# gizlang:xlsx

XLSX (Office Open XML SpreadsheetML) workbooks, written: sheets of typed cells with a bold, frozen and filtered head row. Text goes inline in each cell (no shared string table), so a sheet is written row by row in one pass. A number keeps its decimal text as given; a date or time becomes Excel's serial day number with a date format, so a spreadsheet sorts and computes with it. Each part is deflated in one zip archive (gizlang:compress). A protected sheet is read-only in a spreadsheet, its filter and sort still free. `rows` reads the first sheet of a workbook back as texts.

```gizlang
import * as Xlsx from "gizlang:xlsx";
```

## Types

### `Cell`

```gizlang
type Cell = | { kind: "blank"; } | { kind: "number"; v: string; } | { kind: "text"; v: string; } | { kind: "boolean"; v: bool; } | { kind: "date"; v: string; } | { kind: "time"; v: string; }
```

One cell: nothing, a number (its decimal text), text, a boolean, a date (`YYYY-MM-DD`) or a time (`YYYY-MM-DD HH:MM:SS`,
with optional fraction; a `T` may stand for the space). A date or time that does not parse is written as text.

- `blank`
- `number`
- `text`
- `boolean`
- `date`
- `time`

### `Sheet`

```gizlang
type Sheet
```

One sheet being written: its name, the XML of its rows so far, its row count, each column's widest text and whether
it is protected.

- `name`: `string`

## Functions

### `sheet`

```gizlang
function sheet(name: string, head: Vec<string>): Sheet
```

A sheet NAME whose first row is HEAD, bold, frozen and filtered. Excel allows 31 characters and no `[]:*?/\` in a name: others are
replaced.

Effects: fail.

### `column`

```gizlang
function column(at: i64): string
```

The letters of the column AT (0: A, 26: AA).

Effects: fail.

### `serial`

```gizlang
function serial(v: string): Option<f64>
```

Excel's serial day of a date or time text: days since 1899-12-30, the time of day as a fraction.

Effects: fail.

### `workbook`

```gizlang
function workbook(sheets: Vec<Sheet>): bytes
```

SHEETS as one XLSX file.

Effects: fail.

### `rows`

```gizlang
function rows(data: bytes, most: i64): Vec<Vec<string>> throws string
```

The rows of the first sheet of the XLSX file DATA, at most MOST of them: each row's cell texts by column, a missing
cell "". A number reads as its decimal text; a cell whose number format shows a date reads as `YYYY-MM-DD`, or
`YYYY-MM-DD HH:MM:SS` with a time of day; a boolean as `true` or `false`; an error as its code (`#N/A`). A formula
reads as the value the spreadsheet saved with it.

Effects: fail, read, write, console, io.

## Methods

### `Sheet.row`

```gizlang
function Sheet.row(self: mut Sheet, cells: Vec<Cell>): void
```

Adds a row of CELLS.

Effects: fail.

### `Sheet.protect`

```gizlang
function Sheet.protect(self: mut Sheet): void
```

Makes the sheet read-only in a spreadsheet: its cells cannot change, while filtering and sorting still work. It holds
no password: protection guards against a slip, never against a person who wants to edit.

### `Sheet.count`

```gizlang
function Sheet.count(self: Sheet): i64
```

How many rows the sheet holds, its head included.