onedrive: Implement --poll-interval for onedrive

Implement ChangeNotifier for onedrive.
Use drive delta queries to listen for modifications.

backend/onedrive/onedrive.go

@@ -301,6 +301,10 @@ type siteResource struct {
 type siteResponse struct {
 	Sites []siteResource `json:"value"`
 }
+type deltaResponse struct {
+	DeltaLink string     `json:"@odata.deltaLink"`
+	Value     []api.Item `json:"value"`
+}
 
 // Get the region and graphURL from the config
 func getRegionURL(m configmap.Mapper) (region, graphURL string) {
@@ -2302,6 +2306,142 @@ func (f *Fs) canonicalDriveID(driveID string) (canonicalDriveID string) {
 	return canonicalDriveID
 }
 
+// ChangeNotify calls the passed function with a path that has had changes.
+// If the implementation uses polling, it should adhere to the given interval.
+//
+// Automatically restarts itself in case of unexpected behavior of the remote.
+//
+// Close the returned channel to stop being notified.
+//
+// The Onedrive implementation gives the whole hierarchy up to the  top when
+// an object is changed. For instance, if a/b/c is changed, this function
+// will call notifyFunc with a, a/b and a/b/c.
+func (f *Fs) ChangeNotify(ctx context.Context, notifyFunc func(string, fs.EntryType), pollIntervalChan <-chan time.Duration) {
+	go func() {
+		// get the StartPageToken early so all changes from now on get processed
+		nextDeltaToken, err := f.changeNotifyStartPageToken(ctx)
+		if err != nil {
+			fs.Errorf(f, "Could not get first deltaLink: %s", err)
+			return
+		}
+
+		fs.Debugf(f, "Next delta token is: %s", nextDeltaToken)
+
+		var ticker *time.Ticker
+		var tickerC <-chan time.Time
+		for {
+			select {
+			case pollInterval, ok := <-pollIntervalChan:
+				if !ok {
+					if ticker != nil {
+						ticker.Stop()
+					}
+					return
+				}
+				if ticker != nil {
+					ticker.Stop()
+					ticker, tickerC = nil, nil
+				}
+				if pollInterval != 0 {
+					ticker = time.NewTicker(pollInterval)
+					tickerC = ticker.C
+				}
+			case <-tickerC:
+				fs.Debugf(f, "Checking for changes on remote")
+				nextDeltaToken, err = f.changeNotifyRunner(ctx, notifyFunc, nextDeltaToken)
+				if err != nil {
+					fs.Infof(f, "Change notify listener failure: %s", err)
+				}
+			}
+		}
+	}()
+}
+
+func (f *Fs) changeNotifyStartPageToken(ctx context.Context) (nextDeltaToken string, err error) {
+	delta, err := f.changeNotifyNextChange(ctx, "latest")
+	parsedURL, err := url.Parse(delta.DeltaLink)
+	if err != nil {
+		return
+	}
+	nextDeltaToken = parsedURL.Query().Get("token")
+	return
+}
+
+func (f *Fs) changeNotifyNextChange(ctx context.Context, token string) (delta deltaResponse, err error) {
+	opts := f.buildDriveDeltaOpts(token)
+
+	_, err = f.srv.CallJSON(ctx, &opts, nil, &delta)
+
+	return
+}
+
+func (f *Fs) buildDriveDeltaOpts(token string) rest.Opts {
+	rootURL := graphAPIEndpoint[f.opt.Region] + "/v1.0/drives"
+
+	return rest.Opts{
+		Method:     "GET",
+		RootURL:    rootURL,
+		Path:       "/" + f.driveID + "/root/delta",
+		Parameters: map[string][]string{"token": {token}},
+	}
+}
+
+func (f *Fs) changeNotifyRunner(ctx context.Context, notifyFunc func(string, fs.EntryType), deltaToken string) (nextDeltaToken string, err error) {
+	delta, err := f.changeNotifyNextChange(ctx, deltaToken)
+	parsedURL, err := url.Parse(delta.DeltaLink)
+	if err != nil {
+		return
+	}
+	nextDeltaToken = parsedURL.Query().Get("token")
+
+	for _, item := range delta.Value {
+		isDriveRootFolder := item.GetParentReference().ID == ""
+		if isDriveRootFolder {
+			continue
+		}
+
+		fullPath, err := getItemFullPath(&item)
+		if err != nil {
+			fs.Errorf(f, "Could not get item full path: %s", err)
+			continue
+		}
+
+		if fullPath == f.root {
+			continue
+		}
+
+		relName, insideRoot := getRelativePathInsideBase(f.root, fullPath)
+		if !insideRoot {
+			continue
+		}
+
+		if item.GetFile() != nil {
+			notifyFunc(relName, fs.EntryObject)
+		} else if item.GetFolder() != nil {
+			notifyFunc(relName, fs.EntryDirectory)
+		}
+	}
+
+	return
+}
+
+func getItemFullPath(item *api.Item) (fullPath string, err error) {
+	err = nil
+	fullPath = item.GetName()
+	if parent := item.GetParentReference(); parent != nil && parent.Path != "" {
+		pathParts := strings.SplitN(parent.Path, ":", 2)
+		if len(pathParts) != 2 {
+			err = fmt.Errorf("invalid parent path: %s", parent.Path)
+			return
+		}
+
+		if pathParts[1] != "" {
+			fullPath = strings.TrimPrefix(pathParts[1], "/") + "/" + fullPath
+		}
+	}
+	return
+}
+
 // getRelativePathInsideBase checks if `target` is inside `base`. If so, it
 // returns a relative path for `target` based on `base` and a boolean `true`.
 // Otherwise returns "", false.