feat(composer): add command preview and autocomplete

internal/command/command.go

@@ -0,0 +1,244 @@
+package command
+
+import (
+	"context"
+	"fmt"
+	"net/url"
+	"slices"
+	"strings"
+
+	"github.com/ayn2op/arikawa/v3/api"
+	"github.com/ayn2op/arikawa/v3/discord"
+	"github.com/sahilm/fuzzy"
+)
+
+type Item struct {
+	Name         string
+	Usage        string
+	Description  string
+	Source       string
+	Builtin      bool
+	Expand       func(args string) string
+	RequiredPerm discord.Permissions
+}
+
+type itemList []Item
+
+func (l itemList) String(i int) string {
+	return l[i].Name
+}
+
+func (l itemList) Len() int {
+	return len(l)
+}
+
+var Builtins = []Item{
+	{
+		Name:        "shrug",
+		Usage:       "[message]",
+		Description: "Appends ¯\\_(ツ)_/¯ to your message",
+		Source:      "Built-in",
+		Builtin:     true,
+		Expand: func(args string) string {
+			if args == "" {
+				return `¯\_(ツ)_/¯`
+			}
+			return args + ` ¯\_(ツ)_/¯`
+		},
+	},
+	{
+		Name:        "tableflip",
+		Usage:       "[message]",
+		Description: "Appends (╯°□°)╯︵ ┻━┻ to your message",
+		Source:      "Built-in",
+		Builtin:     true,
+		Expand: func(args string) string {
+			if args == "" {
+				return `(╯°□°)╯︵ ┻━┻`
+			}
+			return args + ` (╯°□°)╯︵ ┻━┻`
+		},
+	},
+	{
+		Name:        "unflip",
+		Usage:       "[message]",
+		Description: "Appends ┬─┬ノ( º _ ºノ) to your message",
+		Source:      "Built-in",
+		Builtin:     true,
+		Expand: func(args string) string {
+			if args == "" {
+				return `┬─┬ノ( º _ ºノ)`
+			}
+			return args + ` ┬─┬ノ( º _ ºノ)`
+		},
+	},
+	{
+		Name:        "me",
+		Usage:       "<message>",
+		Description: "Displays text with emphasis",
+		Source:      "Built-in",
+		Builtin:     true,
+		Expand: func(args string) string {
+			if args == "" {
+				return ""
+			}
+			return "*" + args + "*"
+		},
+	},
+	{
+		Name:        "spoiler",
+		Usage:       "<message>",
+		Description: "Marks your message as a spoiler",
+		Source:      "Built-in",
+		Builtin:     true,
+		Expand: func(args string) string {
+			if args == "" {
+				return ""
+			}
+			return "||" + args + "||"
+		},
+	},
+	{
+		Name:         "nick",
+		Usage:        "[new_nickname]",
+		Description:  "Changes your nickname on the current server",
+		Source:       "Built-in",
+		Builtin:      true,
+		RequiredPerm: discord.PermissionChangeNickname,
+	},
+}
+
+// ExpandBuiltin expands recognized built-in slash commands if matched.
+func ExpandBuiltin(text string) (string, bool) {
+	if !strings.HasPrefix(text, "/") {
+		return text, false
+	}
+	parts := strings.SplitN(text[1:], " ", 2)
+	name := parts[0]
+	var args string
+	if len(parts) > 1 {
+		args = parts[1]
+	}
+
+	for _, cmd := range Builtins {
+		if strings.EqualFold(cmd.Name, name) && cmd.Expand != nil {
+			return cmd.Expand(args), true
+		}
+	}
+	return text, false
+}
+
+// Search filters built-in and bot application commands based on query and permissions.
+func Search(query string, channelID discord.ChannelID, userPerms discord.Permissions, botCmds []Item, limit int) []Item {
