DemoQueue_CBLModel

/*========================================= h file =========================================*/
#import <CouchbaseLite/CouchbaseLite.h>

@interface DemoQueue : CBLModel

/** Query for for queue based with queue_id. */
+ (CBLQuery*) queryDemoQueueInDatabase: (CBLDatabase*)db forDemoQueueId: (NSString*)DQueueId;

/** Get an existing queue using queue_id, if no queue object exist, create it. */
+ (instancetype) getDemoQueueInDatabase: (CBLDatabase*)db forDemoQueueId: (NSString*)DQueueId;

/** Push a string to queue */
- (void) pushString:(NSString *)string;

/** Pop a string from queue */
- (NSString *) popString;


/** The queue */
@property (readwrite) NSArray   *queue;

@end
/*========================================= m file =========================================*/

#import "DemoQueue.h"

#define kDemoQueueDocType @"demoqueue"

@implementation DemoQueue

@dynamic queue;

/** Query for for queue based with queue_id. */
+ (CBLQuery*) queryDemoQueueInDatabase: (CBLDatabase*)db forDemoQueueId: (NSString*)DQueueId {
    CBLView *view = [db viewNamed:@"demoqueueview"];
    if (!view.mapBlock) {
        [view setMapBlock: MAPBLOCK({
            if ([doc[@"type"] isEqualToString:kDemoQueueDocType] //type as annotation
                )
            {
                emit(@[doc[@"_id"]],doc[@"queue"]);
            }
        }) reduceBlock: nil version: @"1"];
    }
    CBLQuery *query = [view createQuery];
//    query.endKey = query.startKey = @[DQueueId];
    return query;
}

/** Get an existing queue using queue_id, if no queue object exist, create it. */
+ (instancetype) getDemoQueueInDatabase: (CBLDatabase*)db forDemoQueueId: (NSString*)DQueueId {
    NSParameterAssert(DQueueId);
    DemoQueue *dq;
    NSString* DQDocId = DQueueId;
    CBLDocument *doc;
    if (DQDocId.length > 0)
        doc = [db existingDocumentWithID: DQDocId];
    if (doc == nil) {
        NSLog(@"Meeting session doc with %@ does not exist, creating a DemoQueue instance with empty array.", DQueueId);
        doc = [db documentWithID:DQDocId];
        dq = [DemoQueue modelForDocument:doc];
        dq.type = kDemoQueueDocType;
        dq.queue = nil;
    } else {
        dq = [DemoQueue modelForDocument:doc];
    }
    return dq;
}

/** Push a string to queue */
- (void) pushString:(NSString *)string {
    NSParameterAssert(string);
    NSMutableArray *newArray = [[NSMutableArray alloc]init];
    if (self.queue && [self.queue count]!=0) { //if queue is not empty, transfer to NSMutableArray for manipulation.
        [newArray addObjectsFromArray:self.queue];
    }
    [newArray addObject:string];
    self.queue = newArray;
}

/** Pop a string from queue */
- (NSString *) popString {
    if (self.queue == nil || self.queue.count == 0) { //if queue is empty, don't modify it and return.
        NSLog(@"DemoQueue is empty");
        return nil;
    }
    //if queue is not empty, transfer to NSMutableArray for manipulation
    NSMutableArray *newArray = [[NSMutableArray alloc] init];
    NSString *firstString = self.queue[0];
    [newArray addObjectsFromArray:self.queue];
    [newArray removeObjectAtIndex:0];
    self.queue = newArray;
    return firstString;
}

@end

DemoQueue_ViewController

/*========================================= h file =========================================*/
#import "ViewController.h"

@interface DemoViewController : ViewController

@end

/*========================================= m file =========================================*/
#import "DemoViewController.h"
#import "AppDelegate.h"
#import "DemoQueue.h"

#define kDemoQueueId @"demoqueue"

@interface DemoViewController ()

@property (weak, nonatomic) IBOutlet UILabel *QueueLabel;

@property (strong, nonatomic) CBLDatabase *database;
@property (strong, nonatomic) CBLLiveQuery *queueLiveQuery;

@end

@implementation DemoViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    [self setup];
}

- (void)setup {
    AppDelegate *app = [[UIApplication sharedApplication] delegate];
    self.database = app.database;
    
    if (self.database != nil) {
        self.queueLiveQuery = [DemoQueue queryDemoQueueInDatabase:self.database forDemoQueueId:kDemoQueueId].asLiveQuery;
        [self.queueLiveQuery addObserver: self forKeyPath: @"demoqueue"
                              options: 0 context: NULL];
        [self.queueLiveQuery start];
    } else {
    }
}

- (IBAction)pushToQueue:(id)sender {
    DemoQueue* demoQueue = [DemoQueue getDemoQueueInDatabase:_database forDemoQueueId:kDemoQueueId];
    [demoQueue pushString:[self randomString]];
    NSError *error;
    if ([demoQueue save:&error]) {
        //do nothing
    } else {
        NSLog(@"Cannot udpate demo queue: %@", [error description]);
    }
}
- (IBAction)popFromQueue:(id)sender {
    DemoQueue*  demoQueue = [DemoQueue getDemoQueueInDatabase:_database forDemoQueueId:kDemoQueueId];
    [demoQueue popString];
    NSError *error;
    if ([demoQueue save:&error]) {
        //do nothing
    } else {
        NSLog(@"Cannot udpate demo queue: %@", [error description]);
    }
}
- (IBAction)refreshLiveQuery:(id)sender {
    NSError *error;
    CBLQueryEnumerator* result = [self.queueLiveQuery run: &error];
    for (CBLQueryRow* row in result) {
        NSLog(@"found a row for demo queue, queue_id: %@, queue: %@", row.key, row.value);
        self.QueueLabel.text = [(NSArray *)row.value componentsJoinedByString:@","];
    }
}

#pragma mark - observe
- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context
{
    if (object == self.queueLiveQuery) {
        for (CBLQueryRow* row in self.queueLiveQuery.rows) {
            NSLog(@"found a row for demo queue, queue_id: %@, queue: %@", row.key, row.value);
            self.QueueLabel.text = row.value;
        }
    }
}

#pragma mark - helper
-(NSString *) randomString {
    NSString *letters = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    NSMutableString *randomString = [NSMutableString stringWithCapacity: 10];
    
    for (int i=0; i<10; i++) {
        [randomString appendFormat: @"%C", [letters characterAtIndex: arc4random_uniform((int)[letters length])]];
    }
    
    return randomString;
}

@end