fix: better error handling

During backup there are multiple operations that may fail which were ignored.
This commit begins to address this issue by forwarding the errors back to the main function
that can tell the user if the backup was successful or not.
Since `panic()` stops the execution of the program, by returning the error
to upper levels we can enable more sophisticated notification modes without
worring updating every single function that may fail.

main.go

@@ -92,17 +92,23 @@ func main() {
 		},
 	}
 
-	backup(client, newchunk, reusechunk, cfg.PxarOut, cfg.BackupSourceDir)
+	err := backup(client, newchunk, reusechunk, cfg.PxarOut, cfg.BackupSourceDir)
 
 	fmt.Printf("New %d , Reused %d\n", newchunk.Load(), reusechunk.Load())
+	var msg string
+	if err == nil {
+		msg = fmt.Sprintf("Backup complete\nChunks New %d , Reused %d\n", newchunk.Load(), reusechunk.Load())
+	} else {
+		msg = fmt.Sprintf("Error occurred while working, backup may be not completed.\nLast error is: %s\n", err.Error())
+	}
 	if runtime.GOOS == "windows" {
 		systray.Quit()
-		beeep.Notify("Proxmox Backup Go", fmt.Sprintf("Backup complete\nChunks New %d , Reused %d\n", newchunk.Load(), reusechunk.Load()), "")
+		beeep.Notify("Proxmox Backup Go", msg, "")
 	}
 
 }
 
-func backup(client *PBSClient, newchunk, reusechunk *atomic.Uint64, pxarOut string, backupdir string) {
+func backup(client *PBSClient, newchunk, reusechunk *atomic.Uint64, pxarOut string, backupdir string) error {
 	knownChunks := hashmap.New[string, bool]()
 
 	fmt.Printf("Starting backup of %s\n", backupdir)
@@ -116,7 +122,10 @@ func backup(client *PBSClient, newchunk, reusechunk *atomic.Uint64, pxarOut stri
 	archive := &PXARArchive{}
 	archive.archivename = "backup.pxar.didx"
 
-	previousDidx := client.DownloadPreviousToBytes(archive.archivename)
+	previousDidx, err := client.DownloadPreviousToBytes(archive.archivename)
+	if err != nil {
+		return err
+	}
 
 	fmt.Printf("Downloaded previous DIDX: %d bytes\n", len(previousDidx))
 
@@ -150,7 +159,10 @@ func backup(client *PBSClient, newchunk, reusechunk *atomic.Uint64, pxarOut stri
 	fmt.Printf("Known chunks: %d!\n", knownChunks.Len())
 	f := &os.File{}
 	if pxarOut != "" {
-		f, _ = os.Create(pxarOut)
+		f, err = os.Create(pxarOut)
+		if err != nil {
+			return err
+		}
 		defer f.Close()
 	}
 	/**/
@@ -161,8 +173,14 @@ func backup(client *PBSClient, newchunk, reusechunk *atomic.Uint64, pxarOut stri
 	pcat1Chunk := ChunkState{}
 	pcat1Chunk.Init()
 
-	pxarChunk.wrid = client.CreateDynamicIndex(archive.archivename)
-	pcat1Chunk.wrid = client.CreateDynamicIndex("catalog.pcat1.didx")
+	pxarChunk.wrid, err = client.CreateDynamicIndex(archive.archivename)
+	if err != nil {
+		return err
+	}
+	pcat1Chunk.wrid, err = client.CreateDynamicIndex("catalog.pcat1.didx")
+	if err != nil {
+		return err
+	}
 
 	archive.writeCB = func(b []byte) {
 		chunkpos := pxarChunk.C.Scan(b)
@@ -175,6 +193,7 @@ func backup(client *PBSClient, newchunk, reusechunk *atomic.Uint64, pxarOut stri
 			pxarChunk.current_chunk = append(pxarChunk.current_chunk, b[:chunkpos]...)
 
 			h := sha256.New()
+			// TODO: error handling inside callback
 			h.Write(pxarChunk.current_chunk)
 			bindigest := h.Sum(nil)
 			shahash := hex.EncodeToString(bindigest)
@@ -189,7 +208,9 @@ func backup(client *PBSClient, newchunk, reusechunk *atomic.Uint64, pxarOut stri
 				reusechunk.Add(1)
 			}
 
+			// TODO: error handling inside callback
 			binary.Write(pxarChunk.chunkdigests, binary.LittleEndian, (pxarChunk.pos + uint64(len(pxarChunk.current_chunk))))
+			// TODO: error handling inside callback
 			pxarChunk.chunkdigests.Write(h.Sum(nil))
 
 			pxarChunk.assignments_offset = append(pxarChunk.assignments_offset, pxarChunk.pos)
@@ -202,6 +223,7 @@ func backup(client *PBSClient, newchunk, reusechunk *atomic.Uint64, pxarOut stri
 		}
 
 		if pxarOut != "" {
+			// TODO: error handling inside callback
 			f.Write(b)
 		}
 		//
@@ -254,7 +276,11 @@ func backup(client *PBSClient, newchunk, reusechunk *atomic.Uint64, pxarOut stri
 
 	if len(pxarChunk.current_chunk) > 0 {
 		h := sha256.New()
-		h.Write(pxarChunk.current_chunk)
+		_, err = h.Write(pxarChunk.current_chunk)
+		if err != nil {
+			return err
+		}
+
 		shahash := hex.EncodeToString(h.Sum(nil))
 		binary.Write(pxarChunk.chunkdigests, binary.LittleEndian, (pxarChunk.pos + uint64(len(pxarChunk.current_chunk))))
 		pxarChunk.chunkdigests.Write(h.Sum(nil))
@@ -276,7 +302,11 @@ func backup(client *PBSClient, newchunk, reusechunk *atomic.Uint64, pxarOut stri
 
 	if len(pcat1Chunk.current_chunk) > 0 {
 		h := sha256.New()
-		h.Write(pcat1Chunk.current_chunk)
+		_, err = h.Write(pcat1Chunk.current_chunk)
+		if err != nil {
+			return err
+		}
+
 		shahash := hex.EncodeToString(h.Sum(nil))
 		binary.Write(pcat1Chunk.chunkdigests, binary.LittleEndian, (pcat1Chunk.pos + uint64(len(pcat1Chunk.current_chunk))))
 		pcat1Chunk.chunkdigests.Write(h.Sum(nil))
@@ -310,6 +340,10 @@ func backup(client *PBSClient, newchunk, reusechunk *atomic.Uint64, pxarOut stri
 
 	client.CloseDynamicIndex(pcat1Chunk.wrid, hex.EncodeToString(pcat1Chunk.chunkdigests.Sum(nil)), pcat1Chunk.pos, pcat1Chunk.chunkcount)
 
-	client.UploadManifest()
-	client.Finish()
+	err = client.UploadManifest()
+	if err != nil {
+		return err
+	}
+
+	return client.Finish()
 }