Gim/internal/command/handlers.go

package command

import (
	"bufio"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"slices"
	"strconv"
	"strings"

	"git.gophernest.net/azpect/TextEditor/internal/action"
	"git.gophernest.net/azpect/TextEditor/internal/core"
	tea "github.com/charmbracelet/bubbletea"
)

// QuitMsg: Message signaling the application should quit.
type QuitMsg struct{}

// ErrorMsg: Message signaling an error to display.
type ErrorMsg struct {
	Err error
}

// --------------------------------------------------
// Quit Commands
// --------------------------------------------------

// cmdQuit: Handles :quit / :q command.
func cmdQuit(m action.Model, args []string, force bool) tea.Cmd {
	// :q! forces quit, ignoring unsaved changes
	if force {
		return tea.Quit
	}

	bufs := m.Buffers()

	// Cannot exit if any buffer has unsaved changes
	for _, buf := range bufs {
		if buf.Modified {
			m.SetCommandOutput(&core.CommandOutput{
				Lines:   []string{fmt.Sprintf("unsaved changes to '%s'", buf.Filename)},
				Inline:  true,
				IsError: true,
			})
			m.ActiveWindow().SetBuffer(buf)
			return nil
		}
	}

	return tea.Quit
}

// cmdQuitAll: Handles :qall / :qa command.
func cmdQuitAll(m action.Model, args []string, force bool) tea.Cmd {
	// TODO: Until splits are implemented, this is the same as cmdQuit
	return cmdQuit(m, args, force)
}

// --------------------------------------------------
// File Commands (write & edit)
// --------------------------------------------------

// cmdWrite: Handles :write / :w command
func cmdWrite(m action.Model, args []string, force bool) tea.Cmd {
	buf := m.ActiveBuffer()
	cmd, err := writeBuffer(m, buf, args, force)
	if err != nil {
		m.SetCommandOutput(&core.CommandOutput{
			Lines:   []string{err.Error()},
			Inline:  true,
			IsError: true,
		})
	}
	return cmd
}

// cmdWriteAll: Handles :wall / :wa command
func cmdWriteAll(m action.Model, args []string, force bool) tea.Cmd {
	var cmds []tea.Cmd

	bufs := m.Buffers()
	for _, buf := range bufs {
		if buf.Modified {
			cmd, err := writeBuffer(m, buf, args, force)
			if err != nil {
				m.SetCommandOutput(&core.CommandOutput{
					Lines:   []string{err.Error()},
					Inline:  true,
					IsError: true,
				})
				return nil
			}
			cmds = append(cmds, cmd)
		}
	}

	return tea.Batch(cmds...)
}

// cmdWriteQuit: Handles :wq command
func cmdWriteQuit(m action.Model, args []string, force bool) tea.Cmd {
	buf := m.ActiveBuffer()
	cmd, err := writeBuffer(m, buf, args, force)
	if err != nil {
		m.SetCommandOutput(&core.CommandOutput{
			Lines:   []string{err.Error()},
			Inline:  true,
			IsError: true,
		})
		return cmd
	}

	return tea.Batch(cmd, tea.Quit)
}

// cmdWriteQuitAll: Handles :wqall / :wqa / :xa command.
// Writes all modified buffers then quits.
func cmdWriteQuitAll(m action.Model, args []string, force bool) tea.Cmd {
	var cmds []tea.Cmd

	bufs := m.Buffers()
	for _, buf := range bufs {
		if buf.Modified {
			cmd, err := writeBuffer(m, buf, args, force)
			if err != nil {
				m.SetCommandOutput(&core.CommandOutput{
					Lines:   []string{err.Error()},
					Inline:  true,
					IsError: true,
				})
				return nil
			}
			cmds = append(cmds, cmd)
		}
	}

	cmds = append(cmds, tea.Quit)
	return tea.Batch(cmds...)
}

// cmdEdit: Handles :edit / :e
func cmdEdit(m action.Model, args []string, force bool) tea.Cmd {
	// must have arguments, cant edit nothing
	if len(args) < 1 {
		m.SetCommandOutput(&core.CommandOutput{
			Lines:   []string{":edit requires an argument"},
			Inline:  true,
			IsError: true,
		})
		return nil
	}