+	if limit <= 0 {
+		limit = 20
+	}
+
+	var candidates []Item
+	isAdmin := userPerms.Has(discord.PermissionAdministrator)
+
+	for _, b := range Builtins {
+		if b.RequiredPerm != 0 && !isAdmin && !userPerms.Has(b.RequiredPerm) {
+			continue
+		}
+		candidates = append(candidates, b)
+	}
+
+	for _, b := range botCmds {
+		if b.RequiredPerm != 0 && !isAdmin && !userPerms.Has(b.RequiredPerm) {
+			continue
+		}
+		candidates = append(candidates, b)
+	}
+
+	if query == "" {
+		if len(candidates) > limit {
+			return candidates[:limit]
+		}
+		return candidates
+	}
+
+	lowerQuery := strings.ToLower(query)
+	var results []Item
+	for _, c := range candidates {
+		if strings.HasPrefix(strings.ToLower(c.Name), lowerQuery) {
+			results = append(results, c)
+			if len(results) >= limit {
+				return results
+			}
+		}
+	}
+
+	matches := fuzzy.FindFrom(query, itemList(candidates))
+	for _, m := range matches {
+		item := candidates[m.Index]
+		if !slices.ContainsFunc(results, func(it Item) bool { return it.Name == item.Name && it.Source == item.Source }) {
+			results = append(results, item)
+			if len(results) >= limit {
+				return results
+			}
+		}
+	}
+
+	return results
+}
+
+type searchResponse struct {
+	Applications []struct {
+		ID   discord.AppID `json:"id"`
+		Name string        `json:"name"`
+	} `json:"applications"`
+	ApplicationCommands []discord.Command `json:"application_commands"`
+}
+
+// FetchBotCommands queries Discord's channel application commands endpoint for slash commands.
+func FetchBotCommands(ctx context.Context, client *api.Client, channelID discord.ChannelID, query string) ([]Item, error) {
+	if client == nil || !channelID.IsValid() {
+		return nil, nil
+	}
+
+	endpoint := fmt.Sprintf("https://discord.com/api/v9/channels/%s/application-commands/search?query=%s&limit=25&include_applications=true",
+		channelID.String(), url.QueryEscape(query))
+
+	var resp searchResponse
+	if err := client.WithContext(ctx).RequestJSONInto(&resp, "GET", endpoint); err != nil {
+		return nil, err
+	}
+
+	appNames := make(map[discord.AppID]string, len(resp.Applications))
+	for _, app := range resp.Applications {
+		appNames[app.ID] = app.Name
+	}
+
+	items := make([]Item, 0, len(resp.ApplicationCommands))
+	for _, cmd := range resp.ApplicationCommands {
+		if cmd.Type != 0 && cmd.Type != discord.ChatInputCommand {
+			continue
+		}
+		source := appNames[cmd.AppID]
+		if source == "" {
+			source = "Bot"
+		}
+
+		var reqPerm discord.Permissions
+		if cmd.DefaultMemberPermissions != nil {
+			reqPerm = discord.Permissions(*cmd.DefaultMemberPermissions)
+		}
+
+		var usageParts []string
+		for _, opt := range cmd.Options {
+			usageParts = append(usageParts, "["+opt.Name()+"]")
+		}
+
+		items = append(items, Item{
+			Name:         cmd.Name,
+			Usage:        strings.Join(usageParts, " "),
+			Description:  cmd.Description,
+			Source:       source,
+			Builtin:      false,
+			RequiredPerm: reqPerm,
+		})
+	}
+
+	return items, nil
+}

