Simplify pager component and fix pager example

examples/pager/main.go

@@ -10,20 +10,87 @@ import (
 )
 
 func main() {
+
+	// Load some text to render
 	content, err := ioutil.ReadFile("artichoke.md")
 	if err != nil {
 		fmt.Println("could not load file:", err)
 		os.Exit(1)
 	}
 
+	// Use the full size of the terminal in its "Alternate Screen Buffer"
 	boba.AltScreen()
 	defer boba.ExitAltScreen()
+
 	if err := boba.NewProgram(
-		pager.Init(string(content)),
-		pager.Update,
-		pager.View,
+		initialize(string(content)),
+		update,
+		view,
 	).Start(); err != nil {
 		fmt.Println("could not run program:", err)
 		os.Exit(1)
 	}
 }
+
+type terminalSizeMsg struct {
+	width  int
+	height int
+	err    error
+}
+
+func (t terminalSizeMsg) Size() (int, int) { return t.width, t.height }
+func (t terminalSizeMsg) Error() error     { return t.err }
+
+type model struct {
+	err     error
+	content string
+	ready   bool
+	pager   pager.Model
+}
+
+func initialize(content string) func() (boba.Model, boba.Cmd) {
+	return func() (boba.Model, boba.Cmd) {
+		return model{
+			content: content,
+		}, getTerminalSize()
+	}
+}
+
+func update(msg boba.Msg, mdl boba.Model) (boba.Model, boba.Cmd) {
+	m, _ := mdl.(model)
+
+	switch msg := msg.(type) {
+	case boba.KeyMsg:
+		if msg.Type == boba.KeyCtrlC {
+			return m, boba.Quit
+		}
+		m.pager, _ = pager.Update(msg, m.pager)
+	case terminalSizeMsg:
+		if msg.Error() != nil {
+			m.err = msg.Error()
+			break
+		}
+		w, h := msg.Size()
+		m.pager = pager.NewModel(w, h)
+		m.pager.SetContent(m.content)
+		m.ready = true
+	}
+
+	return m, nil
+}
+
+func view(mdl boba.Model) string {
+	m, _ := mdl.(model)
+	if m.err != nil {
+		return "\nError:" + m.err.Error()
+	} else if m.ready {
+		return "\n" + pager.View(m.pager)
+	}
+	return "\nInitalizing..."
+}
+
+func getTerminalSize() boba.Cmd {
+	return boba.GetTerminalSize(func(w, h int, err error) boba.TerminalSizeMsg {
+		return terminalSizeMsg{width: w, height: h, err: err}
+	})
+}