'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);
}

// Build a download URL from PDF bytes. Firefox's background is a real page
// (URL.createObjectURL available) and supports blob: URLs in downloads.
// Chrome MV3 runs the background as a service worker where URL.createObjectURL
// is NOT available, but its downloads API accepts base64 data: URLs.
// Firefox rejects data: URLs in browser.downloads.download with
// "Access denied for URL data:...", so pick per-browser.
function buildDownloadUrl(bytes) {
  if (typeof URL !== 'undefined' && typeof URL.createObjectURL === 'function') {
    const blob = new Blob([bytes], { type: 'application/pdf' });
    return URL.createObjectURL(blob);
  }
  // Fallback: Chrome MV3 service worker. PDFs here are small (~150KB), well
  // within data-URL length limits.
  let binary = '';
  const chunk = 0x8000;
  for (let i = 0; i < bytes.length; i += chunk) {
    binary += String.fromCharCode.apply(null, bytes.subarray(i, i + chunk));
  }
  return 'data:application/pdf;base64,' + btoa(binary);
}

browser.runtime.onMessage.addListener((msg, sender, sendResponse) => {
  if (msg && msg.type === 'generate-pdf') {
    generatePdf(msg.data)
      .then(() => sendResponse({ ok: true }))
      .catch((err) => sendResponse({ ok: false, error: errMsg(err) }));
    return true;
  }
});

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);
  // Firefox accepts blob: object URLs; Chrome MV3 service worker has no
  // URL.createObjectURL, so it falls back to a base64 data: URL there.
  const url = buildDownloadUrl(bytes);
  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';
  const safeFilename = filename || fallback;

  try {
    const id = await browser.downloads.download({ url, 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) {
    throw err;
  }
}