tabs: optimize switching by offsets

I imagine no sane user requires aerc to correctly handle commands like
`:next-tab 1000000000`, but I tried anyway and it froze aerc while
also eating up many GBs of system memory. This behavior is not ideal,
so I improved it.

This commit adds functions for selecting a tab at an offset from the
currently-selected tab and changes the next-tab, prev-tab, and
change-tab commands to use these functions instead of looping.

Signed-off-by: delitako <delitako@delitako.xyz>
Tested-by: Thomas Böhler <witcher@wiredspace.de>
Reviewed-by: Thomas Böhler <witcher@wiredspace.de>
Acked-by: Robin Jarry <robin@jarry.cc>

5 files changed, 30 insertions, 18 deletions

diff --git a/app/aerc.go b/app/aerc.go
index c7307540..31d3a44b 100644
--- a/app/aerc.go
+++ b/app/aerc.go
@@ -525,6 +525,10 @@ func (aerc *Aerc) SelectTabIndex(index int) bool {
 	return ok
 }
 
+func (aerc *Aerc) SelectTabAtOffset(offset int) {
+	aerc.tabs.SelectOffset(offset)
+}
+
 func (aerc *Aerc) TabNames() []string {
 	return aerc.tabs.Names()
 }
diff --git a/app/app.go b/app/app.go
index ea4e4d26..ca9c59bb 100644
--- a/app/app.go
+++ b/app/app.go
@@ -55,6 +55,7 @@ func SelectPreviousTab() bool                           { return aerc.SelectPrev
 func SelectedTab() *ui.Tab                              { return aerc.SelectedTab() }
 func SelectedTabContent() ui.Drawable                   { return aerc.SelectedTabContent() }
 func SelectTabIndex(index int) bool                     { return aerc.SelectTabIndex(index) }
+func SelectTabAtOffset(offset int)                      { aerc.SelectTabAtOffset(offset) }
 func RemoveTab(tab ui.Drawable, closeContent bool)      { aerc.RemoveTab(tab, closeContent) }
 func NewTab(clickable ui.Drawable, name string) *ui.Tab { return aerc.NewTab(clickable, name) }
 func ReplaceTab(tabSrc ui.Drawable, tabTarget ui.Drawable, name string, closeSrc bool) {
diff --git a/commands/ct.go b/commands/ct.go
index 1f99c6a5..4f908fcf 100644
--- a/commands/ct.go
+++ b/commands/ct.go
@@ -37,20 +37,12 @@ func (c ChangeTab) Execute(args []string) error {
 	} else {
 		n, err := strconv.Atoi(c.Tab)
 		if err == nil {
-			switch {
-			case strings.HasPrefix(c.Tab, "+"):
-				for ; n > 0; n-- {
-					app.NextTab()
-				}
-			case strings.HasPrefix(c.Tab, "-"):
-				for ; n < 0; n++ {
-					app.PrevTab()
-				}
-			default:
+			if strings.HasPrefix(c.Tab, "+") || strings.HasPrefix(c.Tab, "-") {
+				app.SelectTabAtOffset(n)
+			} else {
 				ok := app.SelectTabIndex(n)
 				if !ok {
-					return errors.New(
-						"No tab with that index")
+					return errors.New("No tab with that index")
 				}
 			}
 		} else {
diff --git a/commands/next-tab.go b/commands/next-tab.go
index adab95ae..12f659c9 100644
--- a/commands/next-tab.go
+++ b/commands/next-tab.go
@@ -21,13 +21,16 @@ func (NextPrevTab) Aliases() []string {
 }
 
 func (np NextPrevTab) Execute(args []string) error {
-	for n := 0; n < np.Offset; n++ {
-		if args[0] == "prev-tab" {
-			app.PrevTab()
-		} else {
-			app.NextTab()
-		}
+	if np.Offset <= 0 {
+		return nil
 	}
+
+	offset := np.Offset
+	if args[0] == "prev-tab" {
+		offset *= -1
+	}
+
+	app.SelectTabAtOffset(offset)
 	app.UpdateStatus()
 	return nil
 }
diff --git a/lib/ui/tab.go b/lib/ui/tab.go
index 43b6e14f..f5e89064 100644
--- a/lib/ui/tab.go
+++ b/lib/ui/tab.go
@@ -209,6 +209,18 @@ func (tabs *Tabs) SelectPrevious() bool {
 	return tabs.selectPriv(index)
 }
 
+func (tabs *Tabs) SelectOffset(offset int) {
+	tabs.m.Lock()
+	tabCount := len(tabs.tabs)
+	newIndex := (tabs.curIndex + offset) % tabCount
+	if newIndex < 0 {
+		// Handle negative offsets correctly
+		newIndex += tabCount
+	}
+	tabs.selectPriv(newIndex)
+	tabs.m.Unlock()
+}
+
 func (tabs *Tabs) MoveTab(to int, relative bool) {
 	tabs.m.Lock()
 	tabs.moveTabPriv(to, relative)