(function (root, factory) {
  if (typeof module === 'object' && module.exports) {
    module.exports = factory();
  } else {
    root.ISMIStools = Object.assign(root.ISMIStools || {}, factory());
  }
})(typeof self !== 'undefined' ? self : this, function () {
  'use strict';

  // ---- Minimal ZIP writer (STORED, no compression) ----
  // Produces a valid ZIP containing the XLSX parts. Stored entries are used
  // because we have no deflate available (browser + zero-dependency Node).
  function crc32(buf) {
    let table = [];
    for (let n = 0; n < 256; n++) {
      let c = n;
      for (let k = 0; k < 8; k++) c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
      table[n] = c >>> 0;
    }
    let crc = 0xffffffff;
    for (let i = 0; i < buf.length; i++) crc = table[(crc ^ buf[i]) & 0xff] ^ (crc >>> 8);
    return (crc ^ 0xffffffff) >>> 0;
  }

  function zipStore(entries) {
    // entries: [{ name, data: Uint8Array }]
    const chunks = [];
    const central = [];
    let offset = 0;
    const enc = new TextEncoder();
    for (const e of entries) {
      const nameBytes = enc.encode(e.name);
      const crc = crc32(e.data);
      const local = new Uint8Array(30 + nameBytes.length);
      const dv = new DataView(local.buffer);
      dv.setUint32(0, 0x04034b50, true); // local file header sig
      dv.setUint16(4, 20, true);          // version needed
      dv.setUint16(6, 0, true);           // flags
      dv.setUint16(8, 0, true);           // method: stored
      dv.setUint16(10, 0, true);          // mod time
      dv.setUint16(12, 0x21, true);       // mod date
      dv.setUint32(14, crc, true);
      dv.setUint32(18, e.data.length, true); // compressed size
      dv.setUint32(22, e.data.length, true); // uncompressed size
      dv.setUint16(26, nameBytes.length, true); // name len
      dv.setUint16(28, 0, true);          // extra len
      local.set(nameBytes, 30);
      chunks.push(local, e.data);

      const cd = new Uint8Array(46 + nameBytes.length);
      const cdv = new DataView(cd.buffer);
      cdv.setUint32(0, 0x02014b50, true); // central dir sig
      cdv.setUint16(4, 20, true);          // version made by
      cdv.setUint16(6, 20, true);          // version needed
      cdv.setUint16(8, 0, true);           // flags
      cdv.setUint16(10, 0, true);          // method stored
      cdv.setUint16(12, 0, true);          // mod time
      cdv.setUint16(14, 0x21, true);       // mod date
      cdv.setUint32(16, crc, true);
      cdv.setUint32(20, e.data.length, true);
      cdv.setUint32(24, e.data.length, true);
      cdv.setUint16(28, nameBytes.length, true);
      cdv.setUint16(30, 0, true);          // extra len
      cdv.setUint16(32, 0, true);          // comment len
      cdv.setUint16(34, 0, true);          // disk start
      cdv.setUint16(36, 0, true);          // internal attrs
      cdv.setUint32(38, 0, true);          // external attrs
      cdv.setUint32(42, offset, true);     // local header offset
      cd.set(nameBytes, 46);
      central.push(cd);

      offset += local.length + e.data.length;
    }

    const cdStart = offset;
    let cdLen = 0;
    for (const c of central) cdLen += c.length;
    const eocd = new Uint8Array(22);
    const eocdv = new DataView(eocd.buffer);
    eocdv.setUint32(0, 0x06054b50, true);
    eocdv.setUint16(8, entries.length, true); // total entries (this disk)
    eocdv.setUint16(10, entries.length, true);
    eocdv.setUint32(12, cdLen, true);
    eocdv.setUint32(16, cdStart, true);

    chunks.push(...central, eocd);
    const total = chunks.reduce((s, c) => s + c.length, 0);
    const out = new Uint8Array(total);
    let pos = 0;
    for (const c of chunks) { out.set(c, pos); pos += c.length; }
    return out;
  }

  // ---- XML helpers ----
  function esc(s) {
    return String(s == null ? '' : s)
      .replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;')
      .replace(/"/g, '&quot;').replace(/'/g, '&apos;');
  }

  // ---- XLSX builder ----
  // Builds a single-sheet workbook: a title/header block + a course table
  // + a totals row, mirroring the CSV layout.
  function buildStudyLoadXlsx(data) {
    const header = data.header || {};
    const enc = new TextEncoder();
    // Gather all strings into a `sharedStrings` table; cells reference them.
    const strings = [];
    const sIndex = new Map();
    function addS(str) {
      const key = String(str == null ? '' : str);
      if (!sIndex.has(key)) { sIndex.set(key, strings.length); strings.push(key); }
      return sIndex.get(key);
    }

