UserPreferencesSerializer.kt

@Singleton
class UserPreferencesSerializer @Inject constructor(
    private val cryptoManager: CryptoManager
) : Serializer<UserPreferences> {
    override val defaultValue: UserPreferences = UserPreferences.getDefaultInstance()
    override suspend fun readFrom(input: InputStream): UserPreferences {
        return try {
            // Decrypt the stream before parsing
            val decryptedStream = cryptoManager.decrypt(input)
            UserPreferences.parseFrom(decryptedStream)
        } catch (exception: InvalidProtocolBufferException) {
            throw CorruptionException("Cannot read proto.", exception)
        }
    }
    override suspend fun writeTo(t: UserPreferences, output: OutputStream) {
        // Encrypt the stream while writing
        val encryptedStream = cryptoManager.encrypt(output)
        t.writeTo(encryptedStream)
        encryptedStream.close() // Important: close to finalize encryption blocks
    }
}