feat: background message routing and PDF download

background.js

@@ -0,0 +1,38 @@
+'use strict';
+
+importScripts('libs/pdf-lib.min.js', 'parsers.js', 'pdf.js');
+
+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';
+  await browser.downloads.download({ url, filename, saveAs: true });
+  setTimeout(() => URL.revokeObjectURL(url), 10000);
+}