lib/model: Refactor out folder and folderscan types, simplify somewhat

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3007

lib/model/folder.go

@@ -0,0 +1,53 @@
+// Copyright (C) 2014 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package model
+
+import "time"
+
+type folder struct {
+	stateTracker
+	scan  folderscan
+	model *Model
+	stop  chan struct{}
+}
+
+func (f *folder) IndexUpdated() {
+}
+
+func (f *folder) DelayScan(next time.Duration) {
+	f.scan.Delay(next)
+}
+
+func (f *folder) Scan(subdirs []string) error {
+	return f.scan.Scan(subdirs)
+}
+func (f *folder) Stop() {
+	close(f.stop)
+}
+
+func (f *folder) Jobs() ([]string, []string) {
+	return nil, nil
+}
+
+func (f *folder) BringToFront(string) {}
+
+func (f *folder) scanSubdirsIfHealthy(subDirs []string) error {
+	if err := f.model.CheckFolderHealth(f.folderID); err != nil {
+		l.Infoln("Skipping folder", f.folderID, "scan due to folder error:", err)
+		return err
+	}
+	l.Debugln(f, "Scanning subdirectories")
+	if err := f.model.internalScanFolderSubdirs(f.folderID, subDirs); err != nil {
+		// Potentially sets the error twice, once in the scanner just
+		// by doing a check, and once here, if the error returned is
+		// the same one as returned by CheckFolderHealth, though
+		// duplicate set is handled by setError.
+		f.setError(err)
+		return err
+	}
+	return nil
+}