GemReader/internal/tui/tui.go

package tui

import (
	"fmt"
	"strings"

	"gemreader/internal/config"

	"github.com/charmbracelet/bubbles/viewport"
	markdown "github.com/MichaelMure/go-term-markdown"
	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"
)

type pane int

const (
	tocPane pane = iota
	contentPane
)

type model struct {
	content         string
	rawLines        []string
	toc             []tocEntry
	selectedTocIndex int
	
	tocViewport     viewport.Model
	contentViewport viewport.Model

	activePane   pane
	helpVisible  bool
	config       config.Config
	windowWidth  int
	windowHeight int
}

type tocEntry struct {
	level int
	text  string
	line  int
}

func NewModel(content string, cfg config.Config) model {
	rawLines := strings.Split(content, "\n")
	toc := generateTOC(rawLines)

	// Create viewports for the TOC and content
	tocVP := viewport.New(0, 0)
	contentVP := viewport.New(0, 0)

	m := model{
		content:         content,
		rawLines:        rawLines,
		toc:             toc,
		tocViewport:     tocVP,
		contentViewport: contentVP,
		activePane:      contentPane,
		helpVisible:     true,
		config:          cfg,
	}

	return m
}

func generateTOC(lines []string) []tocEntry {
	var toc []tocEntry
	for i, line := range lines {
		trimmed := strings.TrimSpace(line)
		if strings.HasPrefix(trimmed, "#") {
			level := 0
			for _, char := range trimmed {
				if char == '#' {
					level++
				} else {
					break
				}
			}
			headerText := strings.TrimSpace(trimmed[level:])
			if headerText != "" {
				toc = append(toc, tocEntry{
					level: level,
					text:  headerText,
					line:  i,
				})
			}
		}
	}
	return toc
}

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

func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	var (
		cmd  tea.Cmd
		cmds []tea.Cmd
	)

	switch msg := msg.(type) {
	case tea.WindowSizeMsg:
		m.windowWidth = msg.Width
		m.windowHeight = msg.Height

		// Calculate pane widths
		tocWidth := int(float64(m.windowWidth) * 0.3)
		contentWidth := m.windowWidth - tocWidth

		// Set viewport dimensions
		m.tocViewport.Width = tocWidth - 2 // Adjust for border
		m.tocViewport.Height = m.windowHeight - 2
		m.contentViewport.Width = contentWidth - 2
		m.contentViewport.Height = m.windowHeight - 2

		// Set content for viewports
		m.tocViewport.SetContent(m.renderTOC())
		renderedContent := string(markdown.Render(m.content, contentWidth-4, 6))
		m.contentViewport.SetContent(renderedContent)


	case tea.KeyMsg:
		switch msg.String() {
		case "q", "ctrl+c":
			return m, tea.Quit
		case "h", "?":
			m.helpVisible = !m.helpVisible
		case "tab":
			if m.activePane == tocPane {
				m.activePane = contentPane
			} else {
				m.activePane = tocPane
			}
		case "enter":
			if m.activePane == tocPane && len(m.toc) > 0 {
				// Jump to selected TOC entry
				tocEntry := m.toc[m.selectedTocIndex]
				
				// Find the line in the rendered content
				renderedLines := strings.Split(m.contentViewport.View(), "\n")
				for i, line := range renderedLines {
					if strings.Contains(strings.ToLower(line), strings.ToLower(tocEntry.text)) {
						m.contentViewport.SetYOffset(i)
						break
					}
				}
				m.activePane = contentPane // Switch to content view after jumping
			}
		case "up", "k":
			if m.activePane == tocPane {
				if m.selectedTocIndex > 0 {
					m.selectedTocIndex--
					m.tocViewport.SetContent(m.renderTOC())
				}
			} else {
				m.contentViewport.LineUp(1)
			}
		case "down", "j":
			if m.activePane == tocPane {
				if m.selectedTocIndex < len(m.toc)-1 {
					m.selectedTocIndex++
					m.tocViewport.SetContent(m.renderTOC())
				}
			} else {
				m.contentViewport.LineDown(1)
			}
		case "pgup", "ctrl+u":
			if m.activePane == contentPane {
				m.contentViewport.ViewUp()
			}
		case "pgdn", "ctrl+d":
			if m.activePane == contentPane {
				m.contentViewport.ViewDown()
			}
		case "g", "home":
			if m.activePane == contentPane {
				m.contentViewport.GotoTop()
			}
		case "G", "end":
			if m.activePane == contentPane {
				m.contentViewport.GotoBottom()
			}
		}
	}

	// Update viewports
	m.tocViewport, cmd = m.tocViewport.Update(msg)
	cmds = append(cmds, cmd)
	m.contentViewport, cmd = m.contentViewport.Update(msg)
	cmds = append(cmds, cmd)

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

func (m model) View() string {
	// Styles
	tocStyle := lipgloss.NewStyle().
		Border(lipgloss.RoundedBorder()).
		BorderForeground(lipgloss.Color("63")) // Default border color
	contentStyle := lipgloss.NewStyle().
		Border(lipgloss.RoundedBorder()).
		BorderForeground(lipgloss.Color("63")) // Default border color

	// Highlight active pane
	if m.activePane == tocPane {
		tocStyle = tocStyle.BorderForeground(lipgloss.Color("226")) // Yellow
	} else {
		contentStyle = contentStyle.BorderForeground(lipgloss.Color("226")) // Yellow
	}

	// Render panes
	tocView := tocStyle.Render(m.tocViewport.View())
	contentView := contentStyle.Render(m.contentViewport.View())

	// Join panes horizontally
	mainView := lipgloss.JoinHorizontal(lipgloss.Top, tocView, contentView)

	// Help text
	var helpText string
	if m.helpVisible {
		s := "Navigate: ↑/↓ j/k | PgUp/PgDn | g/G | Tab (switch panes) | h/? (help) | q (quit)"
		helpText = lipgloss.NewStyle().Foreground(lipgloss.Color("240")).Render(s)
	}

	return mainView + helpText
}

func (m model) renderTOC() string {
	if len(m.toc) == 0 {
		return "No table of contents found."
	}

	var content strings.Builder
	content.WriteString("Table of Contents:\n\n")
	for i, entry := range m.toc {
		indent := strings.Repeat("  ", entry.level-1)
		if i == m.selectedTocIndex {
			content.WriteString(fmt.Sprintf("%s> %s\n", indent, entry.text))
		} else {
			content.WriteString(fmt.Sprintf("%s  %s\n", indent, entry.text))
		}
	}
	return content.String()
}