feaT: add excel
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// Dependency-free .xlsx writer. An .xlsx is just a ZIP of XML parts, so we
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// build the parts by hand and pack them with STORE (no compression) — that
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// keeps us from needing a deflate implementation while still producing a file
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// Excel opens natively, with no "format and extension don't match" warning.
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type Cell = string | number | null | undefined;
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/* --------------------------------- ZIP ---------------------------------- */
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const CRC_TABLE = (() => {
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const table = new Uint32Array(256);
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for (let i = 0; i < 256; i++) {
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let c = i;
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for (let k = 0; k < 8; k++) c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
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table[i] = c >>> 0;
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}
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return table;
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})();
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function crc32(bytes: Uint8Array): number {
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let c = 0xffffffff;
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for (let i = 0; i < bytes.length; i++) {
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c = CRC_TABLE[(c ^ bytes[i]) & 0xff] ^ (c >>> 8);
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}
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return (c ^ 0xffffffff) >>> 0;
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}
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interface ZipEntry {
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name: string;
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data: Uint8Array;
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crc: number;
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offset: number;
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}
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// Builds a ZIP archive with stored (uncompressed) entries. Fixed DOS timestamp
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// so repeated exports of the same data are byte-identical.
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function zip(files: { name: string; content: string }[]): Blob {
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const encoder = new TextEncoder();
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const chunks: Uint8Array[] = [];
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const entries: ZipEntry[] = [];
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let offset = 0;
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const DOS_TIME = 0; // 00:00:00
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const DOS_DATE = (2020 - 1980) << 9 | (1 << 5) | 1; // 2020-01-01
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function push(bytes: Uint8Array) {
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chunks.push(bytes);
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offset += bytes.length;
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}
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function header(size: number) {
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const buf = new ArrayBuffer(size);
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return { view: new DataView(buf), bytes: new Uint8Array(buf) };
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}
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for (const file of files) {
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const nameBytes = encoder.encode(file.name);
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const data = encoder.encode(file.content);
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const crc = crc32(data);
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const local = header(30 + nameBytes.length);
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local.view.setUint32(0, 0x04034b50, true); // local file header signature
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local.view.setUint16(4, 20, true); // version needed
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local.view.setUint16(6, 0x0800, true); // flags: UTF-8 names
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local.view.setUint16(8, 0, true); // method: stored
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local.view.setUint16(10, DOS_TIME, true);
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local.view.setUint16(12, DOS_DATE, true);
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local.view.setUint32(14, crc, true);
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local.view.setUint32(18, data.length, true); // compressed size
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local.view.setUint32(22, data.length, true); // uncompressed size
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local.view.setUint16(26, nameBytes.length, true);
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local.view.setUint16(28, 0, true); // extra field length
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local.bytes.set(nameBytes, 30);
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entries.push({ name: file.name, data, crc, offset });
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push(local.bytes);
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push(data);
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}
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const centralStart = offset;
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for (const entry of entries) {
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const nameBytes = encoder.encode(entry.name);
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const central = header(46 + nameBytes.length);
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central.view.setUint32(0, 0x02014b50, true); // central directory signature
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central.view.setUint16(4, 20, true); // version made by
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central.view.setUint16(6, 20, true); // version needed
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central.view.setUint16(8, 0x0800, true); // flags: UTF-8 names
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central.view.setUint16(10, 0, true); // method: stored
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central.view.setUint16(12, DOS_TIME, true);
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central.view.setUint16(14, DOS_DATE, true);
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central.view.setUint32(16, entry.crc, true);
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central.view.setUint32(20, entry.data.length, true);
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central.view.setUint32(24, entry.data.length, true);
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central.view.setUint16(28, nameBytes.length, true);
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central.view.setUint16(30, 0, true); // extra
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central.view.setUint16(32, 0, true); // comment
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central.view.setUint16(34, 0, true); // disk number
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central.view.setUint16(36, 0, true); // internal attrs
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central.view.setUint32(38, 0, true); // external attrs
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central.view.setUint32(42, entry.offset, true);
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central.bytes.set(nameBytes, 46);
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push(central.bytes);
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}
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const end = header(22);
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end.view.setUint32(0, 0x06054b50, true); // end of central directory
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end.view.setUint16(8, entries.length, true);
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end.view.setUint16(10, entries.length, true);
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end.view.setUint32(12, offset - centralStart, true);
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end.view.setUint32(16, centralStart, true);
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push(end.bytes);
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return new Blob(chunks as BlobPart[], {
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type: "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
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});
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}
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/* --------------------------------- XML ---------------------------------- */
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// Built via RegExp so the source file stays free of literal control bytes.
