Repository caching mechanisms

RepositoryMechanisms.kt

/**
 * Cache-Aside (Lazy Loading): Read from cache and return it, then update the cache later.
 */
fun getUserConfigLazily(): Flow<UserConfig?> = flow {
    emitAll(local.getUserConfigAsFlow())
    if (onlineChecker.isOnline) {
        val remoteConf = remote.getUserConfig()
        if (remoteConf != null) {
            local.updateUserConfig(remoteConf)
        }
    }
}

/**
 * Cache-First : Read from cache; if missed, read from remote and return.
 */
fun getUserConfigCacheFirst(): Flow<UserConfig?> = flow {
    val userConfig = local.getUserConfig()
    if (userConfig != null) {
        emit(userConfig)
    } else {
        emitAll(getUserConfigReadThrough())
    }
}

/**
 * Read-Through Cache: Read from remote and return, then update the cache.
 */
fun getUserConfigReadThrough(): Flow<UserConfig?> = flow {
    if (onlineChecker.isOnline) {
        val remoteConf = remote.getUserConfig()
        if (remoteConf != null) {
            local.updateUserConfig(remoteConf)
            emit(remoteConf)
        } else {
            emit(null)
        }
    } else {
        emit(null)
    }
}