VSTagAuthority.m

//
//  VSTagAuthority.m
//  Vesper
//
//  Created by Brent Simmons on 2/28/14.
//  Copyright (c) 2014 Q Branch LLC. All rights reserved.
//

#import "VSTagAuthority.h"
#import "VSTag.h"


@interface VSTagAuthority ()

@property (nonatomic, readonly) NSManagedObjectContext *context;
@property (nonatomic, readonly) NSMutableDictionary *tagIDs;

@end


@implementation VSTagAuthority


#pragma mark - Init

- (instancetype)initWithPersistentStoreCoordinator:(NSPersistentStoreCoordinator *)storeCoordinator {

	NSParameterAssert(storeCoordinator != nil);

	self = [super init];
	if (!self) {
		return nil;
	}

	_context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
	[_context setPersistentStoreCoordinator:storeCoordinator];
	[_context setUndoManager:nil];
	NSAssert(_context != nil, nil);

	_tagIDs = [NSMutableDictionary new];
	[self fetchTags];

	return self;
}


#pragma mark - Tag Cache

- (void)fetchTags {

	[self.context performBlock:^{

		NSArray *allTags = [VSTag allObjects:self.context];

		for (VSTag *oneTag in allTags) {

			NSString *oneClientID = oneTag.clientID; /*clientID is the unique ID for tag.*/
			NSAssert(oneClientID != nil, nil);

			self.tagIDs[oneClientID] = [oneTag objectID];
		}
	}];
}


#pragma mark - API

- (VSTag *)existingTagWithName:(NSString *)name context:(NSManagedObjectContext *)context {

	NSParameterAssert(name != nil && [name length] > 0);
	NSParameterAssert(context != nil);

	__block NSManagedObjectID *objectID = nil;

	[self.context performBlockAndWait:^{

		NSString *clientID = [VSTag clientIDForTagName:name];
		objectID = self.tagIDs[clientID];
		NSAssert(![objectID isTemporaryID], nil);

	}];

	if (objectID) {
		return (VSTag *)[context objectWithID:objectID];
	}

	return nil;
}


- (VSTag *)tagWithName:(NSString *)name context:(NSManagedObjectContext *)context error:(NSError **)error {

	NSParameterAssert(name != nil && [name length] > 0);
	NSParameterAssert(context != nil);

	__block NSManagedObjectID *objectID = nil;

	[self.context performBlockAndWait:^{

		NSString *clientID = [VSTag clientIDForTagName:name];
		objectID = self.tagIDs[clientID];

		if (!objectID) {
			VSTag *tag = [VSTag insertObject:self.context];
			tag.name = name;
			tag.clientID = clientID;

			if ([self.context save:error]) {

				objectID = [tag objectID];
				NSAssert(![objectID isTemporaryID], nil); /*Just saved -- should be permanent.*/

				self.tagIDs[clientID] = objectID;
			}

			else {
				NSLog(@"Error inserting tag: %@", *error);
			}
		}
	}];

	if (objectID) {
		return (VSTag *)[context objectWithID:objectID];
	}

	return nil;
}

@end