add copy function

storage.go

@@ -246,3 +246,30 @@ func (s *Storage) Stat(name string) (*FileInfo, error) {
 
 	return fileInfo, nil
 }
+
+// Copy copies a file from one place to another.
+// It takes the file name, and the destination name as its parameter.
+// The function returns an error, if any.
+func (s *Storage) Copy(name string, dest string) error {
+	if s.s3Client != nil {
+		if _, err := s.s3Client.CopyObject(s.ctx, minio.CopyDestOptions{
+			Bucket: s.config.S3BucketName,
+			Object: dest,
+		}, minio.CopySrcOptions{
+			Bucket: s.config.S3BucketName,
+			Object: name,
+		}); err != nil {
+			return err
+		}
+		return nil
+	} else {
+		fileContent, err := os.ReadFile(filepath.Join(s.config.Path, name))
+		if err != nil {
+			return err
+		}
+		if err := os.WriteFile(filepath.Join(s.config.Path, dest), fileContent, 0600); err != nil {
+			return err
+		}
+		return nil
+	}
+}

storage_test.go

@@ -31,6 +31,16 @@ func TestStorageLocal(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, []byte("hi"), fileContent)
 
+	t.Log("== Copy ==")
+	err = stor.Copy("test.txt", "test2.txt")
+	assert.NoError(t, err)
+
+	copyFileInfo, err := stor.Stat("test2.txt")
+	assert.NoError(t, err)
+	assert.Equal(t, fs.FileMode(0600), copyFileInfo.Mode)
+	assert.Equal(t, "test2.txt", copyFileInfo.Name)
+	assert.Equal(t, int64(len("hi")), fileInfo.Size)
+
 	t.Log("== Open ==")
 	file, err := stor.Open("test.txt")
 	assert.NoError(t, err)
@@ -76,6 +86,16 @@ func TestStorageS3(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, []byte("hi"), fileContent)
 
+	t.Log("== Copy ==")
+	err = stor.Copy("test.txt", "test2.txt")
+	assert.NoError(t, err)
+
+	copyFileInfo, err := stor.Stat("test2.txt")
+	assert.NoError(t, err)
+	assert.Equal(t, fs.FileMode(0777), copyFileInfo.Mode)
+	assert.Equal(t, "test2.txt", copyFileInfo.Name)
+	assert.Equal(t, int64(len("hi")), fileInfo.Size)
+
 	t.Log("== Open ==")
 	file, err := stor.Open("test.txt")
 	assert.NoError(t, err)