Pager With RemoteMediator

PagerRemote.kt

class Repository(val db: CryptoDatabase, val api : NetworkInterface) {

    fun getCryptos() : Flow<PagingData<CryptoCurrency>> {
        return Pager(
            config = PagingConfig(PAGE_SIZE),
            initialKey = 0,
            remoteMediator = RepositoryMediator(db,api), 
            pagingSourceFactory = { db.cryptoDao().getCryptos() }
        ).flow
    }
  
}

class RepositoryMediator(val db: CryptoDatabase, val api: NetworkInterface) : RemoteMediator<Int, CryptoCurrency>() {

    override suspend fun load(loadType: LoadType, state: PagingState<Int, CryptoCurrency>): MediatorResult {

        val offset : Int = when(loadType) {
            LoadType.REFRESH -> 0
            LoadType.PREPEND -> return MediatorResult.Success(endOfPaginationReached = true)
            LoadType.APPEND -> {
                db.cryptoDao().getCryptoInDb()
            }
        }

        val cryptos = api.getCryptos(limit = state.config.pageSize, offset = offset).body()?.data

        db.withTransaction {
            if (loadType == LoadType.REFRESH) {
                db.cryptoDao().deleteAllCryptos()
            }

            cryptos?.let {
                db.cryptoDao().insertCryptos(it)
            }
        }

        return MediatorResult.Success( endOfPaginationReached = cryptos?.isEmpty() ?: true)
    }
}

// Paging Library dependencies in build.gradle
implementation "androidx.paging:paging-runtime:3.0.0-alpha02"