest-Fetch-date"];

	[responseHeaders writeToFile:headerPath atomically:NO];

	if ([request responseData]) {

		[[request responseData] writeToFile:dataPath atomically:NO];

	} else if ([request downloadDestinationPath] && ![[request downloadDestinationPath] isEqualToString:dataPath]) {

		NSError *error = nil;

		[[NSFileManager defaultManager] copyItemAtPath:[request downloadDestinationPath] toPath:dataPath error:&error];

	}

	[[self accessLock] unlock];

}

- (NSDictionary *)cachedResponseHeadersForURL:(NSURL *)url

{

	NSString *path = [self pathToCachedResponseHeadersForURL:url];

	if (path) {

		return [NSDictionary dictionaryWithContentsOfFile:path];

	}

	return nil;

}

- (NSData *)cachedResponseDataForURL:(NSURL *)url

{

	NSString *path = [self pathToCachedResponseDataForURL:url];

	if (path) {

		return [NSData dataWithContentsOfFile:path];

	}

	return nil;

}

- (NSString *)pathToCachedResponseDataForURL:(NSURL *)url

{

	[[self accessLock] lock];

	if (![self storagePath]) {

		[[self accessLock] unlock];

		return nil;

	}

	// Grab the file extension, if there is one. We do this so we can save the cached response with the same file extension - this is important if you want to display locally cached data in a web view 

	NSString *extension = [[url path] pathExtension];

	if (![extension length]) {

		extension = @"html";

	}

	// Look in the session store

	NSString *path = [[self storagePath] stringByAppendingPathComponent:sessionCacheFolder];

	NSString *dataPath = [path stringByAppendingPathComponent:[[[self class] keyForURL:url] stringByAppendingPathExtension:extension]];

	if ([[NSFileManager defaultManager] fileExistsAtPath:dataPath]) {

		[[self accessLock] unlock];

		return dataPath;

	}

	// Look in the permanent store

	path = [[self storagePath] stringByAppendingPathComponent:permanentCacheFolder];

	dataPath = [path stringByAppendingPathComponent:[[[self class] keyForURL:url] stringByAppendingPathExtension:extension]];

	if ([[NSFileManager defaultManager] fileExistsAtPath:dataPath]) {

		[[self accessLock] unlock];

		return dataPath;

	}

	[[self accessLock] unlock];

	return nil;

}

- (NSString *)pathToCachedResponseHeadersForURL:(NSURL *)url

{

	[[self accessLock] lock];

	if (![self storagePath]) {

		[[self accessLock] unlock];

		return nil;

	}

	// Look in the session store

	NSString *path = [[self storagePath] stringByAppendingPathComponent:sessionCacheFolder];

	NSString *dataPath = [path stringByAppendingPathComponent:[[[self class] keyForURL:url] stringByAppendingPathExtension:@"cachedheaders"]];

	if ([[NSFileManager defaultManager] fileExistsAtPath:dataPath]) {

		[[self accessLock] unlock];

		return dataPath;

	}

	// Look in the permanent store

	path = [[self storagePath] stringByAppendingPathComponent:permanentCacheFolder];

	dataPath = [path stringByAppendingPathComponent:[[[self class] keyForURL:url] stringByAppendingPathExtension:@"cachedheaders"]];

	if ([[NSFileManager defaultManager] fileExistsAtPath:dataPath]) {

		[[self accessLock] unlock];

		return dataPath;

	}

	[[self accessLock] unlock];

	return nil;

}

- (NSString *)pathToStoreCachedResponseDataForRequest:(ASIHTTPRequest *)request

{

	[[self accessLock] lock];

	if (![self storagePath]) {

		[[self accessLock] unlock];

		return nil;

	}

	NSString *path = [[self storagePath] stringByAppendingPathComponent:([request cacheStoragePolicy] == ASICacheForSessionDurationCacheStoragePolicy ? sessionCacheFolder : permanentCacheFolder)];

	// Grab the file extension, if there is one. We do this so we can save the cached response with the same file extension - this is important if you want to display locally cached data in a web view 

	NSString *extension = [[[request url] path] pathExtension];

	if (![extension length]) {

		extension = @"html";

	}

	path =  [path stringByAppendingPathComponent:[[[self class] keyForURL:[request url]] stringByAppendingPathExtension:extension]];

	[[self accessLock] unlock];

	return path;

}

- (NSString *)pathToStoreCachedResponseHeadersForRequest:(ASIHTTPRequest *)request

{

	[[self accessLock] lock];

	if (![self storagePath]) {

		[[self accessLock] unlock];

		return nil;

	}

	NSString *path = [[self storagePath] stringByAppendingPathComponent:([request cacheStoragePolicy] == ASICacheForSessionDurationCacheStoragePolicy ? sessionCacheFolder : permanentCacheFolder)];

	path =  [path stringByAppendingPathComponent:[[[self class] keyForURL:[request url]] stringByAppendingPathExtension:@"cachedheaders"]];