	// Vim's Approach:
	// " When you do :edit filename.txt
	// 1. Check if file exists and is readable (if not, open new buffer)
	// 2. Detect file encoding (UTF-8, etc.)
	// 3. Read entire file into memory
	// 4. Split by line endings (respecting fileformat)
	// 5. Create new buffer with these lines
	// 6. Set buffer metadata:
	//    - buftype = "" (normal file)
	//    - modified = 0 (not modified)
	//    - fileformat = "unix" | "dos" | "mac"
	//    - fileencoding = "utf-8" (etc.)

	filename := args[0]
	ext := filepath.Ext(filename)

	// If the buffer already exists, just switch to it.
	bufs := m.Buffers()
	for _, buf := range bufs {
		if buf.Filename == filename {
			m.ActiveWindow().SetBuffer(buf)
			return nil
		}
	}

	file, err := os.Open(filename)
	notFound := errors.Is(err, os.ErrNotExist)

	if err != nil && !notFound {
		m.SetCommandOutput(&core.CommandOutput{
			Lines:   []string{err.Error()},
			Inline:  true,
			IsError: true,
		})
		return nil
	}
	if file != nil {
		defer file.Close()
	}

	// Create a buffer with the new file name, writing the file will
	// handle the saving logic
	if notFound {
		buf := core.NewBufferBuilder().
			WithType(core.FileBuffer).
			WithFilename(filename).
			WithFiletype(ext).
			Listed().
			Loaded().
			Build()

		m.SetBuffers(append(m.Buffers(), &buf))
		m.ActiveWindow().SetBuffer(&buf)

		// Need to adjust the cursor when we make a new file
		m.ActiveWindow().ClampCursor()
		return nil
	}

	var lines []string

	// BUG: We are unable to open and edit files owned by root. How do we handle that?

	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		line := scanner.Text()
		line = strings.TrimSuffix(line, "\r")

		// BUG: This is bad, we don't want to this, but we have to
		cleaned := strings.ReplaceAll(line, "\t", strings.Repeat(" ", m.Settings().TabStop))
		lines = append(lines, cleaned)
	}

	buf := core.NewBufferBuilder().
		WithType(core.FileBuffer).
		WithFilename(filename).
		WithFiletype(ext).
		WithLines(lines).
		Listed().
		Loaded().
		Build()

	m.SetBuffers(append(m.Buffers(), &buf))
	m.ActiveWindow().SetBuffer(&buf)

	return nil
}

// --------------------------------------------------
// Register Commands
// --------------------------------------------------

// cmdRegisters: Handles :register command
func cmdRegisters(m action.Model, args []string, force bool) tea.Cmd {
	if len(args) < 1 {
		regs := m.Registers()
		lines := []string{"Type Name Content"}

		for name, reg := range regs {
			if len(reg.Content) > 0 {
				line := fmt.Sprintf(
					"  %s  \"%c   %s",
					reg.Type.ToString(),
					name,
					strings.Join(reg.Content, "\\n"),
				)
				lines = append(lines, line)
			}
		}

		m.SetMode(core.CommandOutputMode)
		m.SetCommandOutput(&core.CommandOutput{
			Title:   ":reg",
			Lines:   lines,
			Inline:  false,
			IsError: false,
		})
		return nil
	}

	// BUG: We can actually handle many now
	// if len(args[0]) != 1 {
	// 	m.SetCommandOutput(&core.CommandOutput{
	// 		Lines:   []string{"Name should be a single character."},
	// 		Inline:  true,
	// 		IsError: true,
	// 	})
	// 	return nil
	// }

	names := []rune(args[0])
	lines := []string{"Type Name Content"}

	for _, name := range names {
		reg, ok := m.GetRegister(name)
		if ok && len(reg.Content) > 0 {
			line := fmt.Sprintf(
				"  %s  \"%c   %s",
				reg.Type.ToString(),
				name,
				strings.Join(reg.Content, "\\n"),
			)
			lines = append(lines, line)
		}
	}

	m.SetMode(core.CommandOutputMode)
	m.SetCommandOutput(&core.CommandOutput{
		Title:   ":reg",
		Lines:   lines,
		Inline:  false,
		IsError: false,
	})
	return nil
}

