adding test for fetching media folders

domains/android/core/src/main/kotlin/app/dapk/st/core/ContentResolverExtensions.kt

@@ -13,11 +13,18 @@ data class ContentResolverQuery(
 )
 
 inline fun <T> ContentResolver.reduce(query: ContentResolverQuery, operation: (Cursor) -> T): List<T> {
-    val result = mutableListOf<T>()
+    return this.reduce(query, mutableListOf<T>()) { acc, cursor ->
+        acc.add(operation(cursor))
+        acc
+    }
+}
+
+inline fun <T> ContentResolver.reduce(query: ContentResolverQuery, initial: T, operation: (T, Cursor) -> T): T {
+    var accumulator: T = initial
     this.query(query.uri, query.projection.toTypedArray(), query.selection, query.selectionArgs.toTypedArray(), query.sortBy).use { cursor ->
         while (cursor != null && cursor.moveToNext()) {
-            result.add(operation(cursor))
+            accumulator = operation(accumulator, cursor)
         }
     }
-    return result
+    return accumulator
 }

features/messenger/src/main/kotlin/app/dapk/st/messenger/gallery/FetchMediaFoldersUseCase.kt

@@ -1,37 +1,39 @@
 package app.dapk.st.messenger.gallery
 
 import android.content.ContentResolver
-import android.content.ContentUris
 import android.net.Uri
 import android.provider.MediaStore.Images
+import app.dapk.st.core.ContentResolverQuery
 import app.dapk.st.core.CoroutineDispatchers
+import app.dapk.st.core.reduce
 import app.dapk.st.core.withIoContext
 
 class FetchMediaFoldersUseCase(
     private val contentResolver: ContentResolver,
+    private val uriAvoidance: MediaUriAvoidance,
     private val dispatchers: CoroutineDispatchers,
 ) {
 
     suspend fun fetchFolders(): List<Folder> {
         return dispatchers.withIoContext {
-            val projection = arrayOf(Images.Media._ID, Images.Media.BUCKET_ID, Images.Media.BUCKET_DISPLAY_NAME, Images.Media.DATE_MODIFIED)
+            val query = ContentResolverQuery(
-            val selection = "${isNotPending()} AND ${Images.Media.BUCKET_ID} AND ${Images.Media.MIME_TYPE} NOT LIKE ?"
+                uriAvoidance.externalContentUri,
-            val sortBy = "${Images.Media.BUCKET_DISPLAY_NAME} COLLATE NOCASE ASC, ${Images.Media.DATE_MODIFIED} DESC"
+                listOf(Images.Media._ID, Images.Media.BUCKET_ID, Images.Media.BUCKET_DISPLAY_NAME, Images.Media.DATE_MODIFIED),
+                "${isNotPending()} AND ${Images.Media.BUCKET_ID} AND ${Images.Media.MIME_TYPE} NOT LIKE ?",
+                listOf("%image/svg%"),
+                "${Images.Media.BUCKET_DISPLAY_NAME} COLLATE NOCASE ASC, ${Images.Media.DATE_MODIFIED} DESC"
+            )
 
-            val folders = mutableMapOf<String, Folder>()
+            contentResolver.reduce(query, mutableMapOf<String, Folder>()) { acc, cursor ->
-            val contentUri = Images.Media.EXTERNAL_CONTENT_URI
+                val rowId = cursor.getLong(cursor.getColumnIndexOrThrow(Images.Media._ID))
-            contentResolver.query(contentUri, projection, selection, arrayOf("%image/svg%"), sortBy).use { cursor ->
+                val thumbnail = uriAvoidance.uriAppender(query.uri, rowId)
-                while (cursor != null && cursor.moveToNext()) {
+                val bucketId = cursor.getString(cursor.getColumnIndexOrThrow(Images.Media.BUCKET_ID))
-                    val rowId = cursor.getLong(cursor.getColumnIndexOrThrow(projection[0]))
+                val title = cursor.getString(cursor.getColumnIndexOrThrow(Images.Media.BUCKET_DISPLAY_NAME)) ?: ""
-                    val thumbnail = ContentUris.withAppendedId(contentUri, rowId)
+                val timestamp = cursor.getLong(cursor.getColumnIndexOrThrow(Images.Media.DATE_MODIFIED))
-                    val bucketId = cursor.getString(cursor.getColumnIndexOrThrow(projection[1]))
+                val folder = acc.getOrPut(bucketId) { Folder(bucketId, title, thumbnail) }
-                    val title = cursor.getString(cursor.getColumnIndexOrThrow(projection[2])) ?: ""
-                    val timestamp = cursor.getLong(cursor.getColumnIndexOrThrow(projection[3]))
-                    val folder = folders.getOrPut(bucketId) { Folder(bucketId, title, thumbnail) }
                 folder.incrementItemCount()
-                }
+                acc
-            }
+            }.values.toList()
-            folders.values.toList()
         }
     }
 

features/messenger/src/main/kotlin/app/dapk/st/messenger/gallery/FetchMediaUseCase.kt

