Maint: rework publicip package

- Use loopstate package
- Loop interface composition
- Return concrete struct from constructors
- Split into more files
- Add publicip/state package

internal/publicip/ticker.go

@@ -0,0 +1,51 @@
+package publicip
+
+import (
+	"context"
+	"time"
+)
+
+type RestartTickerRunner interface {
+	RunRestartTicker(ctx context.Context, done chan<- struct{})
+}
+
+func (l *Loop) RunRestartTicker(ctx context.Context, done chan<- struct{}) {
+	defer close(done)
+	timer := time.NewTimer(time.Hour)
+	timer.Stop() // 1 hour, cannot be a race condition
+	timerIsStopped := true
+	if period := l.state.GetSettings().Period; period > 0 {
+		timerIsStopped = false
+		timer.Reset(period)
+	}
+	lastTick := time.Unix(0, 0)
+	for {
+		select {
+		case <-ctx.Done():
+			if !timerIsStopped && !timer.Stop() {
+				<-timer.C
+			}
+			return
+		case <-timer.C:
+			lastTick = l.timeNow()
+			l.start <- struct{}{}
+			timer.Reset(l.state.GetSettings().Period)
+		case <-l.updateTicker:
+			if !timerIsStopped && !timer.Stop() {
+				<-timer.C
+			}
+			timerIsStopped = true
+			period := l.state.GetSettings().Period
+			if period == 0 {
+				continue
+			}
+			var waited time.Duration
+			if lastTick.UnixNano() > 0 {
+				waited = l.timeNow().Sub(lastTick)
+			}
+			leftToWait := period - waited
+			timer.Reset(leftToWait)
+			timerIsStopped = false
+		}
+	}
+}