VSTagAuthoritySQL.m

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

#import <libkern/OSAtomic.h>
#import "VSTagAuthoritySQL.h"
#import "QSDatabaseQueue.h"
#import "FMDatabase.h"


@interface VSTagAuthoritySQL ()

@property (nonatomic, readonly) QSDatabaseQueue *databaseQueue;
@property (nonatomic, readonly) NSMutableDictionary *tags;

@end


static OSSpinLock tagsLock = OS_SPINLOCK_INIT;

@implementation VSTagAuthoritySQL


#pragma mark - Init

- (instancetype)initWithDatabaseQueue:(QSDatabaseQueue *)databaseQueue {

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

	_databaseQueue = databaseQueue;
	_tags = [NSMutableDictionary new];
	[self fetchTags];

	return self;
}


#pragma mark - Database

static NSString *VSTagNameKey = @"name";
static NSString *VSTagClientIDKey = @"clientID";

- (void)fetchTags {

	OSSpinLockLock(&tagsLock);

	[self.databaseQueue fetch:^(FMDatabase *database) {

		FMResultSet *rs = [database executeQuery:@"select name, clientID from tags;"];
		while ([rs next]) {

			/*In real life there would be a +VSTag tagWithResultSet: method.
			 This is just to illustrate.*/

			VSTag *oneTag = [VSTag new];
			oneTag.name = [rs stringForColumn:VSTagNameKey];
			oneTag.clientID = [rs stringForColumn:VSTagClientIDKey];

			self.tags[oneTag.clientID] = oneTag;
		}

		OSSpinLockUnlock(&tagsLock);
	}];
}


- (void)insertTagInDatabase:(VSTag *)tag {

	/*In real life there would be a
	 -[VSTag insertInDatabase:(QSDatabaseQueue *)queue] method.*/
	
	NSString *name = tag.name;
	NSString *clientID = tag.clientID;

	[self.databaseQueue update:^(FMDatabase *database) {

		[database executeUpdate:@"insert into tags (name, clientID) values (?, ?);", name, clientID];
	}];
}


#pragma mark - API

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

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

	NSString *clientID = [VSTag clientIDForTagName:name];

	OSSpinLockLock(&tagsLock);
	VSTag *tag = self.tags[clientID];
	OSSpinLockUnlock(&tagsLock);

	return tag;
}


- (VSTag *)tagWithName:(NSString *)name {

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

	NSString *clientID = [VSTag clientIDForTagName:name];

	OSSpinLockLock(&tagsLock);
	VSTag *tag = self.tags[clientID];

	if (!tag) {
		tag = [VSTag new];
		tag.name = name;
		tag.clientID = clientID;

		self.tags[clientID] = tag;
		[self insertTagInDatabase:tag];
	}

	OSSpinLockUnlock(&tagsLock);

	return tag;
}

@end