@@ -10,7 +10,7 @@ import app.dapk.st.core.withIoContext
 
 class FetchMediaUseCase(
     private val contentResolver: ContentResolver,
-    private val uriAvoidance: UriAvoidance,
+    private val uriAvoidance: MediaUriAvoidance,
     private val dispatchers: CoroutineDispatchers
 ) {
 
@@ -54,11 +54,6 @@ class FetchMediaUseCase(
 
     private fun getHeightColumn(orientation: Int) =
         if (orientation == 0 || orientation == 180) MediaStore.Images.Media.HEIGHT else MediaStore.Images.Media.WIDTH
-
-    class UriAvoidance(
-        val uriAppender: (Uri, Long) -> Uri,
-        val externalContentUri: Uri,
-    )
 }
 
 data class Media(

features/messenger/src/main/kotlin/app/dapk/st/messenger/gallery/ImageGalleryModule.kt

@@ -7,7 +7,6 @@ import app.dapk.st.core.CoroutineDispatchers
 import app.dapk.st.core.JobBag
 import app.dapk.st.core.ProvidableModule
 import app.dapk.st.core.createStateViewModel
-import app.dapk.st.messenger.gallery.FetchMediaUseCase.UriAvoidance
 import app.dapk.st.messenger.gallery.state.ImageGalleryState
 import app.dapk.st.messenger.gallery.state.imageGalleryReducer
 
@@ -17,17 +16,14 @@ class ImageGalleryModule(
 ) : ProvidableModule {
 
     fun imageGalleryState(roomName: String): ImageGalleryState = createStateViewModel {
-        imageGalleryReducer(
+        val uriAvoidance = MediaUriAvoidance(
-            roomName = roomName,
-            FetchMediaFoldersUseCase(contentResolver, dispatchers),
-            FetchMediaUseCase(
-                contentResolver,
-                UriAvoidance(
             uriAppender = { uri, rowId -> ContentUris.withAppendedId(uri, rowId) },
             externalContentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI
-                ),
+        )
-                dispatchers,
+        imageGalleryReducer(
-            ),
+            roomName = roomName,
+            FetchMediaFoldersUseCase(contentResolver, uriAvoidance, dispatchers),
+            FetchMediaUseCase(contentResolver, uriAvoidance, dispatchers),
             JobBag(),
         )
     }

features/messenger/src/main/kotlin/app/dapk/st/messenger/gallery/MediaUriAvoidance.kt

@@ -0,0 +1,8 @@
+package app.dapk.st.messenger.gallery
+
+import android.net.Uri
+
+class MediaUriAvoidance(
+    val uriAppender: (Uri, Long) -> Uri,
+    val externalContentUri: Uri,
+)

features/messenger/src/test/kotlin/app/dapk/st/messenger/gallery/FetchMediaFoldersUseCaseTest.kt

