FirebaseDataSourceImpl.kt

private val database = FirebaseDatabase.getInstance()

    override fun getSummary(): Observable<OweSummaryDomain> =
        Observable.create { emitter ->
            val summary = database.getReference("summary")
            summary.addValueEventListener(object : ValueEventListener {
                override fun onCancelled(error: DatabaseError) {
                    Timber.e("summary error: ${error.message}")
                    emitter.onError(error.toException())
                }

                override fun onDataChange(data: DataSnapshot) {
                    data.children.forEach {
                        val value = it.getValue(OweSummary::class.java)
                        Timber.e("summary: $value")
                        emitter.onNext(value?.toDomain())
                        emitter.onComplete()
                    }
                }

            })

        }