tui-shell/main.go

// main.go
package main

import (
	"fmt"
	"log"
	"os"
	"path"
	"strings"

	"github.com/charmbracelet/bubbles/textarea"
	"github.com/charmbracelet/bubbles/viewport"
	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"
)

type TreeNode struct {
	Label    string
	Children []*TreeNode
	Expanded bool
}

type Command struct {
	Input  string
	Result string
}

type model struct {
	width  int
	height int

	leftWidth int

	treeRoot   *TreeNode
	treeCursor int
	textarea   textarea.Model

	commands []Command
	viewport viewport.Model

	focusPane string // "prompt", "fileview", "commands"
}

var (
	borderStyle = lipgloss.NormalBorder()

	paneBoxStyle = lipgloss.NewStyle().
			Padding(0, 1).
			Border(borderStyle).
			BorderForeground(lipgloss.Color("0"))

	paneBoxFocusedStyle = lipgloss.NewStyle().
				Padding(0, 1).
				Border(borderStyle).
				BorderForeground(lipgloss.Color("6"))

	commandBoxInputStyle = lipgloss.NewStyle().
				Bold(true)

	commandBoxResultStyle = lipgloss.NewStyle().
				Background(lipgloss.Color("15")).
				MaxHeight(8)
)

func main() {
	p := tea.NewProgram(initialModel(), tea.WithAltScreen(), tea.WithMouseCellMotion())

	_, err := p.Run()
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error running program: %v\n", err)
		os.Exit(1)
	}
}

// returns both the string representation and corresponding nodes
func flattenTreeWithNodes(n *TreeNode, depth int) ([]string, []*TreeNode) {
	var lines []string
	var nodes []*TreeNode
	prefix := strings.Repeat("  ", depth)
	icon := "▸"
	if n.Expanded && len(n.Children) > 0 {
		icon = "▾"
	} else if len(n.Children) == 0 {
		icon = " "
	}
	lines = append(lines, fmt.Sprintf("%s%s %s", prefix, icon, n.Label))
	nodes = append(nodes, n)
	if n.Expanded {
		for _, c := range n.Children {
			childLines, childNodes := flattenTreeWithNodes(c, depth+1)
			lines = append(lines, childLines...)
			nodes = append(nodes, childNodes...)
		}
	}
	return lines, nodes
}

func flattenTree(n *TreeNode, depth int) []string {
	lines, _ := flattenTreeWithNodes(n, depth)
	return lines
}

// toggleNodeExpansion toggles the expanded state of a node if it has children
func (m *model) toggleNodeExpansion(node *TreeNode) {
	if len(node.Children) > 0 {
		node.Expanded = !node.Expanded
	}
}

func (m *model) renderCommandsContent() string {
	if len(m.commands) == 0 {
		return "(no commands yet)"
	}

	commandBoxes := []string{}

	for _, c := range m.commands {
		// input header + result with limited height per card (visual truncation)
		commandBoxes = append(commandBoxes,
			paneBoxStyle.Render(
				lipgloss.JoinVertical(
					lipgloss.Left,
					commandBoxInputStyle.Render(
						fmt.Sprintf("$ %s",
							strings.ReplaceAll(strings.TrimSpace(c.Input), "\n", " ↵ "),
						),
					),
					commandBoxResultStyle.
						Render(limitedResult(c.Result, 8)),
				),
			),
		)
	}

	return lipgloss.JoinVertical(lipgloss.Left, commandBoxes...)
}

func limitedResult(result string, maxLines int) string {
	lines := strings.Split(result, "\n")
	if len(lines) <= maxLines {
		return strings.Join(lines, "\n")
	}
	trunc := strings.Join(lines[:maxLines], "\n")
	trunc += "\n" + lipgloss.NewStyle().Italic(true).Render("…")
	return trunc
}

func (m model) rightWidth() int {
	return m.width - m.leftWidth - 1
}

func (m model) rightContentWidth() int {
	return m.rightWidth() - 4
}

func (m model) promptContentHeight() int {
	return 1 + len(m.textarea.Value())/(m.rightContentWidth()-5)
}

func (m *model) resize(w, h int) {
	m.width = w
	m.height = h
	m.leftWidth = w / 5

	m.viewport.Width = m.rightContentWidth()
	m.viewport.Height = h - m.promptContentHeight() - 5

	m.textarea.SetWidth(m.rightContentWidth() - 2)
	m.textarea.SetHeight(m.promptContentHeight())

	m.viewport.SetContent(m.renderCommandsContent())
}

func (m model) Init() tea.Cmd {
	return nil
}

func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	cmds := []tea.Cmd{}

	if m.focusPane == "" {
		m.focusPane = "prompt"
		cmds = append(cmds, m.textarea.Focus())
	}

	switch msg := msg.(type) {
	case tea.KeyMsg:
		switch msg.String() {
		case "ctrl+c", "q":
			return m, tea.Quit
		case "tab":
			// cycle focus: prompt -> fileview -> commands -> prompt
			switch m.focusPane {
			case "prompt":
				m.focusPane = "fileview"
				m.textarea.Blur()
			case "fileview":
				m.focusPane = "commands"
				m.textarea.Blur()
			default:
				m.focusPane = "prompt"
				return m, m.textarea.Focus()
			}
			return m, nil
		}

