s3podcast.js

const AWS = require('aws-sdk');
const s3 = new AWS.S3();

exports.handler = async (event) => {
    const filename = 'feed.xml';
    const { bucket, object } = event.Records[0].s3;
    const { eventTime, awsRegion } = event.Records[0];
    const date = new Date(eventTime).toUTCString();
    console.info(JSON.stringify(event, null, 2));
    const res = await s3.getObject({ Bucket: bucket.name, Key: filename }).promise();
    let xml = res.Body.toString('utf-8').replace(/\s*<\/channel>[\n\s]*<\/rss>/, '').split('<item>');
    xml[0] = xml[0].replace(/<pubDate>[^<]+<\/pubDate>/, `<pubDate>${date}</pubDate>`);
    xml[0] = xml[0].replace(/<lastBuildDate>[^<]+<\/lastBuildDate>/, `<lastBuildDate>${date}</lastBuildDate>`);
    while(xml.length > 49) {
        xml.pop();
    }
    const url = `https://${bucket.name}.s3.${awsRegion}.amazonaws.com/${object.key}`;
    xml.splice(1, 0, `
          <title>${object.key.replace(/\.m4a$/, '')}</title>
          <link>${url}</link>
          <pubDate>${date}</pubDate>
          <description></description>
          <enclosure url="${url}" length="${object.size}" type="audio/m4a" />
          <guid>${url}</guid>
          <itunes:explicit>no</itunes:explicit>
        </item>`)
    await s3.putObject({
        ACL: 'public-read',
        Body: xml.join('<item>').replace(/\s*\n+\s*/g, '') + '</channel></rss>', 
        Bucket: bucket.name, 
        ContentType: 'application/rss+xml',
        Key: filename,
    }).promise();
    return null;
};