internal/command/command_test.go

@@ -0,0 +1,83 @@
+package command
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/ayn2op/arikawa/v3/discord"
+)
+
+func TestBuiltinsSearch(t *testing.T) {
+	// Query "shrug"
+	results := Search("shrug", 0, discord.PermissionSendMessages, nil, 10)
+	if len(results) == 0 {
+		t.Fatal("expected results for 'shrug', got none")
+	}
+	if results[0].Name != "shrug" {
+		t.Errorf("expected top result 'shrug', got %q", results[0].Name)
+	}
+
+	// Query "flip"
+	flipResults := Search("flip", 0, discord.PermissionSendMessages, nil, 10)
+	if len(flipResults) < 2 {
+		t.Fatalf("expected at least 2 flip results, got %d", len(flipResults))
+	}
+}
+
+func TestPermissionFiltering(t *testing.T) {
+	perm := discord.Permissions(discord.PermissionManageMessages)
+	botCmds := []Item{
+		{
+			Name:         "purge",
+			Description:  "Delete messages",
+			Source:       "ModBot",
+			RequiredPerm: perm,
+		},
+	}
+
+	// Without manage messages permission
+	noPerm := Search("purge", 0, discord.PermissionSendMessages, botCmds, 10)
+	if len(noPerm) != 0 {
+		t.Errorf("expected purge to be filtered out without permission, got %v", noPerm)
+	}
+
+	// With manage messages permission
+	withPerm := Search("purge", 0, discord.PermissionSendMessages|discord.PermissionManageMessages, botCmds, 10)
+	if len(withPerm) != 1 {
+		t.Fatalf("expected purge to be visible with permission, got %v", withPerm)
+	}
+
+	// With administrator permission
+	admin := Search("purge", 0, discord.PermissionAdministrator, botCmds, 10)
+	if len(admin) != 1 {
+		t.Fatalf("expected purge to be visible with admin permission, got %v", admin)
+	}
+}
+
+func TestExpandBuiltin(t *testing.T) {
+	tests := []struct {
+		input    string
+		want     string
+		expanded bool
+	}{
+		{"/shrug", `¯\_(ツ)_/¯`, true},
+		{"/shrug hello", `hello ¯\_(ツ)_/¯`, true},
+		{"/tableflip", `(╯°□°)╯︵ ┻━┻`, true},
+		{"/tableflip angry", `angry (╯°□°)╯︵ ┻━┻`, true},
+		{"/unflip", `┬─┬ノ( º _ ºノ)`, true},
+		{"/me dancing", `*dancing*`, true},
+		{"/spoiler secret text", `||secret text||`, true},
+		{"normal message", `normal message`, false},
+		{"/unknown command", `/unknown command`, false},
+	}
+
+	for _, tt := range tests {
+		got, ok := ExpandBuiltin(tt.input)
+		if ok != tt.expanded {
+			t.Errorf("ExpandBuiltin(%q) ok = %v, want %v", tt.input, ok, tt.expanded)
+		}
+		if ok && strings.TrimSpace(got) != strings.TrimSpace(tt.want) {
+			t.Errorf("ExpandBuiltin(%q) = %q, want %q", tt.input, got, tt.want)
+		}
+	}
+}

internal/ui/chat/commandslist/item.go

@@ -0,0 +1,13 @@
+package commandslist
+
+import "github.com/ayn2op/tview"
+
+type Item struct {
+	Name        string
+	Usage       string
+	Description string
+	Source      string
+	InsertText  string
+	DisplayText string
+	Style       tview.Style
+}