// --------------------------------------------------
// History Commands
// --------------------------------------------------
func cmdHistory(m action.Model, args []string, force bool) tea.Cmd {
	_, _ = args, force

	history := m.CommandHistory()
	reversed := slices.Clone(history)
	slices.Reverse(reversed)

	m.SetMode(core.CommandOutputMode)
	m.SetCommandOutput(&core.CommandOutput{
		Title:   ":history",
		Lines:   reversed,
		Inline:  false,
		IsError: false,
	})

	return nil
}

// --------------------------------------------------
// Buffer Commands
// --------------------------------------------------

// Switching
// - :b <n> — switch to buffer number n
// - :b <name> — switch by partial filename match
// - :bn — next buffer (wraps)
// - :bp — previous buffer (wraps, currently panics on wrap-back)
// - :bf — first buffer
// - :bl — last buffer

// Opening / closing
// - :e <file> — open file into new buffer
// - :bd — delete (unload) current buffer
// - :bd <n> — delete buffer n
// - :bw — wipe buffer completely // TODO: Implement this

// cmdListBuffers: Handles :buffers & :ls command. Lists the active buffers.
func cmdListBuffers(m action.Model, args []string, force bool) tea.Cmd {
	_, _ = args, force

	// What we should display
	// ------------------------------
	// - % — current buffer
	// - # — alternate buffer (last active)
	// - a — active (loaded and visible)
	// - h — hidden (loaded but not visible)
	// - + — modified (unsaved changes)
	// - - — not modifiable

	curBuf := m.ActiveBuffer()
	bufs := m.Buffers()
	var lines []string
	for _, buf := range bufs {
		// Skip unlisted buffers
		if !buf.Listed {
			continue
		}
		var flags strings.Builder
		if buf.Id == curBuf.Id {
			flags.WriteRune('%')
		} else {
			flags.WriteRune(' ')
		}
		// TODO: Implement alternate buffer

		// Cannot really display the a and h, since we don't have visible flags yet
		// For now, we will have a loaded flag, 'l'
		if buf.Loaded {
			flags.WriteRune('l')
		}
		flags.WriteRune(' ')
		if buf.Modified {
			flags.WriteRune('+')
		}
		if buf.ReadOnly {
			flags.WriteRune('-')
		}

		line := fmt.Sprintf("%3d %s \"%s\"", buf.Id, flags.String(), buf.Filename)
		lines = append(lines, line)
	}

	m.SetMode(core.CommandOutputMode)
	m.SetCommandOutput(&core.CommandOutput{
		Title:   ":buffers",
		Lines:   lines,
		Inline:  false,
		IsError: false,
	})

	return nil
}

// cmdNextBuffer: Handles :bn command. Moves to the next buffer based on ID.
func cmdNextBuffer(m action.Model, args []string, force bool) tea.Cmd {
	_, _ = args, force

	bufs := m.Buffers()
	curBuf := m.ActiveBuffer()

	ids := make([]int, len(bufs))
	var curIndex int
	for i, buf := range bufs {
		if buf.Listed {
			ids[i] = buf.Id
			if buf.Id == curBuf.Id {
				curIndex = i
			}
		}
	}

	nextId := (curIndex + 1) % len(ids)

	m.ActiveWindow().SetBuffer(bufs[nextId])

	return nil
}

// cmdPrevBuffer: Handles :bp command. Moves to the previous buffer based on ID.
func cmdPrevBuffer(m action.Model, args []string, force bool) tea.Cmd {
	_, _ = args, force

	bufs := m.Buffers()
	curBuf := m.ActiveBuffer()

	ids := make([]int, len(bufs))
	var curIndex int
	for i, buf := range bufs {
		if buf.Listed {
			ids[i] = buf.Id
			if buf.Id == curBuf.Id {
				curIndex = i
			}
		}
	}

	prevId := ((curIndex - 1) + len(ids)) % len(ids)

	m.ActiveWindow().SetBuffer(bufs[prevId])

	return nil
}

// cmdFirstBuffer: Handles :bf command. Moves to the first buffer based on ID.
func cmdFirstBuffer(m action.Model, args []string, force bool) tea.Cmd {
	_, _ = args, force

	bufs := m.Buffers()

	ids := make([]int, len(bufs))
	for i, buf := range bufs {
		if buf.Listed {
			ids[i] = buf.Id
		}
	}

	m.ActiveWindow().SetBuffer(bufs[0])

	return nil
}

// cmdLastBuffer: Handles :bf command. Moves to the last buffer based on ID.
func cmdLastBuffer(m action.Model, args []string, force bool) tea.Cmd {
	_, _ = args, force

	bufs := m.Buffers()

	ids := make([]int, len(bufs))
	for i, buf := range bufs {
		if buf.Listed {
			ids[i] = buf.Id
		}
	}

	m.ActiveWindow().SetBuffer(bufs[len(bufs)-1])

	return nil
}

// cmdSelectBuffer: Handles :b command. Moves to the selected buffer based on ID or filename.
func cmdSelectBuffer(m action.Model, args []string, force bool) tea.Cmd {
	_ = force

