feat(download): show progress before a link download starts

The source check, folder access and request ran before the first
byte with no visible feedback. Enter the loading state on tap and
show an indeterminate wavy indicator until download progress is
known. File import is unchanged. An early cancel deletes only files
created by the current download, so installed dictionaries survive.

app/src/main/java/com/example/research/common/progress/DictionaryProgressModel.kt

@@ -21,14 +21,16 @@ object DictionaryProgressModel {
         val progress: Float,
         val percent: Int,
         @param:StringRes val titleRes: Int,
+        val indeterminate: Boolean = false,
     ) {
         override fun equals(other: Any?): Boolean {
             if (this === other) return true
             if (other !is Snapshot) return false
-            return percent == other.percent && titleRes == other.titleRes
+            return percent == other.percent && titleRes == other.titleRes &&
+                indeterminate == other.indeterminate
         }
         override fun hashCode(): Int {
-            return 31 * percent + titleRes
+            return 31 * (31 * percent + titleRes) + indeterminate.hashCode()
         }
     }
     fun computeProgressSnapshot(
@@ -92,6 +94,7 @@ object DictionaryProgressModel {
             progress = p,
             percent = pct,
             titleRes = R.string.notification_download_title,
+            indeterminate = dl <= 0f,
         )
     }
 

app/src/main/java/com/example/research/feature/download/DownloadManager.kt

@@ -57,6 +57,7 @@ class DownloadManager(
         if (!downloadScope.isActive) return
         onFlowStarted?.invoke()
         cancelCleanupJob = null
+        updateDownloadProgressState(DownloadState.Loading, 0f)
         downloadJob = downloadScope.launch {
             mutex.withLock {
                 try {
@@ -81,8 +82,6 @@ class DownloadManager(
                         return@withLock
                     }
 
-                    updateDownloadProgressState(DownloadState.Loading, 0f)
-
                     var lastReportedProgressBucket = -1
                     val result = ReSearchTrace.asyncSection(ReSearchTrace.DICTIONARY_DOWNLOAD) {
                         dictionaryRepository.downloadSources(downloadableSources) { progress ->
@@ -149,6 +148,7 @@ class DownloadManager(
         if (!downloadScope.isActive) return
         onFlowStarted?.invoke()
         cancelCleanupJob = null
+        updateDownloadProgressState(DownloadState.Loading, 0f)
         downloadJob = downloadScope.launch {
             mutex.withLock {
                 try {
@@ -177,8 +177,6 @@ class DownloadManager(
                         return@withLock
                     }
 
-                    updateDownloadProgressState(DownloadState.Loading, 0f)
-
                     var lastReportedProgressBucket = -1
                     val result = ReSearchTrace.asyncSection(ReSearchTrace.DICTIONARY_DOWNLOAD) {
                         dictionaryRepository.downloadSources(downloadableSources) { progress ->

app/src/main/java/com/example/research/feature/download/repository/DictionaryRepository.kt

@@ -25,8 +25,10 @@ class DictionaryRepository(
     private val extractor = DictionaryExtractor(context, fileStorageManager)
     private val cleaner = DictionaryCleaner(context, fileStorageManager)
 
-    private var filesBeforeDownload = mutableSetOf<String>()
-    private var downloadedPrefixes = mutableSetOf<String>()
+    private class DownloadSession(val filesBefore: Set<String>, val prefixes: Set<String>)
+
+    @Volatile
+    private var session: DownloadSession? = null
 
     companion object {
         private const val TAG = "DictionaryRepository"
@@ -81,15 +83,10 @@ class DictionaryRepository(
         val files = fileStorageManager.listFilesInFolder(uri)
         cleaner.deleteCorruptedArchives(uri, files)
 
-        synchronized(filesBeforeDownload) {
-            filesBeforeDownload = files.map { it.name }.toMutableSet()
-        }
-
-        synchronized(downloadedPrefixes) {
-            downloadedPrefixes = sources.mapNotNull {
-                DictionarySource.extractPrefix(it.urlTemplate)
-            }.toMutableSet()
-        }
+        session = DownloadSession(
+            filesBefore = files.mapTo(mutableSetOf()) { it.name },
+            prefixes = sources.mapNotNullTo(mutableSetOf()) { DictionarySource.extractPrefix(it.urlTemplate) },
+        )
 
         downloader.downloadDictionaries(
             folderUri = uri,
@@ -114,63 +111,22 @@ class DictionaryRepository(
 
         cleaner.deleteUnprocessedFiles(uri, files)
 
-        val filesAfterStandardCleanup = fileStorageManager.listFilesInFolder(uri)
+        val current = session ?: return@withContext Result.success(Unit)
+        session = null
 
