This closes #1076, add new function MoveSheet to support changing she…

…et order in the workbook (#1996)

- Add unit tests

sheet.go

@@ -600,6 +600,49 @@ func (f *File) DeleteSheet(sheet string) error {
 	return err
 }
 
+// MoveSheet moves a sheet to a specified position in the workbook. The function
+// moves the source sheet before the target sheet. After moving, other sheets
+// will be shifted to the left or right. If the sheet is already at the target
+// position, the function will not perform any action. Not that this function
+// will be ungroup all sheets after moving. For example, move Sheet2 before
+// Sheet1:
+//
+//	err := f.MoveSheet("Sheet2", "Sheet1")
+func (f *File) MoveSheet(source, target string) error {
+	if strings.EqualFold(source, target) {
+		return nil
+	}
+	wb, err := f.workbookReader()
+	if err != nil {
+		return err
+	}
+	sourceIdx, err := f.GetSheetIndex(source)
+	if err != nil {
+		return err
+	}
+	targetIdx, err := f.GetSheetIndex(target)
+	if err != nil {
+		return err
+	}
+	if sourceIdx < 0 {
+		return ErrSheetNotExist{source}
+	}
+	if targetIdx < 0 {
+		return ErrSheetNotExist{target}
+	}
+	_ = f.UngroupSheets()
+	activeSheetName := f.GetSheetName(f.GetActiveSheetIndex())
+	sourceSheet := wb.Sheets.Sheet[sourceIdx]
+	wb.Sheets.Sheet = append(wb.Sheets.Sheet[:sourceIdx], wb.Sheets.Sheet[sourceIdx+1:]...)
+	if targetIdx > sourceIdx {
+		targetIdx--
+	}
+	wb.Sheets.Sheet = append(wb.Sheets.Sheet[:targetIdx], append([]xlsxSheet{sourceSheet}, wb.Sheets.Sheet[targetIdx:]...)...)
+	activeSheetIdx, _ := f.GetSheetIndex(activeSheetName)
+	f.SetActiveSheet(activeSheetIdx)
+	return err
+}
+
 // deleteAndAdjustDefinedNames delete and adjust defined name in the workbook
 // by given worksheet ID.
 func deleteAndAdjustDefinedNames(wb *xlsxWorkbook, deleteLocalSheetID int) {

sheet_test.go

@@ -547,6 +547,43 @@ func TestDeleteSheet(t *testing.T) {
 	assert.NoError(t, f.SaveAs(filepath.Join("test", "TestDeleteSheet2.xlsx")))
 }
 
+func TestMoveSheet(t *testing.T) {
+	f := NewFile()
+	defer f.Close()
+	for i := 2; i < 6; i++ {
+		_, err := f.NewSheet("Sheet" + strconv.Itoa(i))
+		assert.NoError(t, err)
+	}
+	assert.Equal(t, []string{"Sheet1", "Sheet2", "Sheet3", "Sheet4", "Sheet5"}, f.GetSheetList())
+
+	// Move target to first position
+	assert.NoError(t, f.MoveSheet("Sheet2", "Sheet1"))
+	assert.Equal(t, []string{"Sheet2", "Sheet1", "Sheet3", "Sheet4", "Sheet5"}, f.GetSheetList())
+	assert.Equal(t, "Sheet1", f.GetSheetName(f.GetActiveSheetIndex()))
+
+	// Move target to last position
+	assert.NoError(t, f.MoveSheet("Sheet2", "Sheet5"))
+	assert.NoError(t, f.MoveSheet("Sheet5", "Sheet2"))
+	assert.Equal(t, []string{"Sheet1", "Sheet3", "Sheet4", "Sheet5", "Sheet2"}, f.GetSheetList())
+
+	// Move target to same position
+	assert.NoError(t, f.MoveSheet("Sheet1", "Sheet1"))
+	assert.Equal(t, []string{"Sheet1", "Sheet3", "Sheet4", "Sheet5", "Sheet2"}, f.GetSheetList())
+
+	// Test move sheet with invalid sheet name
+	assert.Equal(t, ErrSheetNameBlank, f.MoveSheet("", "Sheet2"))
+	assert.Equal(t, ErrSheetNameBlank, f.MoveSheet("Sheet1", ""))
+
+	// Test move sheet on not exists worksheet
+	assert.Equal(t, ErrSheetNotExist{"SheetN"}, f.MoveSheet("SheetN", "Sheet2"))
+	assert.Equal(t, ErrSheetNotExist{"SheetN"}, f.MoveSheet("Sheet1", "SheetN"))
+
+	// Test move sheet with unsupported workbook charset
+	f.WorkBook = nil
+	f.Pkg.Store("xl/workbook.xml", MacintoshCyrillicCharset)
+	assert.EqualError(t, f.MoveSheet("Sheet2", "Sheet1"), "XML syntax error on line 1: invalid UTF-8")
+}
+
 func TestDeleteAndAdjustDefinedNames(t *testing.T) {
 	deleteAndAdjustDefinedNames(nil, 0)
 	deleteAndAdjustDefinedNames(&xlsxWorkbook{}, 0)