	// Cannot function without args
	if len(args) == 0 {
		return nil
	}

	if len(args) > 1 {
		m.SetCommandOutput(&core.CommandOutput{
			Lines:   []string{fmt.Sprintf("Trailing characters: %s", strings.Join(args[1:], " "))},
			Inline:  true,
			IsError: true,
		})
		return nil
	}

	bufs := m.Buffers()

	// If we can parse the input as number, try an ID
	tgtId, err := strconv.Atoi(args[0])
	if err == nil {
		for i, buf := range bufs {
			if buf.Id == tgtId && buf.Listed {
				m.ActiveWindow().SetBuffer(bufs[i])
				return nil
			}
		}

		m.SetCommandOutput(&core.CommandOutput{
			Lines:   []string{fmt.Sprintf("Buffer id %d does not exist", tgtId)},
			Inline:  true,
			IsError: true,
		})
		return nil
	}

	// Otherwise, try to match using filename
	query := args[0]
	var matches []int
	for i, buf := range bufs {
		if strings.Contains(buf.Filename, query) && buf.Listed {
			matches = append(matches, i)
		}
	}

	if len(matches) == 0 {
		m.SetCommandOutput(&core.CommandOutput{
			Lines:   []string{fmt.Sprintf("No matches for for %s", query)},
			Inline:  true,
			IsError: true,
		})
		return nil
	}

	if len(matches) > 1 {
		m.SetCommandOutput(&core.CommandOutput{
			Lines:   []string{fmt.Sprintf("More than one match for %s", query)},
			Inline:  true,
			IsError: true,
		})
		return nil
	}

	m.ActiveWindow().SetBuffer(bufs[matches[0]])

	return nil
}

// cmdDeleteBuffer: Handles :bd command. Deletes (unloads) a buffer.
func cmdDeleteBuffer(m action.Model, args []string, force bool) tea.Cmd {
	// This will be as dynamic as possible, just get a list of indexes, then unlist them all
	var indexes []int
	bufs := m.Buffers()

	// If the deleted buffer was the active one, Vim switches to the most recent entry in the jump
	// list that points into a loaded buffer. This is not simply "the previous buffer" — it's
	// jump-list-based, so it could be any recently visited loaded buffer.
	// THOUGH: I am not building vim, so it does not have to be the same

	// Need to close any windows associated with the closed buffers. Once many windows are implemented.

	// No args, unlist current buffer
	if len(args) == 0 {
		curBuf := m.ActiveBuffer()

		if curBuf.Modified && !force {
			m.SetCommandOutput(&core.CommandOutput{
				Lines:   []string{fmt.Sprintf("No write since last change to buffer %d (Add ! to continue)", curBuf.Id)},
				Inline:  true,
				IsError: true,
			})
			return nil
		}

		for i, buf := range bufs {
			if buf.Id == curBuf.Id {
				indexes = append(indexes, i)
			}
		}
	}

	if len(args) > 0 {

		// Arg can be ID or name
	ArgumentList:
		for _, arg := range args {
			// Try to get ID, if we can, move until we find it
			id, err := strconv.Atoi(arg)
			if err == nil {
				for index, buf := range bufs {
					if buf.Id == id && buf.Listed {
						if buf.Modified && !force {
							m.SetCommandOutput(&core.CommandOutput{
								Lines:   []string{fmt.Sprintf("No write since last change to buffer %d (Add ! to continue)", buf.Id)},
								Inline:  true,
								IsError: true,
							})
							return nil
						}
						indexes = append(indexes, index)
						continue ArgumentList
					}
				}
				continue ArgumentList
			}

