migration_android.kt

actual fun getNonEncryptedSettings(context: AppContext?): Settings = SharedPreferencesSettings(
    PreferenceManager.getDefaultSharedPreferences(context)
)

actual fun getEncryptedSettings(context: AppContext?): Settings {
    requireNotNull(context)

    val masterKey = MasterKey.Builder(context)
        .setKeyScheme(KeyScheme.AES256_GCM)
        .build()

    val encryptedPreferences = EncryptedSharedPreferences.create(
        context,
        context.packageName + "_encrypted_preferences",
        masterKey,
        EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
        EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
    )

    val oldPreferences = getNonEncryptedSettings(context)

    return SharedPreferencesSettings(MigrationPreferences(listOf("key1", "key2"), oldPreferences, encryptedPreferences))
}

class MigrationPreferences(
    keysToMigrate: List<String>,
    oldPreferences: Settings,
    private val encryptedPreferences: SharedPreferences
) : SharedPreferences by encryptedPreferences {

    init {
        encryptedPreferences.edit {
            keysToMigrate.forEach { key ->
                val value = oldPreferences.getStringOrNull(key)
                value?.let {
                    putString(key, it)
                    oldPreferences.remove(key)
                }
            }
        }
    }
}