feat(oo): sheet-aware spreadsheet export (docs csv/json)

- lib: WorkbookSheetNames/CSV/JSON (excelize) — sheet selection + JSON rows
- oo docs csv  SRC... [--sheet N] [--delimiter ,|;|||tab] [--out]
- oo docs json SRC... [--sheet N] [--out]
- SRC = OO file id or local path; --sheet is 1-based (default first)
- DS csv output is first-sheet-only (verified) -> local reader for selection/JSON
- test: TestWorkbookSheetExport

sheets_test.go

@@ -0,0 +1,54 @@
+package onlyoffice
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+
+	"github.com/xuri/excelize/v2"
+)
+
+func TestWorkbookSheetExport(t *testing.T) {
+	f := excelize.NewFile()
+	f.SetSheetName("Sheet1", "first")
+	_ = f.SetCellValue("first", "A1", "name")
+	_ = f.SetCellValue("first", "B1", "age")
+	_ = f.SetCellValue("first", "A2", "Alice")
+	_ = f.SetCellValue("first", "B2", 30)
+	_, _ = f.NewSheet("second")
+	_ = f.SetCellValue("second", "A1", "city")
+	_ = f.SetCellValue("second", "A2", "Lisbon")
+	var buf bytes.Buffer
+	if err := f.Write(&buf); err != nil {
+		t.Fatal(err)
+	}
+	data := buf.Bytes()
+
+	names, err := WorkbookSheetNames(data)
+	if err != nil || len(names) != 2 {
+		t.Fatalf("names=%v err=%v", names, err)
+	}
+
+	csv0, err := WorkbookSheetCSV(data, 0, 0)
+	if err != nil || !strings.Contains(csv0, "Alice") {
+		t.Fatalf("sheet0 csv=%q err=%v", csv0, err)
+	}
+	csv1, err := WorkbookSheetCSV(data, 1, 0)
+	if err != nil || !strings.Contains(csv1, "Lisbon") || strings.Contains(csv1, "Alice") {
+		t.Fatalf("sheet1 csv=%q err=%v", csv1, err)
+	}
+	// negative index = first sheet
+	csvDefault, _ := WorkbookSheetCSV(data, -1, 0)
+	if !strings.Contains(csvDefault, "Alice") {
+		t.Fatalf("default csv=%q", csvDefault)
+	}
+
+	js, err := WorkbookSheetJSON(data, 1)
+	if err != nil || len(js) != 1 || js[0]["city"] != "Lisbon" {
+		t.Fatalf("sheet1 json=%#v err=%v", js, err)
+	}
+
+	if _, err := WorkbookSheetCSV(data, 5, 0); err == nil {
+		t.Fatal("expected out-of-range error")
+	}
+}