session-ios/SignalServiceKit/src/Loki/Database/OWSPrimaryStorage+Loki.swift

public extension OWSPrimaryStorage {
    
    private func getDeviceLinkCollection(for masterHexEncodedPublicKey: String) -> String {
        return "LokiDeviceLinkCollection-\(masterHexEncodedPublicKey)"
    }
    
    public func setDeviceLinksInCache(_ deviceLinks: Set<DeviceLink>) {
        self.deviceLinkCache = deviceLinks
    }
    
    public func syncDeviceLinkCacheToDatabase(in transaction: YapDatabaseReadWriteTransaction) {
        if !self.deviceLinkCache.isEmpty {
            self.setDeviceLinks(self.deviceLinkCache, in: transaction)
            self.deviceLinkCache.removeAll()
        }
    }

    public func setDeviceLinks(_ deviceLinks: Set<DeviceLink>, in transaction: YapDatabaseReadWriteTransaction) {
        // TODO: Clear collections first?
        deviceLinks.forEach { addDeviceLink($0, in: transaction) } // TODO: Check the performance impact of this
    }

    public func addDeviceLink(_ deviceLink: DeviceLink, in transaction: YapDatabaseReadWriteTransaction) {
        let collection = getDeviceLinkCollection(for: deviceLink.master.hexEncodedPublicKey)
        transaction.setObject(deviceLink, forKey: deviceLink.slave.hexEncodedPublicKey, inCollection: collection)
    }

    public func removeDeviceLink(_ deviceLink: DeviceLink, in transaction: YapDatabaseReadWriteTransaction) {
        let collection = getDeviceLinkCollection(for: deviceLink.master.hexEncodedPublicKey)
        transaction.removeObject(forKey: deviceLink.slave.hexEncodedPublicKey, inCollection: collection)
    }
    
    public func getDeviceLinks(for masterHexEncodedPublicKey: String, in transaction: YapDatabaseReadTransaction) -> Set<DeviceLink> {
        if !self.deviceLinkCache.isEmpty {
            return self.deviceLinkCache
        }
        let collection = getDeviceLinkCollection(for: masterHexEncodedPublicKey)
        guard !transaction.allKeys(inCollection: collection).isEmpty else { return [] } // Fixes a crash that used to occur on Josh's device
        var result: Set<DeviceLink> = []
        transaction.enumerateRows(inCollection: collection) { _, object, _, _ in
            guard let deviceLink = object as? DeviceLink else { return }
            result.insert(deviceLink)
        }
        return result
    }
    
    public func getDeviceLink(for slaveHexEncodedPublicKey: String, in transaction: YapDatabaseReadTransaction) -> DeviceLink? {
        let query = YapDatabaseQuery(string: "WHERE \(DeviceLinkIndex.slaveHexEncodedPublicKey) = ?", parameters: [ slaveHexEncodedPublicKey ])
        let deviceLinks = DeviceLinkIndex.getDeviceLinks(for: query, in: transaction)
        guard deviceLinks.count <= 1 else {
            print("[Loki] Found multiple device links for slave hex encoded public key: \(slaveHexEncodedPublicKey).")
            return nil
        }
        return deviceLinks.first
    }
    
    public func getMasterHexEncodedPublicKey(for slaveHexEncodedPublicKey: String, in transaction: YapDatabaseReadTransaction) -> String? {
        return getDeviceLink(for: slaveHexEncodedPublicKey, in: transaction)?.master.hexEncodedPublicKey
    }
    
    public func getUserCount(for publicChat: LokiPublicChat, in transaction: YapDatabaseReadTransaction) -> Int? {
        return transaction.object(forKey: publicChat.id, inCollection: "LokiPublicChatUserCountCollection") as? Int
    }
    
    public func setUserCount(_ userCount: Int, forPublicChatWithID publicChatID: String, in transaction: YapDatabaseReadWriteTransaction) {
        transaction.setObject(userCount, forKey: publicChatID, inCollection: "LokiPublicChatUserCountCollection")
    }
}