SilentDragonAndroid/app/src/main/java/cash/z/ecc/android/ui/scan/ScanFragment.kt

package cash.z.ecc.android.ui.scan

import android.os.Bundle
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Toast
import androidx.camera.core.*
import androidx.camera.lifecycle.ProcessCameraProvider
import androidx.core.content.ContextCompat
import androidx.fragment.app.activityViewModels
import androidx.fragment.app.viewModels
import androidx.window.layout.WindowInfoTracker
import androidx.window.layout.WindowMetricsCalculator
import cash.z.ecc.android.R
import cash.z.ecc.android.databinding.FragmentScanBinding
import cash.z.ecc.android.ext.onClickNavBack
import cash.z.ecc.android.ui.base.BaseFragment
import cash.z.ecc.android.ui.send.SendViewModel
import kotlinx.coroutines.launch
import java.util.concurrent.ExecutorService
import java.util.concurrent.Executors
import kotlin.math.abs
import kotlin.math.max
import kotlin.math.min


class ScanFragment : BaseFragment<FragmentScanBinding>() {

    private var _fragmentCameraBinding: FragmentScanBinding? = null
    private val fragmentCameraBinding get() = _fragmentCameraBinding!!
    private var displayId: Int = -1
    private var lensFacing: Int = CameraSelector.LENS_FACING_BACK
    private var preview: Preview? = null
    private var imageCapture: ImageCapture? = null
    private var imageAnalyzer: ImageAnalysis? = null
    private var camera: Camera? = null
    private var cameraProvider: ProcessCameraProvider? = null
    private val viewModel: ScanViewModel by viewModels()
    private val sendViewModel: SendViewModel by activityViewModels()
    private lateinit var windowManager: WindowInfoTracker

    /** Blocking camera operations are performed using this executor */
    private lateinit var cameraExecutor: ExecutorService

    override fun inflate(inflater: LayoutInflater): FragmentScanBinding =
        FragmentScanBinding.inflate(inflater)

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        // Initialize our background executor
        cameraExecutor = Executors.newSingleThreadExecutor()

        //Initialize WindowManager to retrieve display metrics
        windowManager = WindowInfoTracker.getOrCreate(view.context)

        // Wait for the views to be properly laid out
        fragmentCameraBinding.viewFinder.post {

            // Keep track of the display in which this view is attached
            displayId = fragmentCameraBinding.viewFinder.display.displayId

            // Set up the camera and its use cases
            setUpCamera()
        }

        // Initialize back button
        _fragmentCameraBinding?.backButtonHitArea?.onClickNavBack()
    }

    override fun onDestroyView() {
        _fragmentCameraBinding = null
        super.onDestroyView()

        // Shut down our background executor
        cameraExecutor.shutdown()
    }

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View {
        _fragmentCameraBinding = FragmentScanBinding.inflate(inflater, container, false)
        return fragmentCameraBinding.root
    }

    /** Initialize CameraX, and prepare to bind the camera use cases  */
    private fun setUpCamera() {
        val cameraProviderFuture = ProcessCameraProvider.getInstance(requireContext())
        cameraProviderFuture.addListener(Runnable {

            // CameraProvider
            cameraProvider = cameraProviderFuture.get()

            // Select lensFacing depending on the available cameras
            lensFacing = when {
                hasBackCamera() -> CameraSelector.LENS_FACING_BACK
                hasFrontCamera() -> CameraSelector.LENS_FACING_FRONT
                else -> throw IllegalStateException("Back and front camera are unavailable")
            }

            // Build and bind the camera use cases
            bindCameraUseCases()
        }, ContextCompat.getMainExecutor(requireContext()))
    }

    /** Declare and bind preview, capture and analysis use cases */
    private fun bindCameraUseCases() {

        // Get screen metrics used to setup camera for full screen resolution
        val windowMetrics = WindowMetricsCalculator.getOrCreate().computeCurrentWindowMetrics(requireActivity())
        Log.d(TAG, "Screen metrics: ${windowMetrics.bounds.width()} x ${windowMetrics.bounds.height()}")

        val screenAspectRatio = aspectRatio(windowMetrics.bounds.width(), windowMetrics.bounds.height())
        Log.d(TAG, "Preview aspect ratio: $screenAspectRatio")

        val rotation = fragmentCameraBinding.viewFinder.display.rotation
        Log.d(TAG, "Rotation: $rotation")

        // CameraProvider
        val cameraProvider = cameraProvider
            ?: throw IllegalStateException("Camera initialization failed.")

