feat: simple timer component (#67)

* feat: simple timer component

Signed-off-by: Carlos Alexandro Becker <caarlos0@gmail.com>

timer/timer.go

@@ -0,0 +1,68 @@
+// Package timer provides a simple timeout component.
+package timer
+
+import (
+	"time"
+
+	tea "github.com/charmbracelet/bubbletea"
+)
+
+// TickMsg is a message that is sent on every timer tick.
+type TickMsg struct{}
+
+// TimeoutMsg is a message that is sent once when the timer times out.
+type TimeoutMsg struct{}
+
+// Model of the timer component.
+type Model struct {
+	// How long until the timer expires.
+	Timeout time.Duration
+
+	// How long to wait before every tick. Defaults to 1 second.
+	Interval time.Duration
+}
+
+// NewWithInterval creates a new timer with the given timeout and tick interval.
+func NewWithInterval(timeout, interval time.Duration) Model {
+	return Model{
+		Timeout:  timeout,
+		Interval: interval,
+	}
+}
+
+// New creates a new timer with the given timeout and default 1s interval.
+func New(timeout time.Duration) Model {
+	return NewWithInterval(timeout, time.Second)
+}
+
+// Init starts the timer.
+func (m Model) Init() tea.Cmd {
+	return tick(m.Interval)
+}
+
+// Update handles the timer tick.
+func (m Model) Update(msg tea.Msg) (Model, tea.Cmd) {
+	switch msg.(type) {
+	case TickMsg:
+		m.Timeout -= m.Interval
+		if m.Timeout <= 0 {
+			return m, func() tea.Msg {
+				return TimeoutMsg{}
+			}
+		}
+		return m, tick(m.Interval)
+	}
+
+	return m, nil
+}
+
+// View of the timer component.
+func (m Model) View() string {
+	return m.Timeout.String()
+}
+
+func tick(d time.Duration) tea.Cmd {
+	return tea.Tick(d, func(_ time.Time) tea.Msg {
+		return TickMsg{}
+	})
+}