		// route keys based on which pane has focus
		if m.focusPane == "prompt" {
			// prompt (textarea) behaviour
			// submit on Enter (textarea normally inserts newlines; here Enter submits)
			if msg.Type == tea.KeyEnter {
				input := strings.TrimSpace(m.textarea.Value())
				if input != "" {
					mock := mockResultFor(input)
					m.commands = append(m.commands, Command{
						Input:  input,
						Result: mock,
					})
					m.viewport.SetContent(m.renderCommandsContent())
					m.viewport.GotoBottom()
					m.textarea.SetValue("")
				}
				if m.width > 0 {
					m.resize(m.width, m.height)
				}
				return m, nil
			}

			m.textarea.SetHeight(m.promptContentHeight())

			// forward other key messages to textarea
			var taCmd tea.Cmd
			m.textarea, taCmd = m.textarea.Update(msg)

			if m.width > 0 {
				m.resize(m.width, m.height)
			}

			cmds = append(cmds, taCmd)

			return m, tea.Batch(cmds...)
		}

		if m.focusPane == "fileview" {
			// fileview tree behaviour (navigation, expand/collapse)
			_, nodes := flattenTreeWithNodes(m.treeRoot, 0)
			switch msg.String() {
			case "up", "k":
				if m.treeCursor > 0 {
					m.treeCursor--
				}
			case "down", "j":
				if m.treeCursor < len(nodes)-1 {
					m.treeCursor++
				}
			case "left", "h":
				if m.treeCursor < len(nodes) {
					node := nodes[m.treeCursor]
					if node.Expanded && len(node.Children) > 0 {
						node.Expanded = false
					}
				}
			case "right", "l":
				if m.treeCursor < len(nodes) {
					node := nodes[m.treeCursor]
					if !node.Expanded && len(node.Children) > 0 {
						node.Expanded = true
					}
				}
			case "enter", " ":
				// toggle
				if m.treeCursor < len(nodes) {
					m.toggleNodeExpansion(nodes[m.treeCursor])
				}
			}

			return m, nil
		}

		if m.focusPane == "commands" {
			// commands viewport behaviour (scrolling)
			switch msg.String() {
			case "up", "k":
				m.viewport.ScrollUp(1)
			case "down", "j":
				m.viewport.ScrollDown(1)
			case "pgup":
				m.viewport.ScrollUp(7)
			case "pgdown":
				m.viewport.ScrollDown(7)
			case "home":
				m.viewport.GotoTop()
			case "end":
				m.viewport.GotoBottom()
			}
			return m, nil
		}

	case tea.WindowSizeMsg:
		m.resize(msg.Width, msg.Height)
		return m, nil
	}

	var cmd tea.Cmd
	m.viewport, cmd = m.viewport.Update(msg)

	cmds = append(cmds, cmd)

	return m, tea.Batch(cmds...)
}

func (m model) View() string {
	var fileviewRows []string

	// TODO: not good practice to throw in View, should add a field to model instead
	homeDir, err := os.UserHomeDir()
	if err != nil {
		log.Fatal(err)
	}
	wd, err := os.Getwd()
	if err != nil {
		log.Fatal(err)
	}

	wd = path.Dir(wd)

	if strings.HasPrefix(wd, homeDir) {
		wd = strings.Replace(wd, homeDir, "~", 1)
	}

	parts := strings.Split(wd, string(os.PathSeparator))

	// show full path as series of folders at top of fileview
	for _, part := range parts {
		fileviewRows = append(fileviewRows,
			lipgloss.NewStyle().
				Bold(true).
				Render("▼ "+part+"/"),
		)
	}

	treeLines := flattenTree(m.treeRoot, 0)

	// highlight the current selection when fileview is focused
	if m.focusPane == "fileview" && m.treeCursor < len(treeLines) {
		selectedStyle := lipgloss.NewStyle().
			Background(lipgloss.Color("6")).
			Foreground(lipgloss.Color("0"))
		treeLines[m.treeCursor] = selectedStyle.Render(treeLines[m.treeCursor])
	}

	// show the tree view content
	fileviewRows = append(fileviewRows, treeLines...)

	// build the main layout
	paneStyleDynamic := func(paneName string) lipgloss.Style {
		if m.focusPane == paneName {
			return paneBoxFocusedStyle
		}

		return paneBoxStyle
	}

	fileviewBox := paneStyleDynamic("fileview").
		Width(m.leftWidth).
		Height(m.height - 2).
		Render(
			strings.Join(fileviewRows, "\n"),
		)

	commandsBox := paneStyleDynamic("commands").
		Width(m.rightContentWidth()).
		Render(m.viewport.View())

	promptBox := paneStyleDynamic("prompt").
		Width(m.rightContentWidth()).
		Height(m.promptContentHeight()).
		Render(m.textarea.View())

	statusBarHelp := lipgloss.NewStyle().
		Faint(true).
		Render(
			strings.Join([]string{
				"tab: toggle focus",
				"enter: submit",
				"up/down/left/right: tree nav",
				"pgup/pgdn: scroll",
				"q/ctrl+c: quit",
			}, " • "),
		)

	return lipgloss.JoinHorizontal(
		lipgloss.Top,
		fileviewBox,
		lipgloss.NewStyle().
			PaddingLeft(1).
			Render(
				lipgloss.JoinVertical(
					lipgloss.Left,
					commandsBox,
					promptBox,
					statusBarHelp,
				),
			),
	)
}