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const CONTROL_CHARS = new RegExp(
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"[\\u0000-\\u0008\\u000B\\u000C\\u000E-\\u001F]",
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"g",
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);
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function escapeXml(value: string): string {
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return value
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.replace(/&/g, "&")
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.replace(/</g, "<")
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.replace(/>/g, ">")
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.replace(/"/g, """)
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// Control characters are illegal in XML 1.0 and make Excel reject the file.
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.replace(CONTROL_CHARS, "");
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}
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// 0 -> A, 25 -> Z, 26 -> AA ...
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function columnName(index: number): string {
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let name = "";
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let n = index;
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while (n >= 0) {
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name = String.fromCharCode(65 + (n % 26)) + name;
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n = Math.floor(n / 26) - 1;
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}
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return name;
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}
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function cellXml(ref: string, value: Cell, style: number): string {
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if (value === null || value === undefined || value === "") {
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return `<c r="${ref}" s="${style}"/>`;
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}
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if (typeof value === "number" && Number.isFinite(value)) {
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return `<c r="${ref}" s="${style}"><v>${value}</v></c>`;
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}
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// Inline strings keep us from having to build a sharedStrings part.
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return `<c r="${ref}" s="${style}" t="inlineStr"><is><t xml:space="preserve">${escapeXml(
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String(value),
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)}</t></is></c>`;
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}
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function sheetXml(headers: string[], rows: Cell[][]): string {
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const width = Math.max(headers.length, ...rows.map((r) => r.length), 1);
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const cols =
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`<cols>` +
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Array.from(
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{ length: width },
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(_, i) => `<col min="${i + 1}" max="${i + 1}" width="22" customWidth="1"/>`,
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).join("") +
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`</cols>`;
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const lines: string[] = [];
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lines.push(
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`<row r="1">${headers
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.map((h, i) => cellXml(`${columnName(i)}1`, h, 1))
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.join("")}</row>`,
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);
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rows.forEach((row, r) => {
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const n = r + 2;
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lines.push(
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`<row r="${n}">${row
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.map((cell, i) => cellXml(`${columnName(i)}${n}`, cell, 0))
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.join("")}</row>`,
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);
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});
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return (
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`<?xml version="1.0" encoding="UTF-8" standalone="yes"?>` +
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`<worksheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">` +
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// rightToLeft so the sheet opens in RTL orientation, and a frozen header row.
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`<sheetViews><sheetView rightToLeft="1" workbookViewId="0" tabSelected="1">` +
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`<pane ySplit="1" topLeftCell="A2" activePane="bottomLeft" state="frozen"/>` +
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`</sheetView></sheetViews>` +
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cols +
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`<sheetData>${lines.join("")}</sheetData>` +
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`<autoFilter ref="A1:${columnName(width - 1)}${rows.length + 1}"/>` +
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`</worksheet>`
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);
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}
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// Two cell formats: 0 = body, 1 = bold header on a grey fill.
