refactor: move Sync() to client

cmd/htp/main.go

@@ -44,17 +44,17 @@ func buildRootCommand() *cobra.Command {
 			}
 
 			trace := &htp.SyncTrace{
-				Before: func(i int) bool { return i < count },
-				After: func(i int, round *htp.SyncRound) bool {
+				Before: func(model *htp.SyncModel) bool { return model.Count() < count },
+				After: func(model *htp.SyncModel, round *htp.SyncRound) bool {
 					logInfo(
-						silent, "(%d/%d) offset: %+.3f (±%.3f) seconds", i+1,
+						silent, "(%d/%d) offset: %+.3f (±%.3f) seconds", model.Count(),
 						count, model.Offset().Sec(), model.Margin().Sec())
 					return true
 				},
 			}
 
 			logInfo(silent, "Syncing with %s ...", host)
-			if err := htp.Sync(client, model, trace); err != nil {
+			if err := client.Sync(model, trace); err != nil {
 				return err
 			}
 

pkg/htp/client.go

@@ -16,6 +16,11 @@ type SyncClient struct {
 	tRecv   NanoSec
 }
 
+type SyncTrace struct {
+	Before func(model *SyncModel) bool
+	After  func(model *SyncModel, round *SyncRound) bool
+}
+
 func NewSyncClient(host string, timeout time.Duration) (*SyncClient, error) {
 	s := &SyncClient{}
 
@@ -67,3 +72,33 @@ func (s *SyncClient) Round() (*SyncRound, error) {
 		Receive: s.tRecv,
 	}, nil
 }
+
+func (s *SyncClient) Sync(model *SyncModel, trace *SyncTrace) error {
+	for {
+		if !trace.Before(model) {
+			break
+		}
+
+		// We wait until the next (estimated) best time to send a request which
+		// will reduce the error margin.
+		//
+		// I.e., we time our request based on the current model so that the
+		// server will reply in a "full" second (see README).
+		model.Sleep()
+
+		round, err := s.Round()
+		if err != nil {
+			return err
+		}
+
+		if err := model.Update(round); err != nil {
+			return err
+		}
+
+		if !trace.After(model, round) {
+			break
+		}
+	}
+
+	return nil
+}

pkg/htp/service_unix.go

@@ -4,7 +4,7 @@ package htp
 
 import "golang.org/x/sys/unix"
 
-func syncSystem(model *SyncModel) error {
+func SyncSystem(model *SyncModel) error {
 	tv := unix.NsecToTimeval(model.Now().UnixNano())
 	return unix.Settimeofday(&tv)
 }

pkg/htp/service_windows.go

@@ -7,7 +7,7 @@ import (
 	"os/exec"
 )
 
-func syncSystem(model *SyncModel) error {
+func SyncSystem(model *SyncModel) error {
 	arg := fmt.Sprintf("Set-Date -Adjust $([TimeSpan]::FromSeconds(%+.3f))", -model.Offset().Sec())
 	return exec.Command("powershell", "-Command", arg).Run()
 }