session-ios/SignalMessaging/environment/migrations/OWSDatabaseMigration.m

//
//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
//

#import "OWSDatabaseMigration.h"
#import <SignalServiceKit/TSStorageManager.h>

NS_ASSUME_NONNULL_BEGIN

@implementation OWSDatabaseMigration

- (instancetype)initWithStorageManager:(TSStorageManager *)storageManager
{
    self = [super initWithUniqueId:[self.class migrationId]];
    if (!self) {
        return self;
    }

    _storageManager = storageManager;

    return self;
}

+ (MTLPropertyStorage)storageBehaviorForPropertyWithKey:(NSString *)propertyKey
{
    if ([propertyKey isEqualToString:@"storageManager"]) {
        return MTLPropertyStorageNone;
    } else {
        return [super storageBehaviorForPropertyWithKey:propertyKey];
    }
}

+ (NSString *)migrationId
{
    OWSRaiseException(NSInternalInconsistencyException, @"Must override %@ in subclass", NSStringFromSelector(_cmd));
}

+ (NSString *)collection
{
    // We want all subclasses in the same collection
    return @"OWSDatabaseMigration";
}

- (void)runUpWithTransaction:(YapDatabaseReadWriteTransaction *)transaction
{
    OWSRaiseException(NSInternalInconsistencyException, @"Must override %@ in subclass", NSStringFromSelector(_cmd));
}

- (void)runUpWithCompletion:(OWSDatabaseMigrationCompletion)completion
{
    OWSAssert(completion);

    OWSDatabaseConnection *dbConnection = (OWSDatabaseConnection *)self.storageManager.newDatabaseConnection;
    // These migrations won't be run until storage registrations are enqueued,
    // but this transaction might begin before all registrations are marked as
    // complete, so disable this checking.
    //
    // TODO: Once we move "app readiness" into AppSetup, we should explicitly
    // not start these migrations until storage is ready.  We can then remove
    // this statement which disables checking.
#ifdef DEBUG
    dbConnection.canWriteBeforeStorageReady = YES;
#endif

    [dbConnection asyncReadWriteWithBlock:^(YapDatabaseReadWriteTransaction *_Nonnull transaction) {
        [self runUpWithTransaction:transaction];
    }
        completionBlock:^{
            DDLogInfo(@"Completed migration %@", self.uniqueId);
            [self save];

            completion();
        }];
}

#pragma mark - Database Connections

#ifdef DEBUG
+ (YapDatabaseConnection *)dbReadConnection
{
    return self.dbReadWriteConnection;
}

// Database migrations need to occur _before_ storage is ready (by definition),
// so we need to use a connection with canWriteBeforeStorageReady set in
// debug builds.
+ (YapDatabaseConnection *)dbReadWriteConnection
{
    static dispatch_once_t onceToken;
    static YapDatabaseConnection *sharedDBConnection;
    dispatch_once(&onceToken, ^{
        sharedDBConnection = [TSStorageManager sharedManager].newDatabaseConnection;

        OWSAssert([sharedDBConnection isKindOfClass:[OWSDatabaseConnection class]]);
        ((OWSDatabaseConnection *)sharedDBConnection).canWriteBeforeStorageReady = YES;
    });

    return sharedDBConnection;
}

- (YapDatabaseConnection *)dbReadConnection
{
    return OWSDatabaseMigration.dbReadConnection;
}

- (YapDatabaseConnection *)dbReadWriteConnection
{
    return OWSDatabaseMigration.dbReadWriteConnection;
}
#endif

@end

NS_ASSUME_NONNULL_END