UserDataSource.kt

class UserDataSource(private val repository: UserRepository,
                     private val query: String,
                     private val sort: String,
                     private val scope: CoroutineScope): PageKeyedDataSource<Int, User>() {

    // FOR DATA ---
    private var supervisorJob = SupervisorJob()
    //...
  
    // OVERRIDE ---
    override fun loadInitial(params: LoadInitialParams<Int>, callback: LoadInitialCallback<Int, User>) {
        // ...
        executeQuery(1, params.requestedLoadSize) {
            callback.onResult(it, null, 2)
        }
    }

    override fun loadAfter(params: LoadParams<Int>, callback: LoadCallback<Int, User>) {
        val page = params.key
        // ...
        executeQuery(page, params.requestedLoadSize) {
            callback.onResult(it, page + 1)
        }
    }
  
    override fun invalidate() {
        super.invalidate()
        supervisorJob.cancelChildren()   // Cancel possible running job to only keep last result searched by user
    }

    // UTILS ---
    private fun executeQuery(page: Int, perPage: Int, callback:(List<User>) -> Unit) {
        // ...
        scope.launch(getJobErrorHandler() + supervisorJob) {
            delay(200) // To handle user typing case
            val users = repository.searchUsersWithPagination(query, page, perPage, sort)
            // ...
            callback(users)
        }
    }

    private fun getJobErrorHandler() = CoroutineExceptionHandler { _, e ->
        Log.e(UserDataSource::class.java.simpleName, "An error happened: $e")
        networkState.postValue(NetworkState.FAILED)
    }

    // ...
}