        // CameraSelector
        val cameraSelector = CameraSelector.Builder().requireLensFacing(lensFacing).build()

        // Preview
        preview = Preview.Builder()
            // We request aspect ratio but no resolution
            .setTargetAspectRatio(screenAspectRatio)
            // Set initial target rotation
            .setTargetRotation(rotation)
            .build()

        // ImageCapture
        imageCapture = ImageCapture.Builder()
            .setCaptureMode(ImageCapture.CAPTURE_MODE_MINIMIZE_LATENCY)
            // We request aspect ratio but no resolution to match preview config, but letting
            // CameraX optimize for whatever specific resolution best fits our use cases
            .setTargetAspectRatio(screenAspectRatio)
            // Set initial target rotation, we will have to call this again if rotation changes
            // during the lifecycle of this use case
            .setTargetRotation(rotation)
            .build()

        // ImageAnalysis
        imageAnalyzer = ImageAnalysis.Builder()
            // We request aspect ratio but no resolution
            .setTargetAspectRatio(screenAspectRatio)
            // Set initial target rotation, we will have to call this again if rotation changes
            // during the lifecycle of this use case
            .setTargetRotation(rotation)
            .setBackpressureStrategy(ImageAnalysis.STRATEGY_KEEP_ONLY_LATEST)
            .build()


            // The analyzer can then be assigned to the instance
            .also {
                it.setAnalyzer(cameraExecutor,
                    QrAnalyzer { q, i ->
                        onQrScanned(q, i)
                    }
                )
            }

        // Must unbind the use-cases before rebinding them
        cameraProvider.unbindAll()

        if (camera != null) {
            // Must remove observers from the previous camera instance
            removeCameraStateObservers(camera!!.cameraInfo)
        }

        try {
            // A variable number of use-cases can be passed here -
            // camera provides access to CameraControl & CameraInfo
            camera = cameraProvider.bindToLifecycle(
                this, cameraSelector, preview, imageCapture, imageAnalyzer)

            // Attach the viewfinder's surface provider to preview use case
            preview?.setSurfaceProvider(fragmentCameraBinding.viewFinder.surfaceProvider)
            observeCameraState(camera?.cameraInfo!!)
        } catch (exc: Exception) {
            Log.e(TAG, "Use case binding failed", exc)
        }
    }

    private fun removeCameraStateObservers(cameraInfo: CameraInfo) {
        cameraInfo.cameraState.removeObservers(viewLifecycleOwner)
    }

    private fun observeCameraState(cameraInfo: CameraInfo) {
        cameraInfo.cameraState.observe(viewLifecycleOwner) { cameraState ->
            run {
                when (cameraState.type) {
                    CameraState.Type.PENDING_OPEN -> {
                        // Ask the user to close other camera apps
                        Toast.makeText(context,
                            "CameraState: Pending Open",
                            Toast.LENGTH_SHORT).show()
                    }
                    CameraState.Type.OPENING -> {
                        // Show the Camera UI
                        Toast.makeText(context,
                            "CameraState: Opening",
                            Toast.LENGTH_SHORT).show()
                    }
                    CameraState.Type.OPEN -> {
                        // Setup Camera resources and begin processing
                        Toast.makeText(context,
                            "CameraState: Open",
                            Toast.LENGTH_SHORT).show()
                    }
                    CameraState.Type.CLOSING -> {
                        // Close camera UI
                        Toast.makeText(context,
                            "CameraState: Closing",
                            Toast.LENGTH_SHORT).show()
                    }
                    CameraState.Type.CLOSED -> {
                        // Free camera resources
                        Toast.makeText(context,
                            "CameraState: Closed",
                            Toast.LENGTH_SHORT).show()
                    }
                }
            }

