Attachments: implements proper caching

app/src/main/java/net/buzzert/kordophonedroid/AppModule.kt

@@ -1,16 +1,16 @@
 package net.buzzert.kordophonedroid
 
+import android.content.Context
 import dagger.Module
 import dagger.Provides
 import dagger.hilt.InstallIn
+import dagger.hilt.android.qualifiers.ApplicationContext
 import dagger.hilt.components.SingletonComponent
 import net.buzzert.kordophone.backend.db.CachedChatDatabase
 import net.buzzert.kordophone.backend.server.APIClientFactory
-import net.buzzert.kordophone.backend.server.Authentication
 import net.buzzert.kordophone.backend.server.ChatRepository
-import net.buzzert.kordophone.backend.server.RetrofitAPIClient
+import net.buzzert.kordophonedroid.ui.attachments.AttachmentImageLoader
 import net.buzzert.kordophonedroid.ui.shared.ServerConfigRepository
-import java.net.URL
 import javax.inject.Singleton
 
 @Module
@@ -28,4 +28,14 @@ object AppModule {
         val database = CachedChatDatabase.liveDatabase()
         return ChatRepository(client, database)
     }
+
+    @Singleton
+    @Provides
+    fun provideAttachmentFactory(
+        chatRepository: ChatRepository,
+        @ApplicationContext context: Context
+    ): AttachmentImageLoader
+    {
+        return AttachmentImageLoader(chatRepository, context)
+    }
 }

app/src/main/java/net/buzzert/kordophonedroid/ui/attachments/AttachmentViewModel.kt

@@ -6,29 +6,25 @@ import androidx.lifecycle.ViewModel
 import coil.Coil
 import coil.ImageLoader
 import coil.ImageLoaderFactory
+import coil.annotation.ExperimentalCoilApi
 import coil.decode.DataSource
 import coil.decode.ImageSource
 import coil.disk.DiskCache
 import coil.fetch.FetchResult
 import coil.fetch.Fetcher
 import coil.fetch.SourceResult
-import coil.memory.MemoryCache
 import coil.request.Options
-import dagger.hilt.android.lifecycle.HiltViewModel
 import dagger.hilt.android.qualifiers.ApplicationContext
 import net.buzzert.kordophone.backend.server.ChatRepository
-import net.buzzert.kordophonedroid.ui.messagelist.MVM_LOG
-import javax.inject.Inject
 
-const val AVM_LOG: String = "AttachmentViewModel"
+const val AVM_LOG: String = "AttachmentImageLoader"
 
 data class AttachmentFetchData(
     val guid: String,
     val preview: Boolean = false
 )
 
-@HiltViewModel
-class AttachmentViewModel @Inject constructor(
+class AttachmentImageLoader(
     private val repository: ChatRepository,
     @ApplicationContext val application: Context,
 ) : ViewModel(), ImageLoaderFactory, Fetcher.Factory<AttachmentFetchData>
@@ -41,17 +37,6 @@ class AttachmentViewModel @Inject constructor(
     override fun newImageLoader(): ImageLoader {
         val factory = this
         return ImageLoader.Builder(application)
-            .memoryCache {
-                MemoryCache.Builder(application)
-                    .maxSizePercent(0.25)
-                    .build()
-            }
-            .diskCache {
-                DiskCache.Builder()
-                    .directory(application.cacheDir.resolve("attachments"))
-                    .maxSizePercent(0.02)
-                    .build()
-            }
             .components {
                 // Adds the FetcherFactory
                 add(factory)
@@ -73,13 +58,59 @@ private class AttachmentFetcher(
     val context: Context,
     val data: AttachmentFetchData
 ): Fetcher {
+    val cache = DiskCache.Builder()
+        .directory(context.cacheDir.resolve("attachments"))
+        .maxSizePercent(0.02)
+        .build()
+
+    val cacheKey: String get() { return data.guid + if (data.preview) "_preview" else "" }
+
+    @OptIn(ExperimentalCoilApi::class)
     override suspend fun fetch(): FetchResult {
+        // Try loading from cache
+        var snapshot = cache.openSnapshot(cacheKey)
+        if (snapshot != null) {
+            Log.d(AVM_LOG, "Found attachment ${data.guid} in disk cache")
+            return SourceResult(
+                source = snapshot.toImageSource(),
+                dataSource = DataSource.DISK,
+                mimeType = null,
+            )
+        }
+
         Log.d(AVM_LOG, "Loading attachment ${data.guid} from network")
         val source = repository.fetchAttachmentDataSource(data.guid, data.preview)
+
+        // Save to cache
+        val editor = cache.openEditor(cacheKey)
+        if (editor != null) {
+            Log.d(AVM_LOG, "Writing attachment ${data.guid} to disk cache")
+
+            cache.fileSystem.write(editor.data) {
+                source.readAll(this)
+            }
+
+            snapshot = editor.commitAndOpenSnapshot()
+            if (snapshot != null) {
+                return SourceResult(
+                    source = snapshot.toImageSource(),
+                    dataSource = DataSource.NETWORK,
+                    mimeType = null
+                )
+            }
+        }
+
+        // We'll go down this path if for some reason we couldn't save to cache.
         return SourceResult(
             source = ImageSource(source, context),
             dataSource = DataSource.NETWORK,
             mimeType = null,
         )
     }
+
+    @OptIn(ExperimentalCoilApi::class)
+    private fun DiskCache.Snapshot.toImageSource(): ImageSource {
+        val fileSystem = cache.fileSystem
+        return ImageSource(data, fileSystem, cacheKey, this)
+    }
 }