    // rows: array of arrays of { text } (all text cells for simplicity)
    const rows = [];
    rows.push([{ text: 'ISMIS HELPER - STUDY LOAD' }]);
    rows.push([{ text: 'Program' }, { text: header.program || '' }]);
    rows.push([{ text: 'Student Name' }, { text: header.fullName || header.studentName || '' }]);
    rows.push([{ text: 'Student ID' }, { text: header.studentId || '' }]);
    rows.push([{ text: 'Semester' }, { text: header.semester || '' }]);
    rows.push([{ text: 'Year Level' }, { text: header.yearLevel || '' }]);
    rows.push([{ text: 'Total Units' }, { text: data.totalUnits || '' }]);
    rows.push([]); // blank
    rows.push([{ text: 'Group' }, { text: 'Course Code' }, { text: 'Description' },
      { text: 'Schedule' }, { text: 'Faculty' }, { text: 'Units' }, { text: 'Status' }]);
    for (const c of (data.courses || [])) {
      rows.push([
        { text: c.group }, { text: c.courseCode }, { text: c.description },
        { text: c.schedule }, { text: c.faculty || c.teacher }, { text: c.units },
        { text: c.status }
      ]);
    }
    rows.push([{ text: 'Total' }, { text: '' }, { text: '' }, { text: '' },
      { text: '' }, { text: data.totalUnits || '' }, { text: '' }]);

    // Pre-compute shared string refs so sheet1.xml can reference them.
    const cellRefs = rows.map((row) => row.map((c) => c.text === '' ? -1 : addS(c.text)));

    // ---- sheet1.xml ----
    let sheetXml = '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>\n';
    sheetXml += '<worksheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">';
    sheetXml += '<cols>' +
      '<col min="1" max="1" width="8" customWidth="1"/>' +
      '<col min="2" max="2" width="14" customWidth="1"/>' +
      '<col min="3" max="3" width="42" customWidth="1"/>' +
      '<col min="4" max="4" width="38" customWidth="1"/>' +
      '<col min="5" max="5" width="24" customWidth="1"/>' +
      '<col min="6" max="6" width="10" customWidth="1"/>' +
      '<col min="7" max="7" width="12" customWidth="1"/>' +
      '</cols>';
    sheetXml += '<sheetData>';
    const colNames = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J'];
    cellRefs.forEach((refs, ri) => {
      sheetXml += '<row r="' + (ri + 1) + '">';
      refs.forEach((s, ci) => {
        if (s < 0) return;
        sheetXml += '<c r="' + colNames[ci] + (ri + 1) + '" t="s"><v>' + s + '</v></c>';
      });
      sheetXml += '</row>';
    });
    sheetXml += '</sheetData></worksheet>';

    // ---- sharedStrings.xml ----
    let ssXml = '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>\n';
    ssXml += '<sst xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main" count="' +
      cellRefs.reduce((s, r) => s + r.filter((x) => x >= 0).length, 0) +
      '" uniqueCount="' + strings.length + '">';
    for (const s of strings) ssXml += '<si><t>' + esc(s) + '</t></si>';
    ssXml += '</sst>';

    // ---- other parts ----
    const ct = '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>\n' +
      '<Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types">' +
      '<Default Extension="rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>' +
      '<Default Extension="xml" ContentType="application/xml"/>' +
      '<Override PartName="/xl/workbook.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.main+xml"/>' +
      '<Override PartName="/xl/worksheets/sheet1.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.worksheet+xml"/>' +
      '<Override PartName="/xl/sharedStrings.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.sharedStrings+xml"/>' +
      '<Override PartName="/xl/styles.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.styles+xml"/>' +
      '</Types>';

    const rels = '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>\n' +
      '<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">' +
      '<Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="xl/workbook.xml"/>' +
      '</Relationships>';

    const wb = '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>\n' +
      '<workbook xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main" ' +
      'xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships">' +
      '<sheets><sheet name="Study Load" sheetId="1" r:id="rId1"/></sheets></workbook>';

    const wbRels = '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>\n' +
      '<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">' +
      '<Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/worksheet" Target="worksheets/sheet1.xml"/>' +
      '<Relationship Id="rId2" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/sharedStrings" Target="sharedStrings.xml"/>' +
      '<Relationship Id="rId3" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/styles" Target="styles.xml"/>' +
      '</Relationships>';

    const xlRels = '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>\n' +
      '<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">' +
      '<Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="xl/workbook.xml"/>' +
      '</Relationships>';

    const styles = '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>\n' +
      '<styleSheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">' +
      '<fonts count="1"><font><sz val="11"/><name val="Calibri"/></font></fonts>' +
      '<fills count="1"><fill><patternFill patternType="none"/></fill></fills>' +
      '<borders count="1"><border><left/><right/><top/><bottom/><diagonal/></border></borders>' +
      '<cellStyleXfs count="1"><xf numFmtId="0" fontId="0" fillId="0" borderId="0"/></cellStyleXfs>' +
      '<cellXfs count="1"><xf numFmtId="0" fontId="0" fillId="0" borderId="0" xfId="0"/></cellXfs>' +
      '<cellStyles count="1"><cellStyle name="Normal" xfId="0" builtinId="0"/></cellStyles>' +
      '</styleSheet>';

    const parts = [
      { name: '[Content_Types].xml', data: enc.encode(ct) },
      { name: '_rels/.rels', data: enc.encode(rels) },
      { name: 'xl/workbook.xml', data: enc.encode(wb) },
      { name: 'xl/_rels/workbook.xml.rels', data: enc.encode(wbRels) },
      { name: 'xl/worksheets/sheet1.xml', data: enc.encode(sheetXml) },
      { name: 'xl/sharedStrings.xml', data: enc.encode(ssXml) },
      { name: 'xl/styles.xml', data: enc.encode(styles) }
    ];
    return zipStore(parts);
  }

  return { buildStudyLoadXlsx };
});