Hyperlink-Android/app/src/main/java/dev/garrettmills/starship/hyperlink/LoginTokenScannerActivity.java

package dev.garrettmills.starship.hyperlink;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.camera.core.Camera;
import androidx.camera.core.CameraSelector;
import androidx.camera.core.ImageAnalysis;
import androidx.camera.core.Preview;
import androidx.camera.lifecycle.ProcessCameraProvider;
import androidx.camera.view.PreviewView;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;
import androidx.lifecycle.LifecycleOwner;

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.util.Size;
import android.widget.Toast;

import com.google.common.util.concurrent.ListenableFuture;

import java.util.concurrent.ExecutionException;

import dev.garrettmills.starship.hyperlink.scanner.QRCodeImageAnalyzer;
import dev.garrettmills.starship.hyperlink.scanner.QRCodeListener;
import dev.garrettmills.starship.hyperlink.util.InvalidLoginTokenException;
import dev.garrettmills.starship.hyperlink.util.LoginToken;

public class LoginTokenScannerActivity extends AppCompatActivity implements QRCodeListener {
    private PreviewView previewView;
    private ListenableFuture<ProcessCameraProvider> cameraProviderFuture;
    private String qrCode;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login_token_scanner);

        previewView = findViewById(R.id.activity_login_token_scanner_previewView);
        cameraProviderFuture = ProcessCameraProvider.getInstance(this);
        requestCamera();
    }

    protected void requestCamera() {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED) {
            startCamera();
        } else {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, Hyperlink.REQUEST_PERMISSION_CAMERA);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (requestCode == Hyperlink.REQUEST_PERMISSION_CAMERA) {
            if (grantResults.length == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                startCamera();
            } else {
                if ( BuildConfig.DEBUG ) {
                    Toast.makeText(this, "Camera permission denied", Toast.LENGTH_SHORT).show();
                }

                // If we denied, go back up to the main activity, w/o any login token
                finish();
            }
        }
    }

    private void startCamera() {
        cameraProviderFuture.addListener(() -> {
            try {
                ProcessCameraProvider cameraProvider = cameraProviderFuture.get();
                bindCameraPreview(cameraProvider);
            } catch (ExecutionException | InterruptedException e) {
                if ( BuildConfig.DEBUG ) {
                    Toast.makeText(this, "Error starting camera: " + e.getMessage(), Toast.LENGTH_LONG).show();
                }

                finish();
            }
        }, ContextCompat.getMainExecutor(this));
    }

    private void bindCameraPreview(@NonNull ProcessCameraProvider cameraProvider) {
        previewView.setPreferredImplementationMode(PreviewView.ImplementationMode.SURFACE_VIEW);

        Preview preview = new Preview.Builder().build();

        CameraSelector cameraSelector = new CameraSelector.Builder()
                .requireLensFacing(CameraSelector.LENS_FACING_BACK)
                .build();

        preview.setSurfaceProvider(previewView.createSurfaceProvider());

        ImageAnalysis imageAnalysis = new ImageAnalysis.Builder()
                .setTargetResolution(new Size(1280, 720))
                .setBackpressureStrategy(ImageAnalysis.STRATEGY_KEEP_ONLY_LATEST)
                .build();

        imageAnalysis.setAnalyzer(ContextCompat.getMainExecutor(this), new QRCodeImageAnalyzer(this));

        Camera camera = cameraProvider.bindToLifecycle((LifecycleOwner) this, cameraSelector, imageAnalysis, preview);
    }

    public void onQRCodeFound(String qrCode) {
        if ( !isValidLoginToken(qrCode) ) return;

        Intent result = new Intent();
        result.putExtra(Hyperlink.EXTRA_LOGIN_TOKEN, qrCode);

        setResult(RESULT_OK, result);
        finish();
    }

    public void onQRCodeNotFound() {}

    public boolean isValidLoginToken(String token) {
        try {
            new LoginToken(token);
            return true;
        } catch (InvalidLoginTokenException e) {
            return false;
        }
    }
}