feat: Implement SHA-1 pre-calculation and image loading abort logic

app/src/main/java/fr/free/nrw/commons/customselector/ui/adapter/ImageAdapter.kt

@@ -20,6 +20,7 @@ import fr.free.nrw.commons.customselector.helper.ImageHelper.CUSTOM_SELECTOR_PRE
 import fr.free.nrw.commons.customselector.helper.ImageHelper.SHOW_ALREADY_ACTIONED_IMAGES_PREFERENCE_KEY
 import fr.free.nrw.commons.customselector.listeners.ImageSelectListener
 import fr.free.nrw.commons.customselector.model.Image
+import fr.free.nrw.commons.customselector.ui.selector.ImageFileLoader
 import fr.free.nrw.commons.customselector.ui.selector.ImageLoader
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.CoroutineScope
@@ -48,6 +49,7 @@ class ImageAdapter(
      * ImageLoader queries images.
      */
     private var imageLoader: ImageLoader,
+    private var imageFileLoader: ImageFileLoader,
 ) : RecyclerView.Adapter<ImageAdapter.ImageViewHolder>(),
     FastScrollRecyclerView.SectionedAdapter {
 
@@ -537,6 +539,8 @@ class ImageAdapter(
      * CleanUp function.
      */
     fun cleanUp() {
+        //abort the device scanning process immediately
+        imageFileLoader.abortLoadImage()
         scope.cancel()
     }
 

app/src/main/java/fr/free/nrw/commons/customselector/ui/selector/CustomSelectorViewModel.kt

@@ -9,6 +9,7 @@ import fr.free.nrw.commons.customselector.model.Image
 import fr.free.nrw.commons.customselector.model.Result
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.cancel
 
 /**
@@ -21,7 +22,7 @@ class CustomSelectorViewModel(
     /**
      * Scope for coroutine task (image fetch).
      */
-    private val scope = CoroutineScope(Dispatchers.Main)
+    private val scope = CoroutineScope(Dispatchers.Main + SupervisorJob())
 
     /**
      * Stores selected images.
@@ -38,7 +39,9 @@ class CustomSelectorViewModel(
      */
     fun fetchImages() {
         result.postValue(Result(CallbackStatus.FETCHING, arrayListOf()))
-        scope.cancel()
+        // fix: instead of scope.cancel(), we call our new abort method in the loader.
+        //this stops the background processing while keeping the ViewModel scope alive.
+        imageFileLoader.abortLoadImage()
         imageFileLoader.loadDeviceImages(
             object : ImageLoaderListener {
                 override fun onImageLoaded(images: ArrayList<Image>) {
@@ -56,6 +59,8 @@ class CustomSelectorViewModel(
      * Clear the coroutine task linked with context.
      */
     override fun onCleared() {
+        //stop the loader immediately when the ViewModel is destroyed
+        imageFileLoader.abortLoadImage()
         scope.cancel()
         super.onCleared()
     }

app/src/main/java/fr/free/nrw/commons/customselector/ui/selector/ImageFileLoader.kt

@@ -6,11 +6,10 @@ import android.provider.MediaStore
 import android.text.format.DateFormat
 import fr.free.nrw.commons.customselector.listeners.ImageLoaderListener
 import fr.free.nrw.commons.customselector.model.Image
-import kotlinx.coroutines.CoroutineScope
-import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.launch
-import kotlinx.coroutines.withContext
+import kotlinx.coroutines.*
 import java.io.File
+import java.io.FileInputStream
+import java.security.MessageDigest
 import java.util.Calendar
 import java.util.Date
 import java.util.Locale
@@ -23,6 +22,12 @@ import kotlin.coroutines.CoroutineContext
 class ImageFileLoader(
     val context: Context,
 ) : CoroutineScope {
+
+    /**
+     * keep track of the current loading job to allow cancellation.
+     */
+    private var loaderJob: Job? = null
+
     /**
      * Coroutine context for fetching images.
      */
@@ -45,7 +50,8 @@ class ImageFileLoader(
      * Load Device Images under coroutine.
      */
     fun loadDeviceImages(listener: ImageLoaderListener) {
-        launch(Dispatchers.Main) {
+        loaderJob?.cancel()
+        loaderJob = launch(Dispatchers.Main) {
             withContext(Dispatchers.IO) {
                 getImages(listener)
             }
@@ -77,18 +83,19 @@ class ImageFileLoader(
         val dateColumn = cursor.getColumnIndex(MediaStore.Images.Media.DATE_ADDED)
 
         val images = arrayListOf<Image>()
-        if (cursor.moveToFirst()) {
-            do {
-                if (Thread.interrupted()) {
-                    listener.onFailed(NullPointerException())
-                    return
-                }
-                val id = cursor.getLong(idColumn)
-                val name = cursor.getString(nameColumn)
-                val path = cursor.getString(dataColumn)
-                val bucketId = cursor.getLong(bucketIdColumn)
-                val bucketName = cursor.getString(bucketNameColumn)
-                val date = cursor.getLong(dateColumn)
+        cursor.use { c -> //using .use automatically closes the cursor
+            if (c.moveToFirst()) {
+                do {
+                    //check if coroutine was cancelled or thread interrupted
+                    if (!isActive || Thread.interrupted()) {
+                        return
+                    }
+                    val id = c.getLong(idColumn)
+                    val name = c.getString(nameColumn)
+                    val path = c.getString(dataColumn)
+                    val bucketId = c.getLong(bucketIdColumn)
+                    val bucketName = c.getString(bucketNameColumn)
+                    val date = c.getLong(dateColumn)
 
                 val file =
                     if (path == null || path.isEmpty()) {
@@ -117,35 +124,52 @@ class ImageFileLoader(
                     val dateFormat = DateFormat.getMediumDateFormat(context)
                     val formattedDate = dateFormat.format(date)
 
