NSData+AsyncCacher.m

//
//  NSData+AsyncCacher.m
//  Meetweet
//
//  Created by Антон Буков on 28.06.13.
//  Copyright (c) 2013 Anton Bukov. All rights reserved.
//

#import "NSData+AsyncCacher.h"
#import "./SAMCache/SAMCache/SAMCache.h"

@implementation NSData (AsyncCacher)

+ (void)getDataFromURL:(NSURL *)url
               toBlock:(void(^)(NSData * data, BOOL * retry))block
{
    return [NSData getDataFromURL:url toBlock:block needCache:YES];
}

+ (void)getDataFromURL:(NSURL *)url
               toBlock:(void(^)(NSData * data, BOOL * retry))block
             needCache:(BOOL)needCache
{
    static SAMCache * cache;
    static NSOperationQueue * mainQueue;
    static NSOperationQueue * parallelQueue;
    static NSMutableDictionary * blocksDict;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        cache = [[SAMCache alloc] initWithName:@"AsyncCacher"];
        mainQueue = [[NSOperationQueue alloc] init];
        mainQueue.maxConcurrentOperationCount = 1;
        parallelQueue = [[NSOperationQueue alloc] init];
        parallelQueue.maxConcurrentOperationCount = 64;
        blocksDict = [NSMutableDictionary dictionary];
        
        NSURLCache *URLCache = [[NSURLCache alloc] initWithMemoryCapacity:4*1024*1024 diskCapacity:20*1024*1024 diskPath:nil];
        [NSURLCache setSharedURLCache:URLCache];
    });
    
    if (url == nil && block == nil)
        return [cache unloadAllObjects];
    
    if (url == nil)
        return;
    
    NSData * object = [cache objectForKey:url.absoluteString];
    if (needCache && object)
    {
        BOOL retry = NO;
        block(object, &retry);
        if (!retry)
            return;
    }
    
    [mainQueue addOperationWithBlock:^{
        NSMutableArray * blocks = blocksDict[url];
        if (blocks == nil)
        {
            blocks = [NSMutableArray array];
            blocksDict[url] = blocks;
        }
        
        [blocks addObject:((id)block ?: (id)[NSNull null])];
        if (blocks.count != 1)
            return;
        
        [parallelQueue addOperationWithBlock:^
        {
            [NSURLConnection sendAsynchronousRequest:[NSURLRequest requestWithURL:url] queue:mainQueue completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError)
            {
                if (data && needCache)
                    [cache setObject:data forKey:url.absoluteString];
                
                for (id a in blocks)
                {
                    void(^aBlock)(NSData *,BOOL *) = a;
                    if ((id)aBlock == [NSNull null])
                        continue;
                    
                    dispatch_async(dispatch_get_main_queue(), ^{
                        BOOL retry = NO;
                        aBlock(data, &retry);
                        if (retry)
                            [NSData getDataFromURL:url toBlock:aBlock needCache:needCache];
                    });
                }
                [blocks removeAllObjects];
            }];
        }];
    }];
}

@end