class MainActivity : AppCompatActivity() {
    private val permReqCode = 10
    private val requiredPerms = arrayOf(Manifest.permission.CAMERA)
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        if (allPermissionsGranted()) {
            startCamera()
        } else {
            ActivityCompat.requestPermissions(
                this, requiredPerms, permReqCode)
        }
    }

    fun recognizeText(image: InputImage, proxy: ImageProxy) {
        val recognizer = TextRecognition.getClient(TextRecognizerOptions.DEFAULT_OPTIONS)
        val result = recognizer.process(image)
                .addOnSuccessListener { visionText ->
                    Log.e("OCE", "success")
                    processTextBlock(visionText)
                }
                .addOnFailureListener { e ->
                    Log.e("OCE", "failed ${e.toString()}")
                }
        result.addOnCompleteListener { _ ->  proxy.close()}
    }

    private fun processTextBlock(result: Text) {
        val resultText = result.text
        for (block in result.textBlocks) {
            val blockText = block.text
            val blockCornerPoints = block.cornerPoints
            val blockFrame = block.boundingBox
            findViewById<TextView>(R.id.textView).text = blockText
            for (line in block.lines) {
                val lineText = line.text
                val lineCornerPoints = line.cornerPoints
                val lineFrame = line.boundingBox
                //findViewById<TextView>(R.id.textView).text = lineText
                for (element in line.elements) {
                    val elementText = element.text
                    val elementCornerPoints = element.cornerPoints
                    val elementFrame = element.boundingBox
                    //findViewById<TextView>(R.id.textView).text = elementText
                }
            }
        }
    }

    @SuppressLint("UnsafeOptInUsageError")
    private fun startCamera() {
        val cameraProviderFuture = ProcessCameraProvider.getInstance(this)
        cameraProviderFuture.addListener(Runnable {
            val cameraProvider: ProcessCameraProvider = cameraProviderFuture.get()
            // Preview
            val preview = Preview.Builder()
                .build()
                .also {
                    it.setSurfaceProvider(findViewById<PreviewView>(R.id.viewFinder).surfaceProvider)
                }

            val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA
            val imageAnalysis = ImageAnalysis.Builder()
                    .setTargetResolution(Size(1280, 720))
                    .setBackpressureStrategy(ImageAnalysis.STRATEGY_KEEP_ONLY_LATEST)
                    .build()

            imageAnalysis.setAnalyzer(ContextCompat.getMainExecutor(this), ImageAnalyzer())

            try {
                cameraProvider.unbindAll()
                cameraProvider.bindToLifecycle(this as LifecycleOwner, cameraSelector, imageAnalysis, preview)

            } catch(exc: Exception) {
                Log.e("OCR", "binding failed", exc)
            }

        }, ContextCompat.getMainExecutor(this))
    }

    inner class ImageAnalyzer : ImageAnalysis.Analyzer {
        @SuppressLint("UnsafeOptInUsageError")
        override fun analyze(imageProxy: ImageProxy) {
            val mediaImage = imageProxy.image
            if (mediaImage != null) {
                val image = InputImage.fromMediaImage(mediaImage, imageProxy.imageInfo.rotationDegrees)
                recognizeText(image, imageProxy)
            }
        }
    }

    private fun allPermissionsGranted() = requiredPerms.all {
        ContextCompat.checkSelfPermission(
            baseContext, it) == PackageManager.PERMISSION_GRANTED
    }

    override fun onRequestPermissionsResult(
        requestCode: Int, permissions: Array<String>, grantResults:
        IntArray) {
        if (requestCode == permReqCode) {
            if (allPermissionsGranted()) {
                startCamera()
            } else {
                Toast.makeText(this,
                    "Permissions not granted by the user.",
                    Toast.LENGTH_SHORT).show()
                finish()
            }
        }
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
    }
}