Add custom sorting for folders

A new config options for accounts.conf (folders-sort) was added to
allow a user to choose which folders should be shown on top.
My use case was to avoid stepping into heavy, but rarely viewed folders
when cycling through other often accessed ones.

To test add this to your account.conf:

folders-sort  = INBOX,Sent,Archive

INBOX, Sent and Archive should then show at the top of your dirlist,
and all other folders should come next in alphabetical order.

1 files changed, 34 insertions, 2 deletions

diff --git a/widgets/dirlist.go b/widgets/dirlist.go
index ef2dd1ef..c0c89170 100644
--- a/widgets/dirlist.go
+++ b/widgets/dirlist.go
@@ -5,6 +5,7 @@ import (
 	"log"
 	"regexp"
 	"sort"
+	"strings"
 
 	"github.com/gdamore/tcell"
 	"github.com/mattn/go-runewidth"
@@ -61,9 +62,10 @@ func (dirlist *DirectoryList) UpdateList(done func(dirs []string)) {
 			case *types.Directory:
 				dirs = append(dirs, msg.Dir.Name)
 			case *types.Done:
-				sort.Strings(dirs)
 				dirlist.store.Update(dirs)
 				dirlist.filterDirsByFoldersConfig()
+				dirlist.sortDirsByFoldersSortConfig()
+				dirlist.store.Update(dirlist.dirs)
 				dirlist.spinner.Stop()
 				dirlist.Invalidate()
 				if done != nil {
@@ -94,6 +96,7 @@ func (dirlist *DirectoryList) Select(name string) {
 					dirlist.dirs = append(dirlist.dirs, dirlist.selected)
 				}
 				sort.Strings(dirlist.dirs)
+				dirlist.sortDirsByFoldersSortConfig()
 			}
 			dirlist.Invalidate()
 		})
@@ -261,7 +264,7 @@ func (dirlist *DirectoryList) Clicked(x int, y int) (string, bool) {
 }
 
 func (dirlist *DirectoryList) NextPrev(delta int) {
-	curIdx := sort.SearchStrings(dirlist.dirs, dirlist.selected)
+	curIdx := findString(dirlist.dirs, dirlist.selected)
 	if curIdx == len(dirlist.dirs) {
 		return
 	}
@@ -297,6 +300,26 @@ func folderMatches(folder string, pattern string) bool {
 	return pattern == folder
 }
 
+// sortDirsByFoldersSortConfig sets dirlist.dirs to be sorted based on the
+// AccountConfig.FoldersSort option. Folders not included in the option
+// will be appended at the end in alphabetical order
+func (dirlist *DirectoryList) sortDirsByFoldersSortConfig() {
+	sort.Slice(dirlist.dirs, func(i, j int) bool {
+		iInFoldersSort := findString(dirlist.acctConf.FoldersSort, dirlist.dirs[i])
+		jInFoldersSort := findString(dirlist.acctConf.FoldersSort, dirlist.dirs[j])
+		if iInFoldersSort >= 0 && jInFoldersSort >= 0 {
+			return iInFoldersSort < jInFoldersSort
+		}
+		if iInFoldersSort >= 0 {
+			return true
+		}
+		if jInFoldersSort >= 0 {
+			return false
+		}
+		return strings.Compare(dirlist.dirs[i], dirlist.dirs[j]) == -1
+	})
+}
+
 // filterDirsByFoldersConfig sets dirlist.dirs to the filtered subset of the
 // dirstore, based on the AccountConfig.Folders option
 func (dirlist *DirectoryList) filterDirsByFoldersConfig() {
@@ -331,3 +354,12 @@ func (dirlist *DirectoryList) SetMsgStore(name string, msgStore *lib.MessageStor
 		dirlist.Invalidate()
 	})
 }
+
+func findString(slice []string, str string) int {
+	for i, s := range slice {
+		if str == s {
+			return i
+		}
+	}
+	return -1
+}