Add support class for mlkit scanning

WordPress/src/main/java/org/wordpress/android/ui/barcodescanner/GoogleMLKitCodeScanner.kt

@@ -0,0 +1,70 @@
+package org.wordpress.android.ui.barcodescanner
+
+import androidx.camera.core.ImageProxy
+import com.google.mlkit.vision.barcode.BarcodeScanner
+import com.google.mlkit.vision.barcode.common.Barcode
+import kotlinx.coroutines.channels.ProducerScope
+import kotlinx.coroutines.channels.awaitClose
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.callbackFlow
+import javax.inject.Inject
+
+class GoogleMLKitCodeScanner @Inject constructor(
+    private val barcodeScanner: BarcodeScanner,
+    private val errorMapper: GoogleCodeScannerErrorMapper,
+    private val barcodeFormatMapper: GoogleBarcodeFormatMapper,
+    private val inputImageProvider: MediaImageProvider,
+) : CodeScanner {
+    private var barcodeFound = false
+    @androidx.camera.core.ExperimentalGetImage
+    override fun startScan(imageProxy: ImageProxy): Flow<CodeScannerStatus> {
+        return callbackFlow {
+            val barcodeTask = barcodeScanner.process(inputImageProvider.provideImage(imageProxy))
+            barcodeTask.addOnCompleteListener {
+                // We must call image.close() on received images when finished using them.
+                // Otherwise, new images may not be received or the camera may stall.
+                imageProxy.close()
+            }
+            barcodeTask.addOnSuccessListener { barcodeList ->
+                // The check for barcodeFound is done because the startScan method will be called
+                // continuously by the library as long as we are in the scanning screen.
+                // There will be a good chance that the same barcode gets identified multiple times and as a result
+                // success callback will be called multiple times.
+                if (!barcodeList.isNullOrEmpty() && !barcodeFound) {
+                    barcodeFound = true
+                    handleScanSuccess(barcodeList.firstOrNull())
+                    this@callbackFlow.close()
+                }
+            }
+            barcodeTask.addOnFailureListener { exception ->
+                this@callbackFlow.trySend(
+                    CodeScannerStatus.Failure(
+                        error = exception.message,
+                        type = errorMapper.mapGoogleMLKitScanningErrors(exception)
+                    )
+                )
+                this@callbackFlow.close()
+            }
+
+            awaitClose()
+        }
+    }
+
+    private fun ProducerScope<CodeScannerStatus>.handleScanSuccess(code: Barcode?) {
+        code?.rawValue?.let {
+            trySend(
+                CodeScannerStatus.Success(
+                    it,
+                    barcodeFormatMapper.mapBarcodeFormat(code.format)
+                )
+            )
+        } ?: run {
+            trySend(
+                CodeScannerStatus.Failure(
+                    error = "Failed to find a valid raw value!",
+                    type = CodeScanningErrorType.Other(Throwable("Empty raw value"))
+                )
+            )
+        }
+    }
+}