Polish BlobCreator and extend its test

app/src/main/java/com/stevesoltys/seedvault/transport/backup/BlobCreator.kt

@@ -5,6 +5,7 @@
 
 package com.stevesoltys.seedvault.transport.backup
 
+import androidx.annotation.WorkerThread
 import com.github.luben.zstd.ZstdOutputStream
 import com.google.protobuf.ByteString
 import com.stevesoltys.seedvault.backend.BackendManager
@@ -17,7 +18,11 @@ import okio.buffer
 import okio.sink
 import org.calyxos.seedvault.chunker.Chunk
 import org.calyxos.seedvault.core.backends.AppBackupFileType
+import java.io.IOException
 
+/**
+ * Creates and uploads new blobs to the current backend.
+ */
 internal class BlobCreator(
     private val crypto: Crypto,
     private val backendManager: BackendManager,
@@ -25,6 +30,11 @@ internal class BlobCreator(
 
     private val buffer = Buffer()
 
+    /**
+     * Creates and returns a new [Blob] from the given [chunk] and uploads it to the backend.
+     */
+    @WorkerThread
+    @Throws(IOException::class)
     suspend fun createNewBlob(chunk: Chunk): Blob {
         buffer.clear()
         val bufferStream = buffer.outputStream()
@@ -36,7 +46,7 @@ internal class BlobCreator(
         }
         val sha256ByteString = buffer.sha256()
         val handle = AppBackupFileType.Blob(crypto.repoId, sha256ByteString.hex())
-        // TODO exception handling and retries
+        // TODO for later: implement a backend wrapper that handles retries for transient errors
         val size = backendManager.backend.save(handle).use { outputStream ->
             val outputBuffer = outputStream.sink().buffer()
             val length = outputBuffer.writeAll(buffer)

app/src/test/java/com/stevesoltys/seedvault/transport/backup/BlobCreatorTest.kt

@@ -17,6 +17,7 @@ import org.calyxos.seedvault.core.backends.AppBackupFileType
 import org.calyxos.seedvault.core.backends.Backend
 import org.calyxos.seedvault.core.toHexString
 import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertNotEquals
 import org.junit.jupiter.api.Test
 import java.io.ByteArrayOutputStream
 import java.io.OutputStream
@@ -34,7 +35,7 @@ internal class BlobCreatorTest : TransportTest() {
     private val blobHandle = slot<AppBackupFileType.Blob>()
 
     @Test
-    fun `test re-use for hashing two chunks`() = runBlocking {
+    fun `test re-use instance for creating two blobs`() = runBlocking {
         val data1 = Random.nextBytes(1337)
         val data2 = Random.nextBytes(2342)
         val chunk1 = Chunk(0L, data1.size, data1, "doesn't matter here")
@@ -48,24 +49,34 @@ internal class BlobCreatorTest : TransportTest() {
         }
         every { crypto.repoId } returns repoId
         every { backendManager.backend } returns backend
-        coEvery { backend.save(capture(blobHandle)) } returns outputStream1
 
-        blobCreator.createNewBlob(chunk1)
+        // create first blob
+        coEvery { backend.save(capture(blobHandle)) } returns outputStream1
+        val blob1 = blobCreator.createNewBlob(chunk1)
         // check that file content hash matches snapshot hash
         val messageDigest = MessageDigest.getInstance("SHA-256")
-        assertEquals(
+        val hash1 = messageDigest.digest(outputStream1.toByteArray()).toHexString()
-            messageDigest.digest(outputStream1.toByteArray()).toHexString(),
+        assertEquals(hash1, blobHandle.captured.name)
-            blobHandle.captured.name,
+
-        )
+        // check blob metadata
+        assertEquals(hash1, blob1.id.hexFromProto())
+        assertEquals(outputStream1.size(), blob1.length)
+        assertEquals(data1.size, blob1.uncompressedLength)
 
         // use same BlobCreator to create another blob, because we re-use a single buffer
         // and need to check clearing that does work as expected
         coEvery { backend.save(capture(blobHandle)) } returns outputStream2
-        blobCreator.createNewBlob(chunk2)
+        val blob2 = blobCreator.createNewBlob(chunk2)
         // check that file content hash matches snapshot hash
-        assertEquals(
+        val hash2 = messageDigest.digest(outputStream2.toByteArray()).toHexString()
-            messageDigest.digest(outputStream2.toByteArray()).toHexString(),
+        assertEquals(hash2, blobHandle.captured.name)
-            blobHandle.captured.name,
+
-        )
+        // both hashes are different
+        assertNotEquals(hash1, hash2)
+
+        // check blob metadata
+        assertEquals(hash2, blob2.id.hexFromProto())
+        assertEquals(outputStream2.size(), blob2.length)
+        assertEquals(data2.size, blob2.uncompressedLength)
     }
 }