'use strict';

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

browser.runtime.onMessage.addListener((msg, sender, sendResponse) => {
  if (msg && msg.type === 'scrape-study-load') {
    browser.tabs.query({ active: true, currentWindow: true })
      .then((tabs) => {
        const tab = tabs[0];
        if (!tab || tab.id == null) throw new Error('No active tab.');
        return browser.tabs.sendMessage(tab.id, { type: 'scrape-study-load' });
      })
      .then((data) => sendResponse(data))
      .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;
  }
});

async function generatePdf(data) {
  const bytes = await ISMIStools.buildStudyLoadPdf(data);
  const blob = new Blob([bytes], { type: 'application/pdf' });
  const url = URL.createObjectURL(blob);
  const name = (data.header && data.header.fullName) || 'Student';
  const filename = 'Study Load - ' + name + '.pdf';
  try {
    const id = await browser.downloads.download({ url, filename, saveAs: true });
    const onChanged = (delta) => {
      if (delta.id === id && delta.state && (delta.state.current === 'complete' || delta.state.current === 'interrupted')) {
        browser.downloads.onChanged.removeListener(onChanged);
        URL.revokeObjectURL(url);
      }
    };
    browser.downloads.onChanged.addListener(onChanged);
  } catch (err) {
    URL.revokeObjectURL(url);
    throw err;
  }
}