BNRFeedStore.m

//
//  BNRFeedStore.m
//  Nerdfeed
//
//  Created by THOMAS PENG on 6/24/12.
//  Copyright (c) 2012 __MyCompanyName__. All rights reserved.
//

#import "BNRFeedStore.h"
#import "RSSChannel.h"
#import "RSSItem.h"
#import "BNRConnection.h"

NSString * const BNRFeedStoreUpdateNotification = @"BNRFeedStoreUpdateNotification";

@implementation BNRFeedStore

- (id)init
{
    self = [super init];
    if (self) {
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(contentChange:) name:NSPersistentStoreDidImportUbiquitousContentChangesNotification object:nil];
        
        model = [NSManagedObjectModel mergedModelFromBundles:nil];
        
        NSPersistentStoreCoordinator *psc = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];
        
        // Find the location of the ubiquity container on the local filesystem
        NSFileManager *fm = [NSFileManager defaultManager];
        NSURL *ubContainer = [fm URLForUbiquityContainerIdentifier:nil];
        
        // Construct the dictionary that tells Core Data where the
        // transaction log should be stored
        NSMutableDictionary *options = [NSMutableDictionary dictionary];
        [options setObject:@"nerdfeed" forKey:NSPersistentStoreUbiquitousContentNameKey];
        [options setObject:ubContainer forKey:NSPersistentStoreUbiquitousContentURLKey];
        
        NSError *error = nil;
        
        // Specify a new directory and create it in the ubiquity container
        NSURL *nosyncDir = [ubContainer URLByAppendingPathComponent:@"feed.nosync"];
        [fm createDirectoryAtURL:nosyncDir withIntermediateDirectories:YES attributes:nil error:nil];
        
        // Specify the new file to store Core Data's SQLite file
        NSURL *dbURL = [nosyncDir URLByAppendingPathComponent:@"feed.db"];
        
        // Set up the persistent store with the transaction log details
        if (![psc addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:dbURL options:options error:&error]) {
            [NSException raise:@"Open failed" format:@"Reason: %@", [error localizedDescription]];
        }
        
        context = [[NSManagedObjectContext alloc] init];
        [context setPersistentStoreCoordinator:psc];
        
        [context setUndoManager:nil];
    }
    return self;
}

- (void)contentChange:(NSNotification *)note
{
    // merge changes into context
    [context mergeChangesFromContextDidSaveNotification:note];
    
    [[NSOperationQueue mainQueue] addOperationWithBlock:^{
        NSNotification *updateNote = [NSNotification notificationWithName:BNRFeedStoreUpdateNotification object:nil];
        [[NSNotificationCenter defaultCenter] postNotification:updateNote];
    }];
}

- (void)setTopSongsCacheDate:(NSDate *)topSongsCacheDate
{
    [[NSUserDefaults standardUserDefaults] setObject:topSongsCacheDate forKey:@"topSongsCacheDate"];
}

- (NSDate *)topSongsCacheDate
{
    return [[NSUserDefaults standardUserDefaults] objectForKey:@"topSongsCacheDate"];
}

+ (BNRFeedStore *)sharedStore
{
    static BNRFeedStore *feedStore = nil;
    
    if (!feedStore)
        feedStore = [[BNRFeedStore alloc] init];
    
    return feedStore;
}

- (void)fetchTopSongs:(int)count withCompletion:(void (^)(RSSChannel *, NSError *))block
{
    // Construct the cache path
    NSString *cachePath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    cachePath = [cachePath stringByAppendingPathComponent:@"apple.archive"];
    
    // Make sure we have cached at least once before by checking to see
    // if this date exists!
    NSDate *tscDate = [self topSongsCacheDate];
    if (tscDate) {
        // How old is the cache?
        NSTimeInterval cacheAge = [tscDate timeIntervalSinceNow];
        
        if (cacheAge > -300.0) {
            // If it is less than 300 seconds (5 minutes) old, return cache
            // in completion block
            NSLog(@"Reading cache!");
            
            RSSChannel *cachedChannel = [NSKeyedUnarchiver unarchiveObjectWithFile:cachePath];
            
            if (cachedChannel) {
                [[NSOperationQueue mainQueue] addOperationWithBlock:^{
                