internal/ui/chat/commandslist/model.go

@@ -0,0 +1,103 @@
+package commandslist
+
+import (
+	"github.com/ayn2op/discordo/internal/config"
+	"github.com/ayn2op/discordo/internal/ui"
+	"github.com/ayn2op/tview"
+	"github.com/ayn2op/tview/layout"
+	"github.com/ayn2op/tview/list"
+	"github.com/ayn2op/tview/scrollbar"
+	"github.com/ayn2op/tview/text"
+	"github.com/ayn2op/tview/viewport"
+	"github.com/rockorager/go-uucode"
+)
+
+// Model shows command suggestions as a list in a box.
+type Model struct {
+	cfg *config.Config
+
+	items       []Item
+	cursor      int
+	scrollState viewport.ScrollState
+}
+
+func NewModel(cfg *config.Config) Model {
+	return Model{cfg: cfg, cursor: -1}
+}
+
+// View shows the list in a box whose bottom corners join the composer's border below it.
+func (m Model) View() tview.Widget {
+	set := m.cfg.UI.Border.NormalSet.BorderSet
+	set.BottomLeft, set.BottomRight = set.BottomT, set.BottomT
+	cfg := m.cfg.UI.MentionsList
+	list, width := m.listView().Height(layout.Shrink.Max(int(cfg.MaxHeight))), layout.Fill
+	if cfg.MinWidth != 0 {
+		list, width = list.Width(layout.Fixed(max(int(cfg.MinWidth), m.maxDisplayWidth()))), layout.Shrink
+	}
+
+	return ui.Box(list, m.cfg, false).Title(ui.Label("Commands", m.cfg.Theme.Title, false)).BorderSet(set).Width(width).Height(layout.Shrink)
+}
+
+func (Model) Init() tview.Cmd { return nil }
+
+func (m Model) listView() viewport.Widget {
+	l := list.New(m.cursor, len(m.items), func(i int) tview.Widget {
+		item := m.items[i]
+		return text.New(item.DisplayText).Style(item.Style).Wrapping(text.WrappingNone)
+	}).
+		SelectedStyle(m.cfg.Theme.MentionsList.SelectedStyle.Style).
+		Keybind(ui.SelectionKeybind(m.cfg.Keybinds.MentionsList.SelectionKeybinds)).
+		Focused(true).
+		OnChange(func(cursor int) tview.Msg { return listMsg(cursor) })
+	return viewport.New(l, m.scrollState).
+		Target(l.Target(m.cursor)).
+		ScrollBar(scrollbar.New(), viewport.ScrollBarVisibilityAutomatic).
+		OnChange(func(s *viewport.ScrollState) tview.Msg { return scrollMsg(*s) })
+}
+
+func (m Model) Update(msg tview.Msg) (Model, tview.Cmd) {
+	switch msg := msg.(type) {
+	case listMsg:
+		m.cursor = int(msg)
+		m.scrollState.ScrollToTarget()
+	case scrollMsg:
+		m.scrollState = viewport.ScrollState(msg)
+	}
+	return m, nil
+}
+
+func (m *Model) Append(item Item) {
+	m.items = append(m.items, item)
+}
+
+func (m *Model) Clear() {
+	m.items = nil
+	m.cursor = -1
+}
+
+func (m Model) ItemCount() int {
+	return len(m.items)
+}
+
+func (m Model) SelectedInsertText() (string, bool) {
+	index := m.cursor
+	if index < 0 || index >= len(m.items) {
+		return "", false
+	}
+	return m.items[index].InsertText, true
+}
+
+func (m Model) maxDisplayWidth() int {
+	width := 0
+	for _, item := range m.items {
+		width = max(width, uucode.StringWidth(item.DisplayText))
+	}
+	return width
+}
+
+func (m *Model) Rebuild() {
+	m.cursor = min(0, len(m.items)-1)
+	m.scrollState.ScrollToTarget()
+}
+
+var _ tview.Model[Model] = Model{}

internal/ui/chat/commandslist/msg.go

@@ -0,0 +1,9 @@
+package commandslist
+
+import "github.com/ayn2op/tview/viewport"
+
+type Msg any
+
+type listMsg int
+
+type scrollMsg viewport.ScrollState

internal/ui/chat/composer/model.go

@@ -22,9 +22,11 @@ import (
 	"github.com/ayn2op/arikawa/v3/state"
 	"github.com/ayn2op/arikawa/v3/utils/json/option"
 	"github.com/ayn2op/arikawa/v3/utils/sendpart"
+	"github.com/ayn2op/discordo/internal/command"
 	"github.com/ayn2op/discordo/internal/config"
 	"github.com/ayn2op/discordo/internal/consts"
 	"github.com/ayn2op/discordo/internal/ui"
+	"github.com/ayn2op/discordo/internal/ui/chat/commandslist"
 	"github.com/ayn2op/discordo/internal/ui/chat/mentionslist"
 	"github.com/ayn2op/ningen/v3"
 	"github.com/ayn2op/tview"
@@ -71,6 +73,8 @@ type Model struct {
 	sendMessageData   *api.SendMessageData
 	memberSearchCache map[string]uint
 	mentionsList      mentionslist.Model
+	commandsList      commandslist.Model
+	botCommands       []command.Item
 	lastSearch        time.Time
 
 	typingUntil time.Time
@@ -87,13 +91,14 @@ func NewModel(cfg *config.Config, state *ningen.State) Model {
 		sendMessageData:   &api.SendMessageData{},
 		memberSearchCache: make(map[string]uint),
 		mentionsList:      mentionslist.NewModel(cfg),
+		commandsList:      commandslist.NewModel(cfg),
 	}
 	return c
 }
 