@@ -0,0 +1,91 @@
+package app.dapk.st.messenger.gallery
+
+import android.net.Uri
+import android.provider.MediaStore
+import fake.CreateCursorScope
+import fake.FakeContentResolver
+import fake.FakeUri
+import fake.createCursor
+import fixture.CoroutineDispatchersFixture.aCoroutineDispatchers
+import kotlinx.coroutines.test.runTest
+import org.amshove.kluent.shouldBeEqualTo
+import org.junit.Test
+
+private val A_EXTERNAL_CONTENT_URI = FakeUri()
+private const val A_BUCKET_ID = "a-bucket-id"
+private const val A_SECOND_BUCKET_ID = "another-bucket"
+private const val A_DISPLAY_NAME = "a-bucket-name"
+private const val A_DATE_MODIFIED = 5000L
+
+class FetchMediaFoldersUseCaseTest {
+
+    private val fakeContentResolver = FakeContentResolver()
+    private val fakeUriAppender = FakeUriAppender()
+    private val uriAvoidance = MediaUriAvoidance(
+        uriAppender = fakeUriAppender,
+        externalContentUri = A_EXTERNAL_CONTENT_URI.instance,
+    )
+
+    private val useCase = FetchMediaFoldersUseCase(fakeContentResolver.instance, uriAvoidance, aCoroutineDispatchers())
+
+    @Test
+    fun `given cursor content, when get folder, then reads unique folders`() = runTest {
+        fakeContentResolver.givenFolderQuery().returns(createCursor {
+            addFolderRow(rowId = 1, A_BUCKET_ID)
+            addFolderRow(rowId = 2, A_BUCKET_ID)
+            addFolderRow(rowId = 3, A_SECOND_BUCKET_ID)
+        })
+
+        val result = useCase.fetchFolders()
+
+        result shouldBeEqualTo listOf(
+            Folder(
+                bucketId = A_BUCKET_ID,
+                title = A_DISPLAY_NAME,
+                thumbnail = fakeUriAppender.get(rowId = 1),
+            ),
+            Folder(
+                bucketId = A_SECOND_BUCKET_ID,
+                title = A_DISPLAY_NAME,
+                thumbnail = fakeUriAppender.get(rowId = 3),
+            ),
+        )
+        result[0].itemCount shouldBeEqualTo 2
+        result[1].itemCount shouldBeEqualTo 1
+    }
+
+    private fun CreateCursorScope.addFolderRow(rowId: Long, bucketId: String) {
+        addRow(
+            MediaStore.Images.Media._ID to rowId,
+            MediaStore.Images.Media.BUCKET_ID to bucketId,
+            MediaStore.Images.Media.BUCKET_DISPLAY_NAME to A_DISPLAY_NAME,
+            MediaStore.Images.Media.DATE_MODIFIED to A_DATE_MODIFIED,
+        )
+    }
+}
+
+private fun FakeContentResolver.givenFolderQuery() = this.givenQueryResult(
+    A_EXTERNAL_CONTENT_URI.instance,
+    arrayOf(
+        MediaStore.Images.Media._ID,
+        MediaStore.Images.Media.BUCKET_ID,
+        MediaStore.Images.Media.BUCKET_DISPLAY_NAME,
+        MediaStore.Images.Media.DATE_MODIFIED
+    ),
+    "${isNotPending()} AND ${MediaStore.Images.Media.BUCKET_ID} AND ${MediaStore.Images.Media.MIME_TYPE} NOT LIKE ?",
+    arrayOf("%image/svg%"),
+    "${MediaStore.Images.Media.BUCKET_DISPLAY_NAME} COLLATE NOCASE ASC, ${MediaStore.Images.Media.DATE_MODIFIED} DESC",
+)
+
+class FakeUriAppender : (Uri, Long) -> Uri {
+
+    private val uris = mutableMapOf<Long, FakeUri>()
+
+    override fun invoke(uri: Uri, rowId: Long): Uri {
+        val fakeUri = FakeUri()
+        uris[rowId] = fakeUri
+        return fakeUri.instance
+    }
+
+    fun get(rowId: Long) = uris[rowId]!!.instance
+}

features/messenger/src/test/kotlin/app/dapk/st/messenger/gallery/FetchMediaUseCaseTest.kt

@@ -10,6 +10,7 @@ import org.amshove.kluent.shouldBeEqualTo
 import org.junit.Test
 
 private val A_EXTERNAL_CONTENT_URI = FakeUri()
+private val ROW_URI = FakeUri()
 private const val A_BUCKET_ID = "a-bucket-id"
 private const val A_ROW_ID = 20L
 private const val A_MIME_TYPE = "image/png"
@@ -23,9 +24,8 @@ private const val A_HEIGHT = 750
 class FetchMediaUseCaseTest {
 
     private val fakeContentResolver = FakeContentResolver()
-    private val appendedUri = FakeUri()
+    private val uriAvoidance = MediaUriAvoidance(
-    private val uriAvoidance = FetchMediaUseCase.UriAvoidance(
+        uriAppender = { _, _ -> ROW_URI.instance },
-        uriAppender = { _, _ -> appendedUri.instance },
         externalContentUri = A_EXTERNAL_CONTENT_URI.instance,
     )
 
@@ -50,7 +50,7 @@ class FetchMediaUseCaseTest {
         result shouldBeEqualTo listOf(
             Media(
                 id = A_ROW_ID,
-                uri = appendedUri.instance,
+                uri = ROW_URI.instance,
                 mimeType = A_MIME_TYPE,
                 width = A_WIDTH,
                 height = A_HEIGHT,
@@ -79,7 +79,7 @@ class FetchMediaUseCaseTest {
         result shouldBeEqualTo listOf(
             Media(
                 id = A_ROW_ID,
-                uri = appendedUri.instance,
+                uri = ROW_URI.instance,
                 mimeType = A_MIME_TYPE,
                 width = A_HEIGHT,
                 height = A_WIDTH,