import android.content.pm.PackageManager;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;

import java.util.Arrays;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

/**
 * Created by Abhishek3.patil on 19-04-2017.
 */

public class PermissionsHelperActivity extends AppCompatActivity
{
    private int                                 PERMISSION_REQUEST_CODE;
    private IPermissionRequest                  mIPermissionRequest;

    public interface IPermissionRequest {
        void onPermissionGranted(boolean allowed, int requestCode);
    }

    public void askForPermission(String[] permissions, int requestCode)
    {
        PERMISSION_REQUEST_CODE = requestCode;
        List<String> permissionList = new LinkedList<>(Arrays.asList(permissions));

        Iterator<String> iterator = permissionList.iterator();
        while(iterator.hasNext()) {
            String permission = iterator.next();
            //first, check the permission is already granted or not. If yes, remove it from permission list.
            boolean check = ContextCompat.checkSelfPermission(this, permission) == PackageManager.PERMISSION_GRANTED;
            if(check) {
                iterator.remove();
            }
        }

        if (permissionList.size() > 0) {
            ActivityCompat.requestPermissions(this, permissionList.toArray(new String[permissionList.size()]), requestCode);
        } else {
            notifyListener(true, requestCode);
        }
    }

    public void setPermissionRequestListener(IPermissionRequest listener) {
        mIPermissionRequest = listener;
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {

        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (requestCode == PERMISSION_REQUEST_CODE && grantResults.length > 0) {
            if (isPermissionDenied(grantResults, PackageManager.PERMISSION_DENIED)) {
                notifyListener(false, PERMISSION_REQUEST_CODE);
            } else {
                notifyListener(true, PERMISSION_REQUEST_CODE);
            }
        }
    }

    private boolean isPermissionDenied(final int[] grantResults, final int granted) {
        boolean result = false;
        for(int i : grantResults) {
            if(i == granted) {
                result = true;
                break;
            }
        }
        return result;
    }

    private void notifyListener(boolean allowed, int requestCode) {
        if(mIPermissionRequest != null) {
            mIPermissionRequest.onPermissionGranted(allowed, requestCode);
        }
    }
}