 // SetChannel sets the channel messages are sent to, disabling the composer if the user may not send messages there.
 func (m *Model) SetChannel(channel *discord.Channel) {
-	m.channel, m.typingUntil = channel, time.Time{}
+	m.channel, m.typingUntil, m.botCommands = channel, time.Time{}, nil
 	isDM := channel.Type == discord.DirectMessage || channel.Type == discord.GroupDM
 
 	// Sending in a thread takes another permission than in the channel it is in.
@@ -266,7 +271,7 @@ func (m Model) Update(msg tview.Msg) (Model, tview.Cmd) {
 			m.pasteText()
 			return m, pasteImage()
 		case keybind.Matches(msg, kbs.Send.Keybind):
-			if m.mentionsListVisible() {
+			if m.mentionsListVisible() || m.commandsListVisible() {
 				return m, m.tabComplete()
 			}
 			return m, m.send()
@@ -277,14 +282,14 @@ func (m Model) Update(msg tview.Msg) (Model, tview.Cmd) {
 			m.stopTabCompletion()
 			return m, m.pickFiles()
 		case keybind.Matches(msg, kbs.Cancel.Keybind):
-			if m.mentionsListVisible() {
+			if m.mentionsListVisible() || m.commandsListVisible() {
 				m.stopTabCompletion()
 				return m, nil
 			}
 			m.reset()
 			return m, nil
 		case keybind.Matches(msg, kbs.TabComplete.Keybind):
-			if m.mentionsListVisible() {
+			if m.mentionsListVisible() || m.commandsListVisible() {
 				return m, m.tabComplete()
 			}
 			m.insert("\t")
@@ -300,6 +305,17 @@ func (m Model) Update(msg tview.Msg) (Model, tview.Cmd) {
 		var cmd tview.Cmd
 		m.mentionsList, cmd = m.mentionsList.Update(msg)
 		return m, cmd
+	case commandslist.Msg:
+		var cmd tview.Cmd
+		m.commandsList, cmd = m.commandsList.Update(msg)
+		return m, cmd
+	case botCommandsMsg:
+		m.botCommands = msg.commands
+		if m.commandsListVisible() || (strings.HasPrefix(m.text, "/") && !strings.Contains(m.text, " ")) {
+			query := strings.TrimPrefix(m.text[:m.cursor], "/")
+			return m, m.suggestCommands(query)
+		}
+		return m, nil
 	}
 	return m, nil
 }
@@ -307,7 +323,7 @@ func (m Model) Update(msg tview.Msg) (Model, tview.Cmd) {
 func (m Model) canEditLastMessage() bool {
 	return !m.Disabled() && m.editing == nil && m.text == "" &&
 		m.sendMessageData.Reference == nil && len(m.sendMessageData.Files) == 0 &&
-		!m.mentionsListVisible()
+		!m.mentionsListVisible() && !m.commandsListVisible()
 }
 
 // StartEdit puts message in the composer to be edited.
@@ -500,12 +516,23 @@ func (m Model) OnGuildMemberRemove(event *gateway.GuildMemberRemoveEvent) {
 	}
 }
 
-// MentionsListView places the mentions list at the bottom of the area above the composer, near the cursor, or returns nil if it is empty or the composer is not focused.
+// AutocompleteView places the active completion list (mentions or commands) at the bottom of the area above the composer, near the cursor, or returns nil if none are active or the composer is not focused.
-func (m Model) MentionsListView(focused bool) tview.Widget {
+func (m Model) AutocompleteView(focused bool) tview.Widget {
-	if !focused || !m.mentionsListVisible() {
+	if !focused {
 		return nil
 	}
+	if m.commandsListVisible() {
+		return commandsPopup{m}
+	}
+	if m.mentionsListVisible() {
 		return mentionsPopup{m}
+	}
+	return nil
+}
+
+// MentionsListView is an alias for AutocompleteView.
+func (m Model) MentionsListView(focused bool) tview.Widget {
+	return m.AutocompleteView(focused)
 }
 
