index.js - BUCKETで指定したバケットの内容を Lambda Function URLs で表示する。

index.js

const AWS = require('aws-sdk');
const BUCKET = process.env.BUCKET;
const ACCESS_KEY = process.env.ACCESS_KEY;
const SECRET_KEY = process.env.SECRET_KEY;
const REGION = process.env.REGION;

AWS.config.update({
  credentials: new AWS.Credentials(ACCESS_KEY, SECRET_KEY)
});

const S3 = new AWS.S3({apiVersion: '2006-03-01'});
const TEXT_PLAIN = 'text/plain; charset=UTF-8';

exports.handler = async (event) => {
  const id = event.requestContext.http.path.substr(1);
  const promise = new Promise((resolve, reject) => {
    S3.getObject({
      Bucket: BUCKET,
      Key: id,
    }).promise().then(data => {
      // https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#getObject-property
      const content_type = id.endsWith(".txt") ? TEXT_PLAIN: data.ContentType;
      resolve({
        statusCode: 200,
        headers: {
          'Content-Type': content_type,
        },
        body: Buffer.from(data.Body).toString('base64'),
        isBase64Encoded: true,
      });
    }).catch(error => {
      console.log(`error = ${error}`);
      resolve({
        statusCode: 404,
        headers: {
          'Content-Type': TEXT_PLAIN,
        },
        body: `Not Found`,
      });
    });
  });
  return promise;
};