hps-thunderbird-templates/background.js

browser.runtime.onMessage.addListener((msg, sender, sendResponse) => {
  if (msg.action !== 'insertTemplate') return false;

  handleInsertTemplate(msg).then(() => sendResponse())
    .catch(err => sendResponse({ error: err.message }));
  return true; // keep channel open for async response
});

async function handleInsertTemplate(msg) {
  try {
    const [tab] = await browser.tabs.query({
      active: true,
      currentWindow: true,
      windowType: 'messageCompose',
    });
    if (!tab) throw new Error('Kein Compose-Fenster gefunden');

    const details = await browser.compose.getComposeDetails(tab.id);
    const isHtmlTemplate = msg.text.includes('<');

    // If compose is plain text but template is HTML, switch to HTML mode first
    if (details.isPlainText && isHtmlTemplate) {
      await browser.compose.setComposeDetails(tab.id, { isPlainText: false });
    }

    if (details.isPlainText && !isHtmlTemplate) {
      // Plain text template in plain text mode - use old method
      const old = details.plainTextBody || '';
      const newBody = msg.text + (old ? '\n' + old : '');
      await browser.compose.setComposeDetails(tab.id, { plainTextBody: newBody });
    } else {
      // HTML mode: use insertText API to go through the editor's rendering pipeline
      const htmlContent = isHtmlTemplate ? msg.text : msg.text.replace(/\n/g, '<br>');

      // Move cursor to beginning of body first via script injection
      await browser.tabs.executeScript(tab.id, {
        code: `
          const editor = document.getElementById('messageEditor');
          const editorDoc = editor ? editor.contentDocument : document;
          const body = editorDoc.body;
          if (body) {
            const range = editorDoc.createRange();
            range.setStart(body, 0);
            range.collapse(true);
            const sel = editorDoc.getSelection();
            sel.removeAllRanges();
            sel.addRange(range);
          }
        `
      }).catch(() => {
        // Fallback: some TB versions structure the editor differently
      });

      // Insert HTML at cursor position - this goes through the editor's render pipeline
      await browser.compose.insertText(tab.id, htmlContent + '<br>', { insertAsText: false });
    }

  } catch (e) {
    console.error('background.js error:', e);

    // Fallback: if insertText fails, try setComposeDetails
    try {
      const [tab] = await browser.tabs.query({
        active: true, currentWindow: true, windowType: 'messageCompose',
      });
      if (tab) {
        const details = await browser.compose.getComposeDetails(tab.id);
        const old = details.body || '';
        const htmlTpl = msg.text.includes('<') ? msg.text : msg.text.replace(/\n/g, '<br>');
        const bodyIdx = old.indexOf('<body');
        let newBody;
        if (bodyIdx !== -1) {
          const insertAt = old.indexOf('>', bodyIdx) + 1;
          newBody = old.slice(0, insertAt) + '\n' + htmlTpl + '\n' + old.slice(insertAt);
        } else {
          newBody = htmlTpl + '<br>' + old;
        }
        await browser.compose.setComposeDetails(tab.id, { body: newBody });
      }
    } catch (e2) {
      console.error('background.js fallback error:', e2);
      browser.notifications.create({
        type: 'basic',
        iconUrl: browser.runtime.getURL('icons/icon.png'),
        title: 'Fehler beim Einfügen',
        message: e2.message,
      });
    }
  }
}