Schedule refreshes more consistently.

Instead of returning the `scheduleRefresh` command only after receiving
an `update` message, do it while handling the `refresh` message. For
this not to cause weird behavior, the refresh deadline should be shorter
than the refresh interval.

tui/asset/asset.go

@@ -112,18 +112,19 @@ func (m Model) Update(msg tea.Msg) (Model, tea.Cmd) {
 			return m, tea.Batch(
 				m.resumeIndicator,
 				m.refresh,
+				m.scheduleRefresh(),
 			)
 		case update:
-			commands := []tea.Cmd{m.scheduleRefresh()}
+			var cmd tea.Cmd
 			if msg.err == nil {
 				m.math = msg.math
 				refillProperties(&m)
 				refillProjections(&m)
-				commands = append(commands, m.stopIndicator())
+				cmd = m.stopIndicator()
 			} else {
 				m.indicator.Style = indicatorErrorStyle
 			}
-			return m, tea.Batch(commands...)
+			return m, cmd
 		case stopIndicator:
 			m.refreshing = false
 			return m, nil
@@ -149,7 +150,7 @@ type stopIndicator struct{}
 func (m Model) refresh() tea.Msg {
 	ctx, cancel := context.WithDeadline(
 		context.Background(),
-		time.Now().Add(time.Second*15))
+		time.Now().Add(refreshDeadline))
 	defer cancel()
 	err := m.math.Refresh(ctx)
 	if err != nil {
@@ -166,7 +167,7 @@ func (m Model) resumeIndicator() tea.Msg {
 }
 
 func (m Model) scheduleRefresh() tea.Cmd {
-	return tea.Tick(time.Second*30,
+	return tea.Tick(refreshInterval,
 		func(t time.Time) tea.Msg {
 			return Msg{m.math.Asset, refresh{}}
 		})
@@ -175,12 +176,16 @@ func (m Model) scheduleRefresh() tea.Cmd {
 func (m Model) stopIndicator() tea.Cmd {
 	// wait a bit to stop the indicator, so that it's more obvious
 	// even when the refresh completes quickly.
-	return tea.Tick(time.Millisecond*500,
+	return tea.Tick(stopIndicatorDelay,
 		func(t time.Time) tea.Msg {
 			return Msg{m.math.Asset, stopIndicator{}}
 		})
 }
 
+var refreshInterval = time.Second * 30
+var refreshDeadline = time.Second * 15
+var stopIndicatorDelay = time.Millisecond * 500
+
 func refillProperties(m *Model) {
 	rows := []table.Row{
 		{"Asset", string(m.math.Asset)},