index.js

'use strict';

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

exports.handler = async (event, context, callback) => {
    console.log("event ==> ", JSON.stringify(event));
    const request = event.Records[0].cf.request;
    console.log(`<< ${request.origin.s3.domainName}${request.origin.s3.path}${request.uri}`);
    const s3DomainName = 'micro-site.s3.amazonaws.com';
    
    const locales = new locale.Locales(request.headers['accept-language'][0].value);
    
    console.log("Our default is: " + locale.Locale["default"]);
    
    const parts = request.uri.split("/");
    const prefix = parts[1];
    const s3options = {Bucket: 'micro-site', Prefix: prefix};
    
    const supportLanguages = await getSupportLanguages(s3options);
    // const supportLanguages = ['zh-CN', 'en'];
    console.log("supportLanguages ==> ", supportLanguages)
    
    const supported = new locale.Locales(supportLanguages)
    
    language = locales.best(supported) 
    console.log("Our best match is: " + language);
    
    parts.splice(2, 0, language);
    request.uri = parts.join("/");
    
    console.log(`<< ${request.origin.s3.domainName}${request.origin.s3.path}${request.uri}`);
    
    request.headers['host'] = [{ key: 'host', value: s3DomainName }];
    console.log("request ==> ", JSON.stringify(request));
    callback(null, request);
};

const getSupportLanguages = async (options) => {
    const languages = [];
    // const start = new Date().getTime();
    const response = await s3.listObjectsV2(options).promise();
    // const end = new Date().getTime();
    // console.log("request s3 languages cost ", end - start, "ms");
    response.Contents.forEach(obj => {
        const lang = obj.Key.split('/')[1];
        // if (lang.endsWith('(default)')) {
        //     lang = lang.substring(0, lang.length - 9);
        //     defaultLanguage = lang
        // }
        languages.push(lang)
        
    })
    return Array.from(new Set(languages));
}