 // mentionsPopup places the mentions list within the area of the messages, which it is drawn over.
@@ -539,6 +566,31 @@ func (p mentionsPopup) area(area tview.Rectangle) tview.Rectangle {
 	return tview.Rectangle{X: area.X + x, Y: area.Y + area.Height - size.Height, Width: size.Width, Height: size.Height}
 }
 
+type commandsPopup struct {
+	c Model
+}
+
+func (commandsPopup) Size() (width, height layout.Length) { return layout.Fill, layout.Fill }
+
+func (commandsPopup) Layout(limits layout.Limits) layout.Size {
+	return layout.Atomic(limits, layout.Fill, layout.Fill)
+}
+
+func (p commandsPopup) Draw(screen tview.Screen, area tview.Rectangle) {
+	p.c.commandsList.View().Draw(screen, p.area(area))
+}
+
+func (p commandsPopup) Handle(msg tview.Msg, area tview.Rectangle) tview.Msg {
+	return p.c.commandsList.View().Handle(msg, p.area(area))
+}
+
+func (p commandsPopup) area(area tview.Rectangle) tview.Rectangle {
+	c := p.c
+	size := c.commandsList.View().Layout(layout.Limits{Max: layout.Size{Width: area.Width, Height: area.Height}})
+	x := c.box(false).InnerArea(tview.Rectangle{}).X
+	return tview.Rectangle{X: area.X + x, Y: area.Y + area.Height - size.Height, Width: size.Width, Height: size.Height}
+}
+
 func (m *Model) addMentionMember(gID discord.GuildID, member *discord.Member) bool {
 	if member == nil {
 		return false
@@ -593,10 +645,11 @@ func (m *Model) addMentionUser(user *discord.User) {
 	})
 }
 
-// stopTabCompletion clears the mentions list, which hides it, when it is in use.
+// stopTabCompletion clears the autocomplete lists, which hides them, when they are in use.
 func (m *Model) stopTabCompletion() {
 	if m.cfg.AutocompleteLimit > 0 {
 		m.mentionsList.Clear()
+		m.commandsList.Clear()
 	}
 }
 
@@ -605,6 +658,10 @@ func (m Model) mentionsListVisible() bool {
 	return m.mentionsList.ItemCount() != 0
 }
 
+func (m Model) commandsListVisible() bool {
+	return m.commandsList.ItemCount() != 0
+}
+
 func (m Model) attach(name string, reader io.Reader) {
 	m.sendMessageData.Files = append(m.sendMessageData.Files, sendpart.File{Name: name, Reader: reader})
 }

internal/ui/chat/composer/model_test.go

@@ -200,3 +200,44 @@ func TestModelProcessText(t *testing.T) {
 		})
 	}
 }
+
+func TestModelCommandSuggest(t *testing.T) {
+	c, _ := newTestModel(t)
+	channel := discord.Channel{ID: 1, Type: discord.DirectMessage}
+	c.SetChannel(&channel)
+	c.setText("/", 1)
+	c.tabSuggest()
+	if got := c.commandsList.ItemCount(); got == 0 {
+		t.Fatal("expected command suggestions for '/', got none")
+	}
+	if !c.commandsListVisible() {
+		t.Fatal("expected commandsListVisible to be true")
+	}
+	if c.mentionsListVisible() {
+		t.Fatal("expected mentionsListVisible to be false")
+	}
+
+	c.setText("/sh", 3)
+	c.tabSuggest()
+	if got := c.commandsList.ItemCount(); got == 0 {
+		t.Fatal("expected command suggestions for '/sh', got none")
+	}
+}
+
+func TestModelCommandComplete(t *testing.T) {
+	c, _ := newTestModel(t)
+	channel := discord.Channel{ID: 1, Type: discord.DirectMessage}
+	c.SetChannel(&channel)
+	c.setText("/sh", 3)
+	c.tabSuggest()
+	if !c.commandsListVisible() {
+		t.Fatal("expected commands list visible")
+	}
+	c.tabComplete()
+	if got := c.text; got != "/shrug " {
+		t.Fatalf("text after completion = %q, want '/shrug '", got)
+	}
+	if c.commandsListVisible() {
+		t.Fatal("expected commands list hidden after completion")
+	}
+}

