From db5b7303c254af467a6458d9025f825ab50b452e Mon Sep 17 00:00:00 2001
From: n-peugnet <n.peugnet@free.fr>
Date: Wed, 22 Sep 2021 21:06:18 +0200
Subject: export unprefix in utils and fix error msg

---
 repo.go              | 10 ++++------
 utils/string.go      | 14 ++++++++++++++
 utils/string_test.go | 24 ++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 6 deletions(-)
 create mode 100644 utils/string.go
 create mode 100644 utils/string_test.go

diff --git a/repo.go b/repo.go
index f36bb65..dc61d01 100644
--- a/repo.go
+++ b/repo.go
@@ -38,7 +38,6 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
-	"strings"
 	"sync"
 
 	"github.com/chmduquesne/rollinghash/rabinkarp64"
@@ -215,15 +214,14 @@ func listFiles(path string) []File {
 }
 
 func unprefixFiles(files []File, prefix string) (ret []File) {
+	var err error
 	ret = make([]File, len(files))
-	preSize := len(prefix)
 	for i, f := range files {
-		if !strings.HasPrefix(f.Path, prefix) {
-			logger.Warning(f.Path, "is not prefixed by", prefix)
+		if f.Path, err = utils.Unprefix(f.Path, prefix); err != nil {
+			logger.Warning(err)
 		} else {
-			f.Path = f.Path[preSize:]
+			ret[i] = f
 		}
-		ret[i] = f
 	}
 	return
 }
diff --git a/utils/string.go b/utils/string.go
new file mode 100644
index 0000000..b3cbb17
--- /dev/null
+++ b/utils/string.go
@@ -0,0 +1,14 @@
+package utils
+
+import (
+	"fmt"
+	"strings"
+)
+
+func Unprefix(path string, prefix string) (string, error) {
+	if !strings.HasPrefix(path, prefix) {
+		return path, fmt.Errorf("%q is not prefixed by %q", path, prefix)
+	} else {
+		return path[len(prefix):], nil
+	}
+}
diff --git a/utils/string_test.go b/utils/string_test.go
new file mode 100644
index 0000000..5d42c24
--- /dev/null
+++ b/utils/string_test.go
@@ -0,0 +1,24 @@
+package utils_test
+
+import (
+	"testing"
+
+	"github.com/n-peugnet/dna-backup/utils"
+)
+
+func TestUnprefix(t *testing.T) {
+	str, err := utils.Unprefix("foo/bar", "foo/")
+	if str != "bar" {
+		t.Errorf("expected: %q, actual: %q", "bar", str)
+	}
+	if err != nil {
+		t.Error(err)
+	}
+	str, err = utils.Unprefix("foo/bar", "baz")
+	if str != "foo/bar" {
+		t.Errorf("expected: %q, actual: %q", "foo/bar", str)
+	}
+	if err == nil {
+		t.Error("err should not be nil")
+	}
+}
-- 
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