From bb2a503425cb92703a12cc85db33b420d138cdfc Mon Sep 17 00:00:00 2001
From: Kenneth Shaw <kenneth.shaw@knq.io>
Date: Tue, 21 Feb 2017 11:25:36 +0700
Subject: [PATCH] Standardizing NavigateBack and NavigateForward API

---
 nav.go      | 40 ++++++++++++++++++++++------------------
 nav_test.go | 14 +++-----------
 2 files changed, 25 insertions(+), 29 deletions(-)

diff --git a/nav.go b/nav.go
index 13f7c5a..6258547 100644
--- a/nav.go
+++ b/nav.go
@@ -41,31 +41,35 @@ func NavigateToHistoryEntry(entryID int64) Action {
 }
 
 // NavigateBack navigates the current frame backwards in its history.
-func NavigateBack(ctxt context.Context, h cdp.Handler) error {
-	cur, entries, err := page.GetNavigationHistory().Do(ctxt, h)
-	if err != nil {
-		return err
-	}
+func NavigateBack() Action {
+	return ActionFunc(func(ctxt context.Context, h cdp.Handler) error {
+		cur, entries, err := page.GetNavigationHistory().Do(ctxt, h)
+		if err != nil {
+			return err
+		}
 
-	if cur <= 0 || cur > int64(len(entries)-1) {
-		return errors.New("invalid navigation entry")
-	}
+		if cur == 0 {
+			return errors.New("already on oldest navigation entry")
+		}
 
-	return page.NavigateToHistoryEntry(entries[cur-1].ID).Do(ctxt, h)
+		return page.NavigateToHistoryEntry(entries[cur-1].ID).Do(ctxt, h)
+	})
 }
 
 // NavigateForward navigates the current frame forwards in its history.
-func NavigateForward(ctxt context.Context, h cdp.Handler) error {
-	cur, entries, err := page.GetNavigationHistory().Do(ctxt, h)
-	if err != nil {
-		return err
-	}
+func NavigateForward() Action {
+	return ActionFunc(func(ctxt context.Context, h cdp.Handler) error {
+		cur, entries, err := page.GetNavigationHistory().Do(ctxt, h)
+		if err != nil {
+			return err
+		}
 
-	if cur < 0 || cur >= int64(len(entries)-1) {
-		return errors.New("invalid navigation entry")
-	}
+		if cur == int64(len(entries)-1) {
+			return errors.New("already on newest navigation entry")
+		}
 
-	return page.NavigateToHistoryEntry(entries[cur+1].ID).Do(ctxt, h)
+		return page.NavigateToHistoryEntry(entries[cur+1].ID).Do(ctxt, h)
+	})
 }
 
 // Stop stops all navigation and pending resource retrieval.
diff --git a/nav_test.go b/nav_test.go
index a6c1ac2..a3958aa 100644
--- a/nav_test.go
+++ b/nav_test.go
@@ -1,12 +1,10 @@
 package chromedp
 
 import (
-	"context"
 	"strings"
 	"testing"
 	"time"
 
-	"github.com/knq/chromedp/cdp"
 	"github.com/knq/chromedp/cdp/page"
 )
 
@@ -193,9 +191,7 @@ func TestNavigateBack(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = c.Run(defaultContext, ActionFunc(func(c context.Context, h cdp.Handler) error {
-		return NavigateBack(c, h)
-	}))
+	err = c.Run(defaultContext, NavigateBack())
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -249,9 +245,7 @@ func TestNavigateForward(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = c.Run(defaultContext, ActionFunc(func(c context.Context, h cdp.Handler) error {
-		return NavigateBack(c, h)
-	}))
+	err = c.Run(defaultContext, NavigateBack())
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -261,9 +255,7 @@ func TestNavigateForward(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = c.Run(defaultContext, ActionFunc(func(c context.Context, h cdp.Handler) error {
-		return NavigateForward(c, h)
-	}))
+	err = c.Run(defaultContext, NavigateForward())
 	if err != nil {
 		t.Fatal(err)
 	}