[#1] mclock: Refactor: split code between files

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

scheduling/clock.go

@@ -0,0 +1,81 @@
+package scheduling
+
+import (
+	"sync"
+	"time"
+)
+
+type clock interface {
+	now() float64
+	runAt(ts float64, f func())
+	close()
+}
+
+type scheduleInfo struct {
+	ts float64
+	f  func()
+}
+
+type systemClock struct {
+	since    time.Time
+	schedule chan scheduleInfo
+	wg       sync.WaitGroup
+}
+
+func newSystemClock() *systemClock {
+	c := &systemClock{
+		since:    time.Now(),
+		schedule: make(chan scheduleInfo),
+	}
+	c.start()
+	return c
+}
+
+func (c *systemClock) now() float64 {
+	return time.Since(c.since).Seconds()
+}
+
+func (c *systemClock) runAt(ts float64, f func()) {
+	c.schedule <- scheduleInfo{ts: ts, f: f}
+}
+
+func (c *systemClock) close() {
+	close(c.schedule)
+	c.wg.Wait()
+}
+
+func (c *systemClock) start() {
+	c.wg.Add(1)
+	go func() {
+		defer c.wg.Done()
+		t := time.NewTimer(time.Hour)
+		var f func()
+		for {
+			select {
+			case <-t.C:
+				if f != nil {
+					f()
+					f = nil
+				}
+			case s, ok := <-c.schedule:
+				if !ok {
+					return
+				}
+				now := c.now()
+				if now >= s.ts {
+					s.f()
+					f = nil
+					continue
+				}
+				if !t.Stop() {
+					select {
+					case <-t.C:
+					default:
+					}
+				}
+				t.Reset(time.Duration((s.ts - now) * 1e9))
+				f = s.f
+			}
+		}
+	}()
+}