Prototype a simple spinner

spinner/spinner.go

@@ -0,0 +1,65 @@
+package spinner
+
+import (
+	"errors"
+	"time"
+
+	"github.com/charmbracelet/tea"
+)
+
+// Spinner animation frames
+var (
+	simple = []string{"|", "/", "-", "\\"}
+)
+
+// Model contains the state for the spinner. Use NewModel to create new models
+// rather than using Model as a struct literal.
+type Model struct {
+	FPS   int
+	frame int
+}
+
+var assertionErr = errors.New("could not perform assertion on model to what the spinner expects. are you sure you passed the right value?")
+
+// NewModel returns a model with default values
+func NewModel() Model {
+	return Model{
+		FPS:   9,
+		frame: 0,
+	}
+}
+
+// TickMsg indicates that the timer has ticked and we should render a frame
+type TickMsg struct{}
+
+// Update is the Tea update function
+func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
+	switch msg.(type) {
+	case TickMsg:
+		m.frame++
+		if m.frame >= len(simple) {
+			m.frame = 0
+		}
+		return m, nil
+	default:
+		return m, nil
+	}
+}
+
+// View renders the model's view
+func View(model Model) string {
+	if model.frame >= len(simple) {
+		return "[error]"
+	}
+	return simple[model.frame]
+}
+
+// Sub is the subscription that allows the spinner to spin
+func Sub(model tea.Model) tea.Msg {
+	m, ok := model.(Model)
+	if !ok {
+		return assertionErr
+	}
+	time.Sleep(time.Second / time.Duration(m.FPS))
+	return TickMsg{}
+}