            cameraState.error?.let { error ->
                when (error.code) {
                    // Open errors
                    CameraState.ERROR_STREAM_CONFIG -> {
                        // Make sure to setup the use cases properly
                        Toast.makeText(context,
                            "Stream config error",
                            Toast.LENGTH_SHORT).show()
                    }
                    // Opening errors
                    CameraState.ERROR_CAMERA_IN_USE -> {
                        // Close the camera or ask user to close another camera app that's using the
                        // camera
                        Toast.makeText(context,
                            "Camera in use",
                            Toast.LENGTH_SHORT).show()
                    }
                    CameraState.ERROR_MAX_CAMERAS_IN_USE -> {
                        // Close another open camera in the app, or ask the user to close another
                        // camera app that's using the camera
                        Toast.makeText(context,
                            "Max cameras in use",
                            Toast.LENGTH_SHORT).show()
                    }
                    CameraState.ERROR_OTHER_RECOVERABLE_ERROR -> {
                        Toast.makeText(context,
                            "Other recoverable error",
                            Toast.LENGTH_SHORT).show()
                    }
                    // Closing errors
                    CameraState.ERROR_CAMERA_DISABLED -> {
                        // Ask the user to enable the device's cameras
                        Toast.makeText(context,
                            "Camera disabled",
                            Toast.LENGTH_SHORT).show()
                    }
                    CameraState.ERROR_CAMERA_FATAL_ERROR -> {
                        // Ask the user to reboot the device to restore camera function
                        Toast.makeText(context,
                            "Fatal error",
                            Toast.LENGTH_SHORT).show()
                    }
                    // Closed errors
                    CameraState.ERROR_DO_NOT_DISTURB_MODE_ENABLED -> {
                        // Ask the user to disable the "Do Not Disturb" mode, then reopen the camera
                        Toast.makeText(context,
                            "Do not disturb mode enabled",
                            Toast.LENGTH_SHORT).show()
                    }
                }
            }
        }
    }

    /**
     *  [androidx.camera.core.ImageAnalysis.Builder] requires enum value of
     *  [androidx.camera.core.AspectRatio]. Currently it has values of 4:3 & 16:9.
     *
     *  Detecting the most suitable ratio for dimensions provided in @params by counting absolute
     *  of preview ratio to one of the provided values.
     *
     *  @param width - preview width
     *  @param height - preview height
     *  @return suitable aspect ratio
     */
    private fun aspectRatio(width: Int, height: Int): Int {
        val previewRatio = width.toDouble() / height
        Log.d(TAG, "previewRatio: $previewRatio")
        if (abs(previewRatio - RATIO_4_3_VALUE) <= abs(previewRatio - RATIO_16_9_VALUE)) {
            return AspectRatio.RATIO_4_3
        }
        return AspectRatio.RATIO_16_9
    }

    /** Returns true if the device has an available back camera. False otherwise */
    private fun hasBackCamera(): Boolean {
        return cameraProvider?.hasCamera(CameraSelector.DEFAULT_BACK_CAMERA) ?: false
    }

    /** Returns true if the device has an available front camera. False otherwise */
    private fun hasFrontCamera(): Boolean {
        return cameraProvider?.hasCamera(CameraSelector.DEFAULT_FRONT_CAMERA) ?: false
    }

    companion object {

        private const val TAG = "SilentDragon"
        private const val RATIO_4_3_VALUE = 4.0 / 3.0
        private const val RATIO_16_9_VALUE = 16.0 / 9.0
    }

    private fun onQrScanned(qrContent: String, image: ImageProxy) {
        resumedScope.launch {
            val parsed = viewModel.parse(qrContent)
            if (parsed == null) {
                val network = viewModel.networkName
                _fragmentCameraBinding?.textScanError?.text =
                    getString(R.string.scan_invalid_address, network, qrContent)
                image.close()
            } else { /* continue scanning*/
                _fragmentCameraBinding?.textScanError?.text = ""
                sendViewModel.toAddress = parsed
                mainActivity?.safeNavigate(R.id.action_nav_scan_to_nav_send)
            }
        }
    }
}