			// Failed to parse, fuzzy match on names
			var matches []int
			for index, buf := range bufs {
				if strings.Contains(buf.Filename, arg) && buf.Listed {
					matches = append(matches, index)
				}
			}
			if len(matches) > 1 {
				m.SetCommandOutput(&core.CommandOutput{
					Lines:   []string{fmt.Sprintf("More than one match for %s", arg)},
					Inline:  true,
					IsError: true,
				})
				return nil
			}

			if len(matches) > 0 {

				if bufs[matches[0]].Modified && !force {
					m.SetCommandOutput(&core.CommandOutput{
						Lines: []string{fmt.Sprintf(
							"No write since last change to buffer %d (Add ! to continue)",
							bufs[matches[0]].Id),
						},
						Inline:  true,
						IsError: true,
					})
					return nil
				}
				indexes = append(indexes, matches[0])
				continue ArgumentList
			}

			m.SetCommandOutput(&core.CommandOutput{
				Lines:   []string{fmt.Sprintf("No matching buffer for %s", arg)},
				Inline:  true,
				IsError: true,
			})
			return nil
		}
	}

	// Simple error output
	if len(indexes) == 0 {
		m.SetCommandOutput(&core.CommandOutput{
			Lines:   []string{"No buffers were deleted"},
			Inline:  true,
			IsError: true,
		})
		return nil
	}

	// Now we can delete the buffers
	for _, i := range indexes {
		bufs[i].SetListed(false)
	}

	// Switch to first listed buffer
	// TODO: Switch to alternate buffer if available, once implemented
	if !m.ActiveBuffer().Listed {
		for _, buf := range bufs {
			if buf.Listed {
				m.ActiveWindow().SetBuffer(buf)
				break
			}
		}
	}

	return nil
}

// --------------------------------------------------
// Settings Commands
// --------------------------------------------------

// cmdSet: Handles :set option[=value] command for configuring editor settings.
// Examples:
//
//	:set number        - enable number
//	:set nonumber      - disable number
//	:set number!       - toggle number
//	:set tabstop=4     - set tabstop to 4
//	:set ts=4          - set tabstop to 4 (abbreviation)
func cmdSet(m action.Model, args []string, force bool) tea.Cmd {
	if len(args) == 0 {
		m.SetCommandOutput(&core.CommandOutput{
			Lines:  []string{fmt.Sprintf("%+v", m.Settings())},
			Inline: true,
		})
		return nil
	}

	for _, arg := range args {
		if err := parseSetOption(m, arg); err != nil {
			m.SetCommandOutput(&core.CommandOutput{
				Lines:   []string{err.Error()},
				Inline:  true,
				IsError: true,
			})
			return nil
		}
	}

	return nil
}

// Setting: Represents a configurable editor option.
type Setting struct {
	Name      string
	ShortForm string
	Type      SettingType
	Get       func(m action.Model) any
	Set       func(m action.Model, val any)
}

// SettingType: Enumeration of setting value types.
type SettingType int

const (
	BoolSetting SettingType = iota
	IntSetting
	StringSetting
)

// settingsMap defines all available settings (both global and window-local)
var settingsMap = []Setting{
	// Global editor settings
	{
		Name:      "tabstop",
		ShortForm: "ts",
		Type:      IntSetting,
		Get:       func(m action.Model) any { return m.Settings().TabStop },
		Set: func(m action.Model, val any) {
			s := m.Settings()
			s.TabStop = val.(int)
			m.SetSettings(s)
		},
	},
	// Window-local settings
	{
		Name:      "number",
		ShortForm: "nu",
		Type:      BoolSetting,
		Get:       func(m action.Model) any { return m.ActiveWindow().Options.Number },
		Set: func(m action.Model, val any) {
			w := m.ActiveWindow()
			o := w.Options
			o.Number = val.(bool)
			w.SetOptions(o)
		},
	},
	{
		Name:      "relativenumber",
		ShortForm: "rnu",
		Type:      BoolSetting,
		Get:       func(m action.Model) any { return m.ActiveWindow().Options.RelativeNumber },
		Set: func(m action.Model, val any) {
			w := m.ActiveWindow()
			o := w.Options
			o.RelativeNumber = val.(bool)
			w.SetOptions(o)
		},
	},
	{
		Name:      "scrolloff",
		ShortForm: "so",
		Type:      IntSetting,
		Get:       func(m action.Model) any { return m.ActiveWindow().Options.ScrollOff },
		Set: func(m action.Model, val any) {
			w := m.ActiveWindow()
			o := w.Options
			o.ScrollOff = val.(int)
			w.SetOptions(o)
		},
	},
	{
		Name:      "guttersize",
		ShortForm: "gu",
		Type:      IntSetting,
		Get:       func(m action.Model) any { return m.ActiveWindow().Options.GutterSize },
		Set: func(m action.Model, val any) {
			w := m.ActiveWindow()
			o := w.Options
			o.GutterSize = val.(int)
			w.SetOptions(o)
		},
	},
}