-                    val image =
-                        Image(
+                        val sha1 = getSha1(file)
+                        val image =
+                            Image(
                             id,
                             name,
                             uri,
                             path,
                             bucketId,
                             bucketName,
-                            date = (formattedDate),
+                            date = formattedDate,
+                            sha1 = sha1
                         )
-                    images.add(image)
-                }
-            } while (cursor.moveToNext())
+                        images.add(image)
+                    }
+                } while (c.moveToNext())
+            }
+        }
+        //return results to the main thread via listener
+        launch(Dispatchers.Main) {
+            listener.onImageLoaded(images)
         }
-        cursor.close()
-        listener.onImageLoaded(images)
     }
 
     /**
      * Abort loading images.
      */
     fun abortLoadImage() {
-        // todo Abort loading images.
+        loaderJob?.cancel()
     }
 
-    /*
-     *
-     * TODO
-     * Sha1 for image (original image).
-     *
+    /**
+     * generates SHA-1 hash for the image file.
      */
+    private fun getSha1(file: File): String {
+        return try {
+            val digest = MessageDigest.getInstance("SHA-1")
+            val fileInputStream = FileInputStream(file)
+            val buffer = ByteArray(8192)
+            var bytesRead: Int
+            while (fileInputStream.read(buffer).also { bytesRead = it } != -1) {
+                digest.update(buffer, 0, bytesRead)
+            }
+            val sha1Bytes = digest.digest()
+            sha1Bytes.joinToString("") { "%02x".format(it) }
+        } catch (e: Exception) {
+            ""
+        }
+    }
 }

app/src/main/java/fr/free/nrw/commons/customselector/ui/selector/ImageFragment.kt

@@ -138,6 +138,12 @@ class ImageFragment :
     @Inject
     lateinit var uploadedStatusDao: UploadedStatusDao
 
+    /**
+     * ImageFileLoader to scan device files.
+     */
+    @Inject
+    lateinit var imageFileLoader: ImageFileLoader
+
     /**
      * FileUtilsWrapper class to get imageSHA1 from uri
      */
@@ -215,7 +221,13 @@ class ImageFragment :
 
         // ensures imageAdapter is initialized
         if (!::imageAdapter.isInitialized) {
-            imageAdapter = ImageAdapter(requireActivity(), activity as ImageSelectListener, imageLoader!!)
+            //fix: Added theimageFileLoader as the 4th parameter
+            imageAdapter = ImageAdapter(
+                requireActivity(),
+                activity as ImageSelectListener,
+                imageLoader!!,
+                imageFileLoader
+            )
             Timber.d("Initialized imageAdapter in onCreateView")
         }
         // Set single selection mode if needed

app/src/main/java/fr/free/nrw/commons/customselector/ui/selector/ImageLoader.kt

@@ -93,7 +93,11 @@ class ImageLoader
                     return@launch
                 }
 
-                val imageSHA1: String =
+                // optimisation: use the SHA1 pre-calculated by ImageFileLoader.
+                // this avoids the redundant file I/O operations.
+                val imageSHA1: String = if (image.sha1.isNotEmpty()) {
+                    image.sha1
+                } else {
                     when (mapImageSHA1[image.uri] != null) {
                         true -> mapImageSHA1[image.uri]!!
                         else ->
@@ -104,6 +108,7 @@ class ImageLoader
                                 context.contentResolver,
                             )
                     }
+                }
                 mapImageSHA1[image.uri] = imageSHA1
 
                 if (imageSHA1.isEmpty()) {

app/src/test/kotlin/fr/free/nrw/commons/customselector/ui/adapter/ImageAdapterTest.kt

@@ -13,6 +13,7 @@ import fr.free.nrw.commons.TestCommonsApplication
 import fr.free.nrw.commons.customselector.listeners.ImageSelectListener
 import fr.free.nrw.commons.customselector.model.Image
 import fr.free.nrw.commons.customselector.ui.selector.CustomSelectorActivity
+import fr.free.nrw.commons.customselector.ui.selector.ImageFileLoader
 import fr.free.nrw.commons.customselector.ui.selector.ImageLoader
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.ExperimentalCoroutinesApi
@@ -45,6 +46,9 @@ class ImageAdapterTest {
     @Mock
     private lateinit var imageLoader: ImageLoader
 
+    @Mock
+    private lateinit var imageFileLoader: ImageFileLoader
+
     @Mock
     private lateinit var imageSelectListener: ImageSelectListener
 
@@ -75,7 +79,7 @@ class ImageAdapterTest {
         MockitoAnnotations.initMocks(this)
         Dispatchers.setMain(testDispatcher)
         activity = Robolectric.buildActivity(CustomSelectorActivity::class.java).get()
-        imageAdapter = ImageAdapter(activity, imageSelectListener, imageLoader)
+        imageAdapter = ImageAdapter(activity, imageSelectListener, imageLoader, imageFileLoader)
         image = Image(1, "image", uri, "abc/abc", 1, "bucket1")
         images = ArrayList()
 
@@ -253,6 +257,8 @@ class ImageAdapterTest {
     @Test
     fun cleanUp() {
         imageAdapter.cleanUp()
+        //verify that abortLoadImage was called on the loader
+        Mockito.verify(imageFileLoader).abortLoadImage()
     }
 
     /**