internal/ui/chat/composer/msg.go

@@ -15,7 +15,10 @@ import (
 	"github.com/ayn2op/arikawa/v3/gateway"
 	"github.com/ayn2op/arikawa/v3/utils/json/option"
 	"github.com/ayn2op/arikawa/v3/utils/sendpart"
+	"github.com/ayn2op/discordo/internal/command"
+	"github.com/ayn2op/discordo/internal/ui/chat/commandslist"
 	"github.com/ayn2op/tview"
+	"github.com/gdamore/tcell/v3"
 	"github.com/ncruces/zenity"
 	"github.com/sahilm/fuzzy"
 	"golang.design/x/clipboard"
@@ -30,6 +33,10 @@ type EditLastMsg struct{}
 // SentMsg reports that the composer sent a message.
 type SentMsg struct{}
 
+type botCommandsMsg struct {
+	commands []command.Item
+}
+
 type editorMsg string
 
 // edit is a text of the composer and the cursor in it.
@@ -141,6 +148,25 @@ func (m *Model) send() tview.Cmd {
 		return nil
 	}
 
+	// Handle /nick command
+	if strings.HasPrefix(text, "/nick ") || text == "/nick" {
+		if selectedChannel.GuildID.IsValid() && m.state != nil && m.state.Client != nil {
+			newNick := strings.TrimSpace(strings.TrimPrefix(text, "/nick"))
+			gID := selectedChannel.GuildID
+			m.reset()
+			return func() tview.Msg {
+				if err := m.state.Client.ModifyCurrentMember(gID, newNick); err != nil {
+					slog.Error("failed to change nickname", "guild_id", gID, "err", err)
+				}
+				return SentMsg{}
+			}
+		}
+	}
+
+	if expanded, ok := command.ExpandBuiltin(text); ok {
+		text = expanded
+	}
+
 	text = m.processText(selectedChannel, []byte(text))
 	data := *m.sendMessageData
 	data.Files = slices.Clone(data.Files)
@@ -168,6 +194,31 @@ func (m *Model) send() tview.Cmd {
 }
 
 func (m *Model) tabComplete() tview.Cmd {
+	if m.commandsListVisible() {
+		return m.completeCommand()
+	}
+	if m.mentionsListVisible() {
+		return m.completeMention()
+	}
+	return nil
+}
+
+func (m *Model) completeCommand() tview.Cmd {
+	insertText, ok := m.commandsList.SelectedInsertText()
+	if !ok {
+		return nil
+	}
+	firstSpace := strings.Index(m.text, " ")
+	endPos := m.cursor
+	if firstSpace != -1 {
+		endPos = firstSpace
+	}
+	m.replace(0, endPos, insertText)
+	m.stopTabCompletion()
+	return nil
+}
+
+func (m *Model) completeMention() tview.Cmd {
 	posEnd, name, r := wordBeforeCursor(m.text, m.cursor, isMentionChar)
 	if r != '@' {
 		m.stopTabCompletion()
@@ -220,6 +271,16 @@ func (m *Model) tabComplete() tview.Cmd {
 }
 
 func (m *Model) tabSuggest() tview.Cmd {
+	if strings.HasPrefix(m.text, "/") {
+		firstSpace := strings.Index(m.text, " ")
+		if firstSpace == -1 || m.cursor <= firstSpace {
+			m.mentionsList.Clear()
+			query := m.text[1:m.cursor]
+			return m.suggestCommands(query)
+		}
+	}
+	m.commandsList.Clear()
+
 	_, name, r := wordBeforeCursor(m.text, m.cursor, isMentionChar)
 	if r != '@' {
 		m.stopTabCompletion()
@@ -273,6 +334,82 @@ func (m *Model) tabSuggest() tview.Cmd {
 	return nil
 }
 
