From c012a7c90f772501f767746d924dd2420fc4ead0 Mon Sep 17 00:00:00 2001
From: Daniel Rocha <daniel@rocha.io>
Date: Tue, 31 Jan 2023 16:43:29 +0100
Subject: [PATCH] refactor: move `Sync()` to client

---
 cmd/htp/main.go            |  8 ++++----
 pkg/htp/client.go          | 35 +++++++++++++++++++++++++++++++++++
 pkg/htp/service.go         | 35 -----------------------------------
 pkg/htp/service_unix.go    |  2 +-
 pkg/htp/service_windows.go |  2 +-
 5 files changed, 41 insertions(+), 41 deletions(-)
 delete mode 100644 pkg/htp/service.go

diff --git a/cmd/htp/main.go b/cmd/htp/main.go
index 53f9a47..f671c3b 100644
--- a/cmd/htp/main.go
+++ b/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
 			}
 
diff --git a/pkg/htp/client.go b/pkg/htp/client.go
index cf50434..83d4bde 100644
--- a/pkg/htp/client.go
+++ b/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
+}
diff --git a/pkg/htp/service.go b/pkg/htp/service.go
deleted file mode 100644
index 14ca26d..0000000
--- a/pkg/htp/service.go
+++ /dev/null
@@ -1,35 +0,0 @@
-package htp
-
-type SyncTrace struct {
-	Before func(i int) bool
-	After  func(i int, round *SyncRound) bool
-}
-
-func Sync(client *SyncClient, model *SyncModel, trace *SyncTrace) error {
-	for i := 0; ; i++ {
-		if !trace.Before(i) {
-			break
-		}
-
-		model.Sleep()
-
-		round, err := client.Round()
-		if err != nil {
-			return err
-		}
-
-		if err := model.Update(round); err != nil {
-			return err
-		}
-
-		if !trace.After(i, round) {
-			break
-		}
-	}
-
-	return nil
-}
-
-func SyncSystem(model *SyncModel) error {
-	return syncSystem(model)
-}
diff --git a/pkg/htp/service_unix.go b/pkg/htp/service_unix.go
index 4000e20..872604f 100644
--- a/pkg/htp/service_unix.go
+++ b/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)
 }
diff --git a/pkg/htp/service_windows.go b/pkg/htp/service_windows.go
index fb557e8..b1ae66f 100644
--- a/pkg/htp/service_windows.go
+++ b/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()
 }