/*

 Copyright (C) 2017 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 Configures the Core Data persistence stack and starts the RSS importer.

 */

#import "AppDelegate.h"

#import "SongsViewController.h"

#import "iTunesRSSImporter.h"

@import CoreData;

// String used to identify the update object in the user defaults storage.

static NSString * const kLastStoreUpdateKey = @"LastStoreUpdate";

// Get the RSS feed for the first time or if the store is older than kRefreshTimeInterval seconds.

static NSTimeInterval const kRefreshTimeInterval = 3600;

// The number of songs to be retrieved from the RSS feed.

static NSUInteger const kImportSize = 300;

@interface AppDelegate() <iTunesRSSImporterDelegate>

@property (nonatomic, strong) SongsViewController *songsViewController;

// Properties for the importer and its background processing queue.

@property (nonatomic, strong) iTunesRSSImporter *importer;

@property (nonatomic, strong) NSOperationQueue *operationQueue;

// Properties for the Core Data stack.

@property (nonatomic, strong) NSManagedObjectContext *managedObjectContext;

@property (nonatomic, strong) NSPersistentStoreCoordinator *persistentStoreCoordinator;

@property (nonatomic, strong) NSString *persistentStorePath;

@end

#pragma mark -

@implementation AppDelegate

// The app delegate must implement the window @property

// from UIApplicationDelegate @protocol to use a main storyboard file.

//

@synthesize window;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(nullable NSDictionary *)launchOptions {

    // check the last update, stored in NSUserDefaults

    NSDate *lastUpdate = [[NSUserDefaults standardUserDefaults] objectForKey:kLastStoreUpdateKey];

    if (lastUpdate == nil || -lastUpdate.timeIntervalSinceNow > kRefreshTimeInterval) {

        // remove the old store; easier than deleting every object

        // first, test for an existing store

        if ([[NSFileManager defaultManager] fileExistsAtPath:self.persistentStorePath]) {

            NSError *error = nil;

            BOOL oldStoreRemovalSuccess = [[NSFileManager defaultManager] removeItemAtPath:self.persistentStorePath error:&error];

            NSAssert3(oldStoreRemovalSuccess, @"Unhandled error adding persistent store in %s at line %d: %@", __FUNCTION__, __LINE__, [error localizedDescription]);

        }

        // create an importer object to retrieve, parse, and import into the CoreData store 

        self.importer = [[iTunesRSSImporter alloc] init];

        self.importer.delegate = self;

        // pass the coordinator so the importer can create its own managed object context

        self.importer.persistentStoreCoordinator = self.persistentStoreCoordinator;

        self.importer.iTunesURL = [NSURL URLWithString:[NSString stringWithFormat:@"http://ax.phobos.apple.com.edgesuite.net/WebObjects/MZStore.woa/wpa/MRSS/newreleases/limit=%ld/rss.xml", (unsigned long)kImportSize]];

        [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;

        // add the importer to an operation queue for background processing (works on a separate thread)

        [self.operationQueue addOperation:self.importer];

    }

    // obtain our current initial view controller on the nav stack and set it's managed object context

    UINavigationController *navController = (UINavigationController *)self.window.rootViewController;

    _songsViewController = (SongsViewController *)navController.visibleViewController;

    self.songsViewController.managedObjectContext = self.managedObjectContext;

    return YES;

}

- (NSOperationQueue *)operationQueue {

    if (_operationQueue == nil) {

        _operationQueue = [[NSOperationQueue alloc] init];

    }

    return _operationQueue;

}

#pragma mark - Core Data stack setup

//

// These methods are very slightly modified from what is provided by the Xcode template

// An overview of what these methods do can be found in the section "The Core Data Stack" 

// in the following article: 

// http://developer.apple.com/iphone/library/documentation/DataManagement/Conceptual/iPhoneCoreData01/Articles/01_StartingOut.html

//

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {

    if (_persistentStoreCoordinator == nil) {

        NSURL *storeUrl = [NSURL fileURLWithPath:self.persistentStorePath];

        _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[NSManagedObjectModel mergedModelFromBundles:nil]];

        NSError *error = nil;

        NSPersistentStore *persistentStore = [_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:nil error:&error];

        NSAssert3(persistentStore != nil, @"Unhandled error adding persistent store in %s at line %d: %@", __FUNCTION__, __LINE__, [error localizedDescription]);

    }

    return _persistentStoreCoordinator;

}

- (NSManagedObjectContext *)managedObjectContext {

    if (_managedObjectContext == nil) {

        _managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];

        self.managedObjectContext.persistentStoreCoordinator = self.persistentStoreCoordinator;

    }

    return _managedObjectContext;

}

- (NSString *)persistentStorePath {

    if (_persistentStorePath == nil) {

        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

        NSString *documentsDirectory = paths.lastObject;

        _persistentStorePath = [documentsDirectory stringByAppendingPathComponent:@"TopSongs.sqlite"];

    }

    return _persistentStorePath;

}

#pragma mark - iTunesRSSImporterDelegate

// This method will be called on a secondary thread. Forward to the main thread for safe handling of UIKit objects.

- (void)importerDidSave:(NSNotification *)saveNotification {

    if ([NSThread isMainThread]) {

        [self.managedObjectContext mergeChangesFromContextDidSaveNotification:saveNotification];

        [self.songsViewController fetch];

    } else {

        [self performSelectorOnMainThread:@selector(importerDidSave:) withObject:saveNotification waitUntilDone:NO];

    }

}

// Helper method for main-thread processing of import completion.

- (void)handleImportCompletion {

    // Store the current time as the time of the last import.

    // This will be used to determine whether an import is necessary when the application runs.

    [[NSUserDefaults standardUserDefaults] setObject:[NSDate date] forKey:kLastStoreUpdateKey];

    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;

    self.importer = nil;

}

// This method will be called on a secondary thread. Forward to the main thread for safe handling of UIKit objects.

- (void)importerDidFinishParsingData:(iTunesRSSImporter *)importer {

    [self performSelectorOnMainThread:@selector(handleImportCompletion) withObject:nil waitUntilDone:NO];

}

// Helper method for main-thread processing of errors received in the delegate callback below.

- (void)handleImportError:(NSError *)error {

    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;

    self.importer = nil;

    // handle errors as appropriate to your application, here we just alert the user

    NSString *errorMessage = error.localizedDescription;

    NSString *alertTitle = NSLocalizedString(@"Error", @"Title for alert displayed when download or parse error occurs.");

    NSString *okTitle = NSLocalizedString(@"OK", @"OK");

    UIAlertController *alert = [UIAlertController alertControllerWithTitle:alertTitle message:errorMessage preferredStyle:UIAlertControllerStyleAlert];

    UIAlertAction *action = [UIAlertAction actionWithTitle:okTitle style:UIAlertActionStyleDefault handler:^(UIAlertAction *act) {

        [self.window.rootViewController dismissViewControllerAnimated:YES completion:nil];

    }];

    [alert addAction:action];

    [self.window.rootViewController presentViewController:alert animated:YES completion:nil];

}

// This method will be called on a secondary thread. Forward to the main thread for safe handling of UIKit objects.

- (void)importer:(iTunesRSSImporter *)importer didFailWithError:(NSError *)error {

    [self performSelectorOnMainThread:@selector(handleImportError:) withObject:error waitUntilDone:NO];

}

@end