+func (m *Model) suggestCommands(query string) tview.Cmd {
+	channel := m.channel
+	if channel == nil {
+		return nil
+	}
+	m.commandsList.Clear()
+
+	var userPerms discord.Permissions
+	if channel.GuildID.IsValid() && m.state != nil {
+		if me, err := m.state.Cabinet.Me(); err == nil {
+			if perms, err := m.state.Permissions(channel.ID, me.ID); err == nil {
+				userPerms = perms
+			}
+		}
+	} else {
+		userPerms = discord.PermissionAll
+	}
+
+	limit := int(m.cfg.AutocompleteLimit)
+	if limit <= 0 {
+		limit = 20
+	}
+
+	results := command.Search(query, channel.ID, userPerms, m.botCommands, limit)
+	for _, item := range results {
+		style := tcell.StyleDefault
+		display := "/" + item.Name
+		if item.Usage != "" {
+			display += " " + item.Usage
+		}
+		if item.Description != "" {
+			display += " - " + item.Description
+		}
+		if item.Source != "" {
+			display += " (" + item.Source + ")"
+		}
+
+		m.commandsList.Append(commandslist.Item{
+			Name:        item.Name,
+			Usage:       item.Usage,
+			Description: item.Description,
+			Source:      item.Source,
+			InsertText:  "/" + item.Name + " ",
+			DisplayText: display,
+			Style:       style,
+		})
+	}
+
+	var fetchCmd tview.Cmd
+	if channel.GuildID.IsValid() && len(m.botCommands) == 0 {
+		fetchCmd = m.fetchBotCommands(channel.ID, query)
+	}
+
+	if m.commandsList.ItemCount() == 0 {
+		m.stopTabCompletion()
+		return fetchCmd
+	}
+	m.commandsList.Rebuild()
+	return fetchCmd
+}
+
+func (m *Model) fetchBotCommands(channelID discord.ChannelID, query string) tview.Cmd {
+	if m.state == nil || m.state.Client == nil {
+		return nil
+	}
+	client := m.state.Client
+	return func() tview.Msg {
+		items, err := command.FetchBotCommands(context.Background(), client, channelID, query)
+		if err != nil {
+			slog.Debug("failed to fetch bot commands", "err", err)
+			return nil
+		}
+		return botCommandsMsg{commands: items}
+	}
+}
+
 // searchMember performs member discovery in a command goroutine.
 // It emits a follow-up suggestion message once results are loaded.
 func (m *Model) searchMember(gID discord.GuildID, name string) tview.Cmd {

internal/ui/chat/model.go

@@ -21,6 +21,7 @@ import (
 	"github.com/ayn2op/discordo/internal/ui"
 	"github.com/ayn2op/discordo/internal/ui/chat/attachmentspicker"
 	"github.com/ayn2op/discordo/internal/ui/chat/channelspicker"
+	"github.com/ayn2op/discordo/internal/ui/chat/commandslist"
 	"github.com/ayn2op/discordo/internal/ui/chat/composer"
 	"github.com/ayn2op/discordo/internal/ui/chat/guildstree"
 	"github.com/ayn2op/discordo/internal/ui/chat/memberstree"
@@ -304,7 +305,7 @@ func (m Model) Update(msg tview.Msg) (Model, tview.Cmd) {
 				ui.DialogButton{Label: "Yes", Cmd: tview.Sequence(closeState(m.state), logout())},
 			)
 		}
-	case composer.TabSuggestMsg, mentionslist.Msg:
+	case composer.TabSuggestMsg, mentionslist.Msg, commandslist.Msg:
 		return m, m.updatePane(paneComposer, msg)
 	case paneMsg:
 		if msg.focus {