	[[self accessLock] unlock];

	return path;

}

- (void)removeCachedDataForRequest:(ASIHTTPRequest *)request

{

	[[self accessLock] lock];

	if (![self storagePath]) {

		[[self accessLock] unlock];

		return;

	}

	NSString *cachedHeadersPath = [self pathToCachedResponseHeadersForURL:[request url]];

	if (!cachedHeadersPath) {

		[[self accessLock] unlock];

		return;

	}

	NSString *dataPath = [self pathToCachedResponseDataForURL:[request url]];

	if (!dataPath) {

		[[self accessLock] unlock];

		return;

	}

	[[NSFileManager defaultManager] removeItemAtPath:cachedHeadersPath error:NULL];

	[[NSFileManager defaultManager] removeItemAtPath:dataPath error:NULL];

	[[self accessLock] unlock];

}

- (BOOL)isCachedDataCurrentForRequest:(ASIHTTPRequest *)request

{

	[[self accessLock] lock];

	if (![self storagePath]) {

		[[self accessLock] unlock];

		return NO;

	}

	NSDictionary *cachedHeaders = [self cachedResponseHeadersForURL:[request url]];

	if (!cachedHeaders) {

		[[self accessLock] unlock];

		return NO;

	}

	NSString *dataPath = [self pathToCachedResponseDataForURL:[request url]];

	if (!dataPath) {

		[[self accessLock] unlock];

		return NO;

	}

	// If we already have response headers for this request, check to see if the new content is different

	if ([request responseHeaders]) {

		// New content is not different

		if ([request responseStatusCode] == 304) {

			[[self accessLock] unlock];

			return YES;

		}

		// If the Etag or Last-Modified date are different from the one we have, we'll have to fetch this resource again

		NSArray *headersToCompare = [NSArray arrayWithObjects:@"Etag",@"Last-Modified",nil];

		for (NSString *header in headersToCompare) {

			if (![[[request responseHeaders] objectForKey:header] isEqualToString:[cachedHeaders objectForKey:header]]) {

				[[self accessLock] unlock];

				return NO;

			}

		}

	}

	if ([self shouldRespectCacheControlHeaders]) {

		// Look for an Expires header to see if the content is out of date

		NSString *expires = [cachedHeaders objectForKey:@"Expires"];

		if (expires) {

			if ([[ASIHTTPRequest dateFromRFC1123String:expires] timeIntervalSinceNow] >= 0) {

				[[self accessLock] unlock];

				return YES;

			}

		}

		// Look for a max-age header

		NSString *cacheControl = [[cachedHeaders objectForKey:@"Cache-Control"] lowercaseString];

		if (cacheControl) {

			NSScanner *scanner = [NSScanner scannerWithString:cacheControl];

			if ([scanner scanString:@"max-age" intoString:NULL]) {

				[scanner scanString:@"=" intoString:NULL];

				NSTimeInterval maxAge = 0;

				[scanner scanDouble:&maxAge];

				NSDate *fetchDate = [ASIHTTPRequest dateFromRFC1123String:[cachedHeaders objectForKey:@"X-ASIHTTPRequest-Fetch-date"]];

				NSDate *expiryDate = [[[NSDate alloc] initWithTimeInterval:maxAge sinceDate:fetchDate] autorelease];

				if ([expiryDate timeIntervalSinceNow] >= 0) {

					[[self accessLock] unlock];

					return YES;

				}

			}

		}

		// No explicit expiration time sent by the server

		return NO;

	}

	[[self accessLock] unlock];

	return YES;

}

- (ASICachePolicy)defaultCachePolicy

{

	[[self accessLock] lock];

	ASICachePolicy cp = defaultCachePolicy;

	[[self accessLock] unlock];

	return cp;

}

- (void)setDefaultCachePolicy:(ASICachePolicy)cachePolicy

{

	[[self accessLock] lock];

	if (!cachePolicy) {

		defaultCachePolicy = ASIAskServerIfModifiedWhenStaleCachePolicy;

	}  else {

		defaultCachePolicy = cachePolicy;	

	}

	[[self accessLock] unlock];

}

- (void)clearCachedResponsesForStoragePolicy:(ASICacheStoragePolicy)storagePolicy

{

	[[self accessLock] lock];

	if (![self storagePath]) {

		[[self accessLock] unlock];

		return;

	}

	NSString *path = [[self storagePath] stringByAppendingPathComponent:(storagePolicy == ASICacheForSessionDurationCacheStoragePolicy ? sessionCacheFolder : permanentCacheFolder)];

	BOOL isDirectory = NO;

	BOOL exists = [[NSFileManager defaultManager] fileExistsAtPath:path isDirectory:&isDirectory];

	if ((exists && !isDirectory) || !exists) {

		[[self accessLock] unlock];

		return;

