This file is responsible for handling of saving data locally in Realm Database, Shared preferences, Android Secure storage, retrieving data and passing it with RxJava Observables

LocalDataSource.kt

open class LocalDataSource private constructor() : DataSource, AnkoLogger {
    private val authorizeTokenAlias = "authorizeTokenAlias"
    private val conversationIdAlias = "conversationIdAlias"

    companion object {
        private var INSTANCE: LocalDataSource? = null


        fun getInstance(): LocalDataSource {
            if (INSTANCE == null) {
                INSTANCE = LocalDataSource()
            }
            return INSTANCE!!

        }
    }
  
  //... some other methods

    override fun getToken(): Flowable<Optional<String>> {
        val secureStorage = RxSecureStorage.create(App.context, authorizeTokenAlias)
        return secureStorage
                .getString(authorizeTokenAlias)
                .toFlowable(BackpressureStrategy.BUFFER)
    }

    override fun getConversationId(): Flowable<Optional<String>> {
        val secureStorage = RxSecureStorage.create(App.context, conversationIdAlias)
        return secureStorage.getString(conversationIdAlias)
                .toFlowable(BackpressureStrategy.BUFFER)
    }


    override fun saveToken(token: String): Single<Boolean> {
        val secureStorage = RxSecureStorage.create(App.context, authorizeTokenAlias)
        return secureStorage
                .putString(authorizeTokenAlias, token)
    }

    override fun removeAll(): Single<Boolean> {
        val deleteRealmSingle = Single.create<Boolean> { emitter ->
            try {
                Realm.getDefaultInstance().use { realm ->
                    realm.executeTransaction(Realm::deleteAll)
                    emitter.onSuccess(true)
                }
            } catch (e: Exception) {
                emitter.onSuccess(false)
            }

        }
        return Single.merge(removeToken(), removeConversationId(), deleteRealmSingle)
                .all { deleted -> deleted }

    }
  
   override fun removeToken(): Single<Boolean> {
        return removeFromRxSecureStorage(authorizeTokenAlias)
    }

    override fun removeConversationId(): Single<Boolean> {
        return removeFromRxSecureStorage(conversationIdAlias)
    }

    override fun saveConversationId(conversationId: String): Single<Boolean> {
        val secureStorage = RxSecureStorage.create(App.context, conversationIdAlias)
        return secureStorage
                .putString(conversationIdAlias, conversationId)
    }

    private fun removeFromRxSecureStorage(alias: String): Single<Boolean> {
        val secureStorage = RxSecureStorage.create(App.context, alias)
        return secureStorage.putString(alias, null)
                .map { notPut -> !notPut } //reverse boolean to show true like it successfully removed
    }
  
  //... some other methods
  
}