Get sheet names based on index

SheetID only seems to indicate the file name for the sheet.
Check the sheets list based on index instead. Reordering sheets
in Excel changes the order they appear in that list.

Fixes #457

2 files changed, 27 insertions, 9 deletions

diff --git a/sheet.go b/sheet.go
index e02782a..935deac 100644
--- a/sheet.go
+++ b/sheet.go
@@ -317,14 +317,11 @@ func (f *File) SetSheetName(oldName, newName string) {
 // string.
 func (f *File) GetSheetName(index int) string {
 	wb := f.workbookReader()
-	if wb != nil {
-		for _, sheet := range wb.Sheets.Sheet {
-			if sheet.SheetID == index {
-				return sheet.Name
-			}
-		}
+	realIdx := index - 1 // sheets are 1 based index, but we're checking against an array
+	if wb == nil || realIdx < 0 || realIdx >= len(wb.Sheets.Sheet) {
+		return ""
 	}
-	return ""
+	return wb.Sheets.Sheet[realIdx].Name
 }
 
 // GetSheetIndex provides a function to get worksheet index of XLSX by given
@@ -357,8 +354,8 @@ func (f *File) GetSheetMap() map[int]string {
 	wb := f.workbookReader()
 	sheetMap := map[int]string{}
 	if wb != nil {
-		for _, sheet := range wb.Sheets.Sheet {
-			sheetMap[sheet.SheetID] = sheet.Name
+		for i, sheet := range wb.Sheets.Sheet {
+			sheetMap[i+1] = sheet.Name
 		}
 	}
 	return sheetMap
diff --git a/sheet_test.go b/sheet_test.go
index ef795ad..3baa084 100644
--- a/sheet_test.go
+++ b/sheet_test.go
@@ -225,3 +225,24 @@ func TestUngroupSheets(t *testing.T) {
 	}
 	assert.NoError(t, f.UngroupSheets())
 }
+
+func TestGetSheetName(t *testing.T) {
+	f, _ := excelize.OpenFile(filepath.Join("test", "Book1.xlsx"))
+	assert.Equal(t, "Sheet1", f.GetSheetName(1))
+	assert.Equal(t, "Sheet2", f.GetSheetName(2))
+	assert.Equal(t, "", f.GetSheetName(0))
+	assert.Equal(t, "", f.GetSheetName(3))
+}
+
+func TestGetSheetMap(t *testing.T) {
+	expectedMap := map[int]string{
+		1: "Sheet1",
+		2: "Sheet2",
+	}
+	f, _ := excelize.OpenFile(filepath.Join("test", "Book1.xlsx"))
+	sheetMap := f.GetSheetMap()
+	for idx, name := range sheetMap {
+		assert.Equal(t, expectedMap[idx], name)
+	}
+	assert.Equal(t, len(sheetMap), 2)
+}