	}

	NSError *error = nil;

	NSArray *cacheFiles = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:path error:&error];

	if (error) {

		[[self accessLock] unlock];

		[NSException raise:@"FailedToTraverseCacheDirectory" format:@"Listing cache directory failed at path '%@'",path];	

	}

	for (NSString *file in cacheFiles) {

		NSString *extension = [file pathExtension];

		if ([extension isEqualToString:@"cacheddata"] || [extension isEqualToString:@"cachedheaders"]) {

			[[NSFileManager defaultManager] removeItemAtPath:[path stringByAppendingPathComponent:file] error:&error];

			if (error) {

				[[self accessLock] unlock];

				[NSException raise:@"FailedToRemoveCacheFile" format:@"Failed to remove cached data at path '%@'",path];	

			}

		}

	}

	[[self accessLock] unlock];

}

+ (BOOL)serverAllowsResponseCachingForRequest:(ASIHTTPRequest *)request

{

	NSString *cacheControl = [[[request responseHeaders] objectForKey:@"Cache-Control"] lowercaseString];

	if (cacheControl) {

		if ([cacheControl isEqualToString:@"no-cache"] || [cacheControl isEqualToString:@"no-store"]) {

			return NO;

		}

	}

	NSString *pragma = [[[request responseHeaders] objectForKey:@"Pragma"] lowercaseString];

	if (pragma) {

		if ([pragma isEqualToString:@"no-cache"]) {

			return NO;

		}

	}

	return YES;

}

// Borrowed from: http://stackoverflow.com/questions/652300/using-md5-hash-on-a-string-in-cocoa

+ (NSString *)keyForURL:(NSURL *)url

{

	NSString *urlString = [url absoluteString];

	// Strip trailing slashes so http://allseeing-i.com/ASIHTTPRequest/ is cached the same as http://allseeing-i.com/ASIHTTPRequest

	if ([[urlString substringFromIndex:[urlString length]-1] isEqualToString:@"/"]) {

		urlString = [urlString substringToIndex:[urlString length]-1];

	}

	const char *cStr = [urlString UTF8String];

	unsigned char result[16];

	CC_MD5(cStr, (CC_LONG)strlen(cStr), result);

	return [NSString stringWithFormat:@"%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X",result[0], result[1], result[2], result[3], result[4], result[5], result[6], result[7],result[8], result[9], result[10], result[11],result[12], result[13], result[14], result[15]]; 	

}

+ (NSDateFormatter *)rfc1123DateFormatter

{

	NSMutableDictionary *threadDict = [[NSThread currentThread] threadDictionary];

	NSDateFormatter *dateFormatter = [threadDict objectForKey:@"ASIDownloadCacheDateFormatter"];

	if (dateFormatter == nil) {

		dateFormatter = [[[NSDateFormatter alloc] init] autorelease];

		[dateFormatter setLocale:[[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"] autorelease]];

		[dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];

		[dateFormatter setDateFormat:@"EEE, dd MMM yyyy HH:mm:ss 'GMT'"];

		[threadDict setObject:dateFormatter forKey:@"ASIDownloadCacheDateFormatter"];

	}

	return dateFormatter;

}

- (BOOL)canUseCachedDataForRequest:(ASIHTTPRequest *)request

{

	// Ensure the request is allowed to read from the cache

	if ([request cachePolicy] & ASIDoNotReadFromCacheCachePolicy) {

		return NO;

	// If we don't want to load the request whatever happens, always pretend we have cached data even if we don't

	} else if ([request cachePolicy] & ASIDontLoadCachePolicy) {

		return YES;

	}

	NSDictionary *headers = [self cachedResponseHeadersForURL:[request url]];

	if (!headers) {

		return NO;

	}

	NSString *dataPath = [self pathToCachedResponseDataForURL:[request url]];

	if (!dataPath) {

		return NO;

	}

	// If we get here, we have cached data

	// If we have cached data, we can use it

	if ([request cachePolicy] & ASIOnlyLoadIfNotCachedCachePolicy) {

		return YES;

	// If we have cached data that is current, we can use it

	} else if ([request cachePolicy] & ASIAskServerIfModifiedWhenStaleCachePolicy) {

		if ([self isCachedDataCurrentForRequest:request]) {

			return YES;

		}

	// If we've got headers from a conditional GET and the cached data is still current, we can use it

	} else if ([request cachePolicy] & ASIAskServerIfModifiedCachePolicy) {

		if (![request responseHeaders]) {

			return NO;

		} else if ([self isCachedDataCurrentForRequest:request]) {

			return YES;

		}

	}

	return NO;

}

@synthesize storagePath;

@synthesize defaultCachePolicy;

@synthesize accessLock;

@synthesize shouldRespectCacheControlHeaders;

@end