ismis-helper/background.js

'use strict';
// Cross-browser API namespace. Firefox provides Promise-based `browser.*`;
// Chrome MV3 exposes `browser.*` too, but some builds only populate the
// `chrome.*` global. Alias to whichever is present.
if (typeof browser === 'undefined' || browser == null) {
  var browser = (typeof chrome !== 'undefined' ? chrome : {});
}

function errMsg(err) {
  return String((err && err.message) || err);
}

browser.runtime.onMessage.addListener((msg, sender, sendResponse) => {
  if (msg && msg.type === 'encrypt-password') {
    encryptPassword(String(msg.password || ''))
      .then((cipher) => sendResponse({ ok: true, cipher }))
      .catch((err) => sendResponse({ ok: false, error: errMsg(err) }));
    return true;
  }
  if (msg && msg.type === 'decrypt-password') {
    decryptPassword(msg.cipher)
      .then((password) => sendResponse({ ok: true, password }))
      .catch((err) => sendResponse({ ok: false, error: errMsg(err) }));
    return true;
  }
  if (msg && msg.type === 'export') {
    runExport(msg.format, msg.data)
      .then(() => sendResponse({ ok: true }))
      .catch((err) => sendResponse({ ok: false, error: errMsg(err) }));
    return true;
  }
  if (msg && msg.type === 'generate-pdf') {
    generatePdf(msg.data)
      .then(() => sendResponse({ ok: true }))
      .catch((err) => sendResponse({ ok: false, error: errMsg(err) }));
    return true;
  }
});

// ---- Password encryption (at-rest) ----
// AES-GCM with a random 256-bit key. The key is stored in browser.storage.local
// so it survives browser/service-worker restarts (otherwise previously-encrypted
// passwords could never be decrypted again). This removes the plaintext-password
// smell from storage — it is NOT strong protection against an attacker who can
// read both the storage and the extension source (the user's threat model is
// only the school portal, no third-party exfiltration).
const CRYPTO_KEY_STORE = 'ismisCryptoKey';

async function getCryptoKey() {
  const { [CRYPTO_KEY_STORE]: stored } = await browser.storage.local.get(CRYPTO_KEY_STORE);
  if (stored) {
    return crypto.subtle.importKey('raw', new Uint8Array(stored), { name: 'AES-GCM' }, false, ['encrypt', 'decrypt']);
  }
  const key = await crypto.subtle.generateKey({ name: 'AES-GCM', length: 256 }, true, ['encrypt', 'decrypt']);
  const raw = await crypto.subtle.exportKey('raw', key);
  await browser.storage.local.set({ [CRYPTO_KEY_STORE]: Array.from(new Uint8Array(raw)) });
  return key;
}

async function encryptPassword(password) {
  const key = await getCryptoKey();
  const iv = crypto.getRandomValues(new Uint8Array(12));
  const data = await crypto.subtle.encrypt(
    { name: 'AES-GCM', iv }, key, new TextEncoder().encode(password));
  return { iv: Array.from(iv), data: Array.from(new Uint8Array(data)) };
}

async function decryptPassword(cipher) {
  if (!cipher || !cipher.iv || !cipher.data) throw new Error('Invalid encrypted password');
  const key = await getCryptoKey();
  const pt = await crypto.subtle.decrypt(
    { name: 'AES-GCM', iv: new Uint8Array(cipher.iv) }, key, new Uint8Array(cipher.data));
  return new TextDecoder().decode(pt);
}

// Generic downloader used by every export format. `filename` is used with
// saveAs so the user picks the location, mirroring the PDF flow.
async function downloadBytes(bytes, mime, filename, fallback) {
  const safeFilename = filename || fallback;
  const blob = new Blob([bytes], { type: mime });
  const url = (typeof URL !== 'undefined' && typeof URL.createObjectURL === 'function')
    ? URL.createObjectURL(blob)
    : null;
  let downloadUrl = url;
  if (!downloadUrl) {
    let binary = '';
    const chunk = 0x8000;
    for (let i = 0; i < bytes.length; i += chunk) {
      binary += String.fromCharCode.apply(null, bytes.subarray(i, i + chunk));
    }
    downloadUrl = 'data:' + mime + ';base64,' + btoa(binary);
  }
  try {
    const id = await browser.downloads.download({ url: downloadUrl, filename: safeFilename, saveAs: true });
    const onChanged = (delta) => {
      if (delta.id === id && delta.state && (delta.state.current === 'complete' || delta.state.current === 'interrupted')) {
        browser.downloads.onChanged.removeListener(onChanged);
      }
    };
    browser.downloads.onChanged.addListener(onChanged);
  } catch (err) {
    if (url) { try { URL.revokeObjectURL(url); } catch (e) {} }
    throw err;
  }
}

async function runExport(format, data) {
  const header = data.header || {};
  const year = parseInt(data.year, 10);
  const period = formatPeriod(data.period || header.semester || '');
  const compactProgram = ISMIStools.compactProgram(header.program || '');
  const schoolYear = Number.isFinite(year) ? year + '-' + (year + 1) : '';
  const core = [
    header.studentId || (header.fullName ? header.fullName.replace(/\s+/g, ' ') : ''),
    compactProgram,
    schoolYear ? 'S.Y. ' + schoolYear : '',
    period
  ].filter(Boolean);
  const base = core.join(' - ') || 'Study Load';

  if (format === 'csv') {
    const text = ISMIStools.buildStudyLoadCsv(data);
    const bytes = new TextEncoder().encode(text);
    await downloadBytes(bytes, 'text/csv', base + '.csv', 'Study Load.csv');
  } else if (format === 'json') {
    const text = JSON.stringify(ISMIStools.buildStudyLoadJson(data), null, 2);
    const bytes = new TextEncoder().encode(text);
    await downloadBytes(bytes, 'application/json', base + '.json', 'Study Load.json');
  } else if (format === 'xlsx') {
    const bytes = ISMIStools.buildStudyLoadXlsx(data);
    await downloadBytes(bytes, 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet', base + '.xlsx', 'Study Load.xlsx');
  } else if (format === 'nextup') {
    const text = ISMIStools.buildNextUpCsv(data);
    const bytes = new TextEncoder().encode(text);
    await downloadBytes(bytes, 'text/csv', base + '-nextup.csv', 'Study Load - nextup.csv');
  } else {
    throw new Error('Unknown export format: ' + format);
  }
}

function formatPeriod(period) {
  if (!period) return '';
  return String(period)
    .replace(/\b1ST\b/g, '1st')
    .replace(/\b2ND\b/g, '2nd')
    .replace(/\b3RD\b/g, '3rd')
    .replace(/\b(\d+)TH\b/g, '$1th')
    .toLowerCase()
    .replace(/^./, (c) => c.toUpperCase());
}

async function generatePdf(data) {
  const bytes = await ISMIStools.buildStudyLoadPdf(data);
  const header = data.header || {};
  const year = parseInt(data.year, 10);
  const period = formatPeriod(data.period || header.semester || '');
  const compactProgram = ISMIStools.compactProgram(header.program || '');
  const schoolYear = Number.isFinite(year) ? `${year}-${year + 1}` : '';
  const parts = [
    header.studentId || (header.fullName ? header.fullName.replace(/\s+/g, ' ') : ''),
    compactProgram,
    schoolYear ? 'S.Y. ' + schoolYear : '',
    period,
    'Study Load'
  ].filter(Boolean);
  const filename = parts.join(' - ') + '.pdf';
  const fallback = 'Study Load - ' + (header.fullName || 'Student') + '.pdf';
  await downloadBytes(bytes, 'application/pdf', filename, fallback);
}