CallbackAsync

package com.demo.poc.merkurvut.login;

import javax.inject.Inject;
import java.lang.ref.WeakReference;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;

import com.demo.poc.merkurvut.base.NetworkAsyncTask;
import com.demo.poc.merkurvut.connection.VutConnection;
import com.demo.poc.merkurvut.dagger.annotations.ApplicationContext;
import com.demo.poc.merkurvut.data.parser.VUTParser;
import com.demo.poc.merkurvut.db.entities.StudentInformation;

/**
 * Asynchronous task to log in.
 *
 * @author Jan Smyčka (jan.smycka@post.cz)
 */
public class LoginAsyncTask extends NetworkAsyncTask {

    /**
     * Interface for class that wants to receive message about finishing this task.
     */
    public interface LoginResultsCallback extends NetworkTaskCallback {

        /**
         * Callback for successful log in.
         *
         * @param studentInformation information about a student
         */
        void onLoginSuccess(@NonNull StudentInformation studentInformation);

        /**
         * Callback for unsuccessful log in.
         */
        void onLoginFailed();
    }

    @NonNull
    private VUTParser mVutParser;

    @NonNull
    private VutConnection mVutConnection;

    private WeakReference<LoginResultsCallback> mLoginTaskCallbackWeakReference;
    private String mLogin;
    private String mPassword;

    @Inject
    LoginAsyncTask(@NonNull @ApplicationContext Context context, @NonNull VutConnection vutConnection, @NonNull VUTParser vutParser) {
        super(context);
        mVutConnection = vutConnection;
        mVutParser = vutParser;
    }

    /**
     * Starts AsyncTask that logs in.
     *
     * @param loginTaskCallback listener for results.
     * @param login             input from user
     * @param password          input from user
     */
    public void logIn(@NonNull LoginResultsCallback loginTaskCallback, @NonNull String login, @NonNull String password) {
        mNetworkTaskCallbackWeakReference = new WeakReference<>(loginTaskCallback);
        mLoginTaskCallbackWeakReference = new WeakReference<>(loginTaskCallback);
        mLogin = login;
        mPassword = password;

        execute();
    }

    @Nullable
    @Override
    protected StudentInformation doInBackground(Void... voids) {
        if (mLoginTaskCallbackWeakReference == null || mLogin == null || mPassword == null) {
            throw new IllegalArgumentException("You must call #logIn with non-null parameters in order to start this AsyncTask.");
        }

        // TODO "Command && Query separation
        if (mVutConnection.login(mLogin, mPassword)) {
            return mVutParser.getStudentInfo();
        } else {
            return null;
        }
    }

    @Override
    protected void onPostExecute(@Nullable Object studentInformation) {
        super.onPostExecute(studentInformation);
        final LoginResultsCallback loginTaskCallback = mLoginTaskCallbackWeakReference.get();

        if (studentInformation != null) {
            loginTaskCallback.onLoginSuccess((StudentInformation) studentInformation);
        } else {
            loginTaskCallback.onLoginFailed();
        }
    }

    @Override
    protected boolean resultObjectClassCheck(@NonNull Object resultObject) {
        return resultObject instanceof StudentInformation;
    }
}