ReactiveCocoa-based wrapper around NSNetServiceBrowser

LTClientBrowser.h

//
//  LTClientBrowser.h
//  LayerTreeServer
//
//  Created by Indragie Karunaratne on 2014-05-21.
//  Copyright (c) 2014 Indragie Karunaratne. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <LayerTreeKit/LayerTreeKit.h>

@interface LTClientBrowser : NSObject

/**
 *  Searches for LayerTree clients.
 *
 *  Trying to search while an existing search is still executing will result in a signal
 *  that errors immediately.
 *
 *  @return A signal that sends an array of `NSNetService`s found once the search completes.
 */
- (RACSignal *)searchForClients;

@end

LTClientBrowser.m

//
//  LTClientBrowser.m
//  LayerTreeServer
//
//  Created by Indragie Karunaratne on 2014-05-21.
//  Copyright (c) 2014 Indragie Karunaratne. All rights reserved.
//

#import "LTClientBrowser.h"

#import <LayerTreeKit/LayerTreeKit.h>

typedef NS_ENUM(NSInteger, LTClientBrowserState) {
	LTClientBrowserStateStopped = 0,
	LTClientBrowserStateSearching,
};

typedef NS_ENUM(NSInteger, LTCollectionMutationType) {
	LTCollectionMutationTypeNone = 0,
	LTCollectionMutationTypeInsertion,
	LTCollectionMutationTypeRemoval
};

@interface LTCollectionMutation : NSObject
@property (nonatomic, assign, readonly) LTCollectionMutationType type;
@property (nonatomic, strong) id object;
- (instancetype)initWithType:(LTCollectionMutationType)type object:(id)object;
@end

static NSString * const LTClientBrowserErrorDomain = @"LTClientBrowserErrorDomain";

static NSError * LTClientBrowserAlreadySearchingError()
{
	NSDictionary *userInfo = @{NSLocalizedDescriptionKey : @"A search is already in progress. Please wait until the existing search has completed before attempting to start another one."};
	return [NSError errorWithDomain:LTClientBrowserErrorDomain code:1 userInfo:userInfo];
}

@interface LTClientBrowser () <NSNetServiceBrowserDelegate>
@property (nonatomic, strong, readonly) NSNetServiceBrowser *serviceBrowser;
@property (nonatomic, assign) LTClientBrowserState state;
@end

@implementation LTClientBrowser

- (id)init
{
	if ((self = [super init])) {
		_serviceBrowser = [[NSNetServiceBrowser alloc] init];
		_serviceBrowser.delegate = self;
		[_serviceBrowser scheduleInRunLoop:NSRunLoop.currentRunLoop forMode:NSRunLoopCommonModes];
	}
	return self;
}

- (void)dealloc
{
	[_serviceBrowser removeFromRunLoop:NSRunLoop.currentRunLoop forMode:NSRunLoopCommonModes];
}

#pragma mark - Searching

- (RACSignal *)mutationSignalForSelector:(SEL)sel type:(LTCollectionMutationType)type
{
	return [[self
		rac_signalForSelector:sel fromProtocol:@protocol(NSNetServiceDelegate)]
		reduceEach:^(NSNetServiceBrowser *browser, NSNetService *service, NSNumber *moreComing) {
			LTCollectionMutation *mutation = [[LTCollectionMutation alloc] initWithType:type object:service];
			return RACTuplePack(mutation, moreComing);
		}];
}

- (RACSignal *)searchForClients
{
	if (self.state == LTClientBrowserStateSearching) {
		return [RACSignal error:LTClientBrowserAlreadySearchingError()];
	}
	
	return [[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
		self.state = LTClientBrowserStateSearching;
		
		RACSignal *insertion = [self mutationSignalForSelector:@selector(netServiceBrowser:didFindService:moreComing:) type:LTCollectionMutationTypeInsertion];
		RACSignal *removal = [self mutationSignalForSelector:@selector(netServiceBrowser:didRemoveService:moreComing:) type:LTCollectionMutationTypeRemoval];
		
		NSMutableArray *services = [[NSMutableArray alloc] init];
		RACDisposable *results = [[[[[RACSignal
			merge:@[insertion, removal]]
			reduceEach:^(LTCollectionMutation *mutation, NSNumber *moreComing) {
				if (mutation.type == LTCollectionMutationTypeInsertion) {
					[services addObject:mutation.object];
				} else if (mutation.type == LTCollectionMutationTypeRemoval) {
					[services removeObject:mutation.object];
				}
				return moreComing;
			}]
			takeUntilBlock:^BOOL(NSNumber *moreComing) {
				return [moreComing isEqualToNumber:@NO];
			}]
			then:^RACSignal *{
				return [RACSignal return:services];
			}]
			subscribe:subscriber];
		
		RACDisposable *failure = [[[[[self
			rac_signalForSelector:@selector(netServiceBrowser:didNotSearch:) fromProtocol:@protocol(NSNetServiceBrowserDelegate)]
			take:1]
			reduceEach:^(NSNetServiceBrowser *browser, NSDictionary *errorDict) {
				return [RACEvent eventWithError:LTErrorFromBonjourErrorDictionary(errorDict)];
			}]
			dematerialize]
			subscribe:subscriber];
		
		[self.serviceBrowser searchForServicesOfType:LTServiceType inDomain:LTServiceDomain];
		
		return [RACDisposable disposableWithBlock:^{
			[results dispose];
			[failure dispose];
			
			[self.serviceBrowser stop];
			self.state = LTClientBrowserStateStopped;
		}];
	}] setNameWithFormat:@"<%@:%p> -searchForClients", self.class, self];
}

#pragma mark - NSNetServiceBrowserDelegate

- (void)netServiceBrowser:(NSNetServiceBrowser *)netServiceBrowser didFindService:(NSNetService *)netService moreComing:(BOOL)moreServicesComing {}
- (void)netServiceBrowser:(NSNetServiceBrowser *)netServiceBrowser didRemoveService:(NSNetService *)netService moreComing:(BOOL)moreServicesComing {}
- (void)netServiceBrowser:(NSNetServiceBrowser *)netServiceBrowser didNotSearch:(NSDictionary *)errorInfo {}

@end

@implementation LTCollectionMutation

- (instancetype)initWithType:(LTCollectionMutationType)type object:(id)object
{
	if ((self = [super init])) {
		_type = type;
		_object = object;
	}
	return self;
}

@end