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/**
 * This method requires a LinearLayoutManager
 */
val RecyclerView.visibleFlow: Flow<List<Int>>
    get() = callbackFlow<List<Int>> {

        val scrollListener = object : RecyclerView.OnScrollListener() {
            override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {

                if (dx == 0 && dy == 0) {

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private fun bindCardDetails(card: CardDetails) {
  owner.text = card.owner
  number.text = card.number
  date.text = "${card.expirationMonth}/${card.expirationYear}"
}

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private fun bindUseCases(cameraProvider: ProcessCameraProvider) {
  val preview = buildPreview()
  val takePicture = buildTakePicture()
  val cameraSelector = buildCameraSelector()

  cameraProvider.bindToLifecycle(this, cameraSelector, preview, takePicture)

  button.setOnClickListener {
    lifecycle.coroutineScope.launchWhenResumed {
      val imageProxy = takePicture.takePicture(executor)

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private val useCase = ExtractDataUseCase(TextRecognition.getClient())

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private fun extractExpiration(lines: List<String>): Pair<String?, String?> {
  val expirationLine = extractExpirationLine(lines)
  val month = expirationLine?.substring(startIndex = 0, endIndex = 2)
  val year = expirationLine?.substring(startIndex = 3)
  return Pair(month, year)
}

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private fun extractExpirationLine(lines: List<String>) =
  lines.flatMap { it.split(" ") }
  .firstOrNull { (it.length == 5 || it.length == 7) && it[2] == '/' }

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private fun extractNumber(lines: List<String>): String? {
  return lines.firstOrNull { line ->
    val subNumbers = line.split(" ")
    subNumbers.isNotEmpty() && subNumbers.flatMap { it.asIterable() }.all { it.isDigit() }
  }
}

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private fun extractOwner(lines: List<String>): String? {
  return lines
  .filter { it.contains(" ") }
  .filter { line -> line.asIterable().none { char -> char.isDigit() } }
  .maxBy { it.length }
}

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object Extractor {
  
  fun extractData(input: String): CardDetails {
    val lines = input.split("\n")
    val owner = extractOwner(lines)
    val number = extractNumber(lines)
    val (month, year) = extractExpiration(lines)
    return CardDetails(
      owner = owner,
      number = number,

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data class CardDetails(
  val owner: String?,
  val number: String?,
  val expirationMonth: String?,
  val expirationYear: String?
)