dirlist: skip unnecessary change-folder action

when traversing the directory list, aerc will fetch the contents for
every directory even though the user might just move on to the next.
This causes an unnecessary delay (and load on the worker) and can be
avoided by skipping the old change-folder action when a newer one
arrives within a predefined time interval.

Signed-off-by: Koni Marti <koni.marti@gmail.com>

widgets/dirlist.go

@@ -6,6 +6,7 @@ import (
 	"math"
 	"regexp"
 	"sort"
+	"time"
 
 	"github.com/gdamore/tcell/v2"
 	"github.com/mattn/go-runewidth"
@@ -30,6 +31,7 @@ type DirectoryList struct {
 	scroll     int
 	spinner    *Spinner
 	worker     *types.Worker
+	skipSelect chan bool
 }
 
 func NewDirectoryList(conf *config.AercConfig, acctConf *config.AccountConfig,
@@ -41,6 +43,7 @@ func NewDirectoryList(conf *config.AercConfig, acctConf *config.AccountConfig,
 		logger:     logger,
 		store:      lib.NewDirStore(),
 		worker:     worker,
+		skipSelect: make(chan bool),
 	}
 	uiConf := dirlist.UiConfig()
 	dirlist.spinner = NewSpinner(&uiConf)
@@ -87,11 +90,19 @@ func (dirlist *DirectoryList) UpdateList(done func(dirs []string)) {
 
 func (dirlist *DirectoryList) Select(name string) {
 	dirlist.selecting = name
+
+	close(dirlist.skipSelect)
+	dirlist.skipSelect = make(chan bool)
+
+	go func() {
+		select {
+		case <-time.After(1 * time.Second):
 			dirlist.worker.PostAction(&types.OpenDirectory{Directory: name},
 				func(msg types.WorkerMessage) {
 					switch msg.(type) {
 					case *types.Error:
 						dirlist.selecting = ""
+						dirlist.selected = ""
 					case *types.Done:
 						dirlist.selected = dirlist.selecting
 						dirlist.filterDirsByFoldersConfig()
@@ -113,6 +124,11 @@ func (dirlist *DirectoryList) Select(name string) {
 					dirlist.Invalidate()
 				})
 			dirlist.Invalidate()
+		case <-dirlist.skipSelect:
+			dirlist.logger.Println("dirlist: skip", name)
+			return
+		}
+	}()
 }
 
 func (dirlist *DirectoryList) Selected() string {