// lookupSetting: Finds a setting by name, short form, or prefix.
func lookupSetting(name string) *Setting {
	for i := range settingsMap {
		s := &settingsMap[i]
		if name == s.Name || name == s.ShortForm {
			return s
		}
		// Prefix matching
		if len(name) >= len(s.ShortForm) && strings.HasPrefix(s.Name, name) {
			return s
		}
	}
	return nil
}

// parseSetOption: Parses and applies a single :set option.
func parseSetOption(m action.Model, opt string) error {
	// Handle toggle: option!
	if name, ok := strings.CutSuffix(opt, "!"); ok {
		setting := lookupSetting(name)
		if setting != nil && setting.Type == BoolSetting {
			currentVal := setting.Get(m).(bool)
			setting.Set(m, !currentVal)
		}
		return nil
	}

	// Handle disable: nooption
	if name, ok := strings.CutPrefix(opt, "no"); ok {
		setting := lookupSetting(name)
		if setting != nil && setting.Type == BoolSetting {
			setting.Set(m, false)
		}
		return nil
	}

	// Handle assignment: option=value
	if strings.Contains(opt, "=") {
		parts := strings.SplitN(opt, "=", 2)
		name, value := parts[0], parts[1]

		setting := lookupSetting(name)
		if setting != nil {
			switch setting.Type {
			case IntSetting:
				intVal, err := strconv.Atoi(value)
				if err != nil {
					return err
				}
				setting.Set(m, intVal)
			case StringSetting:
				setting.Set(m, value)
			case BoolSetting:
				// Handle :set option=true / :set option=false
				boolVal := value == "true" || value == "1" || value == "yes"
				setting.Set(m, boolVal)
			}
		}
		return nil
	}

	// Handle enable: option (boolean only)
	setting := lookupSetting(opt)
	if setting != nil && setting.Type == BoolSetting {
		setting.Set(m, true)
	}

	return nil
}

// --------------------------------------------------
// Colorscheme Commands
// --------------------------------------------------

// TODO: Implement this using the new colorschemes
func cmdColorscheme(m action.Model, args []string, force bool) tea.Cmd {
	_ = force

	// No args, just print the current scheme
	if len(args) == 0 {
		name, _ := m.Theme()
		m.SetCommandOutput(&core.CommandOutput{
			Lines:   []string{name},
			Inline:  true,
			IsError: false,
		})
		return nil
	}

	// Theme switching is disabled while migrating away from Chroma.
	name := strings.TrimSpace(strings.Join(args, " "))
	_, found := m.Themes()[name]

	if name == "" || !found {
		m.SetCommandOutput(&core.CommandOutput{
			Lines:   []string{fmt.Sprintf("colorscheme not found: %s", name)},
			Inline:  true,
			IsError: true,
		})
		return nil
	}

	m.SetTheme(name)
	return nil
}

func cmdListColorschemes(m action.Model, args []string, force bool) tea.Cmd {
	_, _ = args, force

	var colors []string
	for k := range m.Themes() {
		colors = append(colors, k)
	}

	slices.Sort(colors)

	m.SetMode(core.CommandOutputMode)
	m.SetCommandOutput(&core.CommandOutput{
		Title:   ":colorschemes",
		Lines:   colors,
		Inline:  false,
		IsError: false,
	})

	return nil
}

func cmdUndoList(m action.Model, args []string, force bool) tea.Cmd {
	_, _ = args, force

	lines := m.ActiveBuffer().UndoStack.List()

	// For now, display an error when empty
	if len(lines) == 0 {
		m.SetCommandOutput(&core.CommandOutput{
			Lines:   []string{"Undo stack is empty"},
			Inline:  true,
			IsError: true,
		})
		return nil
	}

	m.SetMode(core.CommandOutputMode)
	m.SetCommandOutput(&core.CommandOutput{
		Title:   ":undo",
		Lines:   lines,
		Inline:  false,
		IsError: false,
	})

	return nil
}