# Excel export standard (FPSMS frontend)

This document defines how **client-side** `.xlsx` exports should look and behave. **Implementation:** `exportChartToXlsx.ts` and `exportMultiSheetToXlsx()` — use these helpers for new reports so styling stays consistent.

## Scope (important)

| Export path | Follows this `.md`? |
|-------------|---------------------|
| **Next.js** builds the file via `exportChartToXlsx` / `exportMultiSheetToXlsx` (e.g. **PO 入倉記錄** / `rep-014`) | **Yes** — rules are enforced in code. |
| **Backend** returns ready-made `.xlsx` or Excel bytes (JasperReports, Apache POI, etc.; most `print-*` report endpoints) | **No — not automatically.** That code does **not** use this TypeScript module. To match the same **look** (grey headers, number formats, alignment), implement equivalent styling in Java/Kotlin or Jasper templates. See the backend companion doc below. |

**Backend companion (visual parity):**  
`FPSMS-backend/docs/EXCEL_EXPORT_STANDARD.md` — same *rules*, for POI/Jasper implementers.

---

## 1. Library

| Item | Value |
|------|--------|
| Package | **`xlsx-js-style`** (not the plain `xlsx` community build) |
| Reason | Plain SheetJS **does not persist** cell styles (`fill`, `alignment`, `numFmt`) in the written file. `xlsx-js-style` is a compatible fork that **does**. |

---

## 2. Data shape

- Rows are **`Record<string, unknown>[]`** (array of plain objects).
- **First object’s keys** become the **header row** (column titles). Every row should use the **same keys** in the same order for a rectangular sheet.
- Prefer **real JavaScript `number`** values for amounts where possible; the exporter will apply number formats. Strings that look like numbers (e.g. `"1,234.56"`) are parsed for money columns.

---

## 3. Processing order (per sheet)

After `json_to_sheet(rows)`:

1. **`!cols`** — column width heuristic (see §4).
2. **`applyHeaderRowStyle`** — header row styling (see §5).
3. **`applyMoneyColumnNumberFormats`** — money columns only, data rows (see §6).
4. **`applyNumericColumnRightAlign`** — money + quantity columns, **all rows including header** (see §7).

---

## 4. Column width (`!cols`)

- For each column: `wch = max(12, headerText.length + 4)`.
- Adjust if a report needs fixed widths; default keeps bilingual headers readable.

---

## 5. Header row style (row 0)

Applied to **every** header cell first; numeric columns get alignment overridden in step 4.

| Property | Value |
|----------|--------|
| Font | Bold, black `rgb: "000000"` |
| Fill | Solid, `fgColor: "D9D9D9"` (light grey) |
| Alignment (default) | Horizontal **center**, vertical **center**, `wrapText: true` |

---

## 6. Money / amount columns — number format

**Detection:** header label matches (case-insensitive):

```text
金額 | 單價 | Amount | Unit Price | Total Amount
```

(Also matches bilingual headers that contain these fragments, e.g. `Amount / 金額`, `Unit Price / 單價`, `Total Amount / 金額`.)

**Rules:**

- Applies to **data rows only** (not row 0).
- Excel format string: **`#,##0.00`** (thousands separator + 2 decimals). Stored on the cell as `z`.
- Cell type `t: "n"` for numeric values.
- If the cell is a **string**, commas are stripped and the value is parsed to a number when possible.

**Naming new reports:** use header text that matches the patterns above so columns pick up formatting automatically.

---

## 7. Quantity columns — alignment only

**Detection:** header label matches:

```text
Qty | 數量 | Demand
```

(Covers e.g. `Qty / 數量`, `Demand Qty / 訂單數量`.)

- No default thousands format (quantities may have up to 4 decimals in app code).
- These columns are **right-aligned** together with money columns (see §8).

---

## 8. Alignment — numeric columns (header + data)

**Detection:** union of **money** (§6) and **quantity** (§7) header patterns.

| Alignment | Value |
|-----------|--------|
| Horizontal | **`right`** |
| Vertical | **`center`** |
| `wrapText` | Preserved / defaulted to `true` where applicable |

Existing style objects are **merged** (fill, font from header styling are kept).

---

## 9. Multi-sheet workbook

| Rule | Detail |
|------|--------|
| API | `exportMultiSheetToXlsx({ name, rows }[], filename)` |
| Sheet name length | Truncated to **31** characters (Excel limit) |
| Each sheet | Same pipeline as §3 if `rows.length > 0` |

---

## 10. Empty sheets

If `rows.length === 0`, a minimal sheet is written; no header styling pipeline runs.

---

## 11. Reports using this standard today

| Feature | Location |
|---------|----------|
| Chart export | Uses `exportChartToXlsx` |
| GRN / PO 入倉記錄 (`rep-014`) | `src/app/(main)/report/grnReportApi.ts` — builds row objects, calls `exportChartToXlsx` / `exportMultiSheetToXlsx` |

Most other reports on `/report` download Excel/PDF **generated on the server** (Jasper, etc.). Those **do not** run this TypeScript pipeline; use **`FPSMS-backend/docs/EXCEL_EXPORT_STANDARD.md`** if you want the same visual rules there.

---

## 12. Checklist for new Excel exports

1. Import from **`xlsx-js-style`** only if building sheets manually; otherwise call **`exportChartToXlsx`** or **`exportMultiSheetToXlsx`**.
2. Use **stable header strings** that match §6 / §7 if the column is amount or quantity.
3. Pass **numbers** for amounts when possible.
4. If you need a **new** category (e.g. “Rate”, “折扣”), extend the regex constants in `exportChartToXlsx.ts` and **update this document**.
5. Keep filenames and sheet names user-readable; remember the **31-character** sheet limit.

---

## 13. Related files

| File | Role |
|------|------|
| `exportChartToXlsx.ts` | Single-sheet export + styling pipeline |
| `grnReportApi.ts` | Example: bilingual headers, money values, multi-sheet GRN report |
| `FPSMS-backend/docs/EXCEL_EXPORT_STANDARD.md` | Backend Excel (POI/Jasper) — same *rules*, separate code |

---

*Last aligned with implementation in `exportChartToXlsx.ts` (header fill `#D9D9D9`, money format `#,##0.00`, right-align numeric columns).*
