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Firebase functions Dynamic OG-Tags
exports.host = functions.https.onRequest((req, res) => {
const userAgent = req.headers['user-agent'].toLowerCase();
let indexHTML = fs.readFileSync('./hosting/index.html').toString();
const path = req.path ? req.path.split('/') : req.path;
const ogPlaceholder = '<meta name="functions-insert-dynamic-og">';
const metaPlaceholder = '<meta name="functions-insert-dynamic-meta">';
const isBot = userAgent.includes('googlebot') ||
userAgent.includes('yahoou') ||
userAgent.includes('bingbot') ||
userAgent.includes('baiduspider') ||
userAgent.includes('yandex') ||
userAgent.includes('yeti') ||
userAgent.includes('yodaobot') ||
userAgent.includes('gigabot') ||
userAgent.includes('ia_archiver') ||
userAgent.includes('facebookexternalhit') ||
userAgent.includes('twitterbot') ||
userAgent.includes('developers\.google\.com') ? true : false;
if (isBot && (path && path.length > 1 && path[1] === 'organisation')) {
const slug = path[2];
admin.database().ref(`published/${slug}`).once('value').then(snapshot => {
const org = snapshot.val();
if (org) {
org.slug = slug;
}
indexHTML = indexHTML.replace(metaPlaceholder, getMeta(org));
indexHTML = indexHTML.replace(ogPlaceholder, getOpenGraph(org));
res.status(200).send(indexHTML);
});
return;
}
// optional - turn on caching: res.set('Cache-Control', 'public, max-age=300, s-maxage=600');
indexHTML = indexHTML.replace(metaPlaceholder, getMeta());
indexHTML = indexHTML.replace(ogPlaceholder, getOpenGraph());
res.status(200).send(indexHTML);
});
const defaultDesc = 'The mobsters, bootleggers and gangsters of the 1920s and 30s, such as Al Capone, Lucky Luciano, and Bugs Moran.';
const defaultTitle = 'Original Gangsters';
const defaultLogo = 'https://example.com/images/headerHQ.jpg';
const getOpenGraph = (org) => {
let og = `<meta property="fb:app_id" content="921373517372" />`;
og += `<meta property="og:type" content="website" />`;
if (!org) {
og += `<meta property="og:title" content="${defaultTitle}" />`;
og += `<meta property="og:description" content="${defaultDesc}" />`;
og += `<meta property="og:image" content="${defaultLogo}" />`;
og += `<meta property="og:url" content="https://example.com" />`;
return og;
}
og += `<meta property="og:title" content="${org.name}" />`;
og += `<meta property="og:description" content="${org.desc || defDesc}" />`;
og += `<meta property="og:image" content="${org.logo_url || defLogo}" />`;
og += `<meta property="og:url" content="https://example.com/organisation/${org.slug}" />`;
return og;
};
const getMeta = (org) => {
// return other meta tags
};
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