NetworkBoundResource

import io.reactivex.Flowable;
import io.reactivex.Observable;
import io.reactivex.disposables.CompositeDisposable;
import io.reactivex.disposables.Disposable;

/**
 * Created by duypham on 4/3/18.
 */

// ResultType: Type for the Resource data
// RequestType: Type for the API response
public abstract class NetworkBoundResource<ResultType, RequestType> {

    private final Observable<Resource<ResultType>> mResourceObservable;

    private CompositeDisposable mCompositeDisposable = new CompositeDisposable();

    protected NetworkBoundResource() {
        mResourceObservable = createResourceObservable();
        // clear all network calls and local database calls when dispose to prevent execution leaks
        mResourceObservable.doOnDispose(() -> mCompositeDisposable.clear());
    }

    /**
     * add an disposable which will be disposed along with the root observable to make sure we have no un-managed
     * executions
     */
    protected void addDisposable(final Disposable disposable) {
        mCompositeDisposable.add(disposable);
    }

    // Called with the data in the database to decide whether it should be
    // fetched from the network.
    protected abstract boolean shouldFetch();

    // Called before executing api request, true if we should wait for api response before populating local data
    // retrieved from database
    protected abstract boolean shouldWaitApiResponseFirst();

    // call to get data from database
    protected abstract Flowable<ResultType> dbCall();

    // call to get data from api
    protected abstract Observable<RequestType> apiCall();

    protected abstract Observable<Resource<ResultType>> createResourceObservable();

    public Observable<Resource<ResultType>> getObservable() {
        return mResourceObservable;
    }
}