Don't include known bad blobs in BlobCache

app/src/main/java/com/stevesoltys/seedvault/repo/BlobCache.kt

@@ -59,14 +59,20 @@ class BlobCache(
         blobMap.clear()
         MemoryLogger.log()
         // create map of blobId to size of blob on backend
-        val blobIds = blobs.associate {
+        val allowedBlobIds = blobs.associate {
             Pair(it.fileHandle.name, it.size.toInt())
+        }.toMutableMap()
+        // remove known bad blob IDs from allowedBlobIds
+        getDoNotUseBlobIds().forEach { knownBadId ->
+            if (allowedBlobIds.remove(knownBadId) != null) {
+                log.info { "Removed known bad blob: $knownBadId" }
+            }
         }
         // load local blob cache and include only blobs on backend
-        loadPersistentBlobCache(blobIds)
+        loadPersistentBlobCache(allowedBlobIds)
         // build up mapping from chunkId to blob from available snapshots
         snapshots.forEach { snapshot ->
-            onSnapshotLoaded(snapshot, blobIds)
+            onSnapshotLoaded(snapshot, allowedBlobIds)
         }
         MemoryLogger.log()
     }
@@ -167,14 +173,14 @@ class BlobCache(
 
     /**
      * Used for populating local [blobMap] cache.
-     * Adds mapping from chunkId to [Blob], if it exists on backend, i.e. part of [blobIds]
+     * Adds mapping from chunkId to [Blob], if it exists on backend, i.e. part of [allowedBlobIds]
-     * and its size matches the one on backend, i.e. value of [blobIds].
+     * and its size matches the one on backend, i.e. value of [allowedBlobIds].
      */
-    private fun onSnapshotLoaded(snapshot: Snapshot, blobIds: Map<String, Int>) {
+    private fun onSnapshotLoaded(snapshot: Snapshot, allowedBlobIds: Map<String, Int>) {
         snapshot.blobsMap.forEach { (chunkId, blob) ->
             // check if referenced blob still exists on backend
             val blobId = blob.id.hexFromProto()
-            val sizeOnBackend = blobIds[blobId]
+            val sizeOnBackend = allowedBlobIds[blobId]
             if (sizeOnBackend == blob.length) {
                 // only add blob to our mapping, if it still exists
                 blobMap.putIfAbsent(chunkId, blob)?.let { previous ->

app/src/test/java/com/stevesoltys/seedvault/repo/BlobCacheTest.kt

@@ -41,6 +41,9 @@ internal class BlobCacheTest : TransportTest() {
 
             // read saved blobs from cache
             every { strictContext.openFileInput(CACHE_FILE_NAME) } returns file.inputStream()
+            every {
+                strictContext.openFileInput(DO_NOT_USE_FILE_NAME)
+            } throws FileNotFoundException()
             cache.populateCache(listOf(fileInfo1, fileInfo2), emptyList())
 
             // now both blobs are in the map
@@ -62,6 +65,9 @@ internal class BlobCacheTest : TransportTest() {
         BlobCache(strictContext).let { cache ->
             // read saved blobs from cache
             every { strictContext.openFileInput(CACHE_FILE_NAME) } returns file.inputStream()
+            every {
+                strictContext.openFileInput(DO_NOT_USE_FILE_NAME)
+            } throws FileNotFoundException()
             cache.populateCache(listOf(fileInfo2), emptyList()) // fileInfo1 is missing
 
             // now only blob2 gets used, because blob1 wasn't on backend
@@ -80,6 +86,9 @@ internal class BlobCacheTest : TransportTest() {
         BlobCache(strictContext).let { cache ->
             // read saved blobs from cache
             every { strictContext.openFileInput(CACHE_FILE_NAME) } returns file.inputStream()
+            every {
+                strictContext.openFileInput(DO_NOT_USE_FILE_NAME)
+            } throws FileNotFoundException()
             cache.populateCache(listOf(info, fileInfo2), emptyList()) // info has different size now
 
             // now only blob2 gets used, because blob1 wasn't on backend
@@ -88,6 +97,32 @@ internal class BlobCacheTest : TransportTest() {
         }
     }
 
+    @Test
+    fun `cached blob doesn't get used if known bad on do-not-use list`(@TempDir tmpDir: Path) {
+        val file = File(tmpDir.toString(), "tmpCache")
+        val doNotUseFile = File(tmpDir.toString(), "doNotUse")
+        BlobCache(strictContext).apply {
+            saveTwoBlobsToCache(file)
+            every { strictContext.openFileOutput(DO_NOT_USE_FILE_NAME, MODE_APPEND) } answers {
+                FileOutputStream(doNotUseFile, true)
+            }
+            doNotUseBlob(blob1.id)
+        }
+
+        BlobCache(strictContext).let { cache ->
+            // read saved blobs from cache
+            every { strictContext.openFileInput(CACHE_FILE_NAME) } returns file.inputStream()
+            every {
+                strictContext.openFileInput(DO_NOT_USE_FILE_NAME)
+            } answers { doNotUseFile.inputStream() }
+            cache.populateCache(listOf(fileInfo1, fileInfo2), emptyList())
+
+            // now only blob2 gets used, because blob1 is on do-not-use-list
+            assertNull(cache[chunkId1])
+            assertEquals(blob2, cache[chunkId2])
+        }
+    }
+
     @Test
     fun `blobs from snapshot get added to cache`() {
         assertEquals(blob1, snapshot.blobsMap[chunkId1])