get pager working for read action

internal/ui/entry.go

@@ -1,22 +1,43 @@
 package ui
 
 import (
+	"fmt"
+	"strings"
+
 	gemlog "git.travisshears.com/travisshears/gemlog-cli/gemlog"
+	"github.com/charmbracelet/bubbles/viewport"
 	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/lipgloss"
 )
 
 type EntryPageModel struct {
-	entry gemlog.GemlogEntry
+	entry    gemlog.GemlogEntry
+	ready    bool
+	viewport viewport.Model
 }
 
 func initialEntryPageModel() EntryPageModel {
 	return EntryPageModel{}
 }
 
+func transformEntryToContent(entry gemlog.GemlogEntry) string {
+	content := entry.Slug
+	content += "\n\n"
+	content += entry.Gemtxt
+	content += "\n\n-------------------------\n"
+	content += "\n\nPress h or left arrow to go back"
+	return content
+}
+
 func (m EntryPageModel) Update(msg tea.Msg, active bool, ctx *context) (EntryPageModel, tea.Cmd) {
+	var (
+		cmd  tea.Cmd
+		cmds []tea.Cmd
+	)
 	switch msg := msg.(type) {
 	case GemLogLoaded:
 		m.entry = msg.Log
+		m.viewport.SetContent(transformEntryToContent(m.entry))
 	case tea.KeyMsg:
 		if !active {
 			return m, nil
@@ -28,17 +49,72 @@ func (m EntryPageModel) Update(msg tea.Msg, active bool, ctx *context) (EntryPag
 			}
 			return m, cmd
 		}
+	case tea.WindowSizeMsg:
+		headerHeight := lipgloss.Height(m.headerView())
+		footerHeight := lipgloss.Height(m.footerView())
+		verticalMarginHeight := headerHeight + footerHeight
+
+		if !m.ready {
+			// Since this program is using the full size of the viewport we
+			// need to wait until we've received the window dimensions before
+			// we can initialize the viewport. The initial dimensions come in
+			// quickly, though asynchronously, which is why we wait for them
+			// here.
+
+			m.viewport = viewport.New(msg.Width, msg.Height-verticalMarginHeight)
+			m.viewport.YPosition = headerHeight
+			m.viewport.SetContent(transformEntryToContent(m.entry))
+			m.ready = true
+		} else {
+			m.viewport.Width = msg.Width
+			m.viewport.Height = msg.Height - verticalMarginHeight
+		}
 	}
 
-	return m, nil
+	// Handle keyboard and mouse events in the viewport
+	m.viewport, cmd = m.viewport.Update(msg)
+	cmds = append(cmds, cmd)
+	return m, tea.Batch(cmds...)
 
 }
 
 func (m EntryPageModel) View() string {
-	s := m.entry.Slug
-	s += "\n\n"
-	s += m.entry.Gemtxt
-	s += "\n\n-------------------------\n"
-	s += "\n\nPress h or left arrow to go back"
-	return s
+	if !m.ready {
+		return "\n  Initializing..."
+	}
+
+	return fmt.Sprintf("%s\n%s\n%s", m.headerView(), m.viewport.View(), m.footerView())
+}
+
+var (
+	titleStyle = func() lipgloss.Style {
+		b := lipgloss.RoundedBorder()
+		b.Right = "├"
+		return lipgloss.NewStyle().BorderStyle(b).Padding(0, 1)
+	}()
+
+	infoStyle = func() lipgloss.Style {
+		b := lipgloss.RoundedBorder()
+		b.Left = "┤"
+		return titleStyle.BorderStyle(b)
+	}()
+)
+
+func (m EntryPageModel) headerView() string {
+	title := titleStyle.Render("Mr. Pager")
+	line := strings.Repeat("─", max(0, m.viewport.Width-lipgloss.Width(title)))
+	return lipgloss.JoinHorizontal(lipgloss.Center, title, line)
+}
+
+func (m EntryPageModel) footerView() string {
+	info := infoStyle.Render(fmt.Sprintf("%3.f%%", m.viewport.ScrollPercent()*100))
+	line := strings.Repeat("─", max(0, m.viewport.Width-lipgloss.Width(info)))
+	return lipgloss.JoinHorizontal(lipgloss.Center, line, info)
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
 }