single-page-app-origin-request

'use strict';

const pointsToFile = uri => /\/[^/]+\.[^/]+$/.test(uri);

exports.handler = (event, context, callback) => {
    
    // Extract the request from the CloudFront event that is sent to Lambda@Edge 
    var request = event.Records[0].cf.request;

    // Extract the URI from the request
    var oldUri = request.uri;
    var newUri;
    
    if (!pointsToFile(oldUri) && !oldUri.endsWith('/')) {
      const newUri = request.querystring ? `${oldUri}/?${request.querystring}` : `${oldUri}/`;
      return callback(null, {
        body: '',
        status: '301',
        statusDescription: 'Moved Permanently',
        headers: {
          location: [{
            key: 'Location',
            value: newUri,
          }],
        }
      });
    } else {
      newUri = oldUri;
    }

    // Match any '/' that occurs at the end of a URI. Replace it with a default index
    newUri = newUri.replace(/\/$/, '\/index.html');
    
    // Log the URI as received by CloudFront and the new URI to be used to fetch from origin
    console.log("Old URI: " + oldUri);
    console.log("New URI: " + newUri);
    
    // Replace the received URI with the URI that includes the index page
    request.uri = newUri;
    
    // Return to CloudFront
    return callback(null, request);

};