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const STYLES_XML =
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`<?xml version="1.0" encoding="UTF-8" standalone="yes"?>` +
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`<styleSheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">` +
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`<fonts count="2"><font><sz val="11"/><name val="Calibri"/></font>` +
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`<font><b/><sz val="11"/><name val="Calibri"/></font></fonts>` +
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`<fills count="3"><fill><patternFill patternType="none"/></fill>` +
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`<fill><patternFill patternType="gray125"/></fill>` +
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`<fill><patternFill patternType="solid"><fgColor rgb="FFEEEEEE"/><bgColor indexed="64"/></patternFill></fill></fills>` +
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`<borders count="1"><border><left/><right/><top/><bottom/><diagonal/></border></borders>` +
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`<cellStyleXfs count="1"><xf numFmtId="0" fontId="0" fillId="0" borderId="0"/></cellStyleXfs>` +
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`<cellXfs count="2">` +
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`<xf numFmtId="0" fontId="0" fillId="0" borderId="0" xfId="0" applyAlignment="1"><alignment vertical="center" wrapText="1"/></xf>` +
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`<xf numFmtId="0" fontId="1" fillId="2" borderId="0" xfId="0" applyFont="1" applyFill="1" applyAlignment="1"><alignment horizontal="center" vertical="center"/></xf>` +
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`</cellXfs><cellStyles count="1"><cellStyle name="Normal" xfId="0" builtinId="0"/></cellStyles></styleSheet>`;
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/* -------------------------------- Public -------------------------------- */
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export function exportToExcel(
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filename: string,
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headers: string[],
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rows: Cell[][],
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sheetName = "Sheet1",
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) {
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const safeSheet = escapeXml(sheetName.replace(/[[\]:*?/\\]/g, "").slice(0, 31)) || "Sheet1";
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const blob = zip([
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{
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name: "[Content_Types].xml",
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content:
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`<?xml version="1.0" encoding="UTF-8" standalone="yes"?>` +
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`<Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types">` +
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`<Default Extension="rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>` +
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`<Default Extension="xml" ContentType="application/xml"/>` +
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`<Override PartName="/xl/workbook.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.main+xml"/>` +
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`<Override PartName="/xl/worksheets/sheet1.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.worksheet+xml"/>` +
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`<Override PartName="/xl/styles.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.styles+xml"/>` +
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`</Types>`,
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},
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{
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name: "_rels/.rels",
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content:
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`<?xml version="1.0" encoding="UTF-8" standalone="yes"?>` +
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`<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">` +
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`<Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="xl/workbook.xml"/>` +
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`</Relationships>`,
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},
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{
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name: "xl/workbook.xml",
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content:
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`<?xml version="1.0" encoding="UTF-8" standalone="yes"?>` +
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`<workbook xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main" ` +
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`xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships">` +
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`<sheets><sheet name="${safeSheet}" sheetId="1" r:id="rId1"/></sheets></workbook>`,
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},
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{
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name: "xl/_rels/workbook.xml.rels",
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content:
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`<?xml version="1.0" encoding="UTF-8" standalone="yes"?>` +
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`<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">` +
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`<Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/worksheet" Target="worksheets/sheet1.xml"/>` +
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`<Relationship Id="rId2" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/styles" Target="styles.xml"/>` +
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`</Relationships>`,
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},
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{ name: "xl/styles.xml", content: STYLES_XML },
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{ name: "xl/worksheets/sheet1.xml", content: sheetXml(headers, rows) },
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]);
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const url = URL.createObjectURL(blob);
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const link = document.createElement("a");
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link.href = url;
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link.download = filename.endsWith(".xlsx") ? filename : `${filename}.xlsx`;
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document.body.appendChild(link);
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link.click();
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document.body.removeChild(link);
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URL.revokeObjectURL(url);
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}
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// Runs `worker` over `items` with a bounded number of in-flight promises so a
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// few thousand rows don't open a few thousand sockets at once.
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export async function mapWithConcurrency<T, R>(
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items: T[],
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limit: number,
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worker: (item: T, index: number) => Promise<R>,
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onProgress?: (done: number, total: number) => void,
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): Promise<R[]> {
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const results = new Array<R>(items.length);
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let cursor = 0;
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let done = 0;
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async function run() {
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while (cursor < items.length) {
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const index = cursor++;
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results[index] = await worker(items[index], index);
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done++;
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onProgress?.(done, items.length);
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}
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}
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await Promise.all(
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Array.from({ length: Math.min(limit, items.length) }, run),
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);
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return results;
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}
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