Add NSOperation subclasses for completing checkout.

Mobile Buy SDK/Mobile Buy SDK/Operations/BUYCheckoutOperation.h

+//
+//  BUYCheckoutOperation.h
+//  Mobile Buy SDK
+//
+//  Created by Dima Bart on 2016-05-12.
+//  Copyright © 2016 Shopify Inc. All rights reserved.
+//
+
+#import "BUYOperation.h"
+
+@class BUYClient;
+@class BUYCheckout;
+@protocol BUYPaymentToken;
+
+typedef void (^BUYOperationCheckoutCompletion)(BUYCheckout *checkout, NSError *error);
+
+@interface BUYCheckoutOperation : BUYOperation
+
+@property (strong, nonatomic, readonly) BUYOperationCheckoutCompletion completion;
+
+- (instancetype)initWithCheckout:(BUYCheckout *)checkout token:(id<BUYPaymentToken>)token client:(BUYClient *)client completion:(BUYOperationCheckoutCompletion)completion;
+
+@end

Mobile Buy SDK/Mobile Buy SDK/Operations/BUYCheckoutOperation.m

+//
+//  BUYCheckoutOperation.m
+//  Mobile Buy SDK
+//
+//  Created by Dima Bart on 2016-05-12.
+//  Copyright © 2016 Shopify Inc. All rights reserved.
+//
+
+#import "BUYCheckoutOperation.h"
+#import "BUYCheckout.h"
+#import "BUYClient.h"
+
+@interface BUYOperation (Private)
+- (void)setExecuting:(BOOL)executing;
+- (void)setFinished:(BOOL)finished;
+@end
+
+@interface BUYCheckoutOperation ()
+
+@property (strong, nonatomic) BUYCheckout *checkout;
+@property (strong, nonatomic) id<BUYPaymentToken> token;
+@property (strong, nonatomic) BUYClient *client;
+
+@end
+
+@implementation BUYCheckoutOperation
+
+#pragma mark - Init -
+
+- (instancetype)initWithCheckout:(BUYCheckout *)checkout token:(id<BUYPaymentToken>)token client:(BUYClient *)client completion:(BUYOperationCheckoutCompletion)completion
+{
+	self = [super init];
+	if (self) {
+		_checkout   = checkout;
+		_token      = token;
+		_client     = client;
+		_completion = completion;
+	}
+	return self;
+}
+
+#pragma mark - Actions -
+
+- (void)finishWithCheckout:(BUYCheckout *)checkout
+{
+	[self setExecuting:NO];
+	self.completion(checkout, nil);
+}
+
+- (void)finishWithError:(NSError *)error
+{
+	[self setExecuting:NO];
+	self.completion(nil, error);
+}
+
+- (void)finishByCancellation
+{
+	[self setFinished:YES];
+	[self setExecuting:NO];
+}
+
+#pragma mark - Start -
+
+- (void)start
+{
+	[super start];
+	[self setExecuting:YES];
+	
+	if (self.isCancelled) {
+		[self finishByCancellation];
+		return;
+	}
+	
+	/* ---------------------------------
+	 * Initiate the checkout process by
+	 * sending the checkout object to the
+	 * backend for processing.
+	 */
+	[self.client completeCheckout:self.checkout paymentToken:self.token completion:^(BUYCheckout *checkout, NSError *error) {
+		if (self.isCancelled) {
+			[self finishByCancellation];
+			return;
+			
+		} else if (checkout) {
+			
+			/* ----------------------------------------
+			 * Recursively poll for checkout completion
+			 * status until we encounter an error or
+			 * get a successful completion status.
+			 */
+			[self pollUntilCheckoutCompletion:^(BOOL success, NSError *error) {
+				if (self.isCancelled ) {
+					[self finishByCancellation];
+					return;
+					
+				} else if (success) {
+					
+					/* ---------------------------------
+					 * Finally, after the checkout is
+					 * complete, we'll need to fetch the
+					 * completed checkout object.
+					 */
+					[self.client getCheckout:self.checkout completion:^(BUYCheckout *checkout, NSError *error) {
+						if (self.isCancelled) {
+							[self finishByCancellation];
+							return;
+							
+						} else if (checkout) {
+							[self finishWithCheckout:checkout];
+						} else {
+							[self finishWithError:error];
+						}
+					}];
+					
+				} else {
+					[self finishWithError:error];
+				}
+			}];
+			
+		} else {
+			[self finishWithError:error];
+		}
+	}];
+}
+
+#pragma mark - Requests -
+
+- (void)pollUntilCheckoutCompletion:(void(^)(BOOL success, NSError *error))completion {
+	[self.client getCompletionStatusOfCheckout:self.checkout completion:^(BUYStatus status, NSError *error) {
+		if (self.isCancelled) {
+			[self finishByCancellation];
+			return;
+			
+		} else if (status == BUYStatusComplete) {
+			completion(YES, nil);
+		} else if (error) {
+			completion(NO, error);
+		} else {
+			dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
+				[self pollUntilCheckoutCompletion:completion];
+			});
+		}
+	}];
+}
+
+@end

Mobile Buy SDK/Mobile Buy SDK/Operations/BUYOperation.h

+//
+//  BUYOperation.h
+//  Mobile Buy SDK
+//
+//  Created by Dima Bart on 2016-05-12.
+//  Copyright © 2016 Shopify Inc. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+@interface BUYOperation : NSOperation
+
+@end

Mobile Buy SDK/Mobile Buy SDK/Operations/BUYOperation.m

+//
+//  BUYOperation.m
+//  Mobile Buy SDK
+//
+//  Created by Dima Bart on 2016-05-12.
+//  Copyright © 2016 Shopify Inc. All rights reserved.
+//
+
+#import "BUYOperation.h"
+
+@interface BUYOperation ()
+
+@property (atomic, assign) BOOL isExecuting;
+@property (atomic, assign) BOOL isFinished;
+
+@end
+
+@implementation BUYOperation
+
+#pragma mark - Init -
+
+- (instancetype)init
+{
+	self = [super init];
+	if (self) {
+		
+	}
+	return self;
+}
+
+#pragma mark - Setters -
+
+- (void)setExecuting:(BOOL)executing
+{
+	[self willChangeValueForKey:@"isExecuting"];
+	self.isExecuting = executing;
+	[self didChangeValueForKey:@"isExecuting"];
+}
+
+- (void)setFinished:(BOOL)finished
+{
+	[self willChangeValueForKey:@"isFinished"];
+	self.isFinished = finished;
+	[self didChangeValueForKey:@"isFinished"];
+}
+
+@end