Origin Request lambda@edge function for header evaluation

cf-origin-switch-header_origin-request.js

'use strict';

const SOURCE_HEADER_NAME = 'x-myapp-origin';

exports.handler = async event => {
    console.group('[INFO] lambda@edge Origin Request')
    const request = event.Records[0].cf.request;

    if (request.headers[SOURCE_HEADER_NAME]) {
        const headerValue = request.headers[SOURCE_HEADER_NAME][0].value;
        const domainName = `web-bucket-${headerValue}.s3.eu-central-1.amazonaws.com`;

        console.log(`[OVERWRITE] Using custom origin: ${domainName}`);

        request.origin = {
            s3: {
                ...request.origin.s3,
                domainName,
            },
        };

        request.headers['host'] = [{ key: 'Host', value: domainName }];

        console.log(request.origin.s3);
        console.log(request.headers.host);
    }
    console.groupEnd()

    return request;
};