export unprefix in utils and fix error msg

2 files changed, 38 insertions, 0 deletions

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")
+	}
+}