app/src/main/java/net/buzzert/kordophonedroid/ui/attachments/AttachmentViewer.kt

@@ -25,10 +25,7 @@ import net.engawapg.lib.zoomable.rememberZoomState
 import net.engawapg.lib.zoomable.zoomable
 
 @Composable
-fun AttachmentViewer(
-    attachmentGuid: String,
-    attachmentViewModel: AttachmentViewModel = hiltViewModel()
-) {
+fun AttachmentViewer(attachmentGuid: String) {
     var topBarVisible = remember { mutableStateOf(true) }
     val navController = LocalNavController.current
     Scaffold(topBar = {

app/src/main/java/net/buzzert/kordophonedroid/ui/messagelist/MessageListScreen.kt

@@ -55,7 +55,6 @@ import net.buzzert.kordophone.backend.model.GUID
 import net.buzzert.kordophonedroid.ui.Destination
 import net.buzzert.kordophonedroid.ui.LocalNavController
 import net.buzzert.kordophonedroid.ui.attachments.AttachmentFetchData
-import net.buzzert.kordophonedroid.ui.attachments.AttachmentViewModel
 import net.buzzert.kordophonedroid.ui.shared.LINK_ANNOTATION_TAG
 import net.buzzert.kordophonedroid.ui.shared.linkify
 import net.buzzert.kordophonedroid.ui.theme.KordophoneTopAppBar
@@ -86,7 +85,6 @@ sealed class MessageListItem: MessageMetadataProvider {
 fun MessageListScreen(
     conversationGUID: GUID,
     viewModel: MessageListViewModel = hiltViewModel(),
-    attachmentViewModel: AttachmentViewModel = hiltViewModel() // unused, but initialized for Coil
 ) {
     viewModel.conversationGUID = conversationGUID
 

app/src/main/java/net/buzzert/kordophonedroid/ui/messagelist/MessageListViewModel.kt

@@ -3,6 +3,7 @@ package net.buzzert.kordophonedroid.ui.messagelist
 import android.content.Context
 import android.net.Uri
 import android.webkit.MimeTypeMap
+import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
@@ -18,13 +19,15 @@ import net.buzzert.kordophone.backend.model.Message
 import net.buzzert.kordophone.backend.model.OutgoingMessage
 import net.buzzert.kordophone.backend.model.UploadingAttachmentMetadata
 import net.buzzert.kordophone.backend.server.ChatRepository
+import net.buzzert.kordophonedroid.ui.attachments.AttachmentImageLoader
 import javax.inject.Inject
 
 const val MVM_LOG: String = "MessageListViewModel"
 
 @HiltViewModel
 class MessageListViewModel @Inject constructor(
-    private val repository: ChatRepository
+    private val repository: ChatRepository,
+    private val imageLoader: AttachmentImageLoader
 ) : ViewModel()
 {
     var conversationGUID: GUID? = null