iOS: Printing PNG files to Google Cloud Print using GTM

Question

I figured out the problem with help from the Google Cloud Print mailing list. Hopefully I can find time to package this into a Pod and make it easier to work with.

Disclaimer: There are some unfinished/not cleaned up pieces here but focus on the Mime Document, ticket, and NSInputStream.

@implementation EBCloudPrint

+(void) printFile:(NSString *)file completion:(void (^)(void))completion{
    [EBCloudPrint printImage:[NSData dataWithContentsOfFile:file] completion:completion];
}

+(void) printImage:(NSData *)image completion:(void (^)(void))completion{
    NSString *printer = [EBPreferences getUserPreference:PREFERENCE_GOOGLE_CLOUD_PRINTER];
    if (printer == nil) {
        NSLog(@"Ignoring print");
        if (completion) {
            completion();
        }
        return;
    }
    GTMOAuth2Authentication *auth = [GTMOAuth2ViewControllerTouch authForGoogleFromKeychainForName:GOOGLE_KEYCHAIN_NAME
                                                                                          clientID:GOOGLE_CLIENT_ID
                                                                                      clientSecret:GOOGLE_CLIENT_SECRET];

    // Return immediately if we haven't auth
    if (![auth canAuthorize]) {
        if (completion) {
            completion();
        }
        return;
    }

    [GTMHTTPFetcher setLoggingEnabled:YES];

    GTMMIMEDocument *doc = [GTMMIMEDocument MIMEDocument];

    // MediaSize docs: https://developers.google.com/cloud-print/docs/cdd#MediaSize
    NSString *ticketJson = @"{\"version\": \"1.0\", \"print\": { \"media_size\": { \"width_microns\": 101600, \"height_microns\": 152400 }}}"; //media_size: 4x6

    [doc addPartWithHeaders:@{@"Content-Disposition": @"form-data; name=\"ticket\"", @"Content-Type": @"text/json"}
                       body:[ticketJson dataUsingEncoding:NSUTF8StringEncoding]];

    [doc addPartWithHeaders:@{@"Content-Disposition": @"form-data; name=\"content\"; filename=\"eb.png\"", @"Content-Type": @"image/png"}
                       body:image];

    NSString *boundary = nil;
    unsigned long long length = -1;

    NSInputStream *stream = nil;
    [doc generateInputStream:&stream
                      length:&length
                    boundary:&boundary];

    if (stream) {
        NSString *url = [NSString stringWithFormat:@"%@?output=json&printerid=%@&contentType=image/png&title=MyApp&tag=my_app", CLOUD_PRINT_JOB_URL, printer];

        NSLog(@"Printing to: %@", url);

        NSMutableURLRequest *jobSubmitRequest;
        NSTimeInterval timeout = 300.0;

        jobSubmitRequest = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:url]
                                                        cachePolicy:NSURLRequestReloadIgnoringCacheData
                                                    timeoutInterval:timeout];

        NSString *httpHeaderContentTypeString = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary];
        [jobSubmitRequest addValue:@"my_app" forHTTPHeaderField:@"X-CloudPrint-Proxy"];
        [jobSubmitRequest addValue:httpHeaderContentTypeString forHTTPHeaderField:@"Content-Type"];
        [jobSubmitRequest setHTTPMethod:@"POST"];

        GTMHTTPFetcher* fetcher = [GTMHTTPFetcher fetcherWithRequest:jobSubmitRequest];
        [fetcher setPostStream:stream];
        [fetcher setAuthorizer:auth];

        [fetcher beginFetchWithCompletionHandler:^(NSData *data, NSError *error) {
            if (data) {
                NSLog(@"data: %@", [NSString stringWithUTF8String:[data bytes]]);
            }
            if (error) {
                NSLog(@"---- error: %@", error.localizedDescription);
            } else if(completion){
                completion();
            }
        }];

        stream = nil;
        fetcher = nil;
    }
}

+(NSArray *) getPrinters{
    return [[NSArray alloc] init];
}

@end