/*

 Copyright (C) 2015 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 Data source object responsible for initiating the download of the XML data and parses the Earthquake objects at view load time.

 */

#import "APLEarthQuakeSource.h"

#import "APLParseOperation.h"

static NSString *feedURLString = @"http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/all_week.quakeml";

@interface APLEarthQuakeSource ()

@property (nonatomic, strong) NSMutableArray *earthquakes;

@property (nonatomic, strong) NSError *error;

@property (nonatomic, strong) NSURLSessionDataTask *sessionTask;

@property (assign) id addEarthQuakesObserver;

@property (assign) id earthQuakesErrorObserver;

// queue that manages our NSOperation for parsing earthquake data

@property (nonatomic, strong) NSOperationQueue *parseQueue;

@end

#pragma mark -

@implementation APLEarthQuakeSource

- (instancetype)init {

    self = [super init];

    if (self != nil) {

        _earthquakes = [NSMutableArray array];

        // Our NSNotification callback from the running NSOperation to add the earthquakes

        _addEarthQuakesObserver = [[NSNotificationCenter defaultCenter] addObserverForName:APLParseOperation.AddEarthQuakesNotificationName

                                                                                    object:nil

                                                                                     queue:nil

                                                                                usingBlock:^(NSNotification *notification) {

            /**

             The NSOperation "ParseOperation" calls this observer with batches of parsed objects.

             The batch size is set via the kSizeOfEarthquakeBatch constant. Use KVO to notify our client.

             */

            NSArray *incomingEarthquakes = [notification.userInfo valueForKey:APLParseOperation.EarthquakeResultsKey];

            [self willChangeValueForKey:@"earthquakes"];

            [self.earthquakes addObjectsFromArray:incomingEarthquakes];

            [self didChangeValueForKey:@"earthquakes"];

        }];

        // Our NSNotification callback from the running NSOperation when a parsing error has occurred

        _earthQuakesErrorObserver = [[NSNotificationCenter defaultCenter] addObserverForName:APLParseOperation.EarthquakesErrorNotificationName

                                                                                      object:nil

                                                                                       queue:nil

                                                                                  usingBlock:^(NSNotification *notification) {

            // The NSOperation "ParseOperation" calls this observer with an error, use KVO to notify our client

            [self willChangeValueForKey:@"error"];

            self.error = [notification.userInfo valueForKey:APLParseOperation.EarthquakesMessageErrorKey];

            [self didChangeValueForKey:@"error"];

        }];

        _parseQueue = [NSOperationQueue new];

    }

    return self;

}

- (void)startEarthQuakeLookup {

    /*

     Use NSURLSession to asynchronously download the data.

     This means the main thread will not be blocked - the application will remain responsive to the user.

     IMPORTANT! The main thread of the application should never be blocked!

     Also, avoid synchronous network access on any thread.

     */

    NSURLRequest *earthquakeURLRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:feedURLString]];

    // create an session data task to obtain and download the app icon

    _sessionTask = [[NSURLSession sharedSession] dataTaskWithRequest:earthquakeURLRequest

                                                   completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {

        [[NSOperationQueue mainQueue] addOperationWithBlock: ^{

            // back on the main thread, check for errors, if no errors start the parsing

            //

            if (error != nil && response == nil) {

                if (error.code == NSURLErrorAppTransportSecurityRequiresSecureConnection) {

                    // if you get error NSURLErrorAppTransportSecurityRequiresSecureConnection (-1022),

                    // then your Info.plist has not been properly configured to match the target server.

                    //

                    NSAssert(NO, @"NSURLErrorAppTransportSecurityRequiresSecureConnection");

                }

                else {

                    // use KVO to notify our client of this error

                    [self willChangeValueForKey:@"error"];

                    self.error = error;

                    [self didChangeValueForKey:@"error"];

                }

            }

            // here we check for any returned NSError from the server,

            // "and" we also check for any http response errors check for any response errors

            if (response != nil) {

                NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;

                if (((httpResponse.statusCode/100) == 2) && [response.MIMEType isEqual:@"application/xml"]) {

                    /* Update the UI and start parsing the data,

                        Spawn an NSOperation to parse the earthquake data so that the UI is not

                        blocked while the application parses the XML data.

                     */

                    APLParseOperation *parseOperation = [[APLParseOperation alloc] initWithData:data];

                    [self.parseQueue addOperation:parseOperation];

                }

                else {

                    NSString *errorString =

                        NSLocalizedString(@"HTTP Error", @"Error message displayed when receiving an error from the server.");

                    NSDictionary *userInfo = @{NSLocalizedDescriptionKey : errorString};

                    // use KVO to notify our client of this error

                    [self willChangeValueForKey:@"error"];

                    self.error = [NSError errorWithDomain:@"HTTP"

                                                    code:httpResponse.statusCode

                                                userInfo:userInfo];

                    [self didChangeValueForKey:@"error"];

                }

            }

        }];

    }];

    [self.sessionTask resume];

}

- (void)dealloc {

    [[NSNotificationCenter defaultCenter] removeObserver:self.addEarthQuakesObserver];

    [[NSNotificationCenter defaultCenter] removeObserver:self.earthQuakesErrorObserver];

}

@end