                    // Execute the controller's completion block to reload its table
                    block(cachedChannel, nil);
                
                }];
                // Don't need to make the request, just get out of this method
                return;
            }
        }
    }
    
    // Prepare a request URL, including the argument from the controller
    NSString *requestString = [NSString stringWithFormat:@"http://itunes.apple.com/us/rss/topsongs/limit=%d/json", count];
    
    NSURL *url = [NSURL URLWithString:requestString];
    
    // Set up the connection as normal
    NSURLRequest *req = [NSURLRequest requestWithURL:url];
    RSSChannel *channel = [[RSSChannel alloc] init];
    
    BNRConnection *connection = [[BNRConnection alloc] initWithRequest:req];
    
    [connection setCompletionBlock:^(RSSChannel *obj, NSError *err) {
        // This is the store's completion code:
        // If everything went smoothly, save the channel to disk and set cache date
        if (!err) {
            [self setTopSongsCacheDate:[NSDate date]];
            [NSKeyedArchiver archiveRootObject:obj toFile:cachePath];
        }
        
        // This is the controller's completion code:
        block(obj, err);
    }];
    
    [connection setJsonRootObject:channel];
    
    [connection start];
}

- (RSSChannel *)fetchRSSFeedWithCompletion:(void (^)(RSSChannel *, NSError *))block
{
    NSURL *url = [NSURL URLWithString:@"http://forums.bignerdranch.com/" @"smartfeed.php?limit=1_DAY&sort_by=standard" @"&feed_type=RSS2.0&feed_style=COMPACT"];
    
    NSURLRequest *req = [NSURLRequest requestWithURL:url];
    
    // Create an empty channel
    RSSChannel *channel = [[RSSChannel alloc] init];
    
    // Create a connection "actor" object that will transfer data from the server
    BNRConnection *connection = [[BNRConnection alloc] initWithRequest:req];
    
    NSString *cachePath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    
    cachePath = [cachePath stringByAppendingPathComponent:@"nerd.archive"];
    
    // Load the cached channel
    RSSChannel *cachedChannel = [NSKeyedUnarchiver unarchiveObjectWithFile:cachePath];
    
    // If one hasn't already been cached, create a blank one to fill up
    if (!cachedChannel)
        cachedChannel = [[RSSChannel alloc] init];
    
    RSSChannel *channelCopy = [cachedChannel copy];
    
    [connection setCompletionBlock:^(RSSChannel *obj, NSError *err) {
        // This is the store's callback code
        if (!err) {
            [channelCopy addItemsFromChannel:obj];
            [NSKeyedArchiver archiveRootObject:channelCopy toFile:cachePath];
        }
        // This is the controller's callback code
        block(channelCopy, err);
    }];
    
    
    // Let the empty channel parse the returning data from the web service
    [connection setXmlRootObject:channel];
    
    // Begin the connection
    [connection start];
    
    return cachedChannel;
}

- (void)markItemAsRead:(RSSItem *)item
{
    // If the item is already in Core Data, no need for duplicates
    if ([self hasItemBeenRead:item])
        return;

    // Create a new Link object and insert it into the context
    NSManagedObject *obj = [NSEntityDescription insertNewObjectForEntityForName:@"Link" inManagedObjectContext:context];

    // Set the Link's urlString from the RSSItem
    [obj setValue:[item link] forKey:@"urlString"];

    // immediately save the changes
    [context save:nil];
}

- (BOOL)hasItemBeenRead:(RSSItem *)item
{
    // Create a request to fetch all Link's with the same urlString as
    // this items link
    NSFetchRequest *req = [[NSFetchRequest alloc] initWithEntityName:@"Link"];
    NSPredicate *pred = [NSPredicate predicateWithFormat:@"urlString like %@", [item link]];
    [req setPredicate:pred];

    // If there is at least one Link, then this item has been read before
    NSArray *entries = [context executeFetchRequest:req error:nil];

    if ([entries count] > 0)
        return YES;

    // If Core Data has never seen this link, then it hasn't been read
    return NO;
}

@end