-        val existingFiles = synchronized(filesBeforeDownload) {
-            filesBeforeDownload.toSet()
+        fileStorageManager.listFilesInFolder(uri)
+            .filter { file ->
+                file.name !in current.filesBefore &&
+                    current.prefixes.any { prefix -> file.name.startsWith("${prefix}_") }
             }
-
-        val prefixes = synchronized(downloadedPrefixes) {
-            downloadedPrefixes.toSet()
-        }
-
-        val finalPrefixes = prefixes.ifEmpty {
-            val sources = preferencesManager.dictionarySources.first()
-            sources.mapNotNull { DictionarySource.extractPrefix(it.urlTemplate) }.toSet()
-        }
-
-        val filesToDelete = if (existingFiles.isEmpty()) {
-            filesAfterStandardCleanup.filter { file ->
-                val fileName = file.name
-                finalPrefixes.any { prefix -> fileName.startsWith("${prefix}_") }
-            }
-        } else {
-            filesAfterStandardCleanup.filter { file ->
-                file.name !in existingFiles &&
-                finalPrefixes.any { prefix -> file.name.startsWith("${prefix}_") }
-            }
-        }
-
-        if (filesToDelete.isNotEmpty()) {
-            var deletedCount = 0
-
-            for ((fileName, uri) in filesToDelete) {
-                val docFile = fileStorageManager.getDocumentFile(uri)
-                if (docFile != null && docFile.exists()) {
-                    val deleted = docFile.delete()
-                    if (deleted) {
-                        deletedCount++
-                    } else {
-                        val forceDeleted = fileStorageManager.forceDeleteFile(docFile, fileName)
-                        if (!forceDeleted) {
+            .forEach { (fileName, fileUri) ->
+                val docFile = fileStorageManager.getDocumentFile(fileUri)
+                if (docFile != null && docFile.exists() && !docFile.delete() &&
+                    !fileStorageManager.forceDeleteFile(docFile, fileName)
+                ) {
                     Log.e(TAG, "deleteUnprocessedFiles() - force delete failed for: $fileName")
-                        } else {
-                            deletedCount++
                 }
             }
-                }
-            }
-        }
-
-        synchronized(filesBeforeDownload) {
-            if (filesBeforeDownload.isNotEmpty()) {
-                filesBeforeDownload.clear()
-            }
-        }
-
-        synchronized(downloadedPrefixes) {
-            downloadedPrefixes.clear()
-        }
 
         Result.success(Unit)
     }
@@ -183,15 +139,7 @@ class DictionaryRepository(
         val prefixes = sources.mapNotNull { DictionarySource.extractPrefix(it.urlTemplate) }.toSet()
         
         val result = cleaner.performAllCleanup(uri, prefixes, files)
-
-        synchronized(filesBeforeDownload) {
-            filesBeforeDownload.clear()
-        }
-
-        synchronized(downloadedPrefixes) {
-            downloadedPrefixes.clear()
-        }
-
+        session = null
         result
     }
 }

app/src/main/java/com/example/research/ui/settings/components/DictionaryManagement.kt

@@ -268,6 +268,7 @@ private fun DictionaryProgressSectionHost(
         label = label,
         onCancel = onCancel,
         percent = progressSnapshot?.percent ?: 0,
+        indeterminate = progressSnapshot?.indeterminate ?: false,
         testTag = progressTestTag,
     )
 }

app/src/main/java/com/example/research/ui/settings/components/DictionaryProgressSection.kt

@@ -12,6 +12,7 @@ import androidx.compose.foundation.layout.*
 import androidx.compose.ui.res.painterResource
 import androidx.compose.material3.*
 import androidx.compose.runtime.*
+import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.platform.testTag
@@ -31,6 +32,7 @@ fun DictionaryProgressSection(
     onCancel: () -> Unit,
     modifier: Modifier = Modifier,
     percent: Int,
+    indeterminate: Boolean,
     testTag: String,
 ) {
     AnimatedVisibility(
@@ -44,6 +46,7 @@ fun DictionaryProgressSection(
         var displayedLabel by remember { mutableStateOf(label) }
         var displayedPercent by remember { mutableIntStateOf(percent) }
         var displayedTestTag by remember { mutableStateOf(testTag) }
+        var displayedIndeterminate by remember { mutableStateOf(indeterminate) }
 
         LaunchedEffect(visible) {
             if (visible) {
@@ -60,6 +63,7 @@ fun DictionaryProgressSection(
                 displayedLabel = label
                 displayedPercent = percent
                 displayedTestTag = testTag
+                displayedIndeterminate = indeterminate
             }
         }
         val animatedState = remember { Animatable(0f) }
@@ -88,13 +92,23 @@ fun DictionaryProgressSection(
                     style = MaterialTheme.typography.bodySmall,
                     color = MaterialTheme.colorScheme.primary
                 )
+                if (!displayedIndeterminate) {
                     Text(
                         text = "$displayedPercent%",
                         style = MaterialTheme.typography.bodySmall,
                         color = MaterialTheme.colorScheme.primary
                     )
                 }
-            Spacer(Modifier.height(8.dp))
+            }
+            Box(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .height(WavyProgressIndicatorDefaults.LinearContainerHeight),
+                contentAlignment = Alignment.Center,
+            ) {
+                if (displayedIndeterminate) {
+                    LinearWavyProgressIndicator(modifier = Modifier.fillMaxWidth())
+                } else {
                     LinearProgressIndicator(
                         progress = { animatedProgress },
                         modifier = Modifier
@@ -102,7 +116,9 @@ fun DictionaryProgressSection(
                             .height(4.dp)
                             .clip(MaterialTheme.shapes.small),
                     )
-            Spacer(Modifier.height(8.dp))
+                }
+            }
+            Spacer(Modifier.height(4.dp))
             OutlinedButton(
                 onClick = onCancel,
                 